TURNER

NSQF LEVEL - 5

1st Year (Volume II of II)

TRADE THEORY

SECTOR: Production & Manufacturing

DIRECTORATE GENERAL OF TRAINING

MINISTRY OF SKILL DEVELOPMENT & ENTREPRENEURSHIP
GOVERNMENT OF INDIA

NATIONAL INSTRUCTIONAL
MEDIA INSTITUTE, CHENNAI
Post Box No. 3142, CTI Campus, Guindy, Chennai - 600 032
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Sector : Turner
Duration : 2 - Years
Trade : Turner 1st Year (Volume II of II) - Trade Theory - NSQF level 5

First Edition : October 2018

Copies : 1,000

Rs.145/-

All rights reserved.

No part of this publication can be reproduced or transmitted in any form or by any means, electronic or mechanical, including
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Instructional Media Institute, Chennai.

Published by:
NATIONAL INSTRUCTIONAL MEDIA INSTITUTE
P. B. No.3142, CTI Campus, Guindy Industrial Estate,
Guindy, Chennai - 600 032.
Phone : 044 - 2250 0248, 2250 0657, 2250 2421
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email : chennai-nimi@nic.in, nimi_bsnl@dataone.in
Website: www.nimi.gov.in

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 FOREWORD

The Government of India has set an ambitious target of imparting skills to 30 crores people, one out of every
four Indians, by 2020 to help them secure jobs as part of the National Skills Development Policy. Industrial
Training Institutes (ITIs) play a vital role in this process especially in terms of providing skilled manpower.
Keeping this in mind, and for providing the current industry relevant skill training to Trainees, ITI syllabus
has been recently updated with the help of Mentor Councils comprising various stakeholder's viz. Industries,
Entrepreneurs, Academicians and representatives from ITIs.

The National Instructional Media Institute (NIMI), Chennai, has now come up with instructional material to
suit the revised curriculum for Turner Trade Theory 1st Year (Volume II of II) NSQF Level - 5 in
Production & Manufacturing Sector under Semester Pattern. The NSQF Level - 5 Trade Practical will
help the trainees to get an International equivalency Standard where their skill proficiency and
competency will be duly recognized across the globe and this will also increase the scope of
recognition of prior learning. NSQF Level - 5 trainees will also get the opportunities to promote life long
learning and skill development. I have no doubt that with NSQF Level - 5 the trainers and trainees of ITIs,
and all stakeholders will derive maximum benefits from these IMPs and that NIMI's effort will go a long
way in improving the quality of Vocational training in the country.

The Executive Director & Staff of NIMI and members of Media Development Committee deserve appreciation
for their contribution in bringing out this publication.

Jai Hind

RAJESH AGGARWAL
Director General/ Addl.Secretary
Ministry of Skill Development & Entrepreneurship,
Government of India.

New Delhi - 110 001

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 PREFACE

The National Instructional Media Institute (NIMI) was established in 1986 at Chennai by then Directorate
General of Employment and Training (D.G.E & T), Ministry of Labour and Employment, (now under Directorate
General of Training, Ministry of Skill Development and Entrepreneurship) Government of India, with technical
assistance from the Govt. of the Federal Republic of Germany. The prime objective of this institute is to
develop and provide instructional materials for various trades as per the prescribed syllabi under the Craftsman
and Apprenticeship Training Schemes.

The instructional materials are created keeping in mind, the main objective of Vocational Training under
NCVT/NAC in India, which is to help an individual to master skills to do a job. The instructional materials are
generated in the form of Instructional Media Packages (IMPs). An IMP consists of Theory book, Practical
book, Test and Assignment book, Instructor Guide, Audio Visual Aid (Wall charts and Transparencies) and
other support materials.

The trade practical book consists of series of exercises to be completed by the trainees in the workshop.
These exercises are designed to ensure that all the skills in the prescribed syllabus are covered. The trade
theory book provides related theoretical knowledge required to enable the trainee to do a job. The test and
assignments will enable the instructor to give assignments for the evaluation of the performance of a trainee.
The wall charts and transparencies are unique, as they not only help the instructor to effectively present a
topic but also help him to assess the trainee's understanding. The Instructor guide enable the instructor to
plan his schedule of instruction, plan the raw material requirements, day to day lessons and demonstrations.

IMPs also deals with the complex skills required to be developed for effective team work. Necessary care
has also been taken to include important skill areas of allied trades as prescribed in the syllabus.

The availability of a complete Instructional Media Package in an Institute helps both the Trainer and
management to impart effective training.

The IMPs are the outcome of collective efforts of the staff members of NIMI and the members of the Media
Development Committees specially drawn from Public and Private sector industries, various training institutes
under the Directorate General of Training (DGT), Government and Private ITIs.

NIMI would like to take this opportunity to convey sincere thanks to the Directors of Employment & Training
of various State Governments, Training Departments of Industries both in the Public and Private sectors,
Officers of DGT and DGT field institutes, proof readers, individual media developers and coordinators, but for
whose active support NIMI would not have been able to bring out this materials.

R. P. DHINGRA
Chennai - 600 032 EXECUTIVE DIRECTOR

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 ACKNOWLEDGEMENT

National Instructional Media Institute (NIMI) sincerely acknowledges with thanks for the co-operation and
contribution extended by the following Media Developers and their sponsoring organisations to bring out this
Instructional Material (Trade Theory) for the trade of Turner under the Production & Manufacturing

MEDIA DEVELOPMENT COMMITTEE MEMBERS

Shri. Natarajan _ Training officer

Govt. I.T.I Salem
Tamil Nadu

Shri. R. Purushothaman _ Assistant Director Gr1

MSME, GOI.

Shri. Dayala moorthy _ Assistant Training officer

Govt. I.T.I Vellore
Tamil Nadu

Shri. N. Sampath _ Assistant Training officer

Govt. I.T.I Chengalpattu
Tamil Nadu

Shri. G. Mani _ Junior Works Manager (Retd)

MDC Member NIMI, Chennai - 32

Shri. M. Sampath _ Training officer (Retd)

MDC Member
Chennai - 600032

Shri. V. Gopalakrishnan _ Assitant Manager,

Co-ordinator, NIMI, Chennai - 32

NIMI records its appreciation for the Data Entry, CAD, DTP operators for their excellent and devoted services in
the process of development of this Instructional Material.

NIMI also acknowledges with thanks the invaluable efforts rendered by all other NIMI staff who have contributed
towards the development of this Instructional Material.

NIMI is also grateful to everyone who has directly or indirectly helped in developing this Instructional Material.

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 INTRODUCTION
TRADE THEORY

The manual of trade theory consists of theorectical information for the 1st Year (Volume II of II) couse of the
Turner Trade. The contents are sequenced according to the practical exercise contained in the manual
on Trade practical. Attempt has been made to relate the theortical aspects with the skill covered in each
exercise to the extent possible. This co-relation is maintained to help the trainees to develop the perceptional
capabilities for performing the skills.

The Trade Theory has to be taught and learnt along with the corresponding exercise contained in the manual
on trade practical. The indication about the corresponding practical exercises are given in every sheet of this
manual.

It will be preferable to teach/learn the trade theory connected to each exercise atleast one class before
performing the related skills in the shop floor. The trade theory is to be treated as an integrated part of each
exercise.

The material is not the purpose of self learning and should be considered as supplementary to class room
instruction.

Module 1 Taper Turning 100 Hrs

Module 2 Eccentric Turning 50 Hrs
Module 3 Thread cutting 175 Hrs
Module 4 Other forms of thread 150 Hrs
Module 5 Special job & Maintenance 50 Hrs
Total 525 Hrs

TRADE PRACTICAL
The trade practical manual is intended to be used in workshop . It consists of a series of practical exercies to
be completed by the trainees during the Second Semester course of the Turner trade supplemented and
supported by instructions/ informations to assist in performing the exercises. These exercises are designed
to ensure that all the skills in the prescribed syllabus are covered.
The manual is divided into five modules. The distribution of time for the practicals in the five modules are given
below.

The skill training in the computer lab is planned through a series of practical exercises centerd around some
practical project. However, there are few instances where the individual exercise does not form a part of project.
While developing the practical manual a sincere effort was made to prepare each exercise which will be easy
to understand and carry out even by a below average traninee. However the Development Team accept that there
can be some scope for further improvement. NIMI, looks forward to the suggestions from the experienced
training faculty for improving the manual.

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 CONTENTS

Lesson No. Title of the lesson Page No.

Module 1 : Taper Turning

2.1.49 Different methods of expressing taper 1

2.1.50 Bevel protractor & Vernier bevel protractor 9

2.1.51 Method of taper angle measurement 12

2.1.52 Sine bar - type & uses 17

2.1.53 Slip gauges, types, uses and selection 20

2.1.54 Method of brazing carbide tipped tool 24

2.1.55 Basic process of soldering, welding & brazing 25

Module 2 : Eccentric Turning

2.2.56 Vernier height gauge, function & description 41

2.2.57 Template, its function & construction 43

2.2.58 Screw thread - definition, purpose & its elements 47

2.2.59 Driving plate & lathe carrier & their usage 50

2.2.60 Fundamentals of thread cutting on lathe 52

Module 3 : Thread cutting

2.3.61 Different type of screw thread - forms, elements & application 53

2.3.62 Drive-train change gear formula calculation 62

2.3.63 Different method of forming thread 63

2.3.64 Calculation involved in finding core dia, gear train 65

2.3.65 Thread chasing dial function, construction & use 68

2.3.66-67 Conventional chart of different profile of metric, BA, whit worth & pipe thread 73

2.3.68 Calculation involving gear ratio & gearing 76

2.3.69 Screw thread micrometer & its use 78

2.3.70 Calculation involving gear ratios for metric threads cutting on inch lead screw
lathe & Vice versa. 81

2.3.71 Tool life, negative top rake 83

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Lesson No. Title of the lesson Page No.

Module 4 : Other forms of thread

2.4.72 - 76 Calculation involving tooth thickness, core dia, depth of cut of square thread 85

2.4.77 - 79 Calculation involved depth, core dia, pitch proportion etc, of ACME 88
& Buttress thread

2.4.80 - 82 Buttress thread cutting (Male & female) & tool grinding 93

Module 5 : Special job & Maintenance

2.5.83 - 84 Different lathe accessories, use & care 97

2.5.85 Lubricant-function, type, sources and method of lubrication 106

2.5.86 Dial test indicator, its use for parallilism & concentricity 112

2.5.87 Grinding wheel abrasive, grit, grade, Bond 114

LEARNING / ASSESSABLE OUTCOME

On completion of this book you shall be able to

• Recognise, understand typical turning operations like Form turn-

ing, taper turning, boring etc.,

• Draw and organise work to make Morse Taper plug, Taper sleeves,
executing complex job involving face plate, angle plate etc.,

• Execute turning of crackshaft, turning of long shaft using lathe

attachments such as revolving steady, roller steady etc.,

• Perform eccentric boring, stepped boring within 50 micron

accuracy level and use of inside micrometer, telescopic gauges
etc for bore measurement.

• Execute metric and British standard thread cutting, multi start

thread cutting, making use of change wheel calculation, and
checking of threads.

• Understand the use and applications of all types of lathe attach-

ments.

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 SYLLABUS

1st Year (Volume II of II) Duration: Six Month

Set different 49. Make taper turning by form Taper – different methods of
27.
components of tool and compound slide expressing
machine & tapers, different standard tapers.
swiveling. (25 hrs.)
parameters to Method of
produce taper/ taper turning, important
angular components dimensions of taper.
and ensure proper Taper turning by swiveling
assembly of the compound slide,
components. its calculation.
[Different
component of
machine: - Form
tool, Compound
slide, tail stock
offset, taper turning
attachment.
Different machine
parameters- Feed,
speed, depth of cut.]

28-29 -do- 50. Male and female taper Bevel protector & Vernier bevel
turning by taper turning protractorits
attachment,offsetting function & reading
tail stock. (22 hrs.)
51. Matching by Prussian Blue.
(2 hrs.) Method of taper angle
52. Checking taper by bevel measurement.
protector and sine bar. (1 Sine bar-types and use. Slip
hrs.) gauges-types,
53. Make MT3 lathe dead centre uses and selection.
and check with female part.
(Proof machining) (25 hrs.)

30. Set the different 54. Turning and boring practice on Method of brazing solder, flux
machining CI (preferable) or steel. (23 used for tip
parameter & tools to hrs.) tools.
prepare job by 55. Tip brazing on shank. (2 hrs.) Basic process of soldering,
performing different welding and
boring operations. brazing.
[Different machine
parameter- Feed,
speed & depth of
cut; Different boring
operation – Plain,
stepped & eccentric]

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 56. Eccentric marking practice. Vernier height gauge, function,
31-32 -do-
(2 hrs.) description &
57. Perform eccentric turning. uses, templates-its function and
(18 hrs.) construction.
58. Use of Vernier height Gauge Screw thread-definition, purpose & it’s
and Vblock.(1 hrs.) different elements.
59. Perform eccentric boring. Driving plate and lathe carrier and their
(18 hrs.) usage. Fundamentals of thread cutting
60. Make a simple eccentric on
with dia. of 22mm and throw/ lathe. Combination set-square head.
Center
offset of 5mm.(11 hrs.)
head, protractor head-its function
construction and uses.

33-35 Set the different 61. Screw thread cutting (B.S.W) Different types of screw thread- their
machining external (including angular forms
parameters to approach method) R/H & L/H, and elements. Application of each
produce different checking of thread by using type of thread. Drive train. Chain
threaded screw thread gauge and thread gear formula calculation.
components plug gauge. (16 hrs.) Different methods of forming
applying method/ 62. Screw thread cutting (B.S.W) threads.
technique and test internal R/H & L/H, checking of Calculation involved in finding core
for proper assembly thread by using screw thread dia., gear train (simple gearing)
of the components. gauge and thread ring gauge. calculation.
[Different thread: - (18 hrs.) Calculations involving driver-driven,
BSW, Metric, 63. Fitting of male & female lead screw pitch and thread to be
Square, ACME, threaded components (BSW) (2 cut.
Buttress.] hrs.)
64. Prepare stud with nut
(standard size).(14 hrs.)

36-37 -do- 65. Grinding of “V” tools for Thread chasing dial function,
threading of Metric 60 degree construction and use. Calculation
threads and check with gauge. involving pitch related to ISO
(3 hrs.) profile. Conventional chart for
66. Screw thread cutting (External) different profiles, metric, B.A., With
metric thread- tool grinding.(15 worth, pipe etc. Calculation
hrs.) involving gear ratios and gearing
67. Screw thread (Internal) metric & (Simple & compound gearing).
threading tool grinding. (16 hrs.) Screw thread micrometer and its
68. Fitting of male and female thread use.
components (Metric) (2 hrs.)
69. Make hexagonal bolt and nut
(metric) and assemble. (14 hrs.)

38. -do- 70. Cutting metric threads on inch Calculation involving gear ratios
lead screw and inch threads on metric threads cutting on inch L/
Metric Lead Screw. (25 hrs.) S Lathe and vice-versa.

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 39. -do- 71. Practice of negative rake tool on Tool life, negative top rake-its
nonferrous metal and thread application and performance with
cutting along with fitting with respect to positive top rake
ferrous metal.(25 hrs.)

72. Cutting Square thread Calculation involving tool

40-41 -do- (External) (16 hrs.) Thickness, core dia., pitch
73. Cutting Square thread proportion, depth of cut etc. of
(Internal). (18 hrs.) sq.thread.
74. Fitting of male and female
Square threaded
components. (2 hrs.)
75. Tool grinding for Square
thread (both External &
Internal). (2 hrs.)
76. Make square thread for
screw jack (standard) for
minimum 100mm length bar.
(12 hrs.)

42-43 -do- 77. Acme threads cutting (male Calculation involved – depth, core
& female) & tool grinding. dia., pitch proportion etc. of Acme
(16 hrs.) thread.
78. Fitting of male and female Calculation involved depth, core
threaded components (14 dia., pitch proportion, use of
hrs.) buttress thread.
79. Cut Acme thread over 25
mm dia rod and within
length of 100mm.(20 hrs.)

44-45 -do- 80. Buttress threads cutting (male Buttress thread cutting ( male &
& female) & tool grinding. (26 female ) & tool grinding
hrs.)
81. Fitting of male & female
threaded components. (2 hrs.)
82. Make carpentry vice lead
screw (22 hrs.)

46. Set the different 83. Make job using different lathe Different lathe accessories,
machining accessories viz., driving plate, their use and care.
parameter & lathe steady rest, dog carrier and
accessories to different centres. (15 hrs.)
produce components 84. Make test mandrel
applying techniques (L=200mm) and counter bore
and rules and check at the end. (10 hrs.)
the accuracy.
[Different
machining
parameters: -
Speed,
feed & depth of cut;
Different lathe
accessories: -
Driving Plate,
Steady rest, dog
carrier and different
centres.]

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47. Plan and perform 85. Balancing, mounting & Lubricant-function, types, sources
basic dressing of grinding wheel of lubricant. Method of lubrication.
maintenance (Pedestal). (5 hrs.) Dial test indicator use for
of lathe & grinding 86. Periodical lubrication parallelism and concentricity etc. in
machine and procedure on lathe. (10 hrs.) respect of lathe work Grinding
examine their 87. Preventive maintenance of wheel abrasive, grit, grade, bond
functionality. lathe. (10 hrs.) etc.

In-plant training / Project work

48-49
1. Drill extension socket
2. conical brush
3. V-belt pulley
4. Tail Stock Centre (MT – 3)
5. Taper ring gauge
6. Sprocket
7. Socket spanner

50-51
Revision

52. Examination

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Production & Manufacturing
Turner - Taper turning Related Theory for Exercise 2.1.49

Different methods of expressing tapers

Objectives : At the end of this lesson you shall be able to
• define a taper
• state the uses of a taper
• identify the elements of a taper
• express the taper and its conversion
• classify the tapers
• state the different Standard tapers and their uses.

Definition of a taper - giving the taper per foot, (Ex: 5/8" TPF means in a 12"
(one foot) taper length , the difference between big &
Taper is a gradual increase or decrease in the diameter
small diameter is 5/8") (Fig 4)
along the length of the job.
- giving the taper in ratio (This is also termed as conicity
Uses of a taper and it is indicated as K) (Ex: Ratio 1:20 means, for a
taper length of 20 units, the difference in diameter is 1
Tapers are used for:
unit.) (Fig 5)
- easy assembly and disassembly of parts
- mentioning by standard taper MT3. (Fig 6)
- giving self-alignments in the assembled parts
- Transmitting the drive in the assembled parts.

Elements of a taper (Fig 1)

Big diameter (D)
Small diameter (d)

Length of the taper (l)

Angle of taper (θ)
Total length of the job (L)

Different methods of expressing tapers

Tapers can be expressed by
- giving the big dia. small dia. and the length of the taper
(Fig 2)
- giving the included angle of the taper in degrees
(Fig 3)

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 Examples
Conversion
Taper shank of drills, reamers and sleeves.
The relationship between the elements of a taper are:
- Quick releasing tapers (Fig 8)
D−d
Tan θ =
2L

TPF
Tan θ =
24

ratio
Tanθ =
2

Classification of tapers
Tapers are classified into the following:
• Self-holding tapers (Figs 7 & 7a)
Self-holding tapers have a low taper angle, limited to a Quick releasing tapers have higher taper angles and they
maximum of 10°. They will not have any locking devices for require locking devices for holding.
holding the components assembled.
Example
Arbor of a milling machine.

Different Standard tapers and their uses

Objectives: At the end of this lesson you shall be able to
• name the standard tapers in use in engineering
• state the speciality of each standard taper
• list out their specific applications in engineering.

The different standard tapers and their uses Jarno taper (JT)
The following are the common standard tapers in use. Metric taper
Morse taper (MT) Pin taper
Brown & Sharpe taper (BS)

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Morse taper Standard pin taper
It is the most commonly used standard taper in the It is used in taper pins. It is a self-holding taper. It is
industry. It is a self-holding taper. This taper is usually available both in Metric and British systems. The amount
used in bores of spindle noses of lathes and drilling of taper is 1:50 in the Metric system and 1:48 (1/4" TPF)
machines, shanks of drills, reamers, centres, etc. The in the British system.
Morse taper is denoted by the letters MT. They are
A taper pin is used to assemble parts which must be held
available from MTO to MT7. The numbers MTO to MT4 are
and positioned for accurate, quick and easy assembly. It
commonly used on taper shanks of twist drills, reamers
also permits to transmit the drive.
and lathe centres. The included angle of Morse taper is
approximately 3° and the taper per foot is 5/8". A chart Uses of standard tapers
showing the angles and TPF of different Morse taper
numbers in detail may be referred to for specific use. Tapers are used for:
- self-alignment/location of components in an assembly
Brown and Sharpe taper
- assembling and dismantling parts easily
Both quick-releasing and self-holding tapers are available
in Brown and Sharpe tapers. The taper used in the arbors - transmitting drive through assembly.
of milling machines is the quick-releasing Brown and Tapers have a variety of applications in engineering
Sharpe taper having a taper of 3 1/2" T.P.F. assembly work.(Figs 1,2 & 3)
Brown and Sharpe self-holding tapers are available from
BS1 to BS18. The taper per foot is 1/2" except BS 10.
BS10 has a taper of 0.5161" taper per foot.

Jarno taper
Jarno tapers are also used on the external taper of the
lathe spindle nose where chuck or face plate is mounted.
They are available from No.l to No.20. The amount of taper
per foot is 0.6". The dimensions of this taper will be found
as follows.

Number
Big diameter =
8
Number
Small diameter =
10
Number
Length of taper =
2
Jarno taper is mostly used in die-sinking machines.

Metric taper
It is available as both self-holding and quick-releasing
tapers. A self-holding metric taper has an included angle
of 2° 51' 51". The commonly used self-holding metric
tapers are expressed in numbers, and they are 4, 6, 80,
100, 120,160 and 200. These numbers indicate the highest
diameter of the taper shank up to which the gauge or
mating part is to match.
Quick-releasing metric tapers are used as the external
tapers of lathe spindle noses. Metric tapers are expressed
by numbers which represent the big diameter of the taper
in millimetres. The equivalent quick (self) releasing taper
in metric also has a taper of 7/24 and the available sizes
are 30, 40, 45, 50.
A 7/24 taper of No.30 will have a maximum diameter of Tapers used in other assembly work
31.75 mm at the larger end and No.60 will have 107.950 A variety of tapers are used in engineering assembly
mm. All other sizes fall within this range. work. The most common ones are:
- pin taper
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- key and keyway taper. Taper pins help in assembling and dismantling of compo-
nents without disturbing the location.

Key and keyway tapers

This taper is 1:100. This taper is used on keys and key-
ways. (Figs 5 & 6)

For further information about the tapers used

for special application refer to: IS:3458-1981

Pin taper
This is the taper used for taper pins used in assembly.
(Fig 4)

The taper is 1:50.

The diameter of taper pins is specified by the small
diameter.

Methods of turning taper on Lathe and important dimensions of taper

Objectives: At the end of this lesson you shall be able to
• point out the taper turning methods on a lathe
• state the features of each method
• list out the important dimension of taper.

Methods of turning taper on a lathe - tailstock offset method

The different methods of taper turning on a lathe are: - taper turning attachment method.
- form tool method
Form tool method (Fig 1)
- swivelling compound slide method
This method is used in mass production for producing a
4 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.1.49

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small length of taper where accuracy is not the criterion. Threads on taper portion cannot be produced.
The form tool should be set at right angles to the axis of
Taper length is limited to the movement of the top slide.
the work. The carriage should be locked while turning taper
by this method. • Fig.3 shows the settings of a top slide for turning
different taper angles.

Swivelling Compound slide method (Fig 2)

Tailstock offset method (Fig 4)

In this method the top slide of the compound rest is

swivelled to half the included angle of the taper, and the
taper is turned.
The amount of taper for setting the angle is found by the
formula
α D-d
Tan =
2 2x l
where
D= larger taper diameter In this method the job is held at an angle and the tool
moves parallel to the axis. The body of the tailstock is
d= smaller taper diameter
shifted on its base to an amount corresponding to the
l = length of taper angle of taper.
α The taper can be turned between centres only and this
= 1/2 included angle in degrees. method is not suitable for producing steep tapers. The
2
amount of offset is found by the formula:
Advantages
Offset =
(D - d) x L
Both internal and external taper can be produced. 2l
Steep taper can be produced. where
D = big dia. of taper
Easy setting of the compound slide.
d = small dia. of taper
Disadvantages l = taper length
Only hand feed can be given. L = total length of job.
Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Exercise 2.1.49 5

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Advantages This attachment is provided on a few modern lathes. Here
the job is held parallel to the axis and the tool moves at an
- Power feed can be given.
angle. The movement of the tool is guided by the attachment.
- Good surface finish can be obtained.
Advantages
- Maximum length of the taper can be produced.
- Both internal and external tapers can be produced.
- External thread on taper portion can be produced.
- Threads on both internal and external taper portions
- Duplicate tapers can be produced. can be cut.
Disadvantages - Power feed can be given.
- Only external taper can be turned. - Lengthy taper can be produced.
- Accurate setting of the offset is difficult. - Good surface finish is obtained.
- Taper turning is possible when work is held between - The alignment of the lathe centres is not disturbed.
centres only. - It is most suitable for producing duplicate tapers
- Damages the centre drilled holes of the work. because the change in length of the job does not affect
- The alignment of the lathe centres will be disturbed. the taper.
- Steep tapers cannot be turned. - The job can be held either in chuck or in between
centres.
Taper turning by attachment (Fig 5)
Disadvantage
- Only limited taper angles can be turned.

Calculation of the compound slide swivel angle

Objectives: At the end of this lesson you shall be able to
• derive a formula to determine the swivel angle
• solve problems involving taper calculation
• refer to tables and determine the value of the angle for the arrived result
• determine the depth of cut to reduce the taper length.

Derivation of the formula The taper is divided into two right angled triangles by the
centre line. By referring to the shaded right angled triangle
For convenience a tapered job whose small diameter is
in figure 1, the side (b) shown against the half included
zero is taken (Fig 1) to illustrate as to how the formula can
angle of taper a/2, is termed as the opposite side. The side
be derived.
(a) is termed as the adjacent side and side (c) is termed
as the hypotenuse. There is a relationship between the
sides of the triangle and the angle a/2. They can be
expressed as ratios. The ratio of the sides (b) and (a) is
a constant value for a given angle a/2. This ratio b/a does
not change for a given value of a/2. This means that if ‘b’
increases or decreases there will be a proportionate
increase or decrease of side ‘a’ making the ratio b/a
constant. This ratio between the opposite side to the
adjacent side of an angle in a right angled triangle is
referred to as the tangent value of the angle.

6 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.1.49

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The equation for the tangent α/2 is, therefore, Tan α/2 = α D−d 1
Tan = x
b/a. Since this value is the same for a particular angle, the 2 l 2
tangent values for all angles are put together into tables
under the heading ‘Natural Tangents’. Therefore, they D−d
need no longer be calculated individually, but can be taken This is the taper ratio
l
from the tables.
Referring to Fig 2, which has a small diameter also, the Hence the formula becomes
shaded triangle D–d refers to ‘b’ of the formula and l refers
to ‘a’ of the formula. Taper ratio
Tan of half the included angle =
2
Example

The taper ratio is given as 1:5.

To determine the compound slide swivel angle (Fig 3), the
Taper ratio=1:5= 1/5

α 1/5 1
Tan = = 0.1
=
2 2 10
D = 30 mm d = 22 mm & l = 40 mm α o '
= 5 45
2
Now the formula becomes
The compound slide swivel angle is 5o45’.
α D-d D-d D-d
Tan = = = Taper per foot is given to determine the compound slide
2 2 2x l 2l
swiveling angle.
l
For example, referring to Fig.3 we have Example
(Given 5/8” TPF)
This means that the difference in diameter (D-d) is 5/8” for
a taper length of 1 foot or 12”.

D-d
Tan α/2 =
2l
Here D-d=5/8” and l=12”

5" 5
Tan α/2 = = 0.0260
=
8 8x24
2x12
D - d 30 − 22 o '
Tangent α/2 = = α/2 = 1 26
2l 80
The formula is Tan of half included
8 1
= = 0.1
=
80 10 Taperper foot
=
Referring to the logarithm tables of Natural Tangents we 24
find that the angle whose tangent value is 0.1, is 5° - Remember that it is the half included angle of the taper to
45‘, and this is the top slide swivelling angle to turn the which the top slide is to be swivelled.
tapered job of Fig 3.
To determine the depth of cut to be given to get a definite
Taper expressed as a ratio to determine the swivel change in length of the taper, the taper angle remaining the
angle same. (Fig. 4)
The general formula is Referring to Fig.4, [9] is the radius at the bigger end, (also
the diference in diameter divided by 2, since the small
α D−d diameter of the taper is zero), [5] is the length of the taper,
Tan =
2 2l [4] is the change in the taper length, [1] is the depth of cut
This can be rewritten as to be given to get the change in taper length.

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 Example
The taper length [5] of Fig 4 with an included angle of 20°
is to be shortened by 2 mm. What should be the depth of
cut?
l = [4] x tan α/2
[1]=2mm x tan 20o/2
=2mm x tan 10o
=2 x 0.1763
=0.3526mm
[6] Opposite side to α/2 Hence a depth of cut of 0.35 mm is to be given in order to
[7] Adjacent side reduce the taper length by 2 mm, the taper included angle
remaining the same 20°.
[8] Hypotenuse
Then [1] = [4] x tan α/2

8 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.1.49

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Production & Manufacturing
Turner-Taper turning Related Theory for Exercise 2.1.50

Bevel protractor and Vernier bevel protractor

Objectives: At the end of this lesson you shall be able to
• identify the parts of a universal bevel protractor
• state the functions of each part
• list the uses of a vernier bevel protractor.

Bevel protractor (Fig 1) : The bevel protractor is a direct Blade

angular measuring instrument, and has graduation marked
This is the other contacting surface of the instrument that
from 0° to 180°. This instrument can measure angles
contacts the work during measurement, preferably the
within an accuracy of ±1°.
inclined surfaces. It is fixed to the dial with the help of the
clamping lever. A parallel groove is provided in the centre
of the blade to enable it to be longitudinally positioned
whenever necessary.

Locking screws
Two knurled locking screws are provided, one to lock the
dial to the disc, and the other to lock the blade to the dial.
All parts are made of good quality alloy steel, properly
heat-treated and highly finished. A magnifying glass is
sometimes fitted for clear reading of the graduations.

Uses of a vernier bevel protractor

The vernier bevel protractor is a precision instrument
meant for measuring angles precisely to an accuracy of
5 minutes. (5')
Parts of a Vernier Bevel Protractor
The following are the parts of a vernier bevel protractor.
(Fig 2)

Stock
This is one of the contacting surfaces during the
measurement of an angle. Preferably it should be kept in
contact with the surface from which the inclination is
measured.
Disc
The disk is an integrated part of the stock. It is circular in
shape, and the edge is graduated in degrees.
Dial
It is pivoted to the disc and can be rotated through 360°.
The vernier scale of the instrument is attached to the dial.
The dial is locked to the disc while reading the measurement.

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The vernier bevel protractor is used to measure acute
angles, i.e. less than 90° (Fig 3), obtuse angles i.e more
than 90° (Fig 4) for setting work-holding devices to angles
on machine tools, work tables etc. (Figs 5 & 6)

Graduations on vernier bevel protractor

Objectives: At the end of this lesson you shall be able to
• state the main scale graduations on the disc
• state the vernier scale graduations on the dial
• determine the least count of the vernier bevel protractor.

The main scale graduations The least count of the vernier bevel protractor
For purposes of taking angular measurements, the full When the zero of the vernier scale coincides with the zero
circumference of the disc is graduated in degrees.The of the main scale, the first division of the vernier scale will
360° are equally divided and marked in four quardrants, be very close to the 2nd main scale division. (Fig 1)
from 0 degree to 90 degrees, 90 degrees to 0 degree, 0 to
Hence, the least count is
90 degrees and 90 degrees to 0 degrees. Every tenth
division is marked longer and numbered. Each division 2 MSD – 1 VSD
represents 1 degree. The graduations on the disc are
11º
known as the main scale divisions. On the dial, 23 i.e. the least count = 2º - 1 , 2 - 1º55'
divisions spacing of the main scale is equally divided into 12
12 equal parts on the vernier. Each 3rd line is marked
longer and numbered as 0, 15, 30, 45, 60. This constitutes 1o
the vernier scale. Similar graduations are marked to the =
12
left of 0 also. (Fig 1)
= 5'
For any setting of the blade and stock, the reading of the
acute angle and the supplementary obtuse angle is
possible, and the two sets of the vernier scale graduations
on the dial assist to achieve this. (Fig 2)

One vernier scale division (VSD) (Fig 2)

23º 11º
= 1
= 1º55'
=
12 12
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Reading of vernier bevel protractor
Objectives: At the end of this lesson you shall be able to
• read a vernier bevel protractor for acute angle setting
• read a vernier bevel protractor for obtuse angle setting.

For reading acute angle set up (Fig 1) To take the vernier scale reading, multiply the coinciding
divisions with the least count.
Example: 8 x 5' = 40'
Sum up both readings to get the measurements. = 41° 40'

If you read the main scale in an anticlockwise

direction, read the vernier scale also in an
anticlockwise direction from zero.
If you read the main scale in a clockwise
direction, read the vernier scale also in a
clockwise direction from zero.

For obtuse angle set up (Fig 3)

The vernier scale reading is taken on the left side as
indicated by the arrow. The reading value is subtracted
from 180° to get the obtuse angle value.
First read the number of whole degrees between zero of
the main scale and zero of the vernier scale. (Fig 1) Reading 22° 30'

Note the line on the vernier scale that exactly coincides Measurement
with any one of the main scale divisions and determine its 180° — 22° 30'=157° 30'
value in minutes. (Fig 2)

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Production & Manufacturing
Turner - Taper turning Related Theory for Exercise 2.1.51

Method of taper angle measurement

Objectives: At the end of this lesson you shall be able to
• state the units and fractional units of angles
• express degrees, minutes and seconds using symbols.

The unit of an angle Subdivisions of an angle

For angular measurements a complete circle is divided For more precise angular measurements, one degree is
into 360 equal parts. Each division is called a degree. (A further divided into 60 equal parts. This division is one
half circle will have 180°) (Fig 1) MINUTE ('). The minute is used to represent a fractional
part of a degree and is written as 30° 15'. One minute is
further divided into smaller units known as seconds (").
There are 60 seconds in a minute.
An angular measurement written in degrees, minutes and
seconds would read as 30° 15' 20".
Examples for angular divisions
1 complete circle 360°
1/2 circle 180°
1/4 of a circle (right angle) 90°
Subdivisions 1 degree or 1° = 60 mts or 60'
1 min or 1' = 60 secs or 60"

Measuring angles with vernier bevel protractor

Objective: At the end of this lesson you shall be able to
• state the methods of measuring angles with a vernier bevel protractor.

A vernier bevel protractor setting depends on the type of Take the reading.
the angle to be measured. It can be set in different ways
for measuring and checking angles. (Figs 1 to 6) When you have finished measuring, clean the
protractor using a soft cloth and put it in its
Before measuring, check that the measuring surfaces (the
case.
blade and the stock of the protractor) are not damaged.
Do not leave the protractor in any place from
Clean the measuring faces of the protractor and the
where it could fall, or be otherwise damaged.
workpiece. Use a soft clean cloth.
While measuring, loosen the vernier scale locking screw.
Loosen the blade locking screw, adjust the blade to suit
the workpiece, tighten the blade screw and place the
protractor on the work-surface.
Adjust the protractor so that the inner surface of the
blade and the base are in contact with the workpiece.
Make sure that the protractor is perpendicular to the
surface being measured.
The protractor must be adjusted so that the blade and
base are in full contact with the surfaces being measured.
(There should not be any gap between the blade, base
and the workpiece surfaces).
Lock the vernier locking nut and carefully remove the vernier
bevel protractor.
12

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Measuring angle of tapered (external) components
Objectives: At the end of this lesson you shall be able to
• name the features of a taper which can be measured using precision rollers and slip gauges
• state the formula for measuring the angle of the taper
• calculate the angle of the taper.

A method used for checking the dimensions of the following elements of the tapers can be checked.
tapered components is by using precision rollers or balls
- Angle of the taper (Fig 1)
along with the slip gauges. Using this method the
Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Exercise 2.1.51 13

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 corresponds to the distance AB. (Fig 5b)
The length AC corresponds to the size of the slip pack
used on one side.

x-y
AB =
2
Then the tangent of the taper angle is
x−y
AB 2 x−y
Tanθ = = =
AC H 2H
- Small end diameter (Fig 2)
Where X is the measurement over the rollers placed on
- Large end diameter (Fig 2) the slip gauge height, Y is the measurement over the
rollers at the smaller end and H is the slip gauge height.
The included angle of the taper will be double the above
angle.

Checking the angle of the taper

For determining this angle two measurements are taken.
i.e. X and Y.
The measurement Y is taken by placing the component
against a datum surface like the surface plate or the
marking table. Two precision rollers are then placed at
the smaller end resting on the datum surface and
contacting the workpiece. (Fig 3)

Measurement ‘X’ is taken by lifting and placing the rollers

on both sides with the help of two sets of slip packs having
the same size.
The measurement is then taken with a micrometer over
the rollers. (Fig 4)
For computing the taper angle the following trigonometrical
ratio is applied. (Fig 5a)

BC a Example
Tan θ = =
AB c Calculate the included angle of the tapered component
From the two measurements taken and the height of the shown in Fig 6.
slip packs the ratio is established by subtracting the
measurement ‘Y’ from ‘X’ and dividing it by two. This
14 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.1.51

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 X = 69.3 MM
Y = 61.5 MM
Height = 70 MM
TAN θ = (69.3)–(61.5)/2X70
= 7.8/2X70

0
.
3 7
9
3
.
9 0

0
.
0
5
5
7
7
= ==

Referring to the log table under Natural Tangents

we find θ = 3° ° 11'
.'
HENCE INCLUDED ANGLE OF THE TAPER
2θ = 3° 11’X 2 = 6° 22'
The measurement 2θ = 6° 22'.
X = 69.3 MM

Determining diameters of tapered components

Objectives: At the end of this lesson you shall be able to
• calculate the small diameter of a tapered component
• calculate the large diameter of a tapered component.

Diameters at any position of tapered components can

be determined when the angle of taper is known.
For inspection of tapered components for dimensional
quality the following diameters are measured.
Small end diameter d (Fig 1)
Large end diameter D (Fig 1)

Determining small end diameter (Fig 2)

The small diameter ‘d’ is = Y – 2 (S + r).
Y - is the diameter over the two precision rollers.
r - is the radius of the roller.
S - is the distance from the centre of the roller to the
end of the component.

Calculating S (Fig 3)

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Exercise 2.1.51 15

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 ⎧ 90 − θ ⎫ r
Tan⎨ ⎬=
⎩ 2 ⎭ s
r
s=
⎧ 90 − θ ⎫
Tan⎨ ⎬
⎩ 2 ⎭
⎡ ⎤
⎢ r ⎥
d = Y − 2⎢ + r⎥
⎢ Tan⎧ 90 − θ ⎫ ⎥
⎢⎣ ⎨ ⎬
⎩ 2 ⎭ ⎥⎦
⎡ ⎧ 90 − θ ⎫ ⎤
= Y − 2r ⎢Cot ⎨ ⎬ + 1⎥
⎣ ⎩ 2 ⎭ ⎦
Example

θ = 3° 11'
θ = 3° 11"
X = 69.3 mm
Y = 61.5 mm
H = 70 mm
r = (radius of roller) 6 mm r = (radius of the roller) 6 mm
Then the diameter of the taper at height H from the
⎡ ⎧ 90 - 3º 11' ⎫⎤ small end. = 69.3 – 12 (1+1.0570)
Then d = 61.5-12 ⎢Cot ⎨ ⎬⎥ + 1
⎣ ⎩ 2 ⎭⎦ = 69.3 – 24.6840 = 44.6160 mm
The length of the taper can be directly measured by
= 61.5 – 12 (1.0570 + 1) using a vernier height gauge. Then the largest diameter
of the taper is determined by computing the known
= 61.5 – 12 x 2.0570 values.

= 61.5 – 24.6840 = 36.3160 mm If ‘M’ is the maximum diameter of the taper, ‘T’ is the
minimum diameter of the taper and L is the tapered
Determining the large diameter of taper at any length
desired heigh (H for example) then M = T + 2L x Tan θ .
The formula is derived by taking into consideration the
measurement over the rollers placed at a known
height ‘H’, the diameter of the roller and the angle of taper.
The diameter ‘D’ at larger end at height ‘H’.
= X – 2 (s + r)

Example (Fig 4)

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Production & Manufacturing
Turner - Taper turning Related Theory for Exercise 2.1.52

Sine bar - Types - Uses

Objectives: At the end of this lesson you shall be able to
• state the different uses of a sine bar
• state the features of a sine bar
• specify the sizes of a sine bar
• state the principle of a sine bar.

A sine bar is a precision instrument meant for setting

work to machine angular surfaces, to determine the
angles of tapered jobs by calculation.

Features
The sine bar is a rectangular bar made of stabilized
chromium steel. (Fig 1)

The surfaces are accurately finished by grinding and

lapping.
Two precision rollers of the same diameters are mounted
on either end of the bar. The centre line of the rollers is
parallel to the top face of the sine bar.
There are holes drilled across the bar. This helps in
reducing the weight, and also facilitates clamping the
sine bar to the angle plates, with bolts and nuts.
The length of the sine bar is the distance between the
centres of the rollers. The commonly available sizes
are 100 mm, 200 mm, 250 mm and 500 mm. A sine bar
is specified by its length. In a right angled triangle the function known as sine of
an angle is the relationship existing between the
Uses hypotenuse and the side opposite to the angle. (Fig 5)
Sine bars are used when high degree of accuracy It may be noted that for setting the sine bar to different
is needed during angles, slip gauges are used.
– the checking of parallelism (Fig 2) A surface plate or marking table provides the datum
– the marking out (Fig 3) surface for the set up.

– the setting up of components for machining angular The sine bar, the slip gauges and the datum surface
surfaces. (Fig 4) upon which they are set form the sides of a right
angle triangle. (Fig 6)
The principle of a sine bar The sine bar forms the hypotenuse (c) and the slip
The principle of a sine bar is based on the trigonometrical gauge stack forms the side opposite to the angle θ (a).
function of sine of an angle.

17

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 Opposite side
Sine of the angle θ =
Hypotenuse

a
Sine θ =
c

Determining taper angle using sine bar and slip gauges

Objectives: At the end of this lesson you shall be able to
• check the correctness of the known angle of the work
• calculate the height of slip gauges to build up the height for a given angle.

A sine bar provides a simple means of checking angles

to a high degree of accuracy.
The use of a sine bar is based on the trigonometrical
function. The sine bar forms the hypotenuse of that
triangle and the slip gauge height forms the opposite side
of the angle. (Fig1)

A dial test indicator is mounted on a suitable stand

or vernier height gauge. (Fig 2) The dial test indicator is
then set in first position as shown in the figure, and the
dial is set to zero. Move the dial indicator to the other
end of the component (second position). If there is any
Checking the correctness of a known angle difference then the angle is incorrect. The height of the
For this purpose first choose the correct slip gauge slip gauge pack can be adjusted until the dial test
combination for the angle to be checked. indicator reads the same reading at both ends. The
actual angle can then be calculated and the deviation,
The component to be checked should be mounted on if any, will be the error.
the sine bar after placing the selected slip gauges under
one roller, with the other roller resting on the datum Method of calculating the slip gauge height
surface. (Fig 2)

18 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.1.52

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Example a 84.52
Sineθ = =
To determine the height of slip gauges for an angle of c 200
25° using a sine bar of 200 mm long. (Fig 3)
Sin θ = 0.4226
The value of sine of the angle is 0.4226.
\ the angle = 25°.
Examples
1 What will be the angle of the workpiece if the slip
gauge pack height is 17.36 mm and the size of the
sine bar used is 100 mm? (Fig 5)

a
Sine θ =
c
θ = 25°
a = C sine q
= 200 x 0.4226
= 84.52 mm.
a 17.36
The height of the slip gauge required is 84.52 mm. Sineθ = =
c 100
Note
= 0.1736
The value of Sine θ can be seen from mathematical
tables. (Natural Sine) Θ = 10°

Use always accurate tables while working with sine bars. 2 Calculate the height of the slip gauge pack required
to raise a 100 mm sine bar to an angle of 3°35'.
Tables are also available with ready worked out sine bar
constants for standard lengths of sine bars. a
Sineθ =
Calculating the angle of tapered components c

The height of the slip gauge used is 84.52 mm. The a

Sine 3º.35' =
length of the sine bar used is 200 mm. 100mm
What will be the angle of the component? (Fig 4) A = 100 MM X SIN 3°.35'
= 100 X 0.0624 MM
Height of the slip gauge = 6.24 mm

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Exercise 2.1.52 19

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Production & Manufacturing
Turner - Taper turning Related Theory for Exercise 2.1.53

Slip Gauges, types uses and selection

Objectives : At the end of this lesson you shall be able to
• state the features of slip gauges
• state the different grades of slip gauges and their uses
• state the number of slips in standard sets
• state the care and maintenance to be followed in the case of slip gauges.

Slip gauges or gauge blocks are used as standards for

precision length measurement. (Fig 1) These gauges
are made in sets and consist of a number of hardened
blocks made of high grade steel with low thermal
expansion. They are hardened throughout, and further
heat treated for stabilization. The two opposite measuring
faces of each block are lapped flat and parallel to a
definite size within extremely close tolerances.

Wringing is the act of joining the slip gauges together

while building up to sizes.
Some sets of slip gauges also contain protector slips of
some standard thickness made from higher wear-
resistant steel or tungsten carbide. These are used for
protecting the exposed faces of the slip gauge pack
from damage. (Fig 5)
These slip gauges are available in various sets with
different numbers. (Fig2) (Ref.Table 1)

B.I.S. recommendations
A particular size can be built up by wringing individual
Four grades of slip gauges are recommended by B.I.S.
slip gauges together. (Figs 3 & 4)
(IS 2984). They are:
Grade 00 Reference
Grade 0 Calibration
Grade i Inspection
Grade ii Workshop
GRADES
Grade oo accuracy
It is a reference grade for reference standard and to
calibrate the calibration grade slip gauges.
20

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Grade o accuracy Use as minimum a number of blocks as possible while
building up for a particular dimension.
It is a calibration grade used to calibrate the inspection
grade slip gauges. While building the slip gauges, start wringing with the
largest slip gauges and finish with the smallest.
Grade i accuracy
While holding the slip gauges do not touch the
It is an inspection grade used to calibrate workshop
lapped surfaces.
grade slip gauges and measuring instruments.
If available use protector slips on exposed faces.
Grade ii accuracy
After use clean the slips with carbon tetrachloride and
It is a workshop grade used for general workshop
apply petroleum jelly for protecting against rust.
applications.
Before use remove the petroleum jelly with carbon
Care and Maintenance tetrachloride. Use chamois leather to wipe the surfaces.
Points to be remembered while using slip gauges

TABLE 1
Different sets of slip gauges.

Set of 112 pieces Set of 78 pieces

Range (mm) Steps No.of Range (mm) Steps No.of

(mm) pieces (mm) pieces
Special
1.0025 - 1
piece - 1
1.005 - 1
1.0005
1.0075 - 1
1st series
1.01 to
1.001 to 0.001 9
1.49 0.01 49
1.009
0.5 to
2nd series
9.5 0.5 19
1.01 to 0.01 49
10.0 to
1.49
50.0 10.0 5
3rd series
75.0 &
0.5 to 0.5 49
100.0 - 2
24.5
4th series
Total pieces 78
25.0 to 25 4
100.0
Set of 47 pieces
Total pieces 112
Range (mm) Steps No.of
(mm) pieces
Set of 103 pieces
1st series
Range (mm) Steps No.of
1.005 - 1
(mm) pieces
2nd series
1.01 to
1st series
1.09 0.01 9
1.005 - 1
3rd series
2nd series 1.1 to 1.9 0.1 9
1.01 to 0.01 49
4th series
1.49
3rd series 1.0 to 24.0 1.0 24
0.5 to 24.5 0.5 49 5th series
4th series 25.0 to
25 to 100 25.0 4 100.0 25.0 4

Total pieces 103

Total pieces 47

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Exercise 2.1.53 21

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Set of 87 pieces Set of 32 pieces

Range (mm) Steps No.of Range (mm) Steps No.of

(mm) pieces (mm) pieces

1st series 1.005 - 1

1.001 to 1st series
1.009 0.001 9 1.01 to 1.09 0.01 9
2nd series 2nd series
1.01 to 1.1 to 1.9 0.1 9
1.49 0.01 49 3rd series
3rd series 1 to 9.0 1.0 9
0.5 to 9.5 0.5 19 4th series
4th series 10.0 to 30.0 10.0 3
10.0 to 60.0 1
100.0 10.0 10
Total pieces 32
Total pieces 87

Set of 86 pieces
Set of 45 pieces
Range (mm) Steps No.of
Range (mm) Steps No.of
(mm) pieces
(mm) pieces
1st series
1st series
1.001 to 1.009 0.001 9
1.001 to
2nd series
1.009 0.001 9
1.01 to 1.49 0.01 49
2nd series
3rd series
1.01 to
0.5 to 9.5 0.5 19
1.09 0.01 9
4th series
3rd series
10.0 to 90.0 10.0 9
1.1 to
1.09 0.1 9
Total pieces 86
4th series
1.0 to
9.0 1.0 9
5th series Even though there are a number of sets of slip gauges
10.0 to 90.0 10.0 9 available, the popularly recommended ones are:
1) Set No.45 (Normal set)
Total pieces 45
2) Set No.86 (Special set).

Selection and determination of slip gauges for different sizes

Objective :At the end of this lesson you shall be able to
• select slip gauges for different sizes.

For determining a particular size, in most cases a - then consider the last digit or the last two digits of
number of slip gauges are to be selected and staked the subsequent value and continue to select pieces
one over the other by wringing the slip gauges. until the required size is available.
While selecting the slip gauges for a particular size Example
using available set of slip gauges:
Building up a size of 44.8725 mm with the help of 112
- first consider the last digit of the size to be built up piece set. (Table 1)

22 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.1.53

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Set of 112 pieces
1.01 to 1.49 0.01 49
Range (mm) Steps No.of 0.5 to 24.5 0.5 49
(mm) pieces 25.0 to 100.0 25.0 4

1.0005 - 1 Total pieces 112

1.001 to 1.009 0.001 9

TABLE 1

Procedure Slip pack Calculation

a) First write the required

dimension. 44.8725

b) Select the slip gauge having 4th

decimal place. 1.0005 Subtract 1.0005

43.8720

c) Select a slip gauge from the 1st series

that has the same last figure. 1.002 Subtract 1.002

42.87

d) Select a slip gauge from the 2nd series

that has the same last figure and 1.37 Subtract 1.37
that .0 will leave or 0.5 as last fig.
41.5

e) Select a slip gauge from the 3rd series

that will leave the nearest 16.5 Subtract 16.5
4th series slip (41.5 25 = 16.5).
25.00

f) Select a slip gauge that eliminates 25.0 Subtract 25.00

the final figure.
44.8725 0.00

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Production & Manufacturing
Turner - Taper turning Related theory for Exercise 2.1.54
Methods of Brazing carbide tipped and tool
• state the brazing materials used for brazing carbide tips on a carbon steel shank
• state the methods of brazing carbide tips
• explain the torch brazing method.

The most common brazing alloys used for sinteredcarbides of brazing, generally to get carburising flame by permitting
are silver alloys and copper alloys. Silver alloys always more acetylene. Heating to the brazing temperature should
contain silver, copper, zinc and various quantities of be done relatively quickly as prolonged heating can lead
nickel, to oxidation.
cadmium and manganese. The melting point lies between
620°C to 850°C. (Most common alloys melt at 690°C)
Silver alloys can be used for tools not subjected to
extreme working conditions or stresses. For silver brazing,
special, easily fusible brazing fluxes are used.
The preparation for brazing the carbide tip on carbon
steel

When big steel shanks are used, it is better to use more

than one torch. Always keep the shank on a fire-brick to
avoid loss of heat due to conduction. Start heating with
the flame directed against the underside of the tool and
behind the seating of the tip, and around the shank until
this is evenly heated. Finally the flame is put on to the
carbide tip so that the solder melts and flows out. When
this occurs, you can easily observe that the tip is
‘swimming’ on the solder. When the brazing material has
run out completely, the heat is removed and the tip moved
to and fro and pressure applied in the middle of the tip by
shank is illustrated Fig 1. Fig 2 shows the shapes of
means of a pointed rod.
carbide tips.
There are three methods of brazing a carbide tip with Safety to be observed for cooling after brazing
a shank.
When the brazing alloy has solidified, the tool must be
• Furnace brazing (Fig 3) slowly cooled in a heat isolating medium. This will allow
• Induction brazing (Fig 4) the joint to adapt itself to the different contractions of
• Torch brazing sintered carbide and steel. Furthermore, it will prevent the
steel from air hardening which may happen due to rapid
Torch brazing
cooling. Rapid cooling is detrimental to both the joint and
The most commonly used method of brazing a carbide tip the carbide. Suitable isolating mediums are mica powder
on a shank is torch brazing, since this method can be or charcoal dust. Even dry sand can be used though it is
worked on a small scale. A welding torch is used for a poor substitute. Sand absorbs humidity of the air and
brazing. A flame adjustment must be made for the purpose can subject the carbide to cooling shocks.
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Production & Manufacturing
Turner - Taper turning Related Theory for Exercise 2.1.55

Basic process of soldering, welding and brazing

Objectives : At the end of this lesson you shall be able to
• state the process of soldering
• state the method of application of soldering iron
• state the different types of solder and their application.

There are different methods of joining metallic sheets.

Soldering is one of them.
Soldering is the process by which metallic materials are
joined with the help of another liquified metal (solder).
The melting point of the solder is lower than that of the
materials being joined.
The solder wets the base material without melting it.

Soldering iron (Fig 1)

Solders
Pure metals or alloys are used for solders.
Solders are applied in the form of wires, sticks, ingots,
rods, threads, tapes, formed sections, powder and pastes.
The soldering iron is used to melt the solder and heat the
(Fig 4)
metal that are to be joinded togerther.
The soldering iron has the following parts,
• Head (copper bit)
• Shank
• Wooden handle
• Edge

Shape of head
The head of the iron is made of forged copper. This is
because copper has a good heat conductivity and has a
Types of solders
strong affinity for the solder so that the solder melts easily
and sticks to the bit. There are two types of solders.
A Hatchet type soldering as in (Fig 1) has shank fitted at - Soft solder
60° to the head. The soldering edge is ‘V’ shaped.
- Hard solder
This type is used for straight soldering joints. (Fig 2)
One distinguishes between soft solders whose melting
The other type is the square pointed soldering iron or a points are below 450° C and hard solders whose melting
slandard workshop pattern soldering iron. (Fig 3) For this points lie above 450° C.
type the edge is shapped to an angle on four sides to form
a pyramid shapr. Soft solders
This is used for taking and soldering of joining points. These are alloys of the metals- tin, lead, antinomy,
(Fig 4) copper, cadmium and zinc and are used for soldering
heavy (thick) and light metals.
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Hard solders phosphorus, and are used for soldering heavy metals.
These are alloys of copper, tin, silver, zinc, cadmium and

Flux
Objectives: At the end of this lesson you shall be able to
• state the criteria for the selection of fluxes
• distinguish between corrosive and non-corrosive fluxes
• name the different types of flux and their application.

Fluxes are non-metalic materials which are used at the water, 2 or 3 times the quantity of the acid, it is used as
time of soldering. dilute hydrochloric acid.
Hydrochloric acid combines with zinc forming zinc chloride
Functions of flux
and acts as a flux. So it cannot be used as a flux for sheet
- Flux removes oxides from the soldering surface. metals other than zinc, iron or galvanised sheets.
- It prevents corrosion.
Zinc chloride
- It helps molten solder to flow easily in the required
It is mainly used for soldering copper sheets, brass sheets
place.
and tin plates.
- It promotes the wet surface.
As it is extremely corrosive, the flux must be perfectly
- It localize the heat in molten fool washed off after soldering.

Selection of flux Ammonium chloride

The following criteria are important for selecting a flux. This is in the form of powder or lump. It evaporates when
- Working temperature of the solder heated.

- Soldering process Ammonium chloride, dissolved in water, is used as a flux

for soldering steel.
- Materials to be joined.
A solution of a mixture of hydrogen chloride, zinc chloride
Classes of flux and ammonium chloride is used as a flux for stainless
steel sheets.
Flux can be classified into corrosive flux, and non-corrosive
flux. Resin
Corrosive flux in acid form and should be washed As resin is not very effective for removing oxidation coating,
immediately after the soldering operation is completed. and, as it is not highly corrosive, it is used as flux for copper
Non-corrosive flux is in the form of lump, powder, paste or and brass. Resin melts at about 80° to 100°C.
liquid.
Paste
Different types of fluxes
This is a mixture of zinc chloride, resin, glycerine and
Hydrochloric acid others and is available as a paste.

Concentrated hydrochloric acid is a liquid which fumes

when it comes into contact with air. After mixing with

Basic process of Welding

Objectives: At the end of this lesson you shall be able to
• define welding process
• state clasification of welding
• state method of welding.

Welding: Welding Porcess:

Welding is a process of joining similar metals by According to the sources of heat, welding process can
application of heat with or without application of pressure be broadly classified as:
and addition of filler materials.
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- electric welding proces (heat source is electricity) Electric resistance welding can be further classi-
fied as:
- gas welding processes (heat source is gas flame)
- spot welding
- other welding processes (heat source is neither
electricity nor gas). - seam welding
- butt welding
Electic welding processes can be classified as:
- flash butt welding
- electric arc welding
- projection welding.
- electric resistance welding
- laser welding Gas welding process can be classified as:
- electron beam welding - oxy-acetylene gas welding
- oxy-hydrogen gas welding
Electric arc welding can be further classified as:
- oxy-coal gas welding
- metallic arc welding
- oxy-liquified petroleum gas welding
- carbon arc welding
- air acetylene gas welding.
- atomic hydrogen arc welding
- inert gas arc welding The other welding processes are:
- CO2 gas arc welding - thermit welding
- submerged arc welding - forge welding
- electro-slag welding - friction welding
- plasma arc welding. - ultrasonic welding
- explosive welding
- cold pressure welding
- plastic welding.

Chart showing welding methods.

WELDING METHODS

Pressure welding Fusion welding

Forge Resistance Thermit Arc Gas Thermit

(Fusion welding)

Butt Metal Carbon Inert gas Atomic

Plain Flash Oxy-acetylene Oxygen-other fuel gases

Welding rods the edges and carefully cleaning the faces to be welded
from dust, sand, grit, oil and grease.
Welding rods also known as filler rods provides extra metal
to the weld. The extra metal is obtained by melting the Different edge preparation which are used for butt welding
end of a rod or piece of wire known as either a filler rod or are shown at fig 1, namely single V, single J single V
welding rod. In many instances the composition of the rod etc.,
is the same as that of the material being welded.
Welded joints
Edge preparation
Weld joint is classified based on the relative position of
To obtain sound welds, good edge preparation is beveling the two metal pieces being joined, determines the type

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of joint. There are five basic type of joints that are used in 4. Corner joint
welding namely butt, lap, corner, edge & T-joints. (Fig 2)
5. Edge joint
1. Butt joint
Gas Welding
2. Lap joint
It is by melting the edges or surfaces to be joined by gas
3. T-joint
flame and allowing the molten metal to flow together, thus
forming a solid continuous joint after cooling. This process
suitable for joining metal thickness of 2mm to 25 mm in
one pass.

Systems of oxy-acetylene
Objectives : At the end of this lesson you shall be able to
• distinguish between high pressure and low pressure acetylene plants
• distinguish the features of low pressure and high pressure blowpipes.

Oxy-acetylene plants can be either high pressure or low

pressure.
A high pressure plant utilizes acetylene under high
pressure, upto 1 kg/cm2. (Fig 1)
Dissolved acetylene (acetylene in cylinder) is a commonly
used source.
A low pressure plant utilizes acetylene under low pressure
(0.017 kg/cm2) produced by an acetylene generator only.
(Fig 2)

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Gases used in gas welding
Objectives: At the end of this lesson you shall be able to
• name the different types of gases used in gas welding
• state the different types of gas flame combinations
• state the temperatures and uses of the different gas flame combinations.

In the different gas welding processes, the welding heat is Different gas flame combinations
obtained from the combustion of the fuel gases.
Oxygen + Acetylene = Oxy-acetylene gas flame
All the fuel gases require oxygen to support combustion.
Oxygen + Hydrogen = Oxy-hydrogen gas flame
As a result of the combustion of the fuel gases and
Oxygen + Coal = Oxy-coal gas flame
oxygen, a flame is obtained. This is used to heat the
metals for welding. (Fig 1) Oxygen + LPG = Oxy-LP gas flame

Temperature and uses of gas flame combinations

Oxy-acetylene gas flame (Fig 2)

Fuel gases used in welding

The following are the gases used as fuel for welding.
- Acetylene gas Flame temperature : 3100° C to 3300° C
- Hydrogen gas The oxy-acetylene gas flame is used for welding all ferrous
- Coal gas and non-ferrous metals and their alloys, gas cutting,
gouging, steel brazing, bronze welding, metal spraying
- Liquid petroleum gas (LPG)
and powder spraying, operations.w
Supporter of combustion gas
Oxy-hydrogen gas flame (Fig 3)
All gases burn with the help of oxygen. Hence it is known
Flame temperature : 2400°C to 2700°C
as the supporter of combustion.

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This type of flame is used only for brazing, silver soldering Flame temperature : 2700°C to 2800°C
and underwater gas cutting of steel.
This flame has carbon and moisture effect.
It is only used for gas cutting of steel, and for heating
purposes.
Oxy-coal gas flame (Fig 5)

Oxy-liquid petroleum gas flame (Fig 4)

Flame temperature : 1800°C to 2200°C

This flame has carbon effect in the flame and is highly
suitable used for silver soldering and brazing.

The most commonly used gas flame

combination is OXY-ACETYLENE.

Types of oxy-acetylene flames

Objectives : At the end of this lesson you shall be able to
• name the different types of oxy-acetylene flames
• state the characteristics of each type of oxy-acetylene flame
• explain the uses of each type of oxy-acetylene flame.

The essential requirement for oxy-acetylene welding is a Neutral flame (Fig 1)

well controlled flame with sufficient heat, which can be
easily manipulated to heat and melt metals without
altering the chemical composition of the metal/weld.
Flame types
The different flame types are
• Neutral flame
• Oxidising flame
• Carburising flame.

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Characteristics Uses
The neutral flame is formed with oxygen and acetylene The oxidising flame is useful only for the welding of brass
in equal proportion. and to control the burning of zinc.
Complete combustion takes place in this flame.
Carburising flame (Fig 3)
This flame does not have bad effect on metals/weld.

Uses
A neutral flame is used to weld most of the common
metals, i.e. mild steel, cast iron, stainless steel, copper
and aluminium.

Oxidising flame (Fig 2)

This flame is formed with excessive acetylene .

The flame has a carburising effect on steel, causing hard,
and brittle weld.

Uses
Useful for stelliting (hard facing), LINDE welding of steel
pipes and flame cleaning.
Characteristics
The selection of the flame is based on the
The oxidising flame is formed with excessive oxygen. metal to be welded.
The flame has oxidising effect on metals. Neutral flame is the most commonly used.

Method of cleaning before welding

Objectives: At the end of this lesson you shall be able to
• state the importance of cleaning before welding
• name the different methods of cleaning.

Importance of cleaning
The basic requirement of any welding process is to clean
the joining edges before welding in order to obtain a sound
weld.
The joining edges or surface may have oil, paint, grease,
rust, moisture, scale or other foreign matter. If these
contaminants are not removed, the weld will become
porous, brittle and weak.
The success of welding depends largely on the condition
of the surfaces to be joined.

Methods of cleaning

Chemical cleaning
This includes washing the joining surface with solvents
such as kerosene, paraffin, thinners, turpentine or petrol Mechanical cleaning
for removing oil, grease etc. (Fig 1 & 2) Mechanical cleaning include wire brushing, grinding,
chipping, sand blasting, scraping, metal gritting, machining
or cleaning with emery paper. (Fig 3)

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Welding Nozzles - sizes and selection
Objectives : At the end of this lesson you shall be able to
• identify the different sizes of nozzles
• select the correct nozzle for the job
• select the correct gas pressure for the nozzles.

The welding nozzle is a part of the welding blowpipe (made Selection of gas pressure for nozzles
of copper with a small orifice) fitted at the end where the
flame is ignited. (Fig 1) Smaller size nozzles require less pressure whereas the
larger size nozzles require more pressure (Table 1)

Selection of Nozzle

Table 1

Plate Nozzle Oxygen

thick- size Acetylene
ness pressure
Nozzle sizes (mm) (kg/cm)
The size of the nozzle is determined by the diameter of its
orifice. 0.8 1
1.2 2
Smaller orifice nozzles make a smaller flame useful for
1.6 3 0.15
welding thin metals, whereas larger hole nozzles make a
2.4 5
larger flame useful for welding thick metals, where more
3.2 7
heat is required.
4.0 10
The common nozzle sizes are 5.0 13 0.20
6.5 18
1,2,3,4,5,7,10,13,18,25,35,45, 55,70 and 90.
8.2 25
The selection of a nozzle is determined by the 10.0 35
13.0 45
- Thickness of the metal to be welded
19.0 55
- Mass of the metal to be welded 25.0 70 0.40
Over 25.0 90 0.45
- Kind of the metal to be welded.
- The gas pressure required for the flame. You may
observe from the table that the nozzle size number
increases with increased thickness of jobs to be
welded.

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Safety precautions in handling gas welding plant
Objectives : At the end of this lesson you shall be able to
• state the general safety precautions in oxy-acetylene plants.
• state the safety rules for handling gas cylindedrs
• state the safety practices for handling gas regulators and hose-pipes.
• state the safety precautions related to blowpipe operations.

To be accident-free, one must know the safety rules first Always keep fire-fighting equipment handy and in working
and then practice them strictly as we all know that condition to put out fires. (Fig 3)
‘’Accident starts when Safety ends’'. Keep the work area free from any form of fire.
Ignorance of rules is no excuse!
In gas welding, the welder must follow the safety precau-
tions in handling gas welding plants and flame-setting to
keep himself and others safe.
Safety precautions are always based on good common
sense.
The following precautions are to be observed, to keep a
gas welder accident-free.

General safety
Do not use lubricants (oil or grease) in any part or
assembly of a gas welding plant. It may cause explosion.
Keep all flammable material away from the welding area.
Always wear goggles with filter lens during gas welding.
(Fig.1)

Safety gas cylinders

Do not roll gas cylinders or use them as rollers.
Use a trolley to the carry the cylinders.
Close the cylinder valves when not in use or empty.
Keep full cylinders seperate and empty cylinders separate.
Always open the cylinder valves slowly, not more than one
and a half turn.
Use the correct cylinder keys to open the cylinders.
Do not remove the cylinder keys from the cylinders while
Always wear fire resistant clothes, asbestos gloves and welding. It will help to close the cylinders QUICKLY in the
apron. case of a back-fire or flash-back.
Always use the cylinders in an upright position for easy
Never wear nylon, greasy and torn clothes
handling and safety.
while welding.
Always crack the cylinder valves to clean the valve
Whenever a leakage is noticed rectify it immediately to sockets before attaching regulators. (Fig 4)
avoid fire hazards. (Fig 2)
Even a small leakage can cause serious accidents.

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 Always use black hose pipes for oxygen and
maroon for acetylene.

Safety for regulators

Prevent hammer blows to the gas cylinders and ensure
that water, dust and oil do not settle on the cylinders.
Note right hand threaded connection for oxygen and left
hand threaded connection for acetylene.

Safety for blowpipes

When a blowpipe is not in use put out the flame and place
the blowpipe in a safe place.
When flame snaps out and backfires, quickly shut both
the blowpipe valves (oxygen first) and dip in water.
While igniting the flame, point the blowpipe nozzle in a
Safety for rubber hose pipes (Fig 5) safe direction. (Fig 6)

Inspect the rubber hose pipes periodically and replace the

damaged ones.
Do not use odd bits of hose pipes / tubes.
Do not replace the hose pipes for acetylene with the ones
used for oxygen.
While extinguishing the flame, shut off the acetylene valve
first and then the oxygen valve to avoid a backfire.

Safety precautions during arc welding

Objective: At the end of this lesson you shall be able to
• state the precautions necessary in arc-welding.

Safety precautions - Do not carry matches or petrol lighters in your pocket

during arc-welding.
• Never stand on a damp or wet place while arc-welding.
- Protect the outsiders from radiation and reflection of
• Always wear all the safety apparels (gloves, apron,
rays, by using portable screens or welding booths.
sleeves, shoes). (Fig 1)
(Fig 2)
- Use welding and a chipping screen during welding and
- Keep the welding area free from moisture and flam-
chipping respectively, for the protection of the eyes and
mable material.
the face.
- Do not try to rectify electrical faults yourself; call an
- Switch off the machine when not in use.
electrician.
- Keep the clothes free from oil and grease.
- Do not throw the electrode stubs on the floor. Put them
- Use tongs while handling hot metals. in a container. (Fig 3)
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 - Use exhaust fans to remove the arc-welding smokeand
fumes. (Fig 4)

Keep the welding area always clean removing unused

metal, scrap etc, to avoid getting hurt.

Arc-welding tools and accessories

Objectives : At the end of this lesson you shall be able to
• identify the different arc-welding tools and accessories
• explain the uses of each.

Chipping hammer (Fig 1) One of its edges is pointed and the other is like that of a
chisel. Pointed edge is used to remove dirt, slag in blow
holes & chisel edge for removing slag.

Wire brush (Fig 2)

It is used to remove the slag from the weldment and is

It is used for cleaning the surface metal as well as the slag
made of medium carbon steel, duly hardened.
from the welds.

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The wire brush is made of stiff steel wires fitted on a They are also used to hold the metal for hammering.
wooden piece in three to five rows.

Welding hand screen (Fig 3)

Electrode holder with cable (Fig 7)

A welding hand screen is used as a shield and to protect

the face and the eyes from the arc radiation.
It is fitted with a filter lens, and plain glass to protect the
lens, from welding chaffers, plain glass is replaced from
time to time.
Welding helmet screen (Fig 4)

An electrode holder is used to hold and manipulate the

electrode.
The cable is insulated with a good quality flexible rubber,
and copper core wires, to carry the high current from the
welding machines.

Earth clamp with cable (Fig 8)

It can be used as a hand screen, also worn on the head of

the welder to enable him to use both his hands .

Chipping goggles (Fig 5)

An earth clamp is used to connect the return lead firmly to

the job or to the welding table, to complete the circuit

Welding table
Chipping goggles are used to protect the eyes while
The welding table is used to keep the jobs and to assemble
chipping the slag.
the pieces during welding. The top of the table is made of
They are fitted with a plain glass to see the area to be metal.
cleaned.
Apron (Fig 9)
Tong (Fig 6)
An apron is used to protect the body.
Tongs are used to handle the hot metal-welding job while
It should be made of leather.
cleaning.
It must be worn for protection from the radiation of the heat
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rays and hot spatters. Hand gloves (Fig 10)
Hand gloves are used to protect the hands from electrical
shock, arc radiation, heat, and hot spatters.
The gloves are also made of leather.

Braze welding
Objective: At the end of this lesson you shall be able to
• distinguish between fusion welding and braze welding.

Fusion welding (Fig 1) Braze welding (Fig 2)

A metal joining process wherein a permanent joint is made Braze welding is a welding process in which a filler metal,
by melting and fusing the joining edges by a welding having a melting point above 840°F (450° C) and below that
process is known as fusion welding. of the base metal, is used. Unlike brazing, in braze
welding, the filler metal is not distributed in the joint by
capillary action.

Differences between fusion and braze welding

Fusion welding Braze welding

Fusion welding makes a permenant joint. Makes a temporary joint.

Requires more heat as the base metal and the filler Requires less heat as a filler metal with a lower
metal are completely fused to effect the joining. melting point is fused into the pre-heated joint.

The welding joint is provided without any colour A distinct colour change is seen.
change.

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 Fusion welding Braze welding

There are more chances of distortion. Less distortion during welding.

Can be done with/without a flux. Cannot be done without a proper flux.

May require dismantling of the parts. Can be done without dismantling the parts.

Cost is higher than that of a braze welding. Can be done with a lesser skill.

Methods of brazing carbide tips

Objectives: At the end of this lesson you shall be able to
• state the brazing materials used for brazing carbide tips on a carbon steel shank
• state the methods of brazing carbide tips
• explain the torch used in brazing method.

The most common brazing alloys used for sintered carbides The preparation for brazing the carbide tip on carbon
are silver alloys and copper alloys. Silver alloys always steel shank is illustrated in Fig 1. Fig 2 shows the shapes
contain silver, copper, zinc and various quantities of of carbide tips.
nickel, cadmium and manganese. The melting point lies
There are three methods of brazing a carbide tip with
between 620°C to 850°C. (Most common alloys melt at
a shank.
690°C) Silver alloys can be used for tools not subjected
to extreme working conditions or stresses. For silver
brazing, special, easily fusible brazing fluxes are used.

Filler rods and fluxes for braze welding

Objectives : At the end of this lesson you shall be able to
• state the different types of filler rods required for braze welding
• state the functions and types of fluxes required for braze welding.

Filler rods for braze welding Manganese bronze (high tensile brass) - Type S-C8
There are many types of braze-welding rods. For use in the braze welding of copper, cast iron and
malleable iron, and for the fusion welding of materials of the
The most common rod used for ferrous metals is a copper-
same or a closely similar composition (oxidising flame).
zinc alloy with the addition of a small percentage of
silicon, manganese, nickel and tin. (Fig 1)
Medium nickel bronze - Type S-C9
For use in the braze welding of mild steel, cast iron and
malleable iron. (oxidising flame)

Fluxes for braze welding

The purpose of the flux is to
- Chemically clean the joint.
- Remove impurities from the weld
- Allow the molten filler metal to flow and spread more
easily into the joint surface.
Types & application (Conforming to IS: 1278-1972) For braze welding using the above filler rods, an oxydising
Brass filler rods - Type S-C6 flame is used.

For use in the braze welding of copper and mild steel and For brazing with brass and bronze filler rods different fluxes
for the fusion welding of materials of the same or a closely are commercially available under different brand names.
similar composition (oxidising flame). Borax may also be used as a flux.

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Melting points of common metals
Objective: At the end of this lesson you shall be able to
• determine the melting points of the common metals used in welding.

Melting point Melting points of some common metals are given in

Table 1.
The temperature at which a solid metal changes to a liquid
is known as its melting point.
Metal Melting Point
Melting points of some common metals are given in (°C)
Table 1.
Copper 1083
Table 1
Cast iron 1150
MELTING POINTS OF COMMON METALS Monel metal 1342
High carbon steel 1371
Metal Melting Point Medium carbon steel 1426
(°C) Stainless steel 1426
Tin 232 Nickel 1449
Lead 327 Low carbon steel 1510
Zinc 419 Wrought iron 1593
Aluminium 659 Tungsten 3410
Bronze 882-915
Brass 850-982
Silver 960

Methods of cleaning (For Brazing)

Objectives : At the end of this lesson you shall be able to
• state the mechanical cleaning methods
• state the chemical cleaning methods.

Necessity for cleaning of 0.2 kg. sodium orthosilicate, 0.2 kg. sodium resinate
and 3.8 litres of water at 51.7° to 82.2°c.
Plates or sheets are often coated with rust, paint, oil,
grease, scale etc. During brazing, they are trapped in the Dipping the plates in the solution or applying the solution
joint and cause defective brazed joints. at the joint will produce a clean surface required for
brazing.
Mechanical cleaning
The joining edges/surfaces may be cleaned by
- Wire brushing (Fig 1)
- Sand blasting
- Filing
- Machining
- Grinding (Fig 2)
- Cleaning with steel wool.

Chemical cleaning
The joining edges/surfaces can also be cleaned chemically
to remove oil, grease, dirt, rust etc.
Ferrous metal surfaces are washed with solvents such as
kerosene, diesel and petrol. (Fig 3)
For cleaning copper and its alloys, use a solution consisting
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Production & Manufacturing
Turner - Eccentric turning Related theory for Exercise 2.2.56
Vernier height gauge, Function and description
Objectives: At the end of this lesson you shall be able to
• name the parts of a vernier height gauge
• state the constructional features of a vernier height gauge
• state the functional features of a vernier height gauge
• list the various applications of the vernier height gauge in engineering.

Parts of a vernier height gauge (Fig 1) which various attachments may be clamped. The jaw is
an intergral part of the main slide.
A Beam
The vernier scale is attached to the main slide which has
B Base
been graduated, to read metric dimensions as well as
C Main slide the inch dimensions. The main slide is attached with the
D Jaw fine adjusting slide. The movable jaw is most widely used
with the chisel pointed scriber blade for accurate marking
E Jaw clamp out as well as for checking the height, steps etc. Care
F Vernier scale should be taken to allow for the thickness of the jaw
depending on whether the attachment is clamped on the
G Main scale top or under the jaw for this purpose. The thickness of the
H Fine adjusting slide jaw is marked on the instrument. As like in a vernier caliper,
the least count of this instrument is also 0.02 mm. An
I Fine adjusting nut offset scriber is also used on the movable jaw when it is
J&K Locking screws required to take measurement from the lower planes. (Fig
2) The complete sliding attachment along with the jaw
can be arrested on the beam to the desired height with
the help of the lock screws. The vernier height gauges
are available, in ranges of capacities reading from zero to
1000 mm.

Functional features of the vernier height gauge

Vernier height gauges are used in conjunction with the

surface plate. In order to move the main slide, both the
locking screws of the slide and the fine adjusting slide
have to be loosened. The main slide along with the chisel
pointed scriber has to be set by hand, for an approximate
height as required.
The fine adjusting slide has to be locked in position, for
Constructional features of a vernier height gauge an approximate height as required. To get an exact mark
The construction of a vernier height gauge is similar to able height, the fine adjustments have to be carried on
that of the vernier caliper except that it is vertical with a the slider with the help of the adjusting nut. After obtaining
rigid base. It is graduated on the same vernier principle the exact markable dimension, the main slide is also to
which is applied to the vernier caliper. be locked in position.
It consists of an upright steel beam fastened to a steel Modern vernier height gauges are designed on the screw
base. The beam is graduated with the main scale in mm rod principle. In these height gauges, the screw rod may
as well as in inches. The main slide carries a jaw upon be operated with the help of the thumb screw at the base.

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In order to have a quick setting of the main slide, it is Application of vernier gauge in Engg
designed with a quick releasing manual mechanism. With
The vernier height gauge is mainly used for layout work,(Fig
the help of this, it is possible to bring the slide to a desired
4)
approximate height without wastage of time. For all other
purposes, these height gauges work as ordinary height
gauges. In order to set the ‘zero’ graduation of the main
scale for the initial reading. Some vernier height gauges
are equipped with a sliding main scale which may be set
immediately for the initial reading. This minimises the
possible errors in reading the various sizes in the same
setting.
Another kind of modern vernier height gauge has a rack
and pinion set up for operating the sliding unit. This is
shown in Fig 3.

It is used for measuring the width of the slot and external

dimension.
The vernier height gauge is used with the dial indicator to
check hole location, pitch dimensions, concentricity and
eccentricity.
It is also used for measuring depth, with a depth
attachment.
It is used to measure sizes from the lower plane with the
help of an offset scriber.

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Production & Manufacturing
Turner - Eccentric turning Related Theory for Exercise 2.2.57

Templates its function and construction

Objectives: At the end of this lesson you shall be able to
• state the uses of templates
• define template.

Templates: Templates are used in the sheet metal and Fig 11 shows a simple sheet metal template may be used
plate fabrication industries. For example to check the form turning job
1 To avoid repetitive measuring and marking the same
dimension, where many identical parts are required.
2 To avoid unnecessary wastage of material and from
information given on drawing, it is almost impossible to
anticipate exactly where to begin in order that the
complete layout can be economically accommodated.
3 To act as a guide for cutting processes.
4 As a simple means of checking bend angles and
contours.
Information given on templates
Written on templates may be as follows:
1 Job or contract number
2 Size and thickness of plate
3 Quantity required
4 Bending or folding instructions
5 Drilling requirement
6 Cutting instructions
7 Assembly reference mark.
Templates as a means of checking is shown in Fig
4,5,6,7,8,9.

Templates for setting out sheet metal fabrications:

For economy reasons, many patterns are made for marking
out the sheet metal prior to cutting and forming operations.
Fig 9,10,11 show a smoke cowl. Here a template is
required to check and to mark out the contours of the
intersection joint lines for the parts A,B & C whose
developed sizes are marked out in the flat with the
appripriate datum lines.
Fig 9 shows a square to round transformer is an isometric
view of the sheet metal trans forming piece which is used
to connect a circular duct to a square duct of equal area
of cross section. In this example the dia of the round duct
is 860 mm and length of one side of the square duct is 762
mm and the distance between the two ducts is 458 mm
and sheet thickness is 1.2 mm.
Fig 10 shows a scale development pattern on which are
marked the full size dimensions. This type of drawings are
supplied by the drawing office for marking out purposes.
Allowances for the seams and the joints must be added to
the layout.

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Difference between gauges & Template:

Gauge Template

• It is made from tool steel It is thin sheet and low cost material
and has more thickness

• More accurate Less accurate

• Not used in heated jobs Normally used in heated job

• It is used for greater Rough and less accuracy jobs.

accuracy

• Treated with heat treatment To make simple and low cost material
and grinding.

44 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.56

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Combination set
Objectives : At the end of this lesson you shall be able to
• identify the parts of a combination set
• state the uses of each attachment in a combination set.

Combination sets can be used for different types of work, Centre head
like layout work, measurement and checking of angles.
This along with the rule is used for locating the centre of
The combination set (Fig 1) has a cylindrical jobs. (Fig 5)
- protractor head (1)
- square head (2) For ensuring accurate results, the combination
set should be cleaned well after use and
- centre head, and (3)
should not be mixed with cutting tools, either
- rule. (4) while using or storing.

Square head
Protractor head
The square head has one measuring face at 90° and
another at 45° to the rule. It is used to mark and check 90° The protractor head can be rotated and set to any required
and 45° angles. It can also be used to set workpieces on angle.
the machines and measure the depth of slots. (Figs 2,3The protractor head is used for marking and measuring
&4) angles within an accuracy of 1°. The spirit level attached
to this is useful for setting jobs in a horizontal plane.
(Fig 6)
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46 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.56

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Production & Manufacturing
Turner - Eccentirc turning Related theory for Exercise 2.2.58

Screw thread - definition, purpose & its elements

Objectives : At the end of this lesson you shall be able to
• define thread
• state the purpose of threads
• identify the parts of a thread (terminology).

Definition
Thread is a ridge of uniform cross-section which follows
the path of a helix around the cylinder or cone, either
externally or internally. (Fig 1)

- Load lifting purposes Ex.Screw-jack

- Elevating arm of radial drilling machines.

Elements of threads (Fig 4)

Elements of threads means naming the parts and other
Helix is a type of curve generated by a point which is terms systematically. The parts of a thread are identified
moving at a uniform speed around the cylinder or cone, and as follows. (Fig 4)
at the same time, moves at a uniform speed parallel to the
axis. (Fig 1)

Purpose of thread
Threads are used for the following purposes.
- For fastening purposes Ex. Bolts & nuts. (Fig 2)

- Transmission of motion Ex. Half nut with lead screw

(Fig.3)
- Used in precision measuring instruments.
Ex. Micrometer spindle.

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 Major diameter Helix angle (Fig 5)
Minor diameter
Pitch diameter
Pitch of the thread
Crest
Root
Flank of the thread
Thread angle
Depth of thread
Lead angle (helix angle)
Lead
Hand
Clearance

Major diameter
It is the largest diameter over which a thread is cut in the
case of an external thread, and in the case of an internal
thread, it is the largest diameter resulting after cutting the
thread. (Fig 4)

Minor diameter
It is the smallest diameter formed after an external thread
is cut, and in the case of internal thread, it is the diameter
over which the thread is cut.

Pitch diameter
It is the diameter of an imaginary cylinder which passes
through the thread such that the width of the space is equal
to the width of the thread. It is equal to the major diameter It is the angle which the helix makes with a line drawn
minus one depth. perpendicular to the axis. It is calculated by the formula
lead
Pitch of thread tan α =
pd
It is the horizontal distance from a point on one thread to
the corresponding point on the adjacent thread measured where a = helix angle in degrees,
parallel to the axis. d = pitch diameter ofthe thread.

Crest Hand of thread

It is the top surface joining the flanks of the same thread. The hand of the thread is the direction in which the thread
is turned to advance. If the direction is clockwise it is right
Root hand thread, and if the direction is anticlockwise, it is left
The bottom surface joining the flanks of the adjacent hand thread.
threads is called the root.
Start of the thread
Flank When there is only one helix formation on a work, the start
It is the surface connecting the crest and the root. of the thread is known as single start. If there are more than
one helix, then the thread is known as a multi-start thread.
Thread angle The starting points of the threads in the case of multi-start
threads are equally spaced on the face of the work, and
It is the included angle between two flanks of the thread. may be determined by a careful look at the face to know
the number of starts.
Depth of thread
Threads of any form can be cut having multi-starts,
It is the perpendicular distance between the crest and the
depending upon their applications. The helix angle of a
root of the thread.
multi-start thread of a definite pitch is greater than that of
a single start thread of the same pitch cut on the same
diameter. Multi-start threads may be left hand or right hand
48 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.58

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threads according to the need. The term ‘lead’ is always
used in conjunction with multi-start threads which will be
equal to the pitch of the thread multiplied by the number
of starts.
Multi-start threads are cut on parts to have faster
transmission of motion with the diameter of the work, the
pitch of the thread being kept to the minimum.

Clearance
It is a space left between the mating of external and
internal threads to facilitate easy rotation of the threaded
parts. (Fig.6)

Multi-start, right hand and left hand threads

Objectives: At the end of this lesson you shall be able to
• distinguish between the features of single start and multi-start threads
• give examples of a multi-start thread’s applications
• distinguish between the features of right hand and left hand threads
• give examples on the application of right hand and left hand threads
• identify right hand and left hand threads.

Threads are formed on screws in a helix. Helix is the path

of a point travelling around an imaginary cylinder such that
its axial and circumferential velocities maintain a constant
ratio.
When a single helix is making a screw, it is called a
SINGLE START thread. In a single start thread the LEAD
and PITCH are the same. (Fig 1)

Lead = Pitch x Number of starts

A screw-thread may have any number of starts. The
general term for such threads other than single start is
MULTI- START. Application of multi-start threads can be
found in fly presses, pen caps etc. A multi-start thread
makes it possible to keep the depth of thread less, and
In the case of TWO START (DOUBLE START) threads,
provides a rapid axial movement of the screws.
one thread is wound within the other exactly in the middle
(Fig.2). This enables the lead of the helix increased
without increasing the pitch.
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Production & Manufacturing
Turner - Eccentric turning Related theory for Exercise 2.2.59

Driving plate and lathe carriers & their usage

Objectives : At the end of this lesson you shall be able to
• name the parts of a driving plate
• distinguish between the different driving plates
• state the uses of the different driving plates
• name the parts of lathe carriers
• understand types of lathe carriers.

Driving plates
When turning a work in between the centres, the driving
plate is used for transmitting the drive to the work, from
drive plates
They are grouped as catch plates and driving plates and
safety driving plates.
Catch plate
It is designed with a 'u' slot and an elliptical slot to
accommodate the bent tail of the lathe carrier. (Fig 1)

The driving plate with a straight tail carrier provides a

positive drive for the workpiece.
A catch plate with a bent tail carrier uses a minimum
clamping length of the workpiece for clamping purposes.
A safety driving plate prevents likely injuries to the operator.
Lathe carriers

Driving plate
It is designed with a projected pin which locates the
straight tail of the lathe carrier. (Fig 2)

Safety driving plate

It is similar in construction to a driving plate but equipped
with a cover to protect the operator from any injuries.
(Fig 3)
The safety driving plates are made of cast steel and are
machined to have their face perfectly at right angles to the
bore. They are provided with a stepped collar at the back.
The bore is designed to suit the spindle nose to which the
plate has to be mounted.
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They are also called lathe dogs. They are used to drive The clamp type lathe carrier is designed with a clamping
the work during turning between centres. The work is plate and adjustable screws. It holds a wide range of
clamped firmly in the lathe carrier. It consists of a cast diameters of work because it is provided with a ‘V’ groove
iron or forged steel body and a clamping screw. It is and adjustable bolts and nuts. This carrier may be used
designed with a straight or bent tail. It is available in a set to hold square and rectangular sectioned rods also. They
of 10, capable of accommodating work of a wide range of are also useful to hold small diameter jobs because of
diameters. The tails of the carriers are meant to locate the provision of the ‘V’ groove. (Fig 7)
and drive the workpiece for turning. (Fig 4) To protect the
finished surface from damages, a soft metal packing piece
is used under the clamping screw.
The following are the four types of lathe carriers.
Straight tail carrier, Bent tail carrier, Clamp type carier
and Safety clamp type carrier.
A straight tailed carrier locates against the driving pin of
the diving plate and provides a positive drive for the
workpiece. (Fig 5)

Safety clamp lathe carriers are desinged with safety - top

and bottom clamping plates. These plates provide a
positive grip of the work during turning. (Fig 8)

A bent tailed lathe carrier engages into a ‘u’ slot of the

catch plate and drives the workpiece. (Fig 6).

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Production & Manufacturing
Turner - Eccentric turning Related theory for Exercise 2.2.60

Fundamentals of thread cutting on lathe

Objectives : At the end of this lesson you shall be able to
• state the principle of thread cutting on lathe
• identify the parts involved in the thread cutting mechanism and state their functions
• State the method of setting tool, depth of cut and feeding method.
Screw threads once, the lead screw should make one revolution to move
the tool by 4 mm. Hence, if the stud gear (driver) has 50
Principle of thread cutting
teeth, the lead screw should be fixed with a gear of 50 teeth
The principle of thread cutting is to produces a uniform (driven) to get the same number of revolutions as the
helical groove on a cylindrical or conical surface by spindle.
rotating the job at a constant speed, and moving the tool
longitudinally at a rate equal to the pitch of the thread per
revolution of the job, with required tool feed.
The cutting tool moves with the lathe carriage by the
engagement of a half nut of the lead screw. The shape of
the thread profile on the work will be the same as that of
the tool ground. The direction of rotation of the lead screw
determines the hand of thread being cut.
Parts involved in thread cutting (Fig 1)

If we have to cut 2 mm pitch threads instead of 4 mm in the

same lathe, then the job makes one rotation and the lead
screw should rotate 1/2 revolution so that the lead screw
rotation is slower. Therefore, the driven wheel (lead screw
gear) should be of 100 teeth if the driver (stud gear) has 50
teeth.
If we have to cut a 8 mm pitch thread on the job, the tool
should move 8 mm per revolution of the job. The lead screw
should rotate 2 revolutions when the job makes one
rotation, making the L.S to run twice the speed of the
spindle. So the driven wheel (lead screw gear) should be
of 25 teeth if the driver wheel has 50 teeth.
Thread cutting on lathe
After the chares gear set up on lathe next step to do lathe
is to turn the blank to required sixe and then setting the V-
tool. The excess material is turned to the required thread
to be cut to major diameter size and chamfered. The
thread cutting tool is set in line with lathe axis and
perpendicular with help of thread tool gauge as shown in
Figure illustrates how the drive is transmitted from the fig.
spindle to the lead screw through the change gear The depth of cut given in two ways:
arrangement. From the lead screw the motion is transmitted
to the carriage by engaging the half nut with the lead 1. Advancing the tool perpendicular to the lathe axis,
screw. usually it varies from 0.05 to 0.2 mm depth
We have to cut a 4 mm pitch (lead) thread on a job in a lathe 2. Advanced at an angle, by setting the compound rest at
having a lead screw of 4 mm pitch. When the job rotates half of the thread angle, if it is metric 30° the methods
52 shown in figure.

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Production & Manufacturing
Turner - ‘V’ Thread Related Theory for Exercise 2.3.61

Different types of screw threads-forms, elements and applications

Objectives: At the end of this lesson your shall be able to
• name different types of screw threads
• name the different form of screw threads
• illustrate their forms and elements
• describe their applications.

The different types of V threads are leakage in the assembly and provides for further adjustment
when slackness is felt.
- BSW Thread: British Standard Whitworth Thread
BA Thread (Fig 2)
- BSF Thread: British Standard Pipe Thread
This thread has an included angle of 47 1/2°. Depth and
- B.A. Thread: British Association Thread
other elements are as shown in the figure. It is used in
- I.S.O. Metric thread: Interantional Standard small screws of electrical appliances, watch screws,
Organisation metric thread screws of scientific apparatus.
- American National or sellers ‘thread Unified thread (Fig 3)
BIS Metric thread: Bureau of Indian Standard metric
thread.
BSW thread (Fig 1)

For both the metric and inch series, ISO has devleoped
this thread. Its angle is 60°. The crest and root are flat and
it has an included angle of 55° and depth of the thread is the other dimensions are as shown in the figure. This
0.6403xP. The crest and root are rounded off to a definite thread is used for general fastening purposes.
radius. The figure shows the relationship betweem the This thread of metric standard is represented in a drawing
pitch and the other elements of the thread. by the letter ‘M’ followed by the major diameter for the
BSW thread is represented in a drawing by giving the coarse series.
major diameter. For example: 1/2” BSW, 1/4” BSW. The
table indicates the standard number of TPI for different
diameters. BSW thread is used for general purpose
fastening threads.
BSF thread
This thread is similar to BSW thread except the number of
TPI for a particular diameter. The number of threads per
inch is more than that for the BSW thread for a particular
diameter. For example, 1” BSW has 8 TPI and 1” BSF has
10 TPI. The table indicates the standard number of TPI for
different dia. of BSF threads. It is used in automobile EX: M14, M12, etc.
industries.
For the fine series, the letter ‘M’ is followed by the major
BSP thread diameter and pitch.
This thread is recommended for pipe and pipe fittigs. The EX: M14 x 1.5
table shows the pitch for different diameters. it is also
similar to BSW thread. The thread is cut externally with a M24 x 2
small taper for the threaded length. This avoids the
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Screw thread applications
In mechanical assemblies and in transfer of power these To make accurate measurements (Fig 4)
thread applications play a vital role. In milling machine
worm& thread helps in indexing the job. The square thread
is generally used for transferring power like screw jack,
and lead screw of a thread in thread cutting.
External threads and internal threads are assembled
together for different engineering uses. (Fig 1)

To apply pressure (Fig 5)

Uses of Screw Threads

Screw threads are used as fasteners to hold together and
dismantle components when needed (Fig 2)

to make adjustments. (Fig 6)

To transmit motion on machines from one unit to another
(Fig 3)

Forms of screw threads

Basic forms of screw threads industrial applications like bolts, nuts and spindles for
micrometers etc.
Screw threads of different forms are available for meeting
the various requirements.The basic forms of screw threads Square and trapezoidal threads
are
Square and trapezoidal threads have more cross-sectional
vee threads area than ‘V’ threads. They are more suitable to transmit
motion or power than ‘V’ threads. They are not used for
square threads
fastening purposes.
trapezoidal threads.
Square thread
Vee threads (Fig 1)
In this thread the flanks are perpendicular to the axis of the
These threads are of a 'V' shape. Vee threads of different thread. The relationship between the pitch and the other
types are available. Vee thread is the most commonly elements is shown in Fig 1.
used form of screw threads, and is used for domestic and
54 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.59

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Square threads are used for transmitting motion or power.
Eg. screw jack, vice handles, cross-slide and compound Buttress thread (Fig 3)
slide, activating screwed shafts.

Modified square thread

Modified square threads are similar to ordinary square
threads except for the depth of the thread. The depth of
thread is less than half pitch of the thread. The depth varies
according to the application. The crest of the thread is
chamfered at both ends to 45° to avoid the formation of
burrs. These threads are used where quick motion is
required.

Trapezoidal threads
These threads have a profile which is neither square nor ‘V’ In buttress thread one flank is perpendicular to the axis of
thread form and have a form of trapezoid. They are used the thread and the other flank is at 45°. These threads are
to transmit motion or power. The different forms of used on the parts where pressure acts at one flank of the
trapezoidal threads are: thread during transmission. Figure 3 shows the various
elements of a buttress thread. These threads are used in
- acme thread power press, carpentry vices, gun breeches, ratchets etc.
- buttress thread
American National Thread (Fig 4)
- saw-tooth thread
These threads are also called as seller’s threads. It was
- worm thread. more commonly used prior to the introduction of the ISO
unified thread.
Acme thread (Fig 2)
This thread is a modification of the square thread. It has an Saw-tooth thread
included angle of 29°. It is preferred for many jobs because This is a modified form of buttress thread. In this thread,
it is fairly easy to machine. the flank taking the load is inclined at an angle of 3°,
Acme threads are used in lathe lead screws. This form of whereas the other flank is inclined at 30°. The basic profile
thread enables the easy engagement of the half nut. The of the thread illustrates this phenomenon. (Fig 5) The
metric acme thread has an included angle of 30°. The proportionate values of the dimensions with respect to the
relationship between the pitch and the various elements is pitch.
shown in the figure.

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.59 55

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 Knuckle threads
The shape of the knuckle thread is not trapezoidal but it
has a rounded shape. It has limited application. The figure
shows the form of knuckle thread. It is not sensitive
against damage as it is rounded. It is used for valve
spindles, railway carriage couplings, hose connections
etc. (Fig 7).

Worm thread
This is similar to acme thread in shape but the depth of
thread is more than that of acme thread. This thread is cut
on the worm shaft which engages with the worm wheel.
Figure 6 shows the elements of a worm thread.
The worm wheel and worm shaft are used in places where
motion is to be transmitted between shafts at right angles.
It also gives a high rate of speed reduction.

Screw thread and elements

A screw thread is a ridge of uniform section formed
helically on the surface of a cylindrical body. (Fig 1)
An external screw thread is formed on the outer surface of
a cylindrical part. Examples: bolts, screws, studs, threaded
spindles, etc. (Fig 1)
An internal screw thread is formed on the inner surface of
a hollow cylindrical part. Examples: nuts, threaded lids
etc.
External threads and internal threads are assembled
together for different engineering uses. (Fig 2)

Uses of Screw Threads To transmit motion on machines from one unit to another
(Fig 4)
Screw threads are used as fasteners to hold together and
dismantle components when needed (Fig 3)
56 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.59

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 Crest
The top surface joining the two sides of a thread.

Root
The bottom surface joining the two sides of adjacent
To make accurate measurements (Fig 5) threads.

Flank
The surface joining the crest and the root.

Thread Angle
The included angle between the flanks of adjacent threads.

Depth
The perpendicular distance between the roots and crest of
the thread.

Major Diameter
In the case of external threads it is the diameter of the
To apply pressure (Fig 6) blank on which the threads are cut and in the case of
internal threads it is the largest diameter after the threads
are cut that are known as the major diameter. (Fig 9)
This is the diameter by which the sizes of screws are
stated.

Minor Diameter
For external threads, the minor diameter is the smallest
diameter after cutting the full thread. In the case of internal
threads, it is the diameter of the hole drilled for forming the
thread which is the minor diameter.

Screws are used to make adjustment on die opening fig 7. Pitch Diameter (effective diameter)
The diameter of the thread at which the thread thickness
Parts of a screw thread fig 8. is equal to one half of the pitch.

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Pitch (Fig 8)
It is the distance from a point on one thread to a corre-
sponding point on the adjacent thread measured parallel
to the axis.

Lead
Lead is the distance a threaded component moves along
the matching component during one complete revolution.
For a single start thread the lead is equal to the pitch.

Helix Angle
The angle of inclination of the thread to the imaginary
perpendicular line.

Hand
The direction in which the thread is turned to advance. A
right hand thread is turned clockwise to advance, while a
left hand thread is turned anticlockwise. (Fig 10)

58 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.2.59

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Production and Manufacturing
Turner - Thread cutting Related theory for Exercise 2.3.62

Drive train - change gear formula & calculation

Objectives : At the end of this lesson you shall be able to
• state what is a change gear train
• identify and name the different types of change gear trains
• distinguish between a simple gear train and a compound gear train.

Change gear train the change gears are obtained from the available set of
gears which will result in having more than one driver and
Change gear train is a train of gears serving the purpose
one driven wheel. Such a change gear train is called a
of connecting the fixed stud gear to the quick change
compound gear train.
gearbox. The lathe is generally supplied with a set of gears
which can be utilized to have a different ratio of motion Fig 3 shows the arrangement of a compound gear train.
between the spindle and the lead screw during thread
cutting. The gears which are utilized for this purpose
comprise the change gear train.
The change gear train consists of driver and driven gears
and idler gears.

Simple gear train

A simple gear train is a change gear train having only one
driver and one driven wheel. Between the driver and the
driven wheel, there may be an idler gear which does not
affect the gear ratio. Its purpose is just to link the driver and
the driven gears, as well as to get the desired direction to
the driven wheel.
Fig 1 shows an arrangement of a simple gear train.

Fig 2 shows mountings of the driver and driven gears in a

lathe. Derivation of the formula for change gears
The driver gear and the driven gear are changed according Examples
to the pitch of the thread to be cut on the job.
CASE 1
Compound gear train We have to cut a 4 mm pitch (lead) thread on a job in a lathe
having a lead screw of 4 mm pitch. When the job rotates
Sometimes, for the required ratio of motion between the
once, the lead screw should make one revolution to move
spindle and the lead screw, it is not possible to obtain one
the tool by 4 mm. Hence, if the stud gear (driver) has 50
driver and one driven wheel. The ratio is split up and then
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teeth, the lead screw should be fixed with a gear of 50 teeth
(driven) to get the same number of revolutions as the
spindle. (Fig 4)

Let us compare the above three examples.

I II III

CASE 2 Pitch(Lead)of job 4 2 8

If we have to cut 2 mm pitch threads instead of 4 mm in the Pitch(Lead) of L.S 4 4 4

same lathe, then the job makes one rotation and the lead
screw should rotate 1/2 revolution so that the lead screw Driver 50 50 50
rotation is slower. Therefore, the driven wheel (lead screw
gear) should be of 100 teeth if the driver (stud gear) has 50 Driven 50 100 25
teeth.(Fig 5)
Stating the above in the form of a formula

Driver Lead of work

the gear ratio = =
Driven Lead of Lead Screw

Solved examples
1 Find the change gears required to cut a 3 mm pitch on
a job in a lathe having a lead screw of 6 mm pitch.
(Fig.7)

CASE 3
If we have to cut a 8 mm pitch thread on the job, the tool
should move 8 mm per revolution of the job. The lead screw
should rotate 2 revolutions when the job makes one
rotation, making the L.S to run twice the speed of the Driver Lead of work 3
Ratio = = =
spindle. So the driven wheel (lead screw gear) should be of Driven Lead of L/S 6
25 teeth if the driver wheel has 50 teeth. (Fig 6)
3 20 60
= × =
6 20 120
Driver 60 teeth
60 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.62

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Driven 120 teeth.
2 Find the change gears to cut a 2.5 mm pitch in a lathe
having a lead screw of 5 mm pitch.

Driver Lead of work

Ratio = =
Driven Lead of Lead Screw
2.5
=
5
2.5 × 20
=
5 × 20
50.0 50
= =
100 100

Driver 50 teeth
Driven 100 teeth. Driver Lead of work
Ratio = =
Driven Lead of Lead screw
3 Calculate the gears required to cut a 1.5 mm pitch in
1.5 3 3 × 10 30
a lathe having a lead screw of 5 mm pitch. (Fig 8) = == =
5 5 × 2 10 × 10 100

Driver 30 teeth
Driven 100 teeth.

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Production & Manufacturing
Turner - Thread cutting Related theory for Exercise 2.3.63

Different methods of forming threads

Objectives : At the end of this lesson you shall be able to
• state the different methods of forming threads
• distinguish the procedure of forming threads by different methods.

The different methods of forming threads depend on many

factors.
Type and number of components required
Type accuracy of thread and its surface finish
Availability of machine tools
Skill of the operator, etc.
The different methods of forming threads are:
by hand tools like tapes and dies
by using a single point cutting tool on the table
by using a multi-point cutting tool called chasers
by using a coventry die-head and collapsible taps in
production lathes
by thread rolling
by thread milling
Taps and dies are commonly used for general purpose
by thread grinding bolts and nuts. Taps are used to produce internal threads.
Dies are used to produce external threads.
by thread casting (die - casting or moulding).
Taps and dies can be used only for products standarad
Using taps and dies (Fig 1 & 2)
‘V’ threads for both coarse and fine pitches. Machine taps
are also available for cutting threads.

Using single point cutting tools on lathe (Fig 3)

Both internal and external right hand and left hand threads
can be cut by this method. Any form of thread to a required
pitch can be cut or produced by using the corresponding
tools. Accuracy of the thread depends on the skill of the
operator.

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Using chasers (Fig 4) is not cut and chips will not be produced. Thread is
produced by rolling. Rolling is a process of cold forging
resulting in a plastic deformation. The job is turned to
pitch diameter before rolling. The rollers may be flat or
disc type. Threads produced by rolling have better strength
and good finish.

Chasers are multi-point cutting tools to produce external

'V' threads. There are different types of chasers, each
one having its own special characteristics.
Usually, hand chasers are used to finish the thread, and
machine chasers for producing the threads. Machine Thread milling (Fig 7)
chasers are used in conjunction with the die-heads.
Threads are produced by thread milling cutters. The
Using coventry die-heads and collapsible taps operation is performed on a special thread milling machine
(Fig 5) to produce accurate threads in small or large quantities.
In this operation there are three driving motions, that is,
for cutter, work, and longitudinal movement of the cutter.
The thread is completed in one cut by setting the cutter
to the full depth of thread and then feeding it along the
entire length of the workpiece. Internal thread milling can
also be performed to produce accurate internal threads.

They are used in mass production to produce threads on

capstan, turret lathes and automats. A highly skilled Thread grinding (Fig 8 and 9)
operator is not essential for cutting threads but for setting, Special grinding machines are required for thread grinding.
skilled setters are required. This method is limited to Both the external threads and internal threads can be
producing 'V' threads. ground.
Collapsible taps are used with floating holders for There are two main types of thread grinding i.e single rib
producing internal threads. and multiple rib.
Thread rolling (Fig 6) Single rib grinding involves the use of a narrow grinding
wheel which is shaped to the required form of thread.
It is used in mass, production. In this method, the thread

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.63 63

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Multiple-rib grinding is done with a grinding wheel with Thread casting
many grooves on its face. This type of wheel grinds many
Threads can be produced by casting for crude threads. It
threads at one time. (Fig 9)
is produced either by die casting or moulding. Threads
on non-metals are produced by this method.

64 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.63

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Production & Manufacturing
Turner - Thread cutting Related theory for Exercise 2.3.64

Calculation involved in finding core dia, gear train

Objectives : At the end of this lesson you shall be able to
• describe change gear calculation
• calculate change gear calculation for simle and compound gear train
• calculate chen

Calculation for change gears Example: The pitch of lead screw is 6mm pitch of the
thread to be cut is 2mm. find change gears.
To calculate change gear to cut thread to required pitch,
for simple gear train.
it is to know ration of driving and driven gear to be fixed.
for example if the lathe lead screw pitch is 12mm and the Driver teeth = pitch of the work 2 2x20 40
thread to be cut 3mm pitch, the spindle must rotate 4
Driven teeth pitch of the lead screw 6 = 6x60 = 120
times the speed of lead screw
Therefore Spindle turn = 4 The driver gear will have 40T and driven gear will have
120T
Lead screw turn 1
for which we must have
Example: The pitch of the leadscrew is 12mm and thread
Driver teeth = 1 = Lead screw turn
to be cut 1.5mm find change gear for compound gear
Driven teeth 4 Spindle turn train.
Driver teeth = Pitch of the work = 1.5
= Pitch of the thread to be cut
Driven teeth Pitch of the lead screw 12
Pitch of the lead screw
= 1.5x2 63 63 1
(for British standard screws 12x2 48 14 12
TPI on lead screw
TPI on work)
The gear fixed on spindle shaft drive called driver.

Change wheel calculations for fractional pitch threads

Objectives : At the end of this lesson you shall be able to
• calculate change wheels for cutting fractional pitch threads (BritishSystem)
• calculate change wheels for cutting decimal fractional pitch threads (BritishSystem)
• calculate change wheels for fractional pitch threads by continued fraction method.

It is necessary to calculate the ratio of change gears to Expressed as a formula:-

cut fractional leads for worms, hobs etc. on a centre lathe
at times. DR Lead screw to be cut
≡ ratio of change gears ≡
DN Lead of lead screw
To obtain a formula; suppose it is required to cut a lead of
1/4" on a lathe which has a lead of 1/2". If one to one ratio
or alternatively:-
were used between the driver and the driven gears, the
carriage would move 1/2" per revolution of the lathe spindle.
lead of screw to be cut 1 Driver
Therefore, to cut a lead of 1/4" the ratio of the driver and x =
driven gears must be as 1 lead of screw Driven
lead of screw to be cut x
11
42 Driver
No.of threads / inch of lead screw =
1/4 1 Driver Driven
That is or ≡
1/2 2 Driven Example
Calculate the change gears necessary to cut a thread
of 7/16" lead on a lathe with a lead screw of 4 threads
per inch.
65

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lead of screw to be cut x When the lead occurs as a decimal, it may be
necessary to use the method of continued fractions to
Driver obtain a suitable approximation of the change gear ratio,
No.of threads / inch of lead screw = for which the change gears may be selected from the
Driven
available set of gears.
7 28 7
= x 4 = =
16 16 4

7 10 70 Driver
= x = =
4 10 40 Driven

If the lead to be cut is a whole number and a vulgar

fraction, change it to an improper fraction and apply the
above formula.
Example
Calculate the change gears required to cut an oil groove
having 8 turns in 11 inches on a lathe with a lead screw
of 4 threads per inch.
Pitch of the groove x

Driver
No.of threads / inch of lead screw =
Driven
Example
travel or given number of turns
Pitch of groove = Calculate the change gears required to cut a worm of 0.55
number of turns inches lead on a lathe, with a lead screw of 6 threads per
inch.
11
= inches
8 DR
lead to be cut x no.of threads/inch of lead screw =
DN
11
= 0.55 x 6
Gear ratio = 8
1
55 6
4 = x
100 1
11 44 4 x 11 4 11 55
= 4= = = = 1st fraction =
8 8 2x4 2 4 100
6 20 120
4 15 60 2nd fraction =x =
First fraction =x = 1 20 20
2 15 30 driver 55 120
11 10 110 = x
2nd fraction = x = driven 100 20
4 10 40
DR 60 110 Example
Thus = x (Fig 1) Calculate the change gears required to cut a worm of 0.95
DN 30 40
inches lead on a lathe with a lead screw of 6 threads per
Example inch.
Calculate the change gears to cut a worm of 0.35 inches DR
lead on a lathe with a lead screw having 4 threads per lead to be cut x no.of threads/inch of lead screw =
DN
inch. lead to be cut x no.of threads/inch of lead screw
= 0.95 x 6
DR
= 0.35 x 4
= 95 (6 x 20) 95 120
DN = x = x
100 (1 x 20) 100 20
35 4
7 10 70 driver
= x = x = = driver 95 120
100 1 5 10 50 driven = x
driven 100 20
66 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.64

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Example
Calculate the change gears to cut 2BA threads (0.81mm 7 1 5 4 3
pitch) on a lathe which has a lead screw of 1/4 inch -
pitch by the continued fraction method. 1 0 1 1 6 25 81
This could be cut exactly if the 1/5 ratio were combined 0 1 7 8 47 196 635
with a 81T driver and a 127T driven change gears.
If special gears are not available we have to obtain the 7 1 5 4 3
nearest fraction by the continued fraction method. For this
nearest fraction gears may be selected from the available
set of gears. 1 1 6 25 81
The convergent s are : ; ; ; ;
7 8 47 196 635
driver 0.81 0.81 25 5 5
Ratio : = = The 4th convergent : may be written x
driven 1/4 x 25.4 6.35 196 14 14
driver 81 1 x 81
= x driver 25 25
driven 635 5 x 127 = x
driven 70 70
Determining the convergents by the continued frac-
tion method. and this could be obtained with duplicate 25 T and 70 T
gears, a circumstance not unlikely, provided two similar
81) 635 (7 lathes are available.
567
______ The actual pitch obtained from this driver and driven gears
68 ) 81 (1 is:
68 an error of 0.00005mm, which is equivalent to a total pitch
______
error of about 0.0016mm (0.00006 in) over a 1 in. length
13 ) 68 (5 of the thread. This is well within the permissible limits of
65 accuracy of an ordinary commercial lead screw.
______

3) 13 (4
12
_____

1) 3 (3

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Production & Manufacturing
Turner - Thread cutting Related Theory for Exercise 2.3.65

Thread chasing dial - Function, construction and use.

Objectives : At the end of this lesson you shall be able to
• state the necessity of a thread chasing dial
• state the constructional details of a British thread chasing dial
• state the functional features of a British thread chasing dial.

Thread chasing dial Each numbered division represents 1 inch travel of the
carriage.
To catch the thread quickly and to save manual labour,
use of a chasing dial is very common during thread cutting Let the worm wheel have 16 teeth, and the lead screw 4
by a single point cutting tool. A thread chasing dial is an TPI. The number of numbered graduations and unnumbered
accessory. graduations are 4 each.
The half nut can be engaged 16 times for one revolution of
Constructional details (Fig 1)
the graduated dial. The movement of the carriage for one
The figure shows constructional details of a British thread complete revolution of the dial is 4". (Fig 2) Since the dial
chasing dial. It consists of a vertical shaft with a worm is having totally 8 graduations marked, each graduation
wheel made out of brass or bronze, attached to the shaft represents 1/2" travel of the carriage.
at the bottom. On the top, it has a graduated dial. The shaft
The chart given here shows the positions at which the half
is carried on a bracket in bearing (bush) which is fixed to
nut is to be engaged when cutting different threads per
the carriage. The worm wheel can be brought into an
inch, when a British thread chasing dial with the above
engaged or disengaged position with the lead screw as
data is fitted to the lathe.
needed. When the lead screw rotates it drives the worm
wheel which causes the dial to rotate. The movement of
the dial is with reference to the fixed mark (‘O’ index line).
The face of the dial is usually graduated into eight (8)
divisions, having 4 numbered main divisions and 4
unnumbered subdivisions in between.

The number of teeth on the worm gear is the product of the

number of threads per inch on the lead screw and the
number of numbered divisions on the dial.

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 THREAD CHASING DIAL CHART

Threads per inch to be cut Dial graduation at which the half nut can Reading on the dial illustrated
be engaged to catch the thread

Threads which are a multiple Engage at any position the half nut Use of dial unnecessary.
of the number of threads meshes.
per inch of the lead screw.

Example T.P.I. to be cut - 8

DR T.P.I. on lead screw 4 1

DN T.P.I. to be cut 8 2

The predetermined travel of 1/4" is represented by the dial position in the exact middle between any numbered division
and adjacent un-numbered division. The half nut engagement can be done at any position at which it can be engaged
(ie. 16 positions).
Referring to the dial is not necessary.
Even number of threads Engage at any graduation 1
on the dial. 1 1/2
2
2 1/2
3
3 1/2
4
8 positions 4 1/2

Example T.P.I. to be cut - 6

DR T.P.I. on lead screw 4 2

DN T.P.I. to be cut 6 3

The predetermined travel of 1/2" is represented by dial movement from any numbered division to the next adjacent
unnumbered division. The half nut can be engaged when any numbered or unnumbered graduation coincides with
the zero line (8 positions).

Odd number of threads Engage at any main division. 1

2
3
4 positions 4

Example T.P.I. to be cut - 5

DR T.P.I. on lead screw 4 4 1”

= = = Predeterminedtravel = 4 x =1”
DN T.P.I. to be cut 5 5 1
The predetermined travel of 1" is represented by the dial movement from any numbered division to the next numbered
division or from any unnumbered division to the next unnumbered division. Therefore, if the first cut is taken when a
numbered division of the dial coincides with zero, then the half nut engagement for successive cuts can be done when
any numbered division coincides with the zero mark. If the first cut is taken when an unnumbered division coincides
with the zero, then the half nut for successive cuts, is engaged when any unnumbered division coincides with the zero.
(4 positions)

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Half fractional number Engage at every other 1&3
of threads main division. or
2&4
2 positions

Example T.P.I. to be cut - 3 1/2

DR T.P.I. on lead screw 4 8

= = =
DN T.P.I. to be cut 3 1/2 7

The half nut can be engaged only at opposite numbered or unnumbered graduations (2 positions).

Quarter fractional number Engage at the same 1

of threads main division. or
2
or
3
or
4
1 position
Example T.P.I. to be cut - 2 3/4

DR T.P.I. on lead screw 4 16

= = =
DN T.P.I. to be cut 2 3/4 11
1"
Predetermined travel = 16 x = 4"
4

The half nut can be engaged to catch the thread only when the same numbered or unnumbered graduated line, at which
the first cut is taken, coincides with the zero line (1 position only).

Example T.P.I. to be cut - 1 3/8

DR T.P.I. on lead screw 4 32

= = =
DN T.P.I. to be cut 1 3/8 11

1"
Predetermined travel = 32 x = 8"
4

The half nut engaged for the first cut should remain at the engaged position till thread cutting is completed and the
machine is reversed as it takes a long time to cover the predetermined travel arrived at by calculation.

70 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.65

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Metric thread chasing dial
Objectives : At the end of this lesson you shall be able to
• state the constructional details of a metric thread chasing dial
• state the functional features of a metric thread chasing dial.

Construction of a metric thread chasing dial (Fig.1) ie. 1,1.25,1.5, 2, 2.5, 3, 3.75, 4, 5, 6, 7.5, 10, 12, 15, 20,
30 and 60.
The figure shows the metric thread chasing dial of an HMT
lathe and the chart indicates the worm wheel and graduated
dial plate to be chosen for cutting threads of different
pitches. (Fig. 2)

LEAD SCREW 6 mm PITCH

Threads Driving No. of Threads Driving No. of
in pinion lines on in pinion lines on
m/m A Disc B m/m A Disc B

The construction of a metric thread chasing dial is similar .5 3.25 39 3

to that of a British chasing dial. The shaft carries a set of .625 35 7 3.5 35 5
worm/spur wheel of different numbers of teeth which vary .75 4 36 18
.875 35 5 4.5 36 12
according to the type of the lathe. But there is always more 5 35 7
1
than one worm/spur wheel. The dial graduation of the 1.125 36 12 5.5 33 3
metric chasing dial also differs from that of the British 1.25 35 7 6
thread chasing dial. 1.375 33 3 6.5 39 3
1.5 7 35 5
Fig 1 shows the construction of a metric thread chasing 1.625 39 3 8 36 9
dial. 1.75 35 5 9 36 12
2 10 35 7
For cutting metric threads, using a metric thread chasing 2.25 36 12 11 33 3
dial, the product of the pitch of the lead screw and the 2.5 35 7 12 36 18
2.75 33 3 13 39 3
number of teeth on the worm wheel must be an exact 14 35 5
3
multiple of the pitch of the thread to be cut. Accordingly
the corresponding worm wheel has to be engaged with the The following are worked out examples, showing the
lead screw. selection of the dial and worm wheel for a given pitch in the
above HMT lathe.
For instance, if the lead screw thread has a 4 mm pitch and
the number of teeth on the worm wheel is 15, then the Example 1
product is 4 x 15 = 60.
TO CUT 0.625 mm PITCH
Therefore, the following pitches can be cut which exactly
divide the product.
DR Pitch to be cut
Gear ratio = =
DN Pitch of lead screw

0.625 5/8
= =
6 6
1 5 5
= x =
8 6 48
The thread will be in unison, if the lead screw makes 5
revolutions when the job makes 48 revolutions
predetermined travel.
P.D.T. = 5 x Pitch of lead screw
= 5 x 6 = 30 mm.
The product of the number of teeth on the worm wheel and
the pitch of the lead screw
= 35 x 6 = 210.
A dial with 7 graduations marked is to be selected since

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.65 71

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 210 210 P.D.T. = 3 x Pitch of lead screw
= = 7.
= 3 x 6 = 18 mm.
PDT 30
The product of the number of teeth on the worm wheel and
So to cut a 0.625 mm pitch, the half nut is engaged for any
the pitch of the lead screw= 36 x 6 = 216
of the 7 graduations coinciding with the zero line.
A dial with 12 graduations marked is selected since
Example 2
216 216
TO CUT A 4.5 mm PITCH
= = 12.
PDT 18
DR Pitch to be cut
So to cut a 4.5 mm pitch, the half nut is engaged for any
Gear ratio = =
of the 12 graduations coinciding with the zero line.
DN Pitch of lead screw

4.5 9/2 9 9 3
= or = = =
6 6 2x6 12 4

72 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.65

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Production & Manufacturing
Turner - Thread cutting Related Theory for Exercise 2.3.66 & 2.3.67

Conventional chart for different profile of metric, BA, whitworth and pipe thread
Objectives : At the end of this lesson you shall be able to
• describe the symbol for internal and external threads
• read the chart to find, pitch, core diameter and depth etc.

Conventional representation of threads

Title Actual Convention Symbol

Projection/Section

External
Threads

Internal
Threads

OD Imperial TPI Pitch Pitch Core Core Thread Thread Thread Thread Hex Head Tapping MM Imperial
MM Imperialin Dia Dia Depth Depth Depth Depth A/ Depth Size
MM Impe- MM Male Male Female female MM Flats MM Imperial
rial imperial MM Imperial MM MM

1 0.0394 102 0.0098 0.25 0.0274 0.693 0.0060 0.153 0.0053 0.135 0.0290 0.75 69
1.1 0.0433 102 0.0098 0.25 0.0312 0.793 0.0060 0.153 0.0053 0.135 0.0335 0.85 65
1.2 0.0472 002 0.0098 0.25 0.0351 0.893 0.0060 0.153 0.0053 0.135 0.0374 0.95 62
1.4 0.0551 85 0.0118 0.30 0.0407 1.032 0.0072 0.184 0.0064 0.612 0.0433 1.10 57
1.6 0.0630 73 0.0138 0.35 0.0460 1.171 0.0085 0.215 0.0074 0.189 3.2 0.0492 1.25 3/64
1.8 0.0709 73 0.0138 0.35 0.0539 1.371 0.0085 0.215 0.0074 0.189 0.0570 1.45 54
2 0.0787 64 0.0157 0.40 0.0595 1.510 0.0096 0.245 0.0085 0.217 4.00 1.5 0.0630 1.60 1/16
2.2 0.0866 56 0.0177 0.45 0.0648 1.648 0.0109 0.276 0.0096 0.244 0.689 1.75 51
2.3 0.0906 56 0.0177 0.45 0.0688 1.750 0.0109 0.276 0.0096 0.244 0.0730 1.85 49
2.5 0.0984 56 0.0177 0.45 0.0766 1.950 0.0109 0.276 0.0096 0.244 0.0810 2.05 46
2.6 0.1024 56 0.0177 0.45 0.0832 2.05 0.0109 0.276 0.0096 0.244 5.00 0.0870 2.20 44
3 0.1181 50.8 0.0197 0.50 0.0967 2.387 0.0121 0.307 0.0107 0.271 5.50 2.13 0.0984 2.50 40
3.5 0.1378 42.3 0.0236 0.60 0.1088 2.767 0.0145 0.368 0.0128 0.325 0.1142 2.90 33
4 0.1575 36.3 0.0276 0.70 0.1237 3.141 0.0169 0.429 0.0149 0.379 7.00 2.93 0.1300 3.30 30
4.5 0.1772 33.9 0.0295 0.75 0.141 3.580 0.0181 0.460 0.0160 0.406 0.1500 3.80 24
5 0.1968 31.8 0.0315 0.80 0.1582 4.019 0.0193 0.491 0.0170 0.433 8.00 3.65 0.1650 4.20 19
5.5 0.2165 28.2 0.0354 0.90 0.1705 4.331 0.0230 0.584 0.0205 0.520 0.1770 4.50 16
6 0.2362 25.4 0.0394 1.00 0.1880 4.773 0.0241 0.613 0.0213 0.541 10.00 4.15 0.1970 5.00 9
7 0.2756 25.4 0.0394 1.00 0.2274 5.773 0.0241 0.163 0.0213 0.541 11.00 0.2362 6.00 B
8 0.3150 20.3 0.0492 1.25 0.2668 6.466 0.0301 0.767 0.0267 0.677 13.00 5.65 0.2720 6.90 I
9 0.3543 20.3 0.0492 1.25 0.2939 7.466 0.0302 0.767 0.0267 0.677 13.00 0.3071 7.80 N
10 0.3937 16.9 0.0590 1.50 0.3213 8.160 0.0362 0.920 0.320 0.812 17.00 7.18 0.3346 8.50 Q
11 0.4331 16.9 0.0590 1.75 0.3878 9.852 0.0423 1.074 0.0373 0.947 19.00 8.18 0.4015 10.20 Y
12 0.4724 14.5 0.0689 1.75 0.3878 9.852 0.0423 1.074 0.0373 .947 19.00 8.18 0.4015 10.20 Y

73

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 OD Imperial TPI Pitch Pitch Core Core Thread Thread Thread Thread Hex Head Tapping MM Imperial
MM Imperial in Dia Dia Depth Depth Depth Depth A/ Depth Size
MM Impe- MM Male Male Female female MM Flats MM Imperial
rial imperial MM Imperial MM MM

14 0.5512 12.7 0.0787 2.00 0.4546 11.546 0.0483 1.227 0.0426 1.083 22.00 0.4724 12.0 15/3

16 0.6299 12.7 0.0787 2.00 0.5333 13.546 0.0483 1.227 0.0426 1.083 24.00 10.18 0.551 14.00 35/64
18 0.7087 10.2 0.0984 2.50 0.5879 14.932 0.0604 1.534 0.0533 1.353 27.00 0.6102 15.50 39/64
20 0.7874 10.2 0.0984 2.50 0.6666 16.932 0.0604 1.534 0.0533 1.353 30.00 13.22 0.6889 17.50 11/16
22 0.8661 10.2 0.0984 2.50 0.7453 18.932 0.0604 1.534 0.0533 1.353 32.00 0.7677 19.50 49/64
24 0.945 8.5 0.1181 3.00 0.8002 20.320 0.0724 1.840 0.0640 1.624 36.00 15.22 0.8267 21.00 53/64
26 1.024 8.5 0.1181 3.00 0.8792 22.32 0.0724 1.840 0.0640 1.624 0.9055 23.00 29/32
27 1.063 8.5 0.1181 3.00 0.9182 23.320 0.0724 1.840 0.0640 1.624 41.00 0.9448 24.00 15/16
28 1.102 8.5 0.1181 3.00 0.9572 24.320 0.0724 1.840 0.0640 1.624 0.9920 25.2 63/64
30 1.181 7.3 0.1378 3.50 1.0120 25.706 0.0845 2.147 0.0781 1.894 46.00 19.26 1.0430 26.50 1-3/64
32 1.299 7.3 0.1378 3.50 1.1300 28.706 0.0845 2.147 0.0781 1.894 50.00 1.1614 29.50 1-5/32
33 1.299 7.3 0.1378 3.50 1.1300 28.706 0.0845 2.147 0.0781 1.894 50.00 1.1614 29.50 1-5/32
34 1.339 7.3 0.1378 3.50 1.1700 29.71 0.0845 2.147 0.0781 1.894 1.210 30.70 1-13/
64
36 1.417 6.4 0.1575 4.00 1.2238 31.093 0.0966 2.454 0.0852 2.165 55.00 23.26 1.260 32.00 1-1/4
38 1.496 6.4 0.1575 4.00 1.3028 33.092 0.0966 2.454 0.0852 2.165 1.377 35.00 1-11/32
39 1.535 6.4 0.1575 4.00 1.3418 34.093 0.0966 2.454 0.0852 2.165 60.00 1.377 35.00 1-3/8
40 1.575 6.4 0.1575 4.00 1.3818 35.100 0.0966 2.454 0.0852 2.165 1.4252 36.20 1-29/
64
42 1.654 5.6 0.1772 4.50 1.4366 36.480 0.1087 2.760 0.959 2.436 1.4252 36.20 1-15/32
44 1.732 5.6 0.1772 4.50 1.5146 38.48 0.1087 2.760 0.959 2.436 1.551 39.4 1-35/
64
45 1.772 5.6 0.1772 4.50 1.5546 39.480 0.1087 2.760 0.0959 2.436 1.594 40.50 1-19/
32
46 1.811 5.6 0.1772 4.50 1.5936 40.48 0.1087 2.760 0.0959 2.435 1.653 42.00 1-21/
32
48 1.890 5.1 0.1968 5.00 1.6486 41.866 0.1207 3.067 0.1065 2.706 1.692 43.00 1-23/
32
50 1.969 5.1 0.1968 5.00 1.7276 43.870 0.1207 3.067 0.1065 2.706 1.772 45.00 1-25/
32
52 2.047 5.1 0.1968 5.00 1.8056 45.866 0.1207 3.067 1.1065 2.706 1.850 47.00 1-55/
64
56 2.205 4.6 0.2165 5.50 1.9394 49.252 0.1328 3.374 0.1172 2.0977 1.988 50.50 2-5/32
60 2.362 4.6 0.2165 5.50 2.0964 53.252 0.1328 3.374 0.1172 2.977 2.283 58.00 2-9/32
64 2.677 4.2 0.2362 6.00 2.3872 60.638 0.1449 3.681 0.1279 3.248 2.283 58.00 2-9/32
68 2.677 4.2 0.2362 6.00 2.3872 60.638 0.1449 3.681 0.1279 3.248 2.441 62.00 2-19/32
72 2.835 4.2 0.2362 6.00 2.5452 64.64 0.1449 3.681 0.1279 3.248 2.598 66.00 2-19/32
76 2.992 4.2 0.2362 6.00 2.7022 68.640 0.1449 3.681 0.1279 3.248 2.756 70.00 2-3/4
80 3.150 4.2 0.2362 6.00 2.8602 72.64 0.1449 3.681 0.1279 3.248 2.933 79.00 3-7/64
85 3.346 4.2 0.2362 6.00 3.0562 77.640 0.1449 3.681 0.1279 3.248 3.110 79.00 3-5/16
90 3.543 4.2 0.2362 6.00 3.2532 82.64 0.1449 3.681 0.1279 3.248 3.504 84.00 3-1/2
95 3.740 4.2 0.2362 6.00 3.4502 87.64 0.1449 3.681 0.1279 3.248 3.504 89.00 3-1/2
100 3.937 4.2 0.2362 6.00 3.6472 92.64 0.1449 3.681 0.1279 3.248 3.700 94.00 3-1/2

74 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.66 & 2.3.67

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 Standard Table
Size
= Bore A B C E

Threads
per inch
dia. of
pipe

in in in in in
1/8 15/32 0.383 0.0230 3/8
1/4 17/32 0.518 0.0335 19 7/16
3/8 11/16 0.656 0.0335 19 1/2
1/2 27/32 0.825 0.0455 14 5/8
3/4 1 1/16 1.041 0.0455 14 3/4
1 1 11/32 1.309 0.0580 11 7/8
Pipe thread
1 1/4 1 11/16 1.650 0.0580 11 1
The Standard table given here helps to identify the diameter 1 1/2 1 29/32 1.882 0.0580 11 1
of the pipes from 1/8" to 10", and corresponding outer
diameter of pipes, depth of threads and threads per 2 2 3/8 2.347 0.0580 11 1 1/8
inch. 2 1/2 3 2.960 0.0580 11 1 1/4
The table also has reference to Fig 2. 3 3 1/2 3.460 0.0580 11 1 3/8
3 1/2 4 3.950 0.0580 11 1 1/2
4 4 1/2 4.450 0.0580 11 1 5/8
4 1/2 5 4.950 0.0580 11 1 5/8
5 5 1/2 5.450 0.0580 11 1 3/4
6 6 1/2 6.450 0.0580 11 2
7 7 1/2 7.450 0.0640 10 2 1/8
8 8 1/2 8.450 0.0640 10 2 1/4
9 9 1/2 9.450 0.0640 10 2 1/4
10 10 1/2 10.450 0.0640 10 2 3/8

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.66 & 2.3.67 75

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Production & Manufacturing
Turner - Thread cutting Related theory for Exercise 2.3.68

Calculation involving gear ratio & gearing

Objectives: At the end of this lesson you shall be able to
• calculate the core dia (minor dia) of thread
• state the methods of measuring core dia (minor dia) of thread.

Calculation of minor dia of thread (metric)

If the thread designation is M12 x 1.5 how much will be
minor dia of the thread
Formula minor dia = major dia - 2 depth
depth of the thread = 0.6134 x pitch of screw
2 depth of thread = 6.134 x 2 x pitch
= 1.226 x 1.5 mm
= 1.839 mm
= 8.161 mm or 8.2 mm
Minor dia (core dia) = 10mm - 1.839 mm
The measurement of the minor diameter and checking
the form of the thread are important for producing accurate
threads.

Checking the thread minor diameter

Use of the vernier caliper
The knife edge of a vernier caliper can be used for
measuring the minor diameter - within a reasonable
degree of accuracy.

Checking with the micrometer

Table 1 will help in determining the correct size of the
Two methods are adopted using the micrometers
prism for the different types and pitches of the threads.
Using Vee piece/prism For determining the minor diameter, first measure the
In this method the minor diameter is determined by using major diameter of the threaded piece.
a Vee piece/prism of known dimensions from the apex to Then measure by placing one prism in the thread as
the base. (Fig. 1 & 2) shown in Figure 3. It may be noted that one of the anvils
of the micrometer is on the prism and the other on the
Selection of the size of the prism is very important for
major diameter of the thread.
accurate measurement.
The sizes of the prisms are indicated by A, B, C and D. TABLE 1

Thread form
Prism
designat- Metric pitch Unified BSW BA No.
ing size threads
in mm inch
A 1.0-1.25 56-44 9-16
B 1.5-2.25 40-28 3-8
C 2.5-4.5 26-14 0-2
D 5.0-6.0 12-4

76

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Using special micrometers
A special micrometer which can accommodate specially
shaped anvils is used for this. This directly measures the
minor diameter. It is important to ensure that the micrometer
is placed perpendicular to the axis of the thread being
measured (Fig 4) for accurate measurement.

Measuring minor diameter of internal threads

The knife edge of a vernier caliper can be used to
measure the minor diameter of an internal thread. This
cannot be adopted when very accurate measurements are
to be taken. (Fig 5)

Using slip gauges and precision rollers

While using slip gauges and precision rollers of known
Direct accurate measurement of internal minor diameter diameter, the rollers are first placed diametrically opposite
is a difficult task. the bore.
The commonly used methods are by using slip gauges Then the slip gauge pack is selected until it just slides
and precision rollers (Figs6&7) and taper parallels and between the rollers.
micrometer. The sum of the size of the slip gauge pack and the
diameters of the rollers is the minor diameter.
Using taper parallels
Precision tapered parallels can be inserted as shown in
Figure 8 and the measurement can be taken using a
micrometer.

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.68 77

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Production & Manufacturing
Turner - Thread cutting Related theory for Exercise 2.3.69

Screw thread micrometer and its uses

Objectives : At the end of this lesson you shall be able to
• state the features of a screw thread micrometer
• state the features of the three-wire system of measurement with the help of tables
• select the best wire with the help of tables for using in the three-wire method.

The screw thread micrometer

This micrometer (Fig 1) is used to measure the effective
diameter of the screw threads. This is very similar to the
ordinary micrometer in construction but has facilities to
change the anvils.

The anvils are replaceable and are changed according to

the profile and pitch of the different systems of threads.
(Figs 2 & 3)

The three-wire method

This method uses three wires of the same diameter for
checking the effective diameter and the flank form. The
wires are finished with a high degree of accuracy.
The size of the wires used depends on the pitch of the
thread to be measured.
For measuring the effective diameter the three wires
suitable for the thread pitch are placed between the
While measuring the screw thread, the holder with one
threads. (Fig 4)
wire is placed on the spindle of the micrometer and the
The measuring wires are fitted in wire-holders which are other holder with two wires is fixed on the fixed anvil.
supplied in pairs. One holder has provisions to fix one wire (Fig.6)
and the other for two wires. (Fig 5)
78

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 Selection of 'best wire' (Fig 7)
The best wire is the one which, when placed in the
thread groove, will make contact at the nearest to the
effective diameter. The selection of the wire is based on
the type of thread and pitch to be measured.
The selection of the wire can be calculated and deter-
mined but readymade charts are available from which the
selection can be made.

TABLE 1

Measurement with measuring wires. Metric

threads with coarse pitch (M)

Thread Pitch Basic Measuring Dimension

designa- measu- wire dia. over wire
tion rement mean
P d2 W1 M1
TABLE 2
mm mm mm mm
Measurement with measuring wires. Metric
M1 0.25 0.838 0.15 1.072 threads with fine pitch (M)
M 1.2 0.25 1.038 0.15 1.272 Thread Basic Measuring
M 1.4 0.3 1.205 0.17 1.456 Dimension
M 1.6 0.35 1.373 0.2 1.671 designa- measure- wire dia. over wire
tion ment mean
M 1.8 0.35 1.573 0.2 1.870
M2 0.4 1.740 0.22 2.055 d2 W1 M1
mm mm mm
M 2.2 0.45 1.908 0.25 2.270
M 2.5 0.45 2.208 0.25 2.569 M 1 x 0.2 0.870 0.12 1.057
M3 0.5 2.675 0.3 3.143 M 1.2 x 0.2 1.070 0.12 1.257
M 3.5 0.6 3.110 0.35 3.642 M 1.6 x 0.2 1.470 0.12 1.557
M4 0.7 3.545 0.4 4.140 M 2 x 0.25 1.838 0.15 2.072
M 4.5 0.75 4.013 0.45 4.715 M 2.5 x 0.35 2.273 0.2 2.570
M5 0.8 4.480 0.45 5.139 M 3 x 0.35 2.773 0.2 3.070
M6 1 5.350 0.6 6.285 M 4 x 0.5 3.675 0.3 4.142
M8 1.25 7.188 0.7 8.207 M 5 x 0.5 4.675 0.3 5.142
M 6 x 0.75 5.513 0.45 6.214
M 10 1.5 9.026 0.85 10.279
M 12 1.75 10.863 1.0 12.350 M 8 x1 7.350 0.6 8.285
M 10 x 1.25 9.188 0.7 10.207
M 14 2 12.701 1.15 14.421
M 12 x 1.25 11.188 0.7 12.206
M 16 2 14.701 1.15 16.420
M 14 x 1.5 13.026 0.85 14.278
M 18 2.5 16.376 1.45 18.564
M 16 x 1.5 13.026 0.85 14.278
M 20 2.5 18.376 1.45 20.563 M 18 x 1.5 17.026 0.85 18.277
M 22 2.5 20.376 1.45 22.563
M 20 x 1.5 19.026 0.85 20.277
M 24 3 22.051 1.75 24.706 M 22 x 1.5 21.026 0.85 22.277
M 27 3 25.051 1.75 27.705 M 24 x2 22.701 1.15 24.420
M 30 3.5 27.727 2.05 30.848 M 27 x2 25.701 1.15 27.420
M 30 x2 28.701 1.15 30.419

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.69 79

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 TABLE 3 TABLE 4

Measurement with measuring wires. Unified Measurement with measuring wires. Unified
fine threads (UNF) coarse threads (UNC)

Thread Pitch Basic Measuring Dimen- Thread Pitch Basic Measuring Dimen
designa- measu- wire dia. sion over designa- measu- wire dia. sionover
tion rement mean wire tion rement mean wire
d2 W1 M1
d2 W1 M1
mm mm mm mm
mm mm mm mm
Nr 1-64 UNC 0.397 1.596 0.22 1.913
Nr 0-80 UNC 0.317 1.318 0.2 1.644 Nr 2-56 UNC 0.454 2.25 2.249
Nr 0-72 UNC 0.353 6.25 0.2 1.920 Nr 3-48 UNC 0.529 2.171 0.3 2.614
Nr 2-64 UNF 0.397 1.927 0.25 2.334
Nr 4-40 UNC 0.635 2.433 0.35 2.935
Nr 3-56 UNF 0.454 2.220 0.25 2.578 Nr 5-40 UNC 0.635 2.763 0.35 2.265
Nr 4-48 UNF 0.529 2.501 0.3 2.944 Nr 6-32 UNC 0.794 2.990 0.45 3.654
Nr 5-44 UNF 0.577 2.800 0.35 3.351
Nr 8-32 UNC 0.794 3.650 0.45 4.314
Nr 6-40 UNF 0.635 3.093 0.35 3.594 Nr 10-24 UNC 1.058 4.139 0.6 5.026
Nr 8-36 UNF 0.706 3.708 0.4 4.298 Nr 12-24 UNC 1.058 4.799 0.6 5.685
Nr10-32 UNF 0.794 4.310 0.45 4.974
1/4"-20 UNC 1.27 5.524 0.7 6.527
Nr 12-28 UNF 0.907 4.897 0.5 5.612 5/16"-18UNC 1.411 7.021 0.85 8.352
1/4"-28 UNF 0.907 5.761 0.5 6.477 3/8"-16 UNC 1.587 8.494 0.9 9.822
5/16"-28 UNF 1.058 7.249 0.6 8.134
1/2"-13 UNC 1.954 11.430 1.15 13.191
3/8"-24 UNF 1.058 8.837 0.6 9.721 5/8"-11 UNC 2.309 14.376 1.3 16.279
1/2"-20 UNF 1.27 11.875 0.7 12.876 3/4"-11 UNC 2.540 17.399 1.45 19.552
5/8"-18 UNF 1.411 14.958 0.85 16.287
7/8"-9 UNC 2.822 20.391 1.6 22.750
3/4"-16 UNF 1.588 18.019 0.9 19.345 1" -8 UNC 3.175 23.338 1.8 25.991
7/8"-14 UNF 1.814 21.046 1.0 22.476 1 1/4"-7 UNC 3.629 29.393 2.05 32.403
1" -12 UNF 2.117 24.026 1.3 26.094
1 1/2"-6 UNC 4.233 35.349 2.4 38.885
1 3/4"-5 UNC 5.08 41.151 3 45.755
2"–4 1/2 UNC 5.644 47.135 3.5 52.751

80 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.69

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Production & Manufacturing
Turner - Thread cutting Related theory for Exercise 2.3.70

Calculation involving gear ratio metric thread cutting on inch lead screw
lathe and vice versa
Objectives : At the end of this lesson you shall be able to
• state the formula of the gear ratio for cutting metric thread on a British lathe
• state the formula of the gear ratio for cutting British thread on a metric lathe
• solve the problems involving cutting metric thread on British lathe and vice versa.

Gear ratio for cutting metric thread on British lathe DR 1 1 127

= x x
The formula of the gear ratio for cutting metric thread on a
DN T.P.I. to be cut Lead of lead screw 5
metric lathe is
As a practice, it is advisable to have a larger wheel as a
Driver Lead to be cut on the job driven gear as far as possible. But in this case the 127
= teeth wheel has to be used as a DRIVER only.
Driven Lead of lead screw
Gear ratio for cutting metric thread on British lathe
Now, for cutting metric thread on a British lathe, the lead using 63 teeth as driver wheel.
of the work to be cut in mm is converted to inches by 5
multiplying with the constant 5/127. Instead of taking the constant
127
Because 25.4 mm = l"
63
1 mm = 1/25.4" is taken because 1 metre = 39.37".
= 10/254 1600
1 metre
= 39.375" (approx.)
= 5/127" 3”
Therefore, 1000 mm = 39.375" = 39
8
Gear ratio 315
DR Lead to be cut in mm on job x 1 x 5 1 mm =
= 1000 x 8
DN Lead of L.S. x 127 63
=
DR Lead to be cut in mm x T.P.I. on L.S. x 5 1600
= Gear ratio
DN 127 DR Lead to be cut in mm x TPI on LS x 63
A translating gear of 127 teeth is provided for cutting met- =
ric thread on a British lathe. This gear wheel is used as DN 1600
the driven wheel. The worked out example illustrates this Gear ratio for cutting British thread on metric lathe using
statement. the 63 teeth wheel as the driven wheel:

Gear ratio for cutting British thread on metric lathe DR 1 1 1600

= x x
The general formula for cutting British thread on a British DN T.P.I. to be cut Lead of lead 63
lathe is screw in mm
DR Lead to be cut on job
Lathe constant
DN Lead of lead screw
Lathe constant is the number of threads per inch that can
Now for cutting British thread on a metric lathe the lead of be cut when the change gear ratio is 1 and the ratio be-
the screw in mm is converted into inches by multiplying tween the main spindle gear and the fixed stud gear is
with a constant of 5/127. also 1.
DR Lead to be cut in inch on job On some machines the ratio of the spindle gear to the
DN lead of lead screw in mm x 5 fixed stud gear is more than 1 in which case the lathe
127 constant is equal to:
DR Lead to be cut in inch on job x 1 x 127 spindle gear x T.P.l on lead screw
DN Lead of lead screw in mm x 5
fixed stud gear
When lathe constant is given 81

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(Gear ratio for DR Lathe constant DR 5 x Lead of work
cutting thread) = Gear ratio = =
DN T.P.I. to be cut DN 127 x Lead of lead screw
5 3
Find the gears required to cut 4.5 mm pitch in a lathe
= x
having a lead screw of 6 T.P.l. Gears available from 20 to
127 1/6
120 teeth by 5 teeth range with a conversion gear of 127
teeth. 5 3x6
= x
DATA
127 1
Lead of work = 4.5 mm
90
T.P.l of L/s = 6 T.P.l =
127
1 90 teeth gear is driver.
Lead of L/s = 127 teeth gear is driven.
T.P.I.
1 Problems involving cutting British threads on metric
Lead of L/s = lathe
6 Find the gears required to cut 6 T.P.l on job in a lathe
DR 5 Lead of work having a lead screw of 6 mm pitch.
Gear ratio = = x Gears available from-20 T to 120 by 5 teeth range with a
DN 127 Lead of lead screw special gear of 127 teeth.
5 4.5 DATA
= x
127 1/6 Lead of work = 1/6"
5 x 6 x 4.5 Lead of L/s = 6 mm
= DR 127 Lead of work
127 x 1 Gear ratio = = x
Now it is not possible to have a change gear train with a DN 5 Lead of L/s.
simple gear train. So a compound gear train is used, 127 1/6
30 4.5 = x
i.e. x 5 6
127 1 127 1
30 45 = x
x 5 6x6
127 10 127 1
45 x (30 x 2) 45 60 = x
= x 30 6
127 x (10 x 2) 127 20 127 (1 x 20)
45 T & 60 T are drivers. = x
30 (6 x 20)
127 T & 20 T are driven.
127 20
Problems involving cutting metric threads on British = x
lathe and vice versa 30 120
Find the gears required to cut a 3 mm pitch in a lathe
127 T & 20 T are driver gears.
having a lead screw of 6 T.P.l. Gears available from 20 to
120 teeth by 5 teeth with a special gear of 127 teeth.
30 T & 120 T are driven gears.
DATA
Lead of work = 3 mm
T.P.l on L/s = 6 T.P.l

1
Lead of L/s =
6

82 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.70

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Production & Manufacturing
Turner - Thread cutting Related Theory for Exercise 2.3.71

Tool Life negative top rake

Objectives: At the end of this lesson you shall be able to
• state the relationship between cutting speed and tool life
• explain tool life index equation
• determine the maximum cutting speed for a given tool life.

Relationship between cutting speed and tool life

Duration of correct cutting to the anticipated surface finish
between grinding is termed as tool life. In metal cutting,
increase in cutting speed increases power requirement.
Therefore, the mechanical energy is converted into heat
energy at the cutting edge. Much of the heat is absorbed
by the cutting tool with corresponding increase in
temperature, resulting in softening of the cutting tool,
which is the reason for inefficient cutting action. The
effect of this reduction in tool life is largely present in high
carbon steels. Hence, they have to be operated at lower
cutting speeds.
Cutting materials such as high speed steel, metallic
carbides and oxides can operate at much higher
temperatures without reduction in hardness.
Fig 1 shows graphically the relationship between cutting
speed and tool life curve in logarithmic form. A small
increase in cutting speed from A to B causes large
reduction in tool life from C to D, while small reduction in Vt n = C
cutting speed causes a large increase in tool life. where V = cutting speed in m/min.
Thus when the machine gearbox does not give the required t = tool life in minutes
cutting speed, it is better to use the next lower speed
rather than the higher speed. n and C are constants for a given set of conditions.
Tool life index The value of n lies between 0.1 to 0.2 and typical values
are given in the following table.
The relationship between tool life and cutting speed can
be represented by the following equation for most practical
purposes.
Table
Tool life index

Material and conditions Tool material n

3 1/2% nickel steel Cemented carbide 0.2

3 1/2% nickel steel (roughing) Highspeed steel 0.14
3 1/2% nickel steel (finishing) Highspeed steel 0.125
High carbon, high chromium die steel Cemented carbide 0.15
High carbon steel Highspeed steel 0.2
Medium carbon steel High-peed steel 0.15
Mild steel Highspeed steel 0.125
Cast iron Cemented carbide 0.1

83

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The following example is shown to determine the maxi- From the calculations, tool life is doubled by reduction of
mum cutting speed for a given tool LIFE. cutting speed by 8.3 percent, or reduction of tool life can
be calculated for an increase of 8.3 percent in cutting
Example speed. Hence, it is always important to select a lower
The life of a lathe tool is 8 hours when operating at a cutting speed, rather than a higher cutting speed, if the
cutting speed of 40 m/min. Given that Vtn = C, find the machine controls do not give optimum value.
highest cutting speed that will give a tool life of 16 hours. Tool life calculations are useful in achieving optimum op-
The value of n is 0.125. erating conditions of cutting tools. Modern cutting tool
(i) Determine the value of Log C from initial conditions. materials are singularly resistant to softening under the
heat of normal cutting and usually fail in two ways as
C = Vt1n where shown in Fig 2.
V = 40 m/min.
t1 = 480 min.
n = 0.125
Log C = Log V + n Log t1
= log40 + (0.125 Log480)
=1.6021 + (0.125 x 2.681)
=1.6021 + 0.3351
=1.9372
(ii) Determine Vmax for revised conditions

C
Vmax =t n
2

Where t2 = 960 min.

Log Vmax = Log C – n Log t2
= 1.9372 – (0.125 x log960) a) Wear of clearance face
= 1.9372 – (0.125 x 2.9823) b) Crater of rake face
= 1.9372 – 0.3728 The above conditions can be corrected only by regrinding
= 1.5644 immediately for effective metal cutting.

Vmax = 36.68 m/min.

84 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.71

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Production & Manufacturing
Turner - Other form thread Related Theory for Exercise: 2.4.72 - 76

Calculation involving tooth thickness, core dia, depth of cut of square thread
Objectives : At the end of this lesson you shall be able to
• calculate the heleix angles of square tool
• brief the clearance angle in squrae threading tool
• read a standard thread chart.

Square threads were often found in vise screws, jacks, To calculate the helix angles of the leading and fol-
and other devices where maximum power transmission lowing sides of a square thread
was required. Because of the difficulty of cutting this thread
with taps and dies, it is being replaced by Acme thread. lead of thread
With care, square threads can be readily cut on a lathe. Tan loading angle =
circumference of minor diameter
The shape of a square threading tool
The square threading tool looks like a short cutting - off lead of thread
Tan following angle =
tool. It differs from it in that both sides of the square thread- circumfere nce of major diameter
ing tool must be ground at an angle to conform to the
helix angle of the thread (Fig.1) Clearance

The helix angle of a thread, and therefore the angle of the

square threading tool, depends on two factors: If a square tool bit is ground to the same helix angles as
the leading and following sides of the thread, it would
1 The helix angle changes for each different lead on a have no clearance and the sides would rub. To prevent
given diameter. The greater the lead of the thread, the the tool the tool from rubbing, it must be provided with
greater will be the helix angle. approximately 1o clearance on each side, making it thin-
2 The helix angle changes for each different diameter of ner at the bottom (Fig. 2). For the leading side of the tool,
thread for a given lead. The larger the diameter, the add 1o to the calculated helix angle. On the following side,
smaller will be the helix angle. subtract 1o from the calculated angle.

The helix angle of either the leading or following side of a Example

square thread can be represented by a right-angle tri- To find the leading and following angles of a threading tool
angle (Fig. 1). The side opposite equals the lead of the to cut a 11/4 in - square thread.
thread, and the side adjacent equals the circumference
of either the major or minor diameter of the thread. The Solution
angle between the hypotenuse and the side adjacent rep- To cut a square thread
resent the helix angle of the thread.
- Grind a threading tool to the proper leading and follow-
ing angles. The width of the tool should be approxi-
mately 0.002 in. (0.05mm) wider than the thread
groove. This will allow the completed screw to fit the
85

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 nut readily. Depending on the size of the thread, it - Calculate the single depth of the thread as
may be wise to grind two tools; a roughing tool 0.015in.
(0.38mm) undersize, and a finishing tool 0.002 in. (0.500 )
(0.05mm) oversize. N
- Start the lathe and just touch the tool to the work di-
Lead = 0.250 in ameter.
0.500 - Set the cross feed graduated collar to zero (0)
single depth =
4 - Set a 0.003 - in. (0.08mm) depth of cut with the cross
= 0.125 in feed screw and take a trial cut.
Double depth = 2x0.125 - Check the thread with a thread pitch gage.
= 0.250 in - Apply cutting fluid and cut the thread to depth, moving
the crossfeed in from 0.002 to 0.010 in. (0.05 to
Minor diameter
= 1.250 − 0.250
0.25mm) for each cut. The depth of the cut will de-
= 1.000 in pend on the thread size and the nature of the
workpiece.
lead
Tan leading angle =
minor dia. circumfere nce Since the thread sides are square, all cuts must
be set using the crossfeed screw.
0.250
=
1.000 x π Standard threads
0.250 Standards of threads describe pitch core diameter and
= =
0.0795 in. major diameter. The standard threads can be cut in stan-
3.1416
dard machine tools with standard cutters and designer
o ' can use them for calculation of sizes and ensure inter-
∴ the angle of the thread = 4 33
changeability. We will see in illustrated examples how
o o
The toolbit angle = 4 33' plus 1 clearance the standards are used by designer. Presently we de-
scribe Indian standard IS 4694-1968 for square threads in
o '
= 5 33 which a thread is identified by its nominal diameter which
lead
Tan following angle = Table 1 : Basic Dimensions of Square Thread, (mm)
major dia. circumfere nce
0.250 0.250 Pitch, p 5
= = 0.0636 in
=
1.250 π 3.927 Core Dia. d1 17 19 24 23
o ' Major Dia. d 22 24 29 28
∴ the angle of the thread = 3 38
o ' o Pitch, p 6
The toolbit angle = 3 38 - 1 clearance
Core dia. d1 24 26 28 30
o
= 2 38' Major dia. d 30 32 34 36
- Align the lathe centers and mount the work. Pitch p 7
- Set the quick change gearbox for the required number Core dia. d1 31 33 35 37
of tpi.
Major dia. d 38 40 42 44
- Set the compound rest at 30o to the right. This will
provide side movement if it becomes necessary to re- Pitch, p 8
set the cutting tool. Core dia. d1 38 40 42 44
- Set the threading tool square tool square with the work Major dia. d 46 48 50 56
and on center.
Pitch, p 9
- Cut the right - hand end of the work to the minor diam-
Core dia. d1, 46 49 51 53
eter for approximately 1/16 in. (1.58mm) long. This
will indicate when the thread is cut to the full depth. Major dia. d 55 58 60 62
- If the work permits, cut a recess at the end of the Pitch, p 10
thread to the minor diameter. This will provide room for
Core dia. d1 55 58 60 62 65 68 70 72
the cutting tool to "run out" at the end of the thread.
Major dia. d 65 68 70 72 75 78 80 82

86 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.72 - 76

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is also the major diameter. According to standard the mm between the outer surface of screw and inner surface
major diameter of nut is 0.5 mm greater then major diam- of nut thread. The basic dimensions of square threads
eter of the screw which will provide a clearance of 0.25 are described in Table 1.

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Production & Manufacturing
Turner - Other form thread Related theory for Exercise 2.4.77 - 79

Calculation involves - depth,core dia, Pitch proportion etc of ACME thread

& Buttress thread
Objectives : At the end of this lesson you shall be able to
• claculation of ACME thread angle
• brief the clearance angle in threading tool
• read a standard thread chart.

ACME Thread Detail For 36X6

This thread is a modification of the square thread. It has This dimensions ac, R1, R2, H, H3 & h3 are changed as
an included angle of 29°. It is preferred for many jobs per pitch for detail see I.S 7008 (Part I,II, III pic)
because it is fairly easy to machine. Acme threads are
ac = 0.5 d = 33 h = 3.5
used in lathe lead screws. This form of thread enables 2 3
the easy engagement of the half nut. The metric acme R = 0.25 d = 29 D = 37
1 3 4
thread has an included angle of 30°. The relationship
R = 0.5 H = 3 D = 33
between the pitch and the various elements is shown in 2 1 2

the figure. dNom = 0.25 H = 3.5 D = 30

3 1

Acme thread (Fig 1) Buttress thread (Fig 2)

The flanks have different angles.One of the flanks have

an angle of 7º with respect to a line perpendicular to the
axis. This flank can take heavy loads and is called the
“pressure flank” of the thread. The other flank has an angle
of 45º.
They are used where great pressures are to be applied in
one direction only.
They are not used for translation motions.

Threads of buttress form

The buttress form of thread has certain advantages in Fig. 1a shows a common form. The front or load-resisting
applications involving exceptionally high stresses along face is perpendicular to the axis of the screw and the
the thread axis in one direction only. The contacting flank thread angle is 45 degrees. According to one rule, the
of the thread, which takes the thrust, is referred to as the pitch P=2 x screw diameter ÷ 15. The thread depth d may
pressure flank and is so nearly perpenticular to the thread equal 3/4 x pitch, making the flat f=1/8 x pitch. Sometimes
axis that the radial component of the thrust is reduced to depth d is reduced to 2/3 x pitch, making f=1/6 x pitch.
a minimum. Because of the small radial thrust, this form
The load - resisting side or flank may be inclined an
of thread is particularly applicable where tubular members
amount ranging usually from 1 to 5 degrees to avoid cutter
are screwed together, as in the case of breech mechanisms
interference in milling the thread. With an angle of 5
of larger guns and airplane propeller hubs.
degrees and an included thread angle of 50 degrees, if the
88

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width of the flat f at both crest and root equals 1/8 x pitch, the “Fillettatura a dente di Sega. “Pitches are standardized
then the thread depth equals 0.69 x pitch or 3/4 d1. from 2 millimeters up to 48 millimeters in the german and
Italian specifications. The front face inclines 3 degrees
The saw - tooth form of thread illustrated by Fig. 1c is
from the perpendicular and the included angle is 33
known in Germany as the “Sagengewinde” and in Italy as
degrees.

The thread depth d for the screw =0.86777 x pitch P. The British Standard Buttress Threads BS 1657:1950 -
thread depth g for the nut=0.75 x pitch. Dimension Specificiations for buttress threads in this standard are
h=0.341 x P. The width of flat at the crest of the thread on similar to those in the American Standard except: 1) A
the screw =0.26384 x pitch. Radius r at the root = 0.12427 basic depth of thread of 0.4p is used instead of 0.6p; 2)
x pitch. The clearance space e=0.11777 x pitch. Sizes below 1 inch are not included; 3) Tolerances on

Table 1 Dimensions of basic profile

All dimensions in millimeters

Pitch P H H/2 H1 w
1.587 8 P 0.793 9 0.75 P 0.263 84 P
(1) (2) (3) (4) (5)
2 3.175 6 1.587 8 1.50 0.527 68
3 4.763 4 2.381 7 2.25 0.791 52
4 6.351 2 3.175 6 3.00 1.055 36

5 7.939 0 3.969 5 3.75 1.319 20

6 9.526 8 4.763 4 4.50 1.583 04
7 11.114 6 5.557 3 5.25 1.846 880

8 12.7024 6.351 2 6.00 2.110 72

9 14.290 2 7.145 1 6.75 2.374 56
10 15.878 0 7.939 0 7.50 2.638 40

12 19.053 6 9.526 8 9.00 3.166 08

14 22.229 2 11.114 6 10.50 3.693 76
16 26.404 8 12.702 4 12.00 4.221 44

18 28.580 4 14.290 2 13.50 4.749 12

20 31.756 0 15.878 0 15.00 5.276 80
22 34.931 6 17.465 8 16.50 5.804 48

24 38.107 2 19.053 6 18.00 6.332 16

28 44.458 4 22.229 2 21.00 7.387 52
32 50.809 6 25.404 8 24.00 8.442 88

36 57.160 8 28.580 4 27.00 9.498 24

40 63.512 0 31.756 0 30.00 10.553 60
44 69.863 2 34.931 6 33.00 11.608 96

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major and minor diameters are the smae as the pitch x the pitch. The screw thread used for measuring
diameter tolerances, whereas in the American Standard instruments, optical apparatus, etc., especially in
separate tolerances are provided; how ever, provision is Germany.
made for smaller major and minor diameter tolerances
The minor diameter clearance and the clearance between
when crest surfaces of screws or nuts are used as datum
the non-stressed thread flank and the fundamental devia-
surfaces, or when the resulting reduction in depth of
tions of the pitch diameter of the stressed thread flank
engagement must be limited; and 4) Certain combinations
are related to these basic sizes.
of large diameters with fine pitches are provided that are
not encouraged in the American Standard. Nominal profiles
Lowenherz or lowenherz thread The nominal profiles to which the deviations and toler-
ances are related have specified clearances on the minor
The lowenherz thread is intended for the fine screws of
diameter and between the non-load bearing thread flanks,
instruments and is based on the metric system. The
relative to the basic profile.
lowenherz thread has flats at the top and bottom the same
as the U.S. standard buttress form, but the angle is 53 The numerical threads data associated with the nominal
degrees 8 minutes. The depth equals 0.75 x the pitch, and profile is given in Table 2.
the width of the flats at the top and bottom is equal to 0.125

Table 2 Basic numerical threads data for nominal profile

All dimensions in millimeters

Pitch P ae a e h3 R
0.117 77 P 0.1 P 0.263 84 P- 0.867 77 P 0.124 27

0.1 P
(1) (2) (3) (4) (5) (6)
2 0.236 0.141 4 0.386 1.736 0.249
3 0.353 0.173 2 0.618 2.603 0.373
4 0.471 0.2 0.855 3.471 0.497
5 0.589 0.223 6 1.096 4.339 0.621
6 0.707 0.244 9 1.338 5.207 0.746
7 0.824 0.264 6 1.582 6.074 0.870

8 0.942 0.282 8 1.828 6.942 0.994

9 1.060 0.3 2.075 7.810 1.118
10 1.178 0.316 2 2.322 8.678 1.243

12 1.413 0.346 4 2.820 10.413 1.491

14 1.649 0.374 2 3.320 12.149 1.740
16 1.884 0.4 3.821 13.884 1.988

18 2.120 0.424 3 4.325 15.620 2.237

20 2.355 0.447 2 4.830 17.355 2.485
22 2.591 0.469 0 5.335 19.091 2.734

24 2.826 0.489 9 5.842 20.826 2.982

28 3.298 0.529 2 6.858 24.298 3.480
32 3.769 0.565 7 7.877 27.769 3.977

36 4.240 0.6 8.898 31.240 4.474

40 4.711 0.632 5 9.921 34.711 4.971
44 5.182 0.663 3 10.946 38.182 5.468

Profiles of threads with clearance on the flank h3=H1+ac=0.867 77 P

The formulae associated with the dimensions indicated
in Fig. 2 and Fig. 3 are given below: a = 0.1 P (axial play)
H1=0.75P ac=0.117 77P

90 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.77 - 79

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w=0.263 84 P S=0.314 9 Ao
Where
e = 0.263 84 P - 0.1=
P w −a
Ao=fundamental deviation (upper deviation) for external
R=0.124 27P thread on the pitch diameter.
D1=d-2H1 = d-1.5P Profile for multiple -start threads
d3=d-2h3 The profile for multiple start threads is given in Fig. 4.
d2=d-0.75P Ph=lead (axial advance at one turn), and
d1=d-0.75P +3.175 8a P=pitch (axial distance between two neighboring flanks
being in the same direction).
The profiles for external and internal threads with clearance
on the non-load bearing flank on the minor diameter but Multiple start (n-start) threads have the same profile as
with no clearance between the load bearing flanks or on single start threads with lead Ph=pitch P. For the pitch P
the major diameter (nominal size) is indicated in Fig.2. of multiple start threads, only the values permitted for the
lead P (which is equal to pitch P) of single start threads
The profile for external and internal threads with clearances
may be selected. However, the multiple of the pitch P of
on the minor diameter and on the flank (standard nut
multiple start threads need not correspond to the value
system) but with no clearance on the major diameter is
permitted for single start threads.
indicated in Fig. 3.

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92 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.77 - 79

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Production & Manufacturing
Turner - Other forms of thread Related theory for Exercise 2.4.80 - 82

Buttress thread cutting (male & female) & tool grinding

Objectives : At the end of this lesson you shall be able to
• grind buttress threading tool
• list the advantages of butters thread
• brief the thread proportion. .

Buttress thread (Fig 1)

In buttress thread one flank is perpendicular to the axis of

the thread and the other flank is at 45°. These threads are
used on the parts where pressure acts at one flank of the
thread during transmission. Figure 1 shows the various
elements of a buttress thread. These threads are used in
power press, carpentry vices, gun breeches, ratchets etc.

Buttress thread as per B.I.S. (Fig 2)

This is a modified form of the buttress thread. Figure 2

shows the various elements of the buttress thread. The
bearing flank is inclined by 7° as per B.I.S. and the other
flank has a 45° inclination.
The equations associated with the dimensions indicated
in the two figures (Figs 5 and 6) are given below.
Saw-tooth thread as per B.I.S. 4696
H1 = 0.75 P
This is a modified form of buttress thread. In this thread,
the flank taking the load is inclined at an angle of 3°, h3 = H1 + ac = 0.867 77 P
whereas the other flank is inclined at 30°. The basic profile
a = 0.1 Ö P (axial play)
of the thread illustrates this phenomenon. (Fig 3) The
proportionate values of the dimensions with respect to the ac = 0.117 77 P
pitch are shown in Figs 4 and 5. W = 0.263 84 P
93

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e = 0.263 84 P - 0.1 Ö P = W - a S = 0.314 99 Ao, where Ao = basic deviation (= upper
R = 0.124 27 P deviation) for external thread in the pitch diameter.

D1 = d - 2 H1 = d - 1.5 P Diagram of CNC machine indicating thread cutting

d3 = d - 2 h3 sequences

d2 = D2 = d - 0.75 P The sequence of thread cuttinng in CNC is explained in

below

94 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.80 - 83

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Internal Threading

Buttress internal thread cutting is more demanding their Flank clearance

external threading, due to threaded need to evacuate chips
The cutting edge clearance between the sides of the
effectively. Chip evacuations especially in blind hole, os
inserts and thread flank a figure indicating side clearance
helped by used left hand tools for R.H. thread and vice
and flank clearance is shown in the sketch.
versa (pull - threading) boring bar section has a strong
influance on the quality of internal threading. Three types Butters thread is designed to handle externally high axial
of bar can be used for internal threading. thread in one direction. The lead bearing thread face is
perpendicular to screw axis.
Boring type Max. overhang
Buttress thread often used in the construction of artilary
Steel 2-3 x dW particularly with screw type breech block. They are also
used in vices and in the form of pipe thread in oil fixed
Steel dampered 5 x dW tubring. This thread gives a tight hydraulic seal.
Carbide 5-7 x dW

dW = Borind bare dia

External threading can be produced in number of ways.
The spindle can rotate clock wose or anticlock wise, with
the tool fed towards or away from the chuck. The thread
turining tool can be used in normal or upside down position
(The later heeps in removal of clips). The internal and
external thread cutting are indicated in the following
sketches.
Important elements in tool grinding is the provision of flank
clearance and radial clearance for precise and accurate
threading.

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.80 - 83 95

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96

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 97

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Production & Manufacturing
Turner - Special jobs maintenance Related theory for Ex 2.5.83 & 84

Different lathe accessories - use and care

Objectives : At the end of this lesson you shall be able to
• identify and name the accessories used on a centre lathe.
• identify the accessories used for in-between centre work.
• name the types of lathe carriers.
• state the uses of each type of lathe carriers.

The lathe accessories are machined, independent units

supplied with the lathe. The accessories are essential for
the lull utilization of the lathe. The accessories can be
grouped into:
- work-holding accessories
- work-supporting accessories.
Work-holding accessories
The work can be directly mounted on these accessories
and held.
The accessories are :
- four jaw independent chuck (Fig 1)

• Lathe centres (Fig 7)

• Lathe carriers (Fig 8)
• Lathe fixed steady (Fig 9)
• Lathe travelling steady (Fig 10)

- three jaw self-centering chuck (Fig 2)

Accessories used for in-between centre work

- face plates (Fig 3)
The accessories used during turning work held in between
- lathe mandrels. (Fig 4) centres are as follows.
These accessories do not hold the work themselves. Live centre, Dead centre, Catch plate, Driving plate, Lathe
They support the work. The following are the work spindle sleeve and Lathe carriers.
sup-porting accessories.
• Catch plate (Fig 5)
• Driving plate (Fig 6)
98

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Lathe accessories - Lathe centres
Objectives : At the end of this lesson you shall be able to
• state what is a lathe centre
• distinguish between a live centre and a dead centre
• state the purpose of lathe centres
• identify and name the different types of centres
• indicate the specific uses of each type of centre.

Lathe centre overhanging end. When the job is held in between centres
to carry out the operation, it functions together with a
It is a lathe accessory. It is used to support a lengthy driving plate and a suitable lathe carrier.
work to carry out lathe operations. When a work is held
The centre, which is accommodated in the main spindle
in a chuck, the centre is assembled to the tailstock, and
sleeve, is known as a ‘live centre’ and the centre fixed in
it supports the overhanging end of the work. The work is
the tailstock spindle is known as a dead centre. In
to be provided with a centre drilled hole on the face of the
Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84 99

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construction, both centres are identical, made as one The dead centre is made out of high carbon steel, hardened
unit that consists of a conical point of 60° included angle, and around whereas the live centre need not have its
a body provided with a Morse taper shank and a tang. conical tip heardened as it revolves with the work. A good
lubricant should be used for the dead centre.

Types of centres and their uses

The following table gives the names of the most widely
used types of lathe centres, their illustrations and their
specific uses.

Various Types of Lathe Centres

1 Ordinary centre- Used for general purpose.

common type

Though it is termed as half cen-

tre, little less than half is reli-
2 Half centre eved at the tip portion. Used
while facing the job without
disturbing the setting.

A carbide or a hard alloy tip is

brazed into an ordinary steel
3 Tipped centre shank. The hard tip is wear-
resistant.

Minimum wear and strain.

4 Ball centre Particularly suitable for taper
turning.

Used for supporting pipes,

5 Pipe centre shells and hollow end jobs.

100 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84

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 Frictionless.
Used for supporting heavy jobs
and jobs revolving with high speeds.
6 Revolving A high-speed steel inserted centre
centre is supported by two bearings housed
in a body. It is also called the
revolving dead centre.

7 Insert-type Economical.
centre Only the small high-speed steel
insert is replaced.

Usually mounted on the head-

stock spindle. Used while
machining the entire length of
8 Self-driving the job in one setting. Grooves
live centre cut around the circumference of
the centre point provide for
good gripping of the job and for
getting the drive. This centre
can be used for only soft jobs
and not for hardened jobs.

9 Female centre the end of the job where no

countersink hole is permitted.

This centre is used to support a

job in the `V' portion and to
10 Swivel 'V' drill holes across the round job
centre by using a drill bit in the head-
stock spindle.

A micro-set adjustable centre fitted into the tailstock

spindle provides a fast and accurate method of aligning
lathe centres.(Fig 3)
Some of these centres contain an eccentric, others con-
tain a dovetail slide which permits slight adjustment of the
centre itself to correct alignment.

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84 101

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Types of mandrels and their uses
Objectives : At the end of this lesson you shall be able to
• define a mandrel
• state the constructional features of a solid mandrel
• identify and name the different types of mandrels
• enumerate the uses of different mandrels.

Types of mandrels and their uses Types of mandrels

• Expansion mandrel
Sometimes it is necessary to machine the outer surfaces
of cylindrical works accurately in relation to a hole concentric • Gang mandrel
that has been previously bored in the centre of the work.
• Stepped mandrel
In such cases the work is mounted on a device known as
a mandrel. • Screw or threaded mandrel
Mandrel (Fig 1) • Taper shank mandrel
Lathe mandrels are devices used to hold the job for • Cone mandrel
machining on lathes. They are mainly used for machining Expansion mandrel (Fig 3)
outside diameters with reference to bores which have
been duly finished by either reaming or boring on a lathe. The two most common types of expansion mandrels are:
- split bushing mandrel
- adjustable strip mandrel.

Constructional features of a solid mandrel (Fig 2)

The standard solid mandrel is generally made of tool steel
which has been hardened and ground to a specific size
and is ground with a taper of 1:2000.

Split bushing mandrel

A split bushing mandrel consists of a solid tapered
mandrel, and a split bushing, which expands when forced
on to the mandrel. The range of application of each solid
mandrel is greatly increased by fitting any number of
different sized bushings. As a result only a few mandrels
are required.
Adjustable strip mandrel
The adjustable strip mandrel consists of a cylindrical body
It is pressed or driven into a bored or reamed hole in a with four tapered grooves cut along its length, and a
workpiece so that it can be mounted on a lathe. The ends sleeve, which is slotted to correspond with the tapered
of the mandrel are machined smaller than the body and grooves. Four strips are fitted in the slots.
and are provided with a flat for the clamping screw of the
lathe carrier. This preserves accuracy and prevents damageWhen the body is driven in,the strips are forced out by the
to the mandrel when the lathe carrier is clamped on. tapering grooves and expanded radially. Sets of different
sized strips greatly increase the range of each mandrel.
The centres made in these mandrels are ‘B’ type i.e. This type of mandrel is not suitable for thin walled work,
protected centres. In such centres the working portion is since the force applied by the strips may distort the
deep and does not get damaged while handling. workpiece.
102 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84

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Gang mandrel (Fig 4)

A gang mandrel consists of a parallel body with a flange

at one end and a threaded portion at the other end. The
internal diameters of workpieces are larger than the
mandrel body diameters by not more than 0.025 mm. A
number of pieces can be mounted and held securely when Expansion stud mandrel
the nut is tightened against the ‘U’ washer. The nut should The expansion stud mandrel is slotted and has an internal
not be over-tightened, otherwise inaccuracies will result. thread. When a tapered screw is tightened, the outside
A gang mandrel is especially useful when machining diameter of the stud expands against the inside of the
operations have to be performed on a number of thin pieces workpiece. This type of mandrel is useful when machining
which might easily be distorted, if held by any other a number of similar parts whose internal diameters vary
method. slightly.

Stepped mandrel Threaded stud mandrel

The stepped mandrel is manufactured in order to reduce The threaded stud mandrel has a projecting portion which
the number of mandrels. It differs from the plain mandrel in is threaded to suit the internal thread of the work to be
the fact that a number of steps are provided on it. Its use machined. This type of mandrel is useful for holding
saves time in holding various bored works. workpieces which have blind holes.

Screw or threaded mandrel (Fig 5) Cone mandrel (Fig 7)

A threaded mandrel is used when it is necessary to hold

and machine workpieces having a threaded hole. A cone mandrel is a solid mandrel. It has a portion taper
turned with a steep taper and integral with the body. One
This mandrel has a threaded portion which corresponds to
end of the mandrel is threaded. A loose cone slides over
the internal thread of the work to be machined. An
the plain turned portion of the body of the mandrel. It has
undercut at the shoulders ensures the work to fit snugly
the same steep taper as that of the tapered integral part.
(tightly) against the flat shoulder.
A job of large bore, can be held between these two tapers
Taper shank mandrel (Fig 6) and tightly secured by means of nut, washer and spacing
Taper shank mandrels are not used between lathe centres. collars.
They are fitted to the internal taper of the headstock
spindle. The extending portion can be machined to suit the
workpiece to be turned. Taper shank mandrels are generally
used to hold small workpieces.
Two common types of taper shank mandrels are:
- expansion stud mandrel
- threaded stud mandrel.
Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84 103

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Chucks other than 3 Jaw and 4 Jaw types and their uses
Objectives : At the end of this lesson you shall be able to
• list the name of the chucks other than the 3 jaw and 4 jaw types
• state their constructional features
• state the uses of each of these chucks.

Apart from the four jaw independent chucks and self- There are three most commonly used types of collet
centering chucks, other types of chucks are also used chucks.
on a centre lathe. The choice depends upon the
component, the nature of the operation, the number of
components to be machined.
Some of the other types of chucks are:
- two jaw concentric chuck
- combination chuck
- collect chuck
- magnetic chuck
- hydraulic chuck or air operated chuck.
• Push-out chucks
Two jaw concentric chuck (Fig 1) • Draw-in chucks
• Dead length bar chucks
The operation of these chucks may be manual, pneumatic,
hydraulic or electrical. They are mainly used to hold round,
square, hexagonal or cast profile bars. (Fig 3)

The constructional features of this chuck are similar to

those of 3 jaw and 4 jaw chucks.
Each jaw is an adjustable jaw which can be operated
independently. In addition to this feature, both jaws may
be operated concentric to the centre. Irregular shaped Push-out chucks (Fig 4)
works can be held. The jaws may be specially machined the collet closes on the workpiece in a forward direction
to hold a particular type of job. and consequently an end-wise movement of the work
results. The cutting pressure tends to reduce the grip of
Combination chuck the collet on the workpiece.
The combination chuck is normally a four jaw chuck in
which the jaws may be adjusted either independently as
done in a 4 jaw chuck, or together, as done in a 3 jaw
universal chuck.

This kind of chuck is used in places where duplicate

workpieces are to be machined. One piece is accurately
set as done in a 4 jaw chuck, and the subsequent jobs
are held by operating the centering arrangement.

Collet Chuck (Fig 2)

A collet is a hardened steel sleeve having slits cut partly
along its length. It is held by a draw-bar which can be
drawn in or out in the lathe spindle. The collet is guided in
the collet sleeve, and held with the nose cap. It is possible
to change the collet for different cross-sections depending
on the cross-section of the raw material.
104 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84

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Draw-in chuck (Fig 5)

The collet closes on the workpiece in a backward direction

and movement of the work. Take special care to avoid
increases the grip of the collet on the workpiece.

Dead length bar chucks (Fig 6)

These chucks are widely used in modern machines as

they provide an accurate end-wise location of the Uses of a two jaw concentric chuck
workpiece. The chuck does not move end-wise during It is mainly employed to hold an irregularly shaped job.
gripping or closing operation. These chucks are made to As the chuck is designed with two jaws, it can be used
hold round, hexagonal or square bars, and when they are as a turning fixture.
not gripping, they maintain contact with the core thus
preventing swarf and chips collecting between the collet Uses of a combination chuck
and the core
This chuck may be used both as a universal 3 jaw chuck
The disadvantage with these chucks is that each collet and as a 4 jaw independent chuck. This chuck is very
cannot be made to grip bars which vary by more than useful where duplicate workpieces are involved in the
about 0.08 mm without adjustment. turning.

Magnetic chuck (Figs 7a & 7b)

This chuck is designed to hold the job by means of
magnetic force. The face of the chuck may be magnetized
by inserting a key in the chuck and turning it to 180°. The
amount of magnetic force may be controlled by reducing
the angle of the key. The truing is done with a light
magnetic force, and then the job is held firmly by using
the full magnetic force.

Hydraulic chuck or air-operated chuck (Fig 8)

These chucks are mainly used for getting a very effective
grip over the job. This mechanism consists of a hydraulic
or an air cylinder which is mounted at the rear end of the
headstock spindle, rotating along with it. In the case of a
hydraulically operated chuck the fluid pressure is
Uses of a collet chuck
transmitted to the cylinder by operaring the valves. This
mechanism may be operated manually or by power. The It is mainly used for holding jobs within a comparatively
movement of the piston is transmitted to the jaws by small diameter. The main advantage of collets lies in their
means of connecting rods and links which enable them ability to centre work automatically and maintain accuracy
to provide a grip on the job. for long periods. It also facilitates to hold the bar work.

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.3.83 & 2.3.84 105

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Uses of a magnetic chuck Uses of hydraulic or air-operated chuck
Magnetic chucks use the magnetic force from a permanent These chucks are mainly used in mass production
or electromagnet, or electro-permanent magnetic material because of their speedy and effective gripping capacity.
to achieve chucking action on recent years magnetic
chucks have replaced mechanical holding chucks.
Magnetic chucks reduces set up time and increase access
to all sides of workpiece. They are an valable tool for
workholding.This type of a chuck is mainly used for
holding thin jobs which cannot be held in an ordinary
chuck. These are suitable for works where a light cut can
be taken on the job.
Advantages of magnetic chucks
• They maintain constant & consisting pressure & no
variation in clamping
• Full support of workpiece surface decreases cycle time
• Have shorter set-up time
• Non ferrous material can be held throw dawping in vice,
attached to magnet.

106 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.83 & 2.5.84

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Production & Manufacturing
Turner - Special job & maintenence Related theory for Exercise 2.5.85

Lubrication-function, types, source & method of lubrication

Objectives : At the end of this lesson you shall be able to
• state the purpose of using lubricants
• state the properties of lubricants
• state the qualities of a good lubricant

With the movement of two mating parts of the machine, pressure or load without squeezing out from the bearing
heat is generated. it is not controlled the temperature may surface.
rise resulting in total damage of the mating parts. Therefore Oiliness
a film of cooling medium, with high viscocity is applied Oiliness refers to a combination of wet ability, surface
between the mating parts which is known as a lubricant. tension and slipperiness. (The capacity of the oil to beave
an oily skin on the metal.)
A ‘lubricant’ is a subtance having an oily property available
in the form of fluid. semi-fluid, semi-fluid, or solid state it
Flash point
is
the lifeblood of the machine, keeping the vital parts in It is the temperature at which the vapour is given off from
perfect condition and prolinging the life of the machine. It the oil (it decomposes under pressure soon).
saves the machine and its parts from corrosion, wear and
tear, and it minimises friction. Fire point
Its is the temperature at which the oil catches fire and
Purposes of using lubricants continues to be in flame.
- Reduces friction.
Pour point
- Prevents wear.
The temperature at which the lubricant is able to flow
- Prevents adhesion. when poured.
- Aids in distributing.
Emulsification and de-emulsibility
- Cools the moving elements.
Emulsification indicates the tendency of an oil to mix
- Prevents correction. intimately with water to form a more or less stable
- Improves machine efficiency. emulsion. De-emulsibility indicates the readiness with
which subsequent separation will occur.
Properties of lubricants

Viscosity
It is the fluidity of an oil by which it can withstand high

Types of lubricant
Objectives : At the end of this lesson you shall be able to
• state base of lubriant
• state sources of lubriant.

Sources of lubricant: Mineral oils:

Paraffin base has high lubricating oil content with high
This is gotten by refining or through distillation of crude
pour point with high viscosity index.
oil. (Paraffin or asphalt base). It most important property
Asphalt base: this has a low lub-oil content with a low is viscosity and must have it is the lowest value for satis-
pour point and low viscosity index. factory under all conditions especially in load seed and
temperature differences.
It is therefore important to subject lubricating oils refined
from paraffin and asphalt base to various treatment to
Synthetic oils:
improve their properties suitable for blending produce
wide range of lub-oils. Silicons possess the properties of synthetic oils. They
are useful where. viscosity is almost independent of tem-
perature. Example is gas turbine machine which is usu-
ally very expensive.
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Grease: Solids:

Greases are semisolid lubricant which has high viscosity Graphite, tale molybdenum disulphide are good source
with filler and metallic soap. The filler enable grease to of the king of lubricant. They are difficult to apply may be
with stand shock and heavy loads. The soap include metal suspended in a fluid when being used and are useful for
base like calcium, sodium with fatty or vegetables oil fillers, high operating temperature.
lead, zine, graphite or molybdenum disulphide
Water:
Grease properties is seen as it act as a real lubricant
useful is accessing difficult areas or parts and large They are used in steel, rubber or steel plastic bearings
clearance it has a continous lubricating ability. e.g. water.
Lubricated stern bearing with rubber bearing surfaces or
Vegetable and Animal oils: impregnated plastic resin compounds.
Fallow, whale, cod-liver, castor and olives oils belongs to
this family but they are unsuitable at usual operating Gases:
conditions especially temperature. They are used in grease Gases like air and Co2 are used when liquids are not
and as additives to mineral oils to give improved boundary allowed. It has very low viscosity and more suitable for
lubrication. hydrostatic lubrication.

Classification of lubricants
Objectives : At the end of this lesson you shall be able to
• state solid lubricants and their application
• state liquid and semi-liquid lubricants and their application
• state the classification of lubricants as per Indian Oil Corporation.

Lubricants are classified in many ways. According to According to the product line of Indian Oil Corporation the
lubricants are classified as:
their state, lubricants are classified as:
- automotive lubricating oils
- solid lubricants
- automotive special oils
- semi-solid or semi-liquid lubricants
- rail-road oils
- liquid lubricants.
- industrial lubrication oils
Solid lubricants
- metal working oils
These are useful in reducing friction where an oil film
- industrial special oils
cannot be maintained because of pressure and temperature.
Graphite, molybdenum disulphide, tale, wax, soap-stone, - industrial greases
mica and French chalk are solid lubricants.
- mineral oils.
Semi-liquid or semi-solid lubricants For industrial purposes the commonly used lubricants for
machine tools are:
Greases are semi-liquid lubricants of higher viscosity than
oil. Greases are employed where slow speed of heavy - turbine oils
pressure exists. Another type of application is for high
- circulation and hydraulic oils (R & O Type)
temperature components, which would not retain liquid
lubricants. - circulating and hydraulic oils (anti-wear type)
- circulating oil (anti-wear type)
Liquid lubricants
- special purpose hydraulic oil (anti-wear type)
According to the nature of their origin, liquid lubricants are
- fire-resistant hydraulic fluid
classified into:
- spindle oil
- mineral oil
- machinery oils
- animal oil
- textile oils
- synthetic oil.
- gear oils

108 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.85

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- straight mineral oils Servomesh oils are industrial gear oils blended with lead
and sulphur compounds. These oils provide resistance to
- morgan bearing oils
deposit formation, protect metal components against rust
- compressor oils. and corrosion, separate easily from water and are non-
In each type, there are different grades of viscosity and corrosive to ferrous and non-ferrous metals.
flash point. According to the suitability, lubricants are These oils are used for plain and anti-friction bearings
selected using the catalogue. subjected to shock and heavy loads, and should be used
in system where the operating temperature does not
Example 1 exceed 90° C. These oils are not recommended for use in
Spindle oils are graded according to their viscosity and food processing units.
flash point. Servomest A-90 is a litumenous product which contains
Servospin - 2 sulphur-lead type and anti-wear additive. It is specially
suitable for lubrication of heavily leaded low-speed open
Servospin - 5 gears.
Servospin - 12 Servomesh - SP 68
Servospin - 22 Servomesh - SP 150
Servospin oils are low viscosity lubricants containing anti- Servomesh - SP 220
wear, anti-oxidant, anti-rust and anti-foam additives. These
oils are recommended for lubrication of textile and machine Servomesh - SP 257
tool spindle bearings, timing gear, positives displacement Servomesh - SP 320
blowers, and for tracer mechanism and hydraulic system
Servomesh - SP 460
of certain high precision machine tools.
Servomesh - SP 680
Example 2
Servomesh SP oils are extreme pressure type industrial
Gear oils are graded according to their viscosity and flash gear oils, which contain sulphur-phosporous compounds
point. and have better thermal stability and higher oxidation
Servomesh - 68 resistance compared to conventional lead-napthenate gear
oils.
Servomesh - 150
These oils have good de-emulsibilty, now foaming
Servomesh - 257 tendency and provide rust and corrosion protection to metal
Servomesh - 320 surfaces. These oils are recommended for all heavy duty
enclosed gear drives with circulation or splash lubrication
Servomesh - 460 system operating under heavy or shock load conditions
Servomesh - 680 up to a temperature of 110° C.

Lubricating System
Objective : At the end of this lesson you shall be able to
• state the methods of applying a lubricant.

There are 3 systems of lubrication.

• Gravity feed system

• Force feed system
• Splash feed system

Gravity feed
The gravity feed principle is employed in oil holes, oil
cups and wick feed lubricators provided on the machines.
(Fig 1 & 2)

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.85 109

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 adhering to it is brought up and fed into the bearing, and
the oil is then led back into the reservoir. (Fig 5) This is as
known as ring oiling.

Force Feed/Pressure Feed

Oil, grease gun and grease cups In other systems one of the rotating elements comes in
The oil hole or grease point leading to each bearing is contact with that of the oil level and splash the whole
fitted with a nipple, and by pressing the nose of the gun system with lubricating oil while working. (Fig 6) Such
against this, the lubricant is forced to the bearing. Greases systems can be found in the headstock of a lathe machine
are also force fed using grease cup. (Fig 3) and oil engine cylinder.

Oil is also pressure fed by hand pump and a charge of oil

is delivered to each bearing at intervals once or twice a
day by operating a lever provided with some machines.
(Fig 4) This is also known as shot lubricator.

Types of grease guns

The following types of grease guns are used for lubricating
machines.

• ‘T’ handle pressure gun (Fig 7)

Oil pump method

In this method an oil pump driven by the machine delivers • Automatic and hydraulic type pressure gun (Fig 8)
oil to the bearings continuously, and the oil afterwards • Lever-type pressure gun (Fig 9)
drains from the bearings to a sump from which it is drawn
by the pump again for lubrication. Lubrication to exposed slideways

Splash lubrication The moving parts experience some kind of resistance even
when the surface of the parts seems to be very smooth.
In this method a ring oiler is attached to the shaft and it
dips into the oil and a stream of lubricant continuously The resistance is caused by irregularities which cannot
splashes around the parts, as the shaft rotates. The be detected by the naked eyes.
rotation of the shaft causes the ring to turn and the oil
110 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.85

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Without a lubricant the irregularities grip each other as Hints for lubricating machines
shown in the diagram. (Fig 10) - identify the oiling and greasing points
- select the right lubricants and lubricating devices
- apply the lubricants.
The manufacturer’s manual contains all the necessary
details for lubrication of parts in machine tools. Lubricants
are to be applied daily, weekly, monthly or at regular
intervals at different points or parts as stipulated in the
manufacturer’s manual.
These places are indicated in the maintenance manuals
with symbols as shown in Fig 12.
The best guarantee for good maintenance is to follow the
manufacturer’s directives for the use of lubricants and
greases. Refer to the Indian Oil Corporation chart for
guidance. The commonly used oils in the workshop is
given in Annexure I.

The lubricant containers should be clearly labelled. The

label must indicate the type of oil or grease and the code
number and other details. Oil containers must be kept in
the horizontal position while the grease container should
be in the vertical position.
With a lubricant the gap between the irregularities fills up
and a film of lubricant is formed in between the mating
components which eases the movement. (Fig 11)

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.85 111

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 Industrial lubrication oils

Product Kinematic VI Flash poin Description/Application

viscosity COC°C
Cst at 40°C

General Purpose
Machinery Oils Lubrex oils are low viscosity index straight mineral
Lubrex 57 54.60 - 160 lubricants having good inherent oxidation stability;
Lubrex 68 64.72 - 160 they protect machine elements from excessive
wear and provide economical lubrication. These
oils are recommended for lubrication of bearings,
open gears, lightly loaded slides and guideways of
machine tools.

Flushing Oil Lubrex Flush 22 is a light coloured, low viscosity,

Lubrex Flush 22 19.22 - 150 straight mineral oil specially developed for slushing
of automotive and industrial equipment. The
characteristics of Lubrex Flush 22 make it possible
to easily clean all inacessible internal surfaces of
various equipments.

Circulating and Servosystem oils are blended from highly refined

Hydraulics Oils base stocks and carefully selected anti-oxidant,
(Anti-wear Type) anti-wear, anti-rust and anti-foam additives. These
Servosystem 32 29.33 95 196 oils have long service life, and are recommended for
Servosystem 57 55.60 95 210 hydaulic systems and a wid of circulation systems
Servosystem 68 64.72 95 210 of industrial and automotive equipment. These oils
Servosystem 81 78-86 90 210 are also used for compressor crank case
Servosystem 100 95-105 90 210 lubrication, but are not recommended for lubrication
Servosystem 150 145-155 90 230 of turbines and equipment having silver coated
components.

Spindle Oils Servospin oils are low viscosity lubricants

Servospin 2 2.0-2.4 - 70 containing anti-wear, anti-oxidant, anti-rust and anti-
Servospin 5 4.5-5.0 - 70 foam additives. These oils are recommended for
Servospin 12 11-14 90 144 lubrication of textile and machine tool spindle
bearings, timing gears, positive displacement
blowers, and for tracer mechanism and hydraulic
systems of certain high precision machine tools.

Machinery Oils Servoline oils provide good oiliness for general

Servoline 32 29.33 - 152 lubrication even under boundary lubrication
Servoline 46 42.50 - 164 conditions, protect parts gaingst rust and corrosion
Servoline 68 64.-72 - 176 and maintain thin film strength and anti-rust
additives. Servoline oils are general purpose
lubricants for all loss lubrication systems of textile
mills, paper mills, machine tools.

Gear OIls Servomesh oils are industrial gear oils blended with
Servomesh 68 64-72 90 204 lead and sulphur compounds. These oils provide
Servomesh 150 145-155 90 204 resistance to desposit formation, protect metal
Servomesh 257 250-280 90 232 components against rust and corrosion, separate
easily from water and are non-corrosive to ferrous and
non-ferrous metals. Servomesh oils are recommended
for lubrication of industrial gears, plain and anti-friction
bearings subjected to shock and heavy loads and
should be used in systems were operating
temperature does not exceed

112 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.85

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Production & Manufacturing
Turner - Special job & Maintenance Related Theory for Exercise 2.5.86

Dial Test indicator use for parallelism and concentricity

Objectives: At the end of this lesson you shall be able to
• checking will movement of fail stock & alingment of the spindle
• test the coil stock sleeve movement relative to the carrrige giveing
• parallelism of bed and carriage movement.

Fix the dial gauge on the carriage. (Fig 1)

For checking in the horizontal plane, set the dial
horizontally and repeat the above procedure.
(Fig 6)

Project the quill of the tailstock to the maximum extent

possible and lock it. (Fig 2) Check the quill in the vertical
and horizontal positions by a dial test indicator.

Clamp the quill during each measurement. If it is not

clamped it will affect the measurement.
Place the dial plunger to contact over the free end of the
quill in the vertical plane. (Fig 3)

Ensure that the dial is set at the topmost point of

the quill.

Set the dial at the zero position. (Fig 4)

Fix the test mandrel into the tailstock spindle. Repeat
Move the carriage slowly towards the entire length of the
the same procedure to test the accuracy of the tailstock
quill. (Fig 5)
spindle bore in the vertical and horizontal positions as
Note the dial reading at the extreme end of the quill. shown in the figure.
Verify the deflection of the dial reading and compare the Insert a hollow test mandrel (300 to 500 mm long) in
value with the test chart supplied. (IS: 6040) between the centres. (Fig 6)

113

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 Set the dial plunger at the top of the mandrel and move
Ensure that the spindle bearing is at its working the saddle along the bed slowly to the entire length of the
temperature. mandrel. (Fig 8)
Fix the dial gauge on the saddle, the plunger touching a
position of the mandrel and set it to zero.(Fig 7)

Observe the reading of the dial as the saddle moves along

the beds and note for variation, if any.

The tailstock centre must be higher than the

spindle centre within the permissible limit.

Verify the deflection of the dial gauge reading and compare

the value with the test chart. (IS: 6040)

Move the carriage from one end to the other end of the
mandrel to check the mandrel is in correct alignment in
the horizontal position.
Rest the dial plunger at right angles (radially) to the
surfaces to be tested.

Checking the true running of a spindle

Objective: This shall help you to
• test the true running of a lathe spindle with a test mandrel.

Locate the taper shank of the test mandrel in the spindle rotated. Verify the deflection of the dial reading and
taper. compare the value with the test chart. (IS: 6040)
Hold a dial gauge, stationary in the carriage, its plunger Adjustment of the spirit level with the plane surface
contacting the mandrel near its free end (Fig 1) and set it
to ‘0’ position.

Rest the dial gauge plunger at right angles

(radially) to the surface to be tested.

Rotate the spindle along with the mandrel slowly by hand.

Observe and note the reading of the dial gauge.
Move the dial gauge near the spindle nose. Rotate the
spindle along with the mandrel slowly by hand and note
the reading.
Take readings of the dial gauge while the spindle is slowly
114 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.86

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Production & Manufacturing
Turner - Special job & Maintenance Related theory for Exercise 2.5.87

Grinding wheel - abrassive, grit, grade and bond

Objectives: At the end of this lesson you shall be able to
• name the two abrasives used to manufacture grinding wheels
• identify and name the bonds used during the manufacture of grinding wheels
• state the cutting action of an abrasive wheel
• specify a grinding wheel as per B.I.S.
• state the factors which affect the selection of abrasive wheels.

Satisfactory results can be obtained only by having the The organic bonded wheels have a safe higher operating
right type of abrasive wheel rotating at the correct speed speed. They are better able to withstand rough usage.
for the kind of work that is to be ground. They are used on portable grinders and for rough foundry
work. Thin cut-off wheels are made with an organic bond.
Abrasive wheels are made from manufactured abrasive
(Fig 1)
grains, held together by a suitable binding material called
the bond.
The two abrasives used in the manufacture of grinding
wheels are:
- aluminium oxide
- silicon carbide.
The aluminium oxide grinding wheels are suitable for grind-
ing high tensile, tough materials, and all types of steels.
The silicon carbide grinding wheels are used to grind hard
materials, such as, stone or ceramics, non-ferrous metals
and other non-ferrous materials.
The type of the abrasive is clearly marked on an abrasive Degree of bond
wheel by the manufacturer.
The bond holds the abrasive particles together and sup-
ports them while they cut. The degree of bond determines
The bond
whether the abrasive grains are held lightly or firmly.
Abrasive particles in a grinding wheel are held together
A wheel is said to be ‘soft’ only when a thin bridge of bond
by a material called the bond.
holds the abrasive grains together so that the grains break
The bond may be: away. A wheel is said to be ‘hard’ when a thick bridge of
bond holds the grains firmly.
- vitrified
- silicate It is the amount or grade of bond that
determines the ‘hardness’ or ‘softness’ of an
- organic. abrasive wheel.
Vitrified bonds produce strong rigid grinding wheels that
are not affected by water, acid or normal temperature
changes. Most of the abrasive wheels are produced with
vitrified bonds.
A silicate bond produces a wheel with a milder cutting
action than a vitrified bonded wheel. Large diameter wheels
have a silicate bond.

The organic bonds may be made of:

- resinoid
- bakelite
- rubber Cutting action of an abrasive wheel
- shellac. The cutting action of a grinding wheel depends to a large
extent on the grade of bond of the wheel. The principle is
that the individual abrasive grains are small cutting tools.
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The bond must be such that it must hold the grinding Grain size (Fig 5)
particles together when they are sharp, and must release
Grain or grit size is the actual size of the abrasive grain.
them when they become blunt so that new sharp grains
The abrasive particles are graded by passing through
take their place to continue the cutting. This continuous
sieves of various sizes. They are indicated by a number
process is known as the cutting action of the wheel.
ranging from 10 (coarse) up to 600 (very fine). Generally a
(Fig 2)
fine grit wheel gives a smooth surface and is used for
finishing work.
Use ‘soft’ light bond wheels to grind hard
materials, and ‘hard’ firm bond wheels to grind
soft materials. (Fig 3)

Abrasive wheel specification

A standard marking system is used to specify and identify
grinding wheels.
The following is the sequence of arrangement.
- Abrasive type
- Structure Grade of bond (Fig 6)
- Grain size The grade or amount of bond in an abrasive wheel is
- Bond type indicated by a letter of the alphabet. The grades range
from ‘A’ indicating a light or ‘soft’ bond to ‘Z’ indicating a
- Grade of bond firm or ‘hard’ bond. The grade of bond selected for a
particular job would be one that produces the most
Abrasive type (Fig 4) satisfactory cutting action from the wheel.

Letters are used to identify each of the two types of

abrasives. Structure
They are: The structure of an abrasive wheel is the spacing of the
abrasive grains. An abrasive wheel can be manufactured
- ‘A’ for aluminium oxide
with the abrasive grains tightly packed together or widely
- ‘C’ for silicon carbide. spaced. This structure is indicated by a number from 1 to
12. The higher numbers indicate a progressively more
The manufacturer may use a number in front of this letter
open structure.
to designate a particular variation of each type.
Examples The structure number need not be shown on
the wheel markings. (Fig 7)
38 A is an aluminium oxide abrasive designed for grinding
high speed steel cutting tools.
39C is a silicon carbide abrasive designed for grinding
cemented carbide tools.
116 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.87

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 BE Manufacturer’s particular bond characteristic.
(Fig 9)

Factors for selecting an abrasive wheel for a

particular job
- The kind of material to be ground. (Fig 10)
- The amount of material to be removed. (Fig 10)
- The surface finish required.
- The type and condition of the machine.
- The wheel speed.(Fig 11)

Bond type
A letter is used to indicate the type of material or the
process used for the bond of the wheel. (Fig 8)

V Vitrified
S Silicate
B Resinoid
R Rubber
E Shellac
O Oxychloride

Wheel marking
An abrasive wheel suitable for the rough grinding of a steel
casting would be marked
A 16 P.5 V BE.
The expansion of the separate components would be:
A Aluminium oxide abrasive
16 Coarse grain size
P Medium to hard grade of bond
5 Medium to dense structure
V Vitrified bond

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.87 117

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Defects in grinding wheel
Objectives: At the end of this lesson you shall be able to
• state the problems which may arise relating to the surface of the wheel
• identify each one of the problems and state the effects.

The problems which may arise relating to the surface of

the grinding wheels by grinding are:
- loading
- glazing
- grooving
- out-of-round.

Loading
Small particles of the material being ground become
embedded in the space between the grains of the wheel.
The surface of the wheel becomes clogged or loaded.
This reduces the cutting efficiency of the wheel. (Fig 1)

A loaded wheel can be easily recognized, and the first

indications will be:
- a rapid reduction of the cutting action of the wheel
- normal pressure of the work against the wheel has
little effect
- the volume of sparks produced by the wheel is reduced.

An increased pressure of the work against the wheel

results in:
- the work heating up Glazing

- a slowing down of the wheel, particularly on the Glazing is caused by grinding hard materials on a wheel
smaller machines. (Fig 2) that has too hard a grade of bond. The abrasive particles
become dull owing to cutting the hard material. The bond
When these symptoms become apparent stop grinding is too firm to allow them to break out. The wheel loses its
and switch off the machine. cutting efficiency. The symptoms of a glazed wheel are
When the wheel has stopped rotating by itself, look at very similar to those of a loaded wheel. The inspection of
the wheel face. See whether the surface is dotted and the wheel face shows a smooth glassy appearance.
streaked with metallic particles. Often these particles will Glazing may be prevented by selecting a wheel with a
have built up on the surface, and will protrude above the softer grade of bond.
wheel face. This accounts for the sudden loss of cutting
action of the wheel. (Fig 3) The manufacturer’s handbook may be referred to for wheel
selection for the job in hand. (Fig 4)
‘Loading’ is the result of using the wrong type
of wheel for the material being ground. Grooving

Refer to the manufacturer’s reference Grooves are formed on the surface of the wheel by the
handbook which gives the recommendations wearing away of the wheel by the pressure that is being
for wheel selection. applied in one position.
118 Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.87

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Grooving may be prevented by moving the work across Out-of-round
the full face of the wheel.
Uneven application, bumping or vibration of the work
against the wheel will cause the wheel to wear out-of-
Avoid grinding on the outside edges of the
round. It will lead to an out of balance condition. Applying
wheel; otherwise,it results in rapid wear and
even pressure and having the work well supported by the
causes a curved surface on the wheel. (Fig 5)
work-rest will help in preventing the wheel from becoming
out-of-round.

Never attempt to perform heavy, rough

grinding on a small bench grinder set-up for
the sharpening of cutting tools.

Production & Manufacturing: Turner (NSQF LEVEL - 5) - Related Theory for Ex 2.5.87 119

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Copyright Free Under CC BY Licence
Copyright Free Under CC BY Licence
Copyright Free Under CC BY Licence