BTBS-P-ES-009-MP

Manufacturing Practices Lab Manual

 Type Code L-T-P Credits Marks
ES BTBS-P- 0-0-2 1 100
Manufacturing Practices Lab
ES-009-MP

Objectives The objective of this practical course is to provide the basic concepts
about tools used in Manufacturing Practice. Detailed concepts are
proposed in all the major trades of current interest.
Pre-Requisites None
Teaching Scheme Demonstration will be given for each job and it is to be executed by
students.
Evaluation Scheme
Daily Lab Test/
Attendance Record Viva-voce Total
Performance Mini Project
10 30 15 30 15 100

Detailed Syllabus
Experiment # Assignment / Experiment
1 Introduction to fitting practice and tools used in fitting.
2 Exercise involving measuring, marking, cutting and filing practice.
3 Fitting of male and female mating parts.
4 Introduction to Lathe. Exercise involving facing, straight turning, step
turning, taper turning and thread cutting in Lathe machine.
5 Introduction of Milling and Shaping machines.
6 Preparing a single step on a square block in a Milling machine.
7 Preparing a keyway on a square block in a Shaping machine.
8 Introduction to basic principles of Arc and Gas Welding.
9 Preparing a lap joint by Gas welding and a butt joint by Arc welding.
10 Sheet metal forming and joining operations.
Text Books:
T1. P. Kannaiah and K. L. Narayana, Workshop Manual, Scitech Publishers, 2009
T2. S. K. Hajra Choudhury, Workshop Technology, Vol-1 and Vol-2
Online Reference Material(s):
1. http://www.technicaltrainingsolutions.co.uk/courses/bench-fitting-course.html
(Fitting practice and tools)
2. http://nptel.ac.in/downloads/112105127 (Machining Processes)
3. http://nptel.ac.in/courses/112107144/27 (Welding Processes)
4. http://nptel.ac.in/courses/112101005/14 (Sheet Metal Forming Processes)

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Course Outcomes:
CO1 Study and practice use of hand tools and their operations in a fitting shop.
CO2 Design and model various basic prototypes in fitting, such as a paperweight.
Design, model and use of various suitable tools for machining processes like facing,
CO3
straight turning, step turning, taper turning and thread cutting.
Identify and use suitable tools for cutting of a mild steel work piece with the help
CO4
of shaping and milling machines.
Design and model various basic prototypes in welding such as a Lap joint and a Butt
CO5
joint.
Design and model various basic prototypes using sheet metal forming and joining
CO6
operations.

Program Outcomes Relevant to the Course:

PO1 Graduates will demonstrate basic knowledge in fundamentals of science.
Design/Development of Solutions: Design solutions for complex engineering
problems and design system components or processes that meet the specified needs
PO3
with appropriate consideration for the public health and safety, and the cultural,
societal, and environmental considerations.
Graduates will apply reasoning informed by the contextual knowledge to assess
PO6 societal, health, safety, legal and cultural issues and the consequent responsibilities
relevant to the professional engineering practice.
Graduates will learn to function effectively as an individual, and as a member or
PO9
leader in diverse teams, and in multidisciplinary settings.
Graduates will be able to demonstrate knowledge and understanding of the
PO11 engineering principles and apply these to one’s own work, as a member and leader
in a team, to manage projects and in multidisciplinary environments.
Graduates will be able to recognize the need for, and have the preparation and ability
PO12 to engage in independent and life-long learning in the broadest context of
technological change
Mapping of CO’s to PO’s: (1: Low, 2: Medium, 3: High)
PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12
CO1 1 1 1 3 3 2
CO2 1 2 1 3 3 2
CO3 1 2 1 3 3 2
CO4 1 2 1 3 3 2
CO5 1 2 1 3 3 2
CO6 1 2 1 3 3 2

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 Manufacturing Practices Instructions

 Every student is required to wear a blue-coloured apron and leather shoes.

 A student shall not be allowed to enter the workshop after five minutes of the scheduled

time.

 Students are required to sign in the issue register before taking the required equipment,

and after returning it in proper order. This protocol must be followed, failing which the

student's names will be entered in the breakage record.

 A student is required to perform all the jobs selected from the syllabus during the

semester.

 A student as required to maintain a practical record book for each semester. The record

book should be written neatly.

 After the completion of each job, a student is required to submit his/her workshop

record book, duly filled out. If the student fails to do so, marks will be deducted.

 The marks given to a student, during his/her job, the related theory and viva-voce

conducted in each class will be added up, which will be the secured mark for sessional.

 Nobody is allowed to leave the workshop class without the permission of the concerned

faculty/workshop instructor.

 Students are instructed to switch off all the machines before leaving the workshop.

 Complete silence is to be maintained inside the workshop.

 Students are required to follow safety rules and safety precautions inside the workshop.

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 Safety Precautions

Safety for Self:

 Don’t move inside the workshop with bare feet. The tiny iron particles may result in a
foot injury.
 Never use mufflers, ties or loose dress inside the workshop while working on a machine.
 Always use goggles while working on a lathe machine or a grinding machine to protect
the eyes from harmful cutting chips.
 Always use hand gloves and safety glasses while doing any welding work.
 Don’t touch moving parts of machines while the machine is in motion.

Safety for Machines:

 Don’t operate the machine if you don’t have full knowledge about the operation of the
machine.
 Always keep the machine neat and clean.
 Make sure that proper oil and grease have been applied on moving parts/bearings etc.,
before operating the machine.

Safety for Tools and Equipment:

 Don’t use a tool or equipment for a wrong propose (for example – don’t use a try square
as a hammer or don’t use a steel rule as a screw driver).
 Always keep precision instruments separately and carefully.
 Coolant should be used at proper places to increase the tool life.
 Don’t use a mushroom head chisel.
 Always use the correct tools for the job.

General Safety:
 Always keep the workshop floor neat and clean.
 Don’t allow oily substances like grease, mobile etc., to be thrown on the workshop
floor.
 Fire fighting equipment should be kept in proper place and in proper manner.

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 Contents

Sl. No Topics Page

1 Introduction to Manufacturing Practices Lab 1

Introduction and description about different types of tools and

2 2-13
equipment used in fitting
3 To make, a mild steel square paperweight 14-15
4 Introduction and description about the Lathe Machine 16-23
5 To make a cylindrical step turning and threading 24-25
6 Introduction and description about the milling machine 26-30
7 To make single step on a mild steel square block 31-32
8 Introduction and description about the shaping machine 33-37
9 To make a keyway on a mild steel square block 38-39
10 Introduction and description about arc welding 40-47
11 To make a butt joint by arc welding 48-49
12 Introduction and description about gas welding 50-53
13 To make a lap joint by gas welding 54-55
Introduction and description about different types of tools and
14 56-57
equipment used in sheet metal work
15 To make a dustpan 58

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 Manufacturing Practices Lab

Introduction:
Manufacturing is the production of products for use or sale by using labor, hand tools, machines
tools, and chemical or biological processing or formulation. The term manufacturing may refer
to a range of human activity, from handicraft to high-tech, but it is mostly applied to industrial
design, in which raw materials from primary industries are transformed into finished goods on
a large scale. Such goods may be sold to other manufacturers for the production of more
complex products (such as an aircraft, household appliances, furniture, sports equipment or
automobiles), or distributed via the tertiary industry to the consumers.
The manufacturing process begins with the product design and materials specification from
which the product is made. These materials are then modified through manufacturing processes
to become the required products. After that the product has to go through many inspections to
check the quality and assurance.
Modern manufacturing includes all intermediate processes required in the production and
integration of different components to get the final product.
The manufacturing sector is closely connected with engineering and industrial design. The
major manufacturers in North America include General Motors Corporation, General Electric,
Procter and Gamble, General Dynamics, Boeing, Pfizer, Precision Cast parts and Fiat Chrysler
Automobiles. In Europe major manufacturers are the Volkswagen Group, Siemens, BASF and
Michelin. In Asia the major manufacturers are Toyota, Yamaha, Panasonic, LG, Samsung,
Reliance and Tata Motors.
The objective of basics of manufacturing practice is to help the students, understand the basic
skills required for fitting, machining, welding and sheet metal; this in turn may enable them to
do different projects, to make some products required for their projects or for some real life
uses. All engineers must have basic knowledge of how to make different components and their
uses. That is why manufacturing practices are compulsory for all the engineering students of
different branches. Here students use various tools and instruments to perform forging,
carpentry, molding, fitting, machining, welding and sheet metal exercise to produces some
products used in day-to-day life (paperweight, dust pan, threading, hexagonal headed bolt, and
making keyways). The lab also has drilling, grinding and Lathe machines along with sheet
metal tools to help the students better understand manufacturing practices.
.

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 Fitting
Introduction:
Machine tools are capable of producing work at a faster rate, but there are occasions when
components are processed at the bench. Sometimes, it becomes necessary to replace or repair
a component which must fit accurately with another component on reassembly. This involves
a certain amount of hand fitting. The assembly of machine tools, jigs, gauges, etc. also involves
some amount of bench work. The accuracy of work done depends upon the experience and
skill of the fitter.
The term ‘bench work’ refers to the production of components by hand on the bench, whereas
fitting deals with the assembly of mating parts with the required fit which can be obtain by
removing surplus metal. Both bench work and fitting require the use of different types of hand
tools and considerable amount of manual effort. The different operations involved in bench
work and fitting consist of measuring, marking, holding, cutting, filing, chipping, scraping,
sawing, drilling, hammering, tapping and finally finishing and checking.
Engineering fits are generally used as a part of geometric dimensioning and tolerancing when
a part or assembly is designed. In engineering terms, the "fit" is the clearance between two
mating parts (i.e., the male part and female part). Engineering fits are generally described as a
"shaft and hole" pairing, but are not necessarily limited to just round components.
Types of fit
The three types of fit are:
1. Clearance: The hole is larger than the shaft, enabling the two parts to slide and / or
rotate when assembled. E.g., piston and valves
2. Location / transition: The hole is fractionally smaller than the shaft and mild force is
required to assemble / disassemble e.g., Shaft key. Push fit and ringing comes under it.
3. Interference: The hole is smaller than the shaft and high force and / or heat is required
to assemble / disassemble E.g., Bearing bush
Classification of Tools
Tools are classified according to the nature of work.
Measuring Tools
Measuring tools are divided into two categories
 Direct measuring tools
 Indirect measuring tools
Direct Measuring Tools
Steel Rule
A steel rule is a direct measuring tool which
is used to measure the liner dimensions e.g.
length, breadth and thickness. Graduations
marked on this instrument are both in Metric
system and in British (inch) system. In the

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Metric system, its least count is 0.5 mm and in the British system, its least count is 1/64”. It is
available in length of 150 mm, 300 mm and 600 mm. In British system it is available in length
of 6 inches, 12 inches and 24 inches. It is specified by its length. It is made of stainless steel.
Outside Micrometre
This is used for measuring external dimensions
accurately. Its least count is 0.01 mm. These are
available in different ranges with interchangeable
anvils.
These are available in 0-25 mm, 25-50 mm, 50-
75 mm, etc. It works on the principle of screw
thread’s pitch and lead. It consists of one jaw or
anvil, fixed to one end of the frame and another movable jaw, in the form of a round bar,
called the spindle. This spindle is mounted on the other end of the frame and housed in the
thimble.
Vernier Callipers
It is a precision and direct
measuring tool. It is used for
measuring outside and inside
dimensions accurately. It is also
used for depth measurement. It
has two jaws. A fixed jaw is
present at one end of its main
scale while a movable jaw is
attached with vernier scale. The least count is defined as the minimum dimension which can
be measured by the instrument. In order to measure the size of an object, it is held in between
the two jaws of vernier calliper and then take the main scale and vernier scale readings. The
vernier callipers is generally made of Nickel-Chromium steel. The size of the Vernier calliper
is specified by the maximum length that can be measured by it. The least count of vernier
calliper in the metric system is 0.02mm and in the British system 0.001”.
Calculation of least count in Metric system
In the Metric system on main scale, 1 cm is divided in 10 equal divisions. So 1 main scale
division (MSD) =1mm.
The total Vernier Scale is divided in 50 equal divisions.
When both the jaws are in close contact, 50 divisions of Vernier scale = 49 division of main
scale. So, 1 Vernier Scale division (VSD) = 49/50mm.
Least count = 1 main scale division (MSD) – 1 Vernier Scale division (VSD)
= (1 – 49/50) mm = 0.02mm.

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Vernier Height Gauge
The vernier height gauge is a direct and precision
measuring tool. It is also used as a marking tool. The
vernier height gauge is clamped with an off-set
scriber. The off-set scriber is used when it is required
to take measurements from the surface, on which the
gauge is standing. The accuracy and working
principle of this gauge is the same as that of the
Vernier calliper. Its size is specified by the maximum
height that can be measured by it. It is made of
Nickel–Chromium steel. The least count of the vernier
height gauge in the Metric system is 0.02mm and in
the British system it is 0.001”.
Indirect Measuring Tools
Outside Callipers
It is an indirect measuring tool. It is used to
measure the external dimensions. It consists of
two legs, bent towards the inside. It is used to
check the outside measurements with the help of
a steel rule. It is specified by the length of the leg.
Inside Callipers
It is an indirect measuring tool. It is used to
measure the internal dimensions. It consists of
two legs, bent towards the outside. It is used to
check the outside measurements with the help of
a steel rule. It is specified by the length of the leg.
Marking Tools
Scriber
A scriber is a slender steel tool, used to scribe or mark
lines on metal work pieces. It is made of hardened
and tempered high carbon steel. The angle of the
scriber tip is generally 12 to 15 degrees. It is
generally available in length range from 125 mm to
250 mm. It has two pointed ends. The bent end is
used for marking lines where the straight end can’t
reach.
Odd-leg callipers
This is also called ‘Jenny Calliper’ or ‘Hermaphrodite Calliper’. This is used
for marking parallel lines and for locating the centre of round objects. It has
one leg which is pointed and the other leg bent inside. It is specified by the
length of the leg up to the hinge point.

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Dividers
It is basically similar to the callipers except that, its legs are kept
straight and pointed at the measuring edge. It is used for marking
circles, arcs and bisecting lines, etc. It is made of case-hardened mild
steel or hardened and tempered low carbon steel. Its size is specified
by the length of the legs.
Punch
These are used for making indention after scribing a line, to make it visible clearly. These are
made of high carbon steel. A punch is specified by its length and diameter. For better grip the
middle part of the punch is knurled. The tapered point of the punch is hardened over a length
of 20 to 30mm.
Dot Punch
It is used to lightly indent along the lay out
lines and to provide, a small dot mark. For this
purpose, the conical point has an included
angle of 600.
Centre Punch
It is similar to the dot punch except that
conical point has a included angle of 900. It is
used to mark the location of the holes to be
drilled.
Number Punch and Letter Punch
These are used for punching the numbers and letters on the job.
Try-square
It is a measuring and marking tool used for checking right angles. In
practice, it is used for checking the squareness of many types of small
work, when extreme accuracy is not required. The blade of the try-
square is made of hardened steel and the beam, of cast iron. The size
of the try- square is specified by the length of the blade.
Surface Gauge/ Universal Scribing Block
It is used for scribing lines for layout work and checking parallel surfaces. Its spindle can be
adjusted to any angle by an adjusting screw. In some
designs, the base of the block will have a “V” shaped
groove, so that the block to rest on round bars if required.

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Surface Plate
Surface plate is used for marking out small works and is more precise
than the marking table, which has a fine machined surface, used for
testing the flatness of the work piece. The degree of fineness of the
finished surface depends upon whether it is designed for bench work
in a fitting shop or for using in an inspection room. It is made of cast
iron, hardened steel or granite stone. It is specified by length, width,
height and grade. Handles are provided on two opposite sides to carry
it while shifting from one place to another.
Angle Plate
It is made of cast iron. It has two surfaces, machined at right angles to each
other. Plate or component, which is to be marked, may be held against the
upright face of the angle plate, to facilitate the marking. Slots are provided
on the angle plate to clamp the work in position.
Holding Tools
Bench Vice
The bench vice is a work holding device. It is the
most commonly used vice in a fitting shop which is
fixed to the bench with bolts and nuts. The vice body
consists of two main parts, fixed jaw and movable
jaw. When the vice handle is turned in clockwise
direction, the sliding jaw forces the work piece
against the fixed jaw. Jaw plates are made of
hardened steel. The surface of the jaws is serrated
for better grip of work piece. Jaw caps are made of
soft material, used to protect the finished surfaces
while holding in the vice. The size of the vice is
specified by the length of the jaws. The vice body is
made of Cast Iron, which is a brittle material
therefore should not be hammered.
C-Clamp
It is used to hold work against an angle plate or V- block or any other surface, when gripping
is required. It looks like English alphabet, “C”. The movable jaw is round in shape and fitted
at the end of the threaded screw. The working principle of this clamp is the same as that of
the bench vice.

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Cutting Tools
Hacksaw
The hacksaw is used for cutting metals by hand. It consists of a frame, which holds a thin
blade, firmly in position. The hacksaw blade is specified by the number of teeth per inch.
Blades having fewer number of teeth per inch are used for cutting soft materials like
aluminium, brass and bronze. Blades having a larger number of teeth per inch are used for
cutting hard materials like Steel and Cast Iron.

Hacksaw blades are classified as (i) All hard

and (ii) flexible type. The all-hard blades are
made of H.S.S (High Speed Steel), hardened
and tempered throughout to retain the life of
cutting edges longer. These are used to cut hard
metals. These blades are hard and brittle and can
break easily by twisting and forcing them into
the work while cutting. Flexible blades are
made of high speed steel or low alloy steel, but
only the teeth are hardened, and the rest of the
blade is soft and flexible. These can be used by both un‐skilled and semi‐skilled persons. The
teeth of the hacksaw blade are staggered, as shown in figure and known as a ‘set of teeth’,
which makes slots wider than the blade thickness, also preventing the blade from getting
stocked.
Chisel
Chisels are used for removing surplus metal or for
cutting thin sheets. These tools are made from 0.9% to
1.0% carbon steel of octagonal or hexagonal section.
Chisels are annealed, hardened and tempered to
produce a tough shank and hard cutting edge.
Annealing relieves the internal stresses in a metal. The
cutting angle of the chisel for general purpose is about
60°.

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Taps and Tap wrenches
A tap is a hardened steel tool, used for cutting internal
thread in a drill hole. Hand Taps are usually supplied in
sets of three in each diameter and thread size. Each set
consists of a tapper tap, intermediate tap and plug or
bottoming tap. These are made of high carbon steel or
high-speed steel.

Dies and die‐holders

Dies are the cutting tools used for making external thread.
Dies are made either solid or split type. They are fixed in
a die stock for holding and adjusting the die gap. They are
made of High Carbon Steel.
Twist Drill
Twist drills are used for making holes. These are made of High-speed steel. The shank of the
twist drills may be straight or tapered. The parallel/straight shank twist drill can be held in an
ordinary self-centring drill chuck, but the tapper shank twist drill fits into a corresponding
tapered bore, provided in the drilling machine spindle.

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Bench Drilling Machine
Holes are drilled for fastening parts with rivets, bolts or for producing internal thread. A bench
drilling machine is the most versatile machine used in different place for making different
types of job. Twist drills, made of tool steel or high-speed steel are used.
Following are the stages in drilling work
 Select the correct size drills, put it into the
chuck and lock it firmly
 Adjust the speed of the machine to suit the
work by changing the belt on the pulleys.
Speed of the machine should be set
according to the metal of the job and
diameter of the drill.
 Locate the centre point of the hole and
mark it with a centre punch.
 Hold the work firmly in the machine vice
on the work table and clamp it. Switch on
the power, place the drill on the punch
mark and apply slight pressure with the
feed handle.
 Once Drilling is commenced at the correct location, apply the required pressure and
continue drilling. When drilling steel, apply cutting oil at the drilling point.
 Release the pressure slightly, when the drill point pierces the lower surface of the
metal. This prevents the drill catching and damaging of the workpiece or drill.
 On completion of drilling retrace the drill out of the work and turn off the power
supply.
Finishing Tools
Reamers
Reaming is an operation of sizing and finishing a drilled hole, with the help
of a cutting tool called reamer having a number of cutting edges. For this, a
hole is first drilled, the size of which is slightly smaller than the finished size
and then a hand reamer or machine reamer is used for finishing the hole to
the correct size.
Hand reamer is made of High Carbon Steel and has left‐hand spiral flutes so
that, it is prevented from screwing into the hole during operation. The shank
end of the reamer is made straight so that it can be held in a tap wrench. It
is operated by hand, with a tap wrench fitted on the square end of the reamer
and with the work piece held in the vice. The body of the reamer is given a
slight tapper at its working end, for its easy entry into the hole during
operation, it is rotated only in clock wise direction and also while removing
it from the hole.
Files
Filing is one of the methods of removing small amounts of material from the surface of a metal
part. A file is a hardened steel tool, having small parallel rows of cutting edges or teeth on its
surfaces. On the faces, the teeth are usually diagonal to the edge. One end of the file is shaped

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to fit into a wooden handle. The figure shows various parts of a hand file. The hand file is
parallel in width and tapering slightly in thickness, towards the tip. It is provided with double

cut teeth on the faces, single cut on one edge and no teeth on the other edge, which is known
as a safe edge.
Files are specified according to their shape,
length, cutting teeth and grade of the teeth.
The figure shows the various types of files
based on their shape.
Length of the File
Length of file is measured from the tip of the
file to heel of the file.
Types of Files
The various types of files based on their shape are shown and described below:

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Hand File
Rectangular cross section, tapered in thickness but parallel in width. The faces have double cut
teeth and one of the edges have single cut. The other edge does not have any teeth and hence
is called as safe edge file. It is used for filing right angle finished surface.
Flat File
Rectangular cross section, 1/3rd length of the file is tapered both in width and thickness. The
faces have double cut teeth and edges have single cut. Used as a general-purpose file.
Square File
Square in cross section, 1/3rd length of the file is tapered both in width and thickness. All the
faces have double-cut teeth. Used for filing corners and slots and keyways.
Triangular File
Equilateral triangular in cross sections, 1/3rd length of the file is tapered both in width and
thickness. All the faces have double-cut teeth. Used for filing internal corners.
Half round File
It has one flat face, connected by a curved face, 1/3rd length of the file is tapered both in width
and thickness. The curved face is not exactly semi-circular but only a part of circle. The flat
face has double-cut teeth and the curved face have single cut. Used for filing concave surfaces.
Round File
Circular cross-section, 1/3rd length of the file is tapered both in width and thickness. It has
double-cut teeth. Used for filing concave surfaces and circular openings.
Grade of Files
Grade of files are determined on the basis of number of teeth per cm. Different grades are
rough, bastard, second cut, smooth and super smooth.
Cut of file
The different cuts of files available are single, double, rasp, curved and spiral cut.

Miscellaneous Tools
File card
It is a metal brush, used for cleaning the files, to free
them from clogged particles (pinning).

Spirit level
It is used to check the levelling.

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Ball‐Peen Hammer
A ball‐peen hammer is named as
per its shape of the peen and
specified by their weight. A ball
peen hammer has a flat face which
is used for striking metal sheets
and the ball end is used,
particularly for riveting.
Straight‐Peen Hammer
This is similar to cross-peen hammer, but its peen is in‐line with the hammer handle. It is used
for swaging, riveting in restricted places and stretching metals.
Cross‐Peen Hammer
It is similar to the ball-peen hammer, except the shape of the peen which is perpendicular to
the axis of the handle. This is used for chipping, riveting, bending and stretching metals and
hammering inside the curves and shoulders.

Screwdriver
A screwdriver is designed to turn screws. The blade
is made of steel and is available in different lengths
and diameters. The grinding of the tip to the correct
shape is very important. A star screw driver is
specially designed to fit the head of star screws. The
end of the blade is fluted instead of flattened. The
screw driver is specified by the length of the metal
part from handle to the tip.

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Anvil
It provides the necessary support during
forging by resisting the heavy blows rendered
to the job. It is also useful for operations such
as bending, swaging etc. Its body is generally
made of forged or cast steel.
Spanners
A spanner or wrench is a tool for turning nuts
and bolts. It is usually made of forged steel.
There are many kinds of spanners. They are named according to the application. The size of
the spanner denotes the size of the bolt on which it can work.

Pliers
It is made of high carbon steel by proper hardening and tempering and is used for cutting as
well as for gripping the work. Its handles are well insulated which makes it suitable for
electrical work uses.
Different types of pliers are:
(i) Flat Pliers
(ii) Nose Pliers

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Job No. : 1
Aim of the Job: To make, a mild steel square paper weight

Raw Material Used: 1. Mild steel flat (50 x 50 x 6) mm

2. Mild steel rod (76 x 6) mm
Tools and Equipment Used:
 Steel rule
 Vernier callipers
 Vernier height gauge
 Scriber
 Odd leg callipers
 Try square
 Surface plate and Angle plate
 Punch (dot and centre)
 Number punch
 Ball peen hammer
 Hacksaw
 Flat rough and smooth file
 Drill bit (4.5mm)
 Bench drilling machine.
 Bench vice
 Anvil
Procedure:
Measuring – After receive the work piece, first measure the raw material size (length, width
and thickness) by steel rule whether it is correct or not as per the nominal size. i.e. (50 x 50 x
6) mm for flat and (76 x 6) mm for rod.
Marking – After measurement, mark a line of length 50 mm on the MS flat using steel rule,
try square and scriber. Similarly, mark another line of length 76 mm on the MS rod.
Cutting – After marking, set the MS flat and rod in bench vice at proper height and cut the
metal as per marking line using a hacksaw.
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Filling – After marking, first file one side of the job using rough file and check the flatness
with the blade of the try square. Then file the adjacent side of the base surface for making a
right angle and check the right angle with a try square. Then set the odd leg calliper in 48mm.
with the help of a steel rule. Then mark the lines in 48 mm on the opposite side of the right-
angle surface with an odd leg calliper. Then set the job in a bench vice and remove the extra
metal from the marking area to get the accurate shape and size using a rough file. Similarly
prepare the MS rod of size (75 x 4.5) mm.
Drilling – After preparing the mild steel flat, draw the diagonals using a scriber and steel rule
and mark the intersecting point of the diagonals using the centre punch and ball peen hammer.
Then set the job in the machine vice in the drilling machine and make a hole of diameter 4.5
mm using drill bit.
Fitting – After preparing both the male and female parts, fit the male part (MS rod) into the
female part (MS flat) using push fit.
Finishing – After fitting the both male and female parts, finish the both parts using a smooth
file.
Checking – Finally after finishing, check the dimensions of both parts using Vernier callipers,
whether it is correct or not as per the given dimension.
Submitting –Finally, punch the roll number on the job using a number punch and a ball peen
hammer and submit it for evaluation.

Shown above is a paper weight, completed

as a job in the manufacturing practices lab

15 | Dept. of Basic Sciences and Humanities

 Lathe Machine

Introduction:
In a machine shop, surplus materials are removed in order to obtain the desired shape. A
machine which performs the material removal operation with tools, to get the desired shape
and size of the workpiece, is known as a machine tool. It saves time, cost of production and to
get better output which cannot be obtained with hand tools. The various types of machine tools
used in workshop are lathe, shaper, planers, milling machine, drilling machine and grinding
machine.
Lathe is known as the mother of Machines, the most important machine tool used widely in a
workshop. Its main objective is to remove material by rotating the workpiece against a cutting
tool. Though a lathe is used to produce a cylindrical surface, yet many other operations such
as drilling, threading, grinding and milling etc. can be performed using it.
Specification of Lathe machine
Lathe machine is specified by the maximum size of work piece that can be held by the lathe.
Size of work piece means, diameter and length of the work piece. The distance between lathe
centres (live centre and dead centre) or of the lathe bed is used to define the maximum length.
Types of Lathe machines
There are different types of lathes used in different places according to their utility. Types of
lathes are classified according to the design, type of drive, arrangement of gears and purposes
of uses. Different types of lathes are:
Speed Lathe: This lathe is the simplest of all types of lathes. It is driven by power. There is
no gearbox, carriage and lead screw. In this lathe tool rests on a support and the tool is fed
into the work by hand and depth of cuts are small. It has a bed on which head stock and tail
stock are mounted. This type of lathe is mainly used for wood working, polishing etc.
Bench Lathe: This type of lathe is very small. It is small enough so that it can be mounted on
a bench. It is used for small work like production of gauge, punch etc
Capstan and Turret Lathe: These lathes are the modification of engine lathe and used
especially for mass production in tool rooms or production centres.
Automatic Lathe: In this lathe tools are automatically fed into the work and withdrawn after
all operations are complete. These lathes are used for mass production.
Engine Lathe: It is the most widely used lathe. When electric motors were not invented, these
machines were operated by steam engines. That’s why it was named as engine lathe. It differs
from a speed lathe that, it has additional mechanism to control the spindle speed and feed of
the cutting tool. In his workshop, an engine lathe is used for different kinds of jobs. An engine
lathe is used to produce a cylindrical workpiece from any shape of workpiece. The shape of
workpiece may be square, rectangular, hexagonal or octagonal. Besides this a lathe can be
used for other operations such as drilling, reaming, boring, taper turning, knurling, thread
cutting (external and internal), grooving etc.

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17 | Dept. of Basic Sciences and Humanities
Principal Parts of a Lathe
The different parts of a lathe machine are:
Bed: It is an essential part of a lathe, which must be strong and rigid. It carries all parts of the
machine and resists the cutting forces. The carriage and the tail stock move along the guide
ways provided on the bed. It is usually made of cast iron.
Head stock: It contains either a cone pulley or gearings to provide the necessary range of
speeds and feeds. It contains the main spindle, on which the work is held and rotated.
Tail stock: It is the counterpart of the headstock, is situated at the right-hand side of the bed.
It may be clamped in any position along the lathe bed. The tail stock spindle has an internal
Morse taper to receive the dead centre that supports the work. Drills, reamers, and taps may
also be fitted into the spindle, for performing operations such as drilling, reaming and tapping.
Carriage or Saddle: It is used to control the movement of the cutting tool. The carriage
assembly consists of the longitudinal slide, cross slide and the compound slide and apron. The
cross slide moves across the length of the bed and perpendicular to the axis of the spindle. This
movement is used for facing and to provide the necessary depth of cut while turning. The apron,
which is bolted to the saddle is on the front of the lathe and contains the longitudinal and cross
slide controls.
Cross-slide: It is mounted on the carriage. The tool is fed perpendicular to the axis of the
workpiece (during facing operation) then depth of cut to the tool is provided by moving the
hand traversing wheel.
Compound-slide: It is mounted on the cross-slide. It has a swivel base on which degree
graduations are marked, which helps to set the compound slide at the desired angle for taper
turning operation. It has no power feed. The feed is given by moving its hand-traversing wheel
manually.
Tool Post: The tool post holds the tool or tool holder (when the tool is small), which may be
adjusted to any working position.
Lead Screw: It is a long-threaded (square thread) shaft, located in front of the carriage, running
from the head stock to the tail stock. It is connected by gears with the spindle and controls the
movement of the tool, either for automatic feeding or for cutting threads.
Centres: There are two centres known as dead centre and live centre. The dead centre is
positioned in the tail stock spindle, and the live centre in the head stock spindle. While turning
between centres, the dead centre does not revolve along with the work while the live centre
revolves along with the work.
Feed Mechanism
Feed: Feed is defined as the distance which the tool advances for each revolution of work
piece. Feeds are of three types:
Longitudinal feed: When the tool travels along the work piece parallel to the bed or axis of
the workpiece that is called longitudinal feed. This feed can be given manually or
automatically.
Cross feed: When the tool travels perpendicular to the axis of work piece by the help of cross
slide is called Cross feed. This feed can be given manually or automatically.

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Angular feed: When the tool travels by the compound-slide in some angle to the axis of the
workpiece that is called angular feed. This feed is only given manually. The feed mechanism
is used in lathe for impacting various feeds to the cutting tool.
Feed mechanism consists of tumbler reversing mechanism, feed gearbox, feed changing lever,
lead screw and feed rod.
Tumbler Reversing Mechanism or Gear Train
Gears are used to transmit power from the spindle to the lead screw or feed rod through the
feed gear box. In gear train, there are stud gear, idler gear (pinion) and a screw gear. The
motion from the stud gear is transmitted to the screw gear through the idler gear. The idler
gear is mounted on a slotted link.
Feed Gear Box
On the front part of this gear box there are two levers. One is the speed changing lever, another
is the feed and lead lever. These two levers help to move the lead screw, feed rod, carriage
and cross- slide at different speeds.
Feed Changing Lever
This lever is mounted on the apron. It is used to give the automatic feed to the tool i.e.
longitudinal feed or cross feed. When lever position is in centre, the longitudinal feed and
cross feed is given manually. When the lever position is in right side then the carriage moves
parallel to the axis automatically (longitudinal feed), and automatic cross feed is given when
the lever position is in left side.
Lead Screw
It is a long-threaded shaft on which square threads are cut. It is used to give auto feed to the
carriage during thread cutting operation.
Feed Rod
It is a plain lengthy shaft which is attached to the feed box below the leads crew. It is used to
give auto feed to the tool i.e., longitudinal feed or cross feed during facing, turning, boring
and knurling operations.
Work Holding Devices Lathe Accessories
Lathe accessories are used for holding and supporting the work piece or cutting tool for
different type of operations. Different types of lathe accessories are:
Lathe centre: Lathe centres are of two types, live centre and dead centre. These are made of
tool steel or high-speed steel or alloy steel. These are solid, tapered or conical in shape. The
head stock spindle carries the live centre which is driven by power of the machine, that’s why
this centre is called live centre. The tail stock spindle carries the dead centre which is not
rotating, that’s why this centre is called dead centre. These centres are used to provide support
to a lengthy job for turning and threading.
Chuck: It is a device which helps to hold the workpiece for different types of operations.
Internal threads are there inside the chuck and external threads are there on the spindle. By
these threads, the chuck easily fits on the head stock spindle. Workpiece which are short,
cylindrical, hollow and irregular in shape (which cannot be mounted between the centres) are
easily held in a chuck. Chucks are of different types according to their utility, those are: two

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jaw chuck, three jaw chuck, four- jaw magnetic chuck, collet chuck, and combination chuck.
But three-jaw chuck and four-jaw chucks are commonly used.
Three-jaw chuck: It is known as universal chuck as movement
of the three jaws takes place simultaneously. Also called self-
cantering chuck as cantering is not required in this case because
all the jaws automatically come to the centre by adjusting any
one of them. Basically, it is used for cylindrical and hexagonal
job.
Four-jaw chuck: Motion of the jaws is independent of each
other so it is known as independent chuck. It takes more time for
setting the job than the three-jaw chuck. Here gripping is better
than three jaw chuck. Can be used for both regular and irregular
jobs.
Faceplate: It is a plate of large diameter, used for turning
operations. Certain types of work that cannot be held in chucks
are held on the face plate with the help of various accessories.

Lathe Dogs and Driving Plate

These are used to drive a work piece that is held between the centres. These are provided with
an opening to receive and clamp the work piece and dog tail, the tail of the dog is carried by
the pin provided in the driving plate for driving the work piece.
Cutting Parameters
Cutting speed: It is defined as the speed at which the material is removed and is specified in
meters per minute. It depends upon the work piece material, feed, depth of cut, type of operation
and so many other cutting conditions.
Spindle speed (RPM) = cutting speed x 1000 / (πD), D is the workpiece diameter in mm.
Feed: It is the distance traversed by the tool along the bed, during one revolution of the work.
Depth of Cut: It is the movement of the tip of the cutting tool, from the surface of the work
piece and perpendicular to the lathe axis.

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Tool Materials
General purpose hand cutting tools are usually made from carbon steel or tool steel. The single
point lathe cutting tools are made of high-speed steel (HSS). The main alloying elements are
Tungsten (18%), Chromium (4%) and Vanadium (1%); 5 to 10 % Cobalt is also added to
improve the heat resisting properties of the tool. Cemented carbide tip tool and cast alloy steel
are also used in various places, depending upon the material to be cut.
Tool Geometry
The tool used in a lathe for general purpose work is single point cutting tool. The different
types of cutting tools are shown below, used for different operations. Also, the figure below
shows the basic angles of a simple turning tool.

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Lathe Operations:
Turning
Turning is the process in which the material is removed by a traversing cutting tool, from the
surface of a rotating work piece. For turning long workpiece, first it should be faced and centre
drilled at one end and then supported by means of the tail stock centre. It is used for reducing
the diameter of the work piece.
Boring
Boring is enlarging a hole and is used when correct size drill is not available. However, it
should be noted that, boring operation can’t be used to make hole.
Facing
Facing is a machining operation, performed to make the end surface of the work piece, flat and
perpendicular to the axis of rotation. For this, the workpiece is held in a chuck and rotated about
the lathe axis and the facing tool is fed perpendicular to the axis of the lathe. The tool is slightly
inclined to the axis of the spindle. It is used for reducing the length of the work piece.
Straight Turning
This is an operation of removing excess amount of metal from the entire surface of cylindrical
workpiece by the help of turning tool. In this operation longitudinal feed is given by carriage
manually or automatically. In this operation the job is held in chuck or in between centre.
Step Turning
It is an operation of producing various steps of different diameters in the workpiece. This
operation is done after the facing and straight turning operation.
Taper Turning
A taper is defined as the uniform change in the diameter of a workpiece, measured along its
length. It is expressed as a ratio of the difference in diameters to the length. Taper turning refers
to the production of a conical surface, on the workpiece on a lathe. Taper turning is done in a
lathe by swivelling the compound rest to the required angle. Here, the cutting tool is fed by
means of the compound slide feed handle. The workpiece is rotated in a chuck or faceplate or
in-between centres.
Drilling
Axial holes in cylindrical parts are produced by drilling operation, using a twist drill. For this,
the work piece is rotated in a chuck or face plate and the drill bit is fitted into the tail stock
spindle directly or through drill chuck. The tail stock is then moved over the bed and clamped
on it near the work. When the job rotates, the drill bit is fed into the work by turning the tail
stock hand wheel.
Knurling
It is the process of embossing a diamond shaped regular pattern on the surface of a work piece
using a special knurling tool. This tool consists of a set of hardened steel rollers in a holder
with the teeth cut on their surface in a definite pattern. The tool is held rigidly on the tool post
and the rollers are pressed against the revolving work piece to squeeze the metal against the
multiple cutting edges. The purpose of knurling is to provide an effective gripping surface on

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a workpiece to prevent it from slipping when operated by hand.
Chamfering
It is the operation of bevelling the extreme end of a work piece. Chamfer is provided for better
look, to remove burrs, to protect the end of the work piece from being damaged and to allow
easy fitting of nut, bolt and shaft.
Threading
Threading is nothing but cutting uniform helical grooves on a cylindrical workpiece. Threads
may be cut either on the internal or external cylindrical surfaces. A specially shaped cutting
tool, known as thread cutting tool, is used for this purpose. Thread cutting in a lathe is
performed by traversing the cutting tool at a definite rate which is in proportion to the rate at
which the workpiece revolves.

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Job No. : 2
Aim of the Job: To make cylindrical step turning and threading part.

Material Used: Mild steel rod (103 x 20) mm

Tools and Equipment Used:
 Lathe Machine
 Steel Rule
 Vernier calliper
 Scriber
 Surface Gauge
 Centre Gauge
 Screw Pitch Gauge
 Facing Tool
 Right hand Turning Tool
 V – Thread cutting Tool
 Flat Smooth File
 Triangular Smooth File
Procedure:
Measuring and Marking: After receive the workpiece, first measure the size of the workpiece
(length and diameter) by vernier calliper whether it is correct or not as per nominal size (103 x
20) mm.
Setting the Job and Tool: After measurement, set the job in three-jaw chuck and fasten it
properly by chuck key. Then check the centre of the job by surface gauge and set the cutting
tool in tool holder. Set the tool holder in the tool post at proper height and check the centre of
the tool by dead centre.
Operation: First set the job and tool, then make one end of the workpiece plain by facing
operation. After that remove the job from the chuck, and mark a line of 100mm by scriber and
depth bar of the vernier calliper, at the other end of the workpiece. Then reduce the diameter
from 20mm to 17.1mm by turning operation with the help of right-hand turning tool. After that,
mark a line of 30mm length, in that portion reduce the diameter to 13.1mm (step turning). After
the step turning, surface finishing is done by a flat smooth file which reduce the diameter of

24 | Dept. of Basic Sciences and Humanities

all steps by 0.1mm. After finishing, thread cutting to be done on the portion of workpiece with
diameter 13mm. A V – thread cutting tool is used to generate the metric v-thread of angle 60
degree. Check the pitch of the thread by screw pitch gauge from time to time. Then do finishing
of the thread by a triangular file.
Checking: After completing all operations, check the length and diameter of each step by a
vernier calliper to see whether it is of required size or not.
Submitting: After checking, punch the roll no and branch on the job, using number punch and
letter punch, then submit it for evaluation.

Shown above is a cylindrical step turning and threading

part, completed as a job in the manufacturing practices lab

25 | Dept. of Basic Sciences and Humanities

 Milling Machine

Introduction:
A milling machine is used to remove metal form a workpiece as the work piece is fed against
a rotating multipoint cutter. In this machine, the cutter rotates at high speed and it removes
metal at a very fast rate due to multipoint cutting edges. This is superior to other machines in
accuracy and for better surface finish.
Specification of Milling Machine
Milling machine is specified according to the (i) Size of the work table i.e. length and breadth,
(ii) Maximum length of longitudinal, cross and vertical travel of the work table.
Types of Milling Machine
Different types of milling machines are used in different place according to their utility. The
different types of milling machines are:
 Column and knee type milling machine
 Fixed bed type milling machine
 Special type of milling machine
Column and Knee Type Milling Machine
This type of milling machine is most commonly used in general workshop. In this machine the
work table is mounted on a knee, which slides on the vertical part of a column by guideways.
This type of milling machine is classified according to the various method of supplying power
to the table, different movements of the table and different axis of rotation of the spindle. The
vertical milling machine, horizontal milling machine and universal milling machines are
further categorised under column and knee types.
Vertical Milling Machine
In the vertical milling machine, the spindle is vertical or perpendicular to the work table. The
vertical head is clamped to the vertical column which can be swivelled at an angle for
machining an angular surface. End milling cutter, face milling cutter, T-slot milling cutters are
used in a vertical milling machine. This machine is used for machining grooves, slots, keyways
and flat surfaces.
Horizontal Milling Machine
In this milling machine workpiece along with the table is fed against a rotating cutter which is
mounted on a horizontal arbor. In this machine the table can be fed in a longitudinal, cross or
vertical direction. If the table is moved at right angles to the spindle, that feed is known as
longitudinal feed. When the table is moved parallel to the spindle that feed is called cross feed
and when it moves vertically upward or downward that is called vertical feed.
Universal Milling Machine
This machine is used in a tool room for very accurate work. It is similar to the horizontal
milling machine but the difference is, a horizontal milling machine has three table movements
(longitudinal, cross and vertical) whereas a universal milling machine has four table

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movements. In this machine, the table is mounted on a swivel base on which graduation are
marked in degrees, which helps to set the table at any angle up to 45 degree with the horizontal
for making helical grooves. This machine is used for producing different types of gears,
threads, drill bits, reamers and also used for cutting slots, grooves, keyways, steps and
producing flat surface (horizontal, vertical or inclined).

Parts of a Milling Machine

Base: The base gives support to all parts of the machine, on which the column is mounted at
the back end. An elevating screw is mounted on the base which gives support to the knee and
helps it to move in both upward and downward direction.
Column: It is a rectangular box shaped part mounted on the base. A gear mechanism is
arranged inside the column for transmitting power from the motor to the spindle. Dovetail
guide ways are present on the front part of the column which helps the knee to move in both
upward and downward directions.
Knee: It moves vertically up and down on the column by the guideways. A spindle is mounted
on the top face of the knee.
Saddle: It slides crosswise i.e., parallel to the axis of the arbor by the guide ways which is
provided on the top face of the knee. Also saddle gives support to the work table.
Table: It slides longitudinally i.e., perpendicular to the axis of the arbor over the saddle by the
guide ways provided on it. T-slots are cut on the surface of the table for clamping the work
piece on it. A lead screw under the table engages a nut on the saddle to move the table
horizontally, either manually or automatically. It can move up and down by raising or lowering
the knee on the column. Also, the table can move cross wise, by rotating the cross-feed handle.
Overarm: It is mounted on the top of the column which can be adjusted horizontally. The over
arm supports the arbor.
Spindle: It is a hollow shaft which is located on the top part of the column. The spindle receives
power from the motor through the belt drive, gears and clutches (provided inside the column).
Front end of the spindle projected from the column face, has a tapered hole into which Arbor
is fitted.
Arbor: It is a shaft whose one end is tapered which fits into the spindle. Milling cutters can be

27 | Dept. of Basic Sciences and Humanities

held at different positions of the arbor.
Spacing Collar: These are hollow cylindrical parts are fitted on the arbor. These are used to
give support to the milling cutters and also helps to setting the cutter on different position on
the arbor for different types of operations.
Mechanism of Milling Machine
The two milling machine mechanism available are spindle drive mechanism and table feed
mechanism.
Spindle Drive Mechanism: In light duty machine, spindle speeds are changed by shifting the
V-belt to the different pullies present in the column. In belt drive machine, spindle can have
eight different speed (four direct speeds and four back gear speeds).
Table Feed Mechanism: In a milling machine a telescopic feed shaft is connected with the
gear box and the other end connected with the table, which helps to give the automatic feed to
the table.
Work Holding Devices of Milling Machine
Different types of holding devices are used in milling machine, for clamping the workpiece on
the table securely, for different types of operations. Holding devices are: T-bolts and clamp,
angle plate, machine vice (plain or swivel base) and fixtures.
Milling Cutters and Its Functions
Material: Milling cutters are made-up high speed steel for
general purpose work, whereas cemented carbide steel is used
for cutting hard metal in production centres and cast alloy steel
for cutting high speed steel metal.
For different types of operations different milling cutters are
used in milling machine. The different milling cutters are:
Plain Milling Cutter: Used for producing flat surfaces which
are parallel to the spindle axis.
Side Milling Cutter: Used for producing flat surfaces,
cutting slots and making steps.
Angle Milling Cutter: Used for dovetail notches or ratchet
wheel, also for machining V-grooves.
End Milling Cutter: Used for producing flat surface,
machining slots, keyways, grooves and also used for making
steps.
T-Slot Cutter: Used for making T-slots on the work table of
the machines.
Gear Cutter: Used for producing gear wheel.
Thread Cutter: Used for cutting different types of threads.

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Milling Methods
Different milling methods performed by the different cutters.
Peripheral Milling: It is the operation performed
by a milling cutter to produce a machined surface
parallel to the axis of rotation of the cutter. In this
method the cutting force is not uniform. Up
milling method and down milling method is under
this method.
Up Milling Method: This is the method in, the
cutter rotates against the direction in which the
workpiece is feeding. This method is suitable for
all operation in all milling machines. In this
method the load on each cutter tooth is gradually increased. It increases the life of the cutting
tool also gives better finish. If the depth of cut is more or the work piece is not properly clamped
in vice, the cutter tends to lift the work piece from the work table. If the depth of cut is more,
some scallop marks show on the finished surface.
Down Milling Method: It is the method; the cutter rotates in the same direction as that in
which the workpiece is feeding. This method is not suited for all machines or all types of work.
For down milling, machines are specially designed. It is a relatively newly-invented method in
which the cutter tends to press the work down on the work table.

Face Milling: The face milling is an operation performed by a milling cutter to produce a flat
surface perpendicular to the axis of rotation of the cutter. In this method both up and down
milling are performed simultaneously on the work surface.
Cutting Speed, Feed and Depth of Cut of Milling Machine
Cutting Speed: The speed at which the metal is removed from the work piece in one revolution
of the cutter.
Feed: It is defined as the distance which the work piece advances for each revolution of the
cutter.
Depth of Cut: It is defined as the thickness of metal to be removed from the workpiece by the
cutter.

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Cutting Fluid: During cutting, due to friction between the job and the cutting tool, heat is
generated. This causes the tools to wear out and their cutting capacity gets reduced which
results in poor finishing and slow cutting rate. Cutting fluid is used to avoid damage of the
cutting tools. For different jobs different kinds of cutting fluids are used i.e. soluble oil, mineral
lard oil, sulphureted oil, kerosene oil and low viscosity oil.

30 | Dept. of Basic Sciences and Humanities

Job No.: 3
Aim of the Job: To make single step on a mild steel square block.

Material Used: Mild steel square block (40 x 40 x 40) mm.

Tools and Equipment Used:
 Milling machine
 Steel rule
 Vernier callipers
 Odd leg callipers
 Dot punch
 Ball peen hammer (200gm)
 Soft hammer
 Flat smooth file
 Side milling cutter
Procedure:
Measuring and Marking: After receive the workpiece check the dimensions (length, width
and height) by Vernier callipers to see whether it meets the required size or not. Then coat any
two adjacent surfaces by a chalk and draw the lines on the coated surface, by an odd leg calliper
and steel rule for the step cutting. The size of the step should be as per the job diagram (4mm
depth and 5mm width). By the help of a dot punch and hammer do punching on the marked
lines.
Setting the Job and Tool: After measurement, set the job in machine vice at the proper height
and set the milling cutter on the arbor.
Operation: By adjusting the cross-feed handle, set the cutting edge of the cutter on the line
that is marked at 5mm on the job. Then remove the extra metal from the marking area by up

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milling method. Increase the depth of cut by adjusting of knee elevating handle time to time,
in order to get proper depth of the step as per the requirement.
Checking: After completing all operation, check the depth and width of the step by the vernier
calliper to see whether it meets the desire dimensions or not.
Submitting: After checking, punch the roll number and branch on the job by a number punch
and letter punch then submit it for evaluation.

Shown above is a single step on a mild steel square block,

completed as a job in the manufacturing practices lab

32 | Dept. of Basic Sciences and Humanities

 Shaping Machine

Introduction:
A shaping machine or shaper is a reciprocating type of machine tool, in which a single point
cutting tool moves in a reciprocating manner over a stationary work piece. This machine is
used to produce any type of flat surface (horizontal, vertical or inclined). Besides producing
flat surface, it is also used for making square, rectangular and v-grooves, keyways, slots and
also for making steps.
Specifications of the Shaping Machine
 Shaping machine is specified according to the maximum length of the stroke
 Size of the table i.e. length, width and depth of the table
 Distance between table surface and ram
 Maximum movement of the table in vertical and horizontal direction
Types of Shaping Machines
Different types of shaping machines are used in different places according to their utility. Types
of shaping machines are classified on the basis of,
 Design of the work table
 Driving mechanism
 Direction of movement of ram and nature of cutting stroke
Design of the Work Table
According to the design of the work table shapers are of two types - Standard shaper and
Universal shaper.
Standard Shaper
In standard shaper, the work table has only two movements i.e., horizontal and vertical. But it
cannot be swivelled or tilted.
Universal Shaper
In universal shaper, the work table moves vertically, horizontally and also swivelled or tilted.
This type of shaper is mostly used in the tool room.
Driving Mechanism
According to the driving mechanism, shapers are of three types - Crank shaper, Gear shaper
and Hydraulic shaper.
Crank Shaper
A crank shaper is the most common type of shaper which has a crank and slotted lever quick
return mechanism. In this machine the bull gear receives power from the motor and a crank is
arranged inside the body of the bull gear. The crank changes the circular motion of the motor
to the reciprocating motion of the ram.
Gear Shaper
In gear shaper, a rack is fixed below the ram which is driven by a spur gear.

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Hydraulic Shaper
This type of shaper is more efficient than crank and gear shaper. In this type of shaper, there
is no crank and gear to move the ram. The reciprocating movement of ram is obtained by the
oil pressure present in the cylinder piston arrangement. One end of the piston is connected to
the ram.
Direction of Movement of the Ram
According to the direction of movement of ram, shapers are of two types i.e., Horizontal shaper
and Vertical shaper.
Horizontal Shaper
In this type of shaper, the ram moves in a horizontal direction. This type of shaper is mainly
used to produce flat surface and also used for making steps, slots and grooves.
Vertical Shaper: -In this type of shaper, the ram moves vertically in both upward and
downward direction. This type of shaper is used for machining internal surfaces, keyways,
slots or grooves.
Nature of Cutting Stroke
According to the nature of cutting stroke, shapers are of two types: Push cut shaper and draw
cut shaper.
Push Cut Shaper
In this shaper, ram pushes the cutting tool across the work piece. The metal is removed from
the work piece in forward stroke so it is known as cutting stroke, but in return stroke it does
not cut the metal so called as idle stroke.
Draw Cut Shaper
In this type of shaper, the metal is removed in back ward stroke. So, in this shaper, the back-
ward stroke is the cutting stroke and the forward stroke is the idle stroke.

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Parts of Shapers
The different parts of shapers are:
Base: The base of the shaper is made of cast iron. The base of the shaper gives support to the
column and other parts.
Column: Column is a box-like part mounted on the base which is made of cast iron. On the
top of the column two dovetail guide ways are present on which the ram reciprocates over
the column. The crank and slotted link mechanism are arranged inside the column which
helps to reciprocate the ram.
Cross-Rail: The cross-rail is mounted on the front part of the vertical guide ways of the
column. A lead screw and an elevating shaft are arranged inside the cross rail. By rotating the
elevating shaft, the cross-rail moves vertically upwards and downwards by the guide ways
provided on the front side of the column.
By rotating the lead screw (by hand or by power) the work table moves longitudinally,
perpendicular to the axis of the ram over the cross-rail.
Work Table: The work table is a box shaped part. T-slots are present on the top of the work
table for clamping the work piece. Also, a machine vice is clamped on the T-slots for holding
the work piece for different type of operations. The work table is bolted to the saddle which
is mounted on the cross-rail. The table can be moved vertically and cross wise with the help
of saddle and cross-rail.
Ram: The ram is located on the top of the column which reciprocates over the column by the
dovetail guide ways. A stroke adjustment lever is present on the ram which helps to adjust
different strokes for different operations. The forward stroke of the ram (in case of push cut
shaper) is called the cutting stroke or working stroke, and the backward stroke is called the
return stroke or idle stroke. One cycle of the shaper means, one forward stroke and backward
stroke.
Tool Head: Tool head is attached to the front portion of the ram with the help of nuts and
bolts. It has a swivel base and degree graduation present on it which helps to turn or rotate
the tool head at an angle from 0 degree to 90 degree. A hand traversing wheel is present on
the top of the tool head which helps to give the down feed or the depth of cut. The tool head
holds the cutting tool by the help of a single screw tool post. The tool-post is mounted on a
clapper box which is attached on the front part of the tool head. The clapper box helps to lift
the cutting tool on the return stroke to save the cutting edge of the tool from being damaged.
Shaper Drive Mechanism (Quick Return Mechanism)
A shaper drive mechanism converts the rotary motion of the motor into the reciprocating
motion of the ram. In standard shaper, metal is removed in the forward stroke, but no metal
is removed in return stroke. To reduce the idle machining time, it is necessary to reduce the
time taken by the return stroke. So that the ram moves in slow speed during cutting stroke
whereas during the return stroke the ram moves at a faster rate to reduce the return time. This
mechanism is called quick return mechanism.
Feed Mechanism
In shaper two types of feeds are used i.e. down feed and cross feed. Down feed is given
manually by rotating the hand wheel of the tool head. Cross feed is given by rotating the

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cross-feed lead screw which is present inside the cross-rail by hand or by power (pawl
mechanism). To give automatic feed to the table, a slotted driving disc is driven by a gear
which is connected to the bull gear shaft. The rotational speed of the driving disc is the same
as the bull gear speed. The driving disc is linked to the rocker arm by a connecting rod. The
rocker arm carries a spring-loaded reversible pawl which is straight on one side and bevel on
the other side. The rocker arm is hinged at the centre of the ratchet wheel which is keyed to
the cross-feed lead screw. As the driving disc rotates it causes the pawl to oscillate. By
offsetting the driving pin on the slotted disc, the rocker arm is made to oscillate to move the
pawl over the teeth of ratchet wheel which helps move the cross-feed lead screw and work
table. To reverse the direction of table, the pawl is lifted by the knob and turned round so that
it moves the ratchet wheel in the opposite direction. When no feed is required, the pawl is
lifted and turned by 90 degrees, so that the pin is out of the groove and the pawl is free from
the ratchet wheel.
Work Holding Devices
For holding or clamping the work piece on the work table different types of holding devices
are used. Shaper holding devices are: machine vice, parallel strips, clamps, angle plate, and
V-block.
Machine Vice: It is a holding device which is used in a shaper to hold the work piece for
different types of operations. Machine vices are of two type i.e. plain machine vice and swivel
base machine vice.
Parallel Strips: Parallel strips are used to give support to the job and raise the surface to be
shaped to the proper height above the vice jaw
Shaper Operations
The different types of operations are carried out in shaper are:
 Horizontal shaping (facing top of the job)
 Vertical shaping (facing sides)
 Cutting slots, grooves, keyways and steps
 Angular shaping (Dovetail cutting)
 Cutting gear teeth
Shaper Cutting Tools
The cutting tools used in shaper are single-point cutting
tool like the lathe cutting tools and the tool holders are
also same as the lathe tool holder.
Shaper tools are made up of high speed steel, cast alloy
or cemented carbide steel. HSS cutting tool is the most
common tool used for general work in a shaper. A
cemented carbide cutting tool is used for hard material
to be machined. Some of the most common cutting tools
are:
Left hand and right-hand cutting tool used for paining.
Left hand and right-hand side facing tool used for vertical shaping and for shaping sharp
corners.

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Round nose cutting tool used for making round grooves and can cut in both left and right
direction.
V-nose cutting tools used for making v-grooves.
Straight nose and flat or square nose tools used for making slots, keyways and cutting steps.
Cutting Speed, Feed and Depth of Cut
Cutting Speed
The speed at which the metal is removed by the cutting tool from the work piece is called
cutting speed.
Feed
It is defined as the distance travelled by the workpiece in the perpendicular direction to the
axis of reciprocation in both the strokes. The feed is always given at the end of return stroke
when the tool is not cutting the metal.
Depth of Cut
Depth of cut is defined as the thickness of metal removed in one cut. In a shaper, depth of
cut is the distance through which the tool penetrates into the metal during cutting stroke.

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Job No. 4:
Aim of the Job: To make a keyway on a mild steel square block.

Material Used: Mild steel square block (40 x 40 x 40) mm.

Tools and equipment Used:
 Shaping Machine
 Steel Rule
 Vernier callipers
 Odd leg callipers
 Dot Punch
 Ball peen Hammer (200gm)
 Soft Hammer
 Flat Smooth File
 Square nose Cutting Tool.
Procedure:
Measuring and Marking: After receive the workpiece check the dimensions (length, width
and height) by Vernier callipers to see whether it meets the required size or not. Then coat any
two adjacent surfaces by a chalk and draw the lines on the coated surface, by an odd leg calliper
and steel rule for the key way. The size of the keyway should be as per the job diagram (4mm
depth and 6mm width). By the help of a dot punch and hammer do punching on the marked
lines.
Setting the Job and Tool: After measurement, set the job in the machine vice at proper height
and set the tool on the tool post. Then set the nose of the tool in between the two marking lines
of the key way on the job.
Operation: After setting the job and tool, set a little depth of cut by touching the cutting edge
of the tool in between the marking from one end. Then remove the extra metal from the marking

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area by increasing the depth of cut which can be done by adjusting the down feed handle time
to time. Continue the process of cutting metal till the proper depth of the keyway is obtained
as per the requirement.
Checking: After completing all operation, check the depth and width of the key way by the
vernier calliper to see whether it meets the desire dimensions or not.
Submitting: After checking, punch the roll number and branch on the job by a number punch
and letter punch then submit it for evaluation.

Shown above is a keyway on a mild steel square block,

completed as a job in the manufacturing practices lab

Arc Welding

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Introduction:
Welding is a process of joining metal parts by the application of heat, with or without
application of pressure or filler metal, in such a way that the joint is equivalent in composition
and characteristics of the metal parts joined together. In the beginning, welding was mainly
used for repairing all kinds of worn or damaged parts. Nowadays, it is extensively used in
manufacturing industries, construction industries (construction of ships, tanks, locomotives and
automobiles), and maintenance work and in replacing riveting and bolting.
The various welding processes are:
1. Electric arc welding
2. Gas welding
3. Thermite welding
4. Electrical Resistance welding and
5. Friction welding
However, here only electric arc welding and gas welding processes are discussed from
the subject point of view.
Electric Arc Welding
Arc welding is the welding process, in which heat is generated by an electric arc struck between
an electrode and the work piece. Electric arc is a luminous electrical discharge between two
electrodes through ionized gas.

Arc welding set up.

Arc welding method is based on an electric circuit consisting of the following parts:
a. Power supply (AC or DC)
b. Welding electrode
c. Workpiece
d. Welding cables connecting the electrode and workpiece to the power supply.
Electric arc between the electrode and workpiece closes the electric circuit. The arc temperature
may reach 10000°F (5500°C), which is sufficient to melt the workpiece edges and joining them.

To supply the current for welding, three types of power sources are available: transformers,

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motor generators and rectifiers. These machines supply high electric current at low voltage and
an electrode is used to produce the necessary arc. The arc melts the surface to be joined whereas
the electrode serves as a filler rod.
Sizes of welding machines are rated according to their approximate amperage capacity at 60%
duty cycle, such as 150, 200, 250, 300, 400, 500 and 600 amperes. This amperage is the rated
current output at the working terminal.
Transformer
The transformer type of welding machine produces AC current and is considered to be the least
expensive. It takes power directly from power supply line and transforms it to the voltage
required for welding. Transformers are available in single phase and three phases in the market.
Motor generators
These are DC generators sets, in which electric motor and alternator are mounted on the same
shaft to produce DC power as per the requirement for welding. These are designed to produce
DC current in either straight or reversed polarity. The polarity selected for welding depends
upon the kind of electrode used and the material to be welded.
Rectifiers
These are essentially transformers, containing an electrical device which changes AC to DC
by virtue of which the operator can use both types of power (A.C or D.C, but only one at a
time). In addition to the welding machine; certain accessories are needed for carrying out the
welding work.
Welding cables
Two welding cables are required, one from machine to the electrode holder and the other, from
the machine to the ground clamp. Flexible cables are usually preferred because of the case of
using and coiling the cables. Cables are specified by their current carrying capacity, say 300A,
400 A, etc.
Electrodes
Filler rods are used in arc welding are called electrodes. These are made of metallic wire called
core wire, having approximately the same composition as the metal to be welded. These are
coated uniformly with a protective coating called flux. While fluxing an electrode; about 20mm
of length is left at one end for holding it with the electrode holder. It helps in transmitting full
current from electrode holder to the front end of the electrode coating. Flux acts as an insulator
of electricity. The figure shows the various parts of an electrode.

Parts of an electrode

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In general, electrodes are classified into five main groups; mild steel, high carbon steel, special
alloy steel, cast iron and non‐ferrous metals. The greatest range of arc welding is done with
electrodes in the mild steel group. Various constituents like titanium oxide, potassium oxide,
cellulose, iron or manganese, ferro‐ silicates, carbonates, gums, clays, asbestos, etc., are used
as coatings on electrodes. While welding, the coating or flux vaporizes and provides a gaseous
shield to prevent atmospheric attack.
The size of electrode is measured and designated by the diameter of the core wire in SWG
(standard wire gauge) and length, apart from the brand and code names, indicating the purpose
for which they are most suitable.
Electrodes may be classified on the basis of thickness of the coated flux
1. Dust-coated or light-coated
2. Semi or medium-coated and
3. Heavily coated or shielded
Electrodes are also classified on the basis of materials
1. Metallic and
2. Non‐metallic or carbon
Metallic arc electrodes are further sub‐divided into
1. Ferrous metal arc electrode (mild steel, low/medium/high carbon steel, cast iron,
stainless steel, etc)
2. Non‐ferrous metal arc electrodes (copper, brass, bronze, aluminium, etc).
In case of non‐metallic arc electrodes, mainly carbon and graphite are used to make the
electrodes.
Welding Tools
Electrode holder
The electrode holder is connected to the end of the welding cable to hold the electrode. It should
be light, strong and easy to handle and should not become hot while doing any operation. Figure
shows one type of electrode holder. The jaws of the holder are insulated, offering protection
from electric shock.

Electrode holder Ground clamp

Ground clamp
It is connected to the end of the ground cable and is clamped to the work or welding table to
complete the electric circuit. It should be strong, durable and give a low resistance connection.
Wire brush and chipping hammer

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A wire brush is used for cleaning and preparing the work for welding. A chipping hammer is
used for removing slag formation on welds. One end of the head is sharpened like a cold chisel
and the other, to a blunt, round point. It is generally made of tool steel. Molten metal dispersed
around the welding heads, in the form of small drops, is known as spatter. When a flux coated
electrode is used in welding process, then a layer of flux material is formed over the welding
bead which contains the impurities of weld material. This layer is known as slag. Removing
the spatter and slag formed on and around the welding beads on the metal surface is known as
chipping.

Welding table and cabin

The welding table is made of steel plate and pipes which is used for positioning the parts to be
welded properly. The welding cabin is made‐up by any suitable thermal resistance material,
which can isolate the surrounding from the heat and light emitted during the welding process.
A suitable draught should also be provided for exhausting the gas produced during welding.
Face shield
A face shield is used to protect the eyes and face from the rays of the arc and from spatter or
flying particles of hot metal. It is available either in hand or helmet type. The hand type is
convenient to use wherever the work can be done with one hand. The helmet type is not
comfortable to wear but leaves both hands free for the work. Shields are made of light weight
non‐reflecting fibre and fitted with dark glasses to filter out the harmful rays of the arc. In some
designs, a cover glass is fitted in front of the dark lens to protect it from spatter.

Hand gloves
These are used to protect the hands from electric shock and hot spatter.

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Preparation of a job for welding.
Before welding, the workpieces must be thoroughly cleaned of rust, scale and other foreign
material. Thin pieces of metal are generally welded without bevelling the edges; however, thick
workpiece should be bevelled or V-shape out to ensure adequate penetration and fusion of all
parts of the weld. But, in either case, the parts to be welded must be separated slightly to allow
for better penetration of the weld.
Before commencing the welding process, the following must be considered
a. Ensure that the welding cables are connected to a proper power source.
b. Set the electrode, as per the thickness of the plate to be welded.
c. Set the welding current, as per the size of the electrode to be used.
Table below gives Electrode current Vs electrode size Vs plate thickness.
Plate
Electrode Electrode current
thickness
size (mm) range (amp)
(mm)
1.6 1.6 40-60
2.5 2.5 50-80
4 3.2 90-130
6 4 120-170
8 5 180-270
25 6 300-400
NOTE: While making butt welds in thin metal, it is a better practice to do tack‐weld (a small
weld) in between the pieces intervals to hold them properly while welding.
Striking an Arc
The following are the stages and methods of striking an arc and running a bead
a. Select an electrode of suitable kind and size for the work and set the welding current at
a proper value.
b. Fasten the ground clamp to either the work or welding table.
c. Start or strike the arc by either of the following methods
Strike and withdraw
In this method the arc is started by moving the end of the electrode onto the work with a slow

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sweeping motion, similar to striking a match.
Touch and withdraw
In this method, the arc is started by keeping the electrode perpendicular to the work and
touching or bouncing it lightly on the work. This
method is preferred as it facilitates restarting the
momentarily broken arc quickly. If the electrode sticks
to the work, quickly bend it back and forth, pulling at
the same time. Make sure to keep the shield in front of
the face, when the electrode is freed from sticking. As
soon as the arc is struck, move the electrode along,
slowly from left to right, keeping at 15º to 25º from vertical and in the direction of welding.
Weaving
A steady, uniform motion of the electrode produces a satisfactory bead. However, a slight
weaving or oscillating motion is preferred, as this keeps the metal molten a little longer and
allows the gas to escape, bringing the slag to the surface. Weaving also produces a wider bead
with better penetration.
Types of Joints
Welds are made at the junction of the various pieces
that make up the weldment. The junctions of parts, or
joints, are defined as the location where two or more
numbers are to be joined. Parts being joined to produce
the weldment may be in the form of rolled plate, sheet,
pipes, castings, forgings, or billets. The five basic types
of joints are listed below.
A butt joint is used to join two members aligned in the
same plane. This joint is frequently used in plate, sheet
metal, and pipe work. A joint of this type may be either
square or grooved.
Corner and tee joints are used to join two members
located at right angles to each other. In cross section, the corner joint forms an L‐shape, and
the tee joint has the shape of the letter T. Various joint designs of both types have uses in many
types of metal structures.
A lap joint, as the name implies, is made by lapping one piece of metal over another. This is
one of the strongest types of joints available; however, for maximum joint efficiency, you
should overlap the metals a minimum of three times the thickness of the thinnest member to be
joined. Lap joints are commonly used with torch brazing and spot-welding applications.
An edge joint is used to join the edges of two or more members lying in the same plane. In
most cases, one of the members is flanged. While this type of joint has some applications in
plate work, it is more frequently used in sheet metal work. An edge joint should only be used
for joining metals 0.25 inch or less in thickness that are not subjected to heavy loads.
Welding Positions

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All welding is done in one of these four positions, depending upon the location of the welding
joints, appropriate position of the electrode and hand movement.
1. Flat
2. Horizontal
3. Vertical
4. Overhead

Flat position welding

In this position, the welding is performed from the upper side of the joint, and the face of the
weld is approximately horizontal. Flat welding is the preferred term; however, the same
position is sometimes called down hand welding.
Horizontal position welding
In this position, welding is performed on the upper side of an approximately horizontal surface
and against an approximately vertical surface.
Vertical position welding
In this position, the axis of the weld is approximately vertical as shown in the figure.
Overhead position welding
In this welding position, the welding is performed from the underside of a joint.
Advantages and Disadvantages of Arc Welding
Advantages
1. Welding process is simple.
2. Equipment is portable and the cost is fairly low.

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 3. All the engineering metals can be welded because of the availability of a wide variety of
electrodes.
Disadvantages
1. Mechanized welding is not possible because of limited length of the electrode.
2. Number of electrodes may have to be used while welding long joints.
A defect (slag inclusion or insufficient penetration) may occur at the place where welding is
restarted with a fresh electrode.
Weld Defects
A welding defect is any flaw that compromises the usefulness of a weldment. There is a great
variety of welding defects. Different weld defects produced during arc and gas welding is
Spatter, Crater, Lack of fusion, Blowholes, Less penetration.
 Spatter: During arc welding molten metal’s spread and deposited around the bead is
known as spatter. It is formed due to excess current and improper arc length.
 Crater: Depression or cavity occurs on the end of the bead is known as crater. It is formed
due to excess current, temperature and improper technique.
 Lack of fusion: Edges are not melted properly during arc and gas welding is known as
lack of fusion. It is formed due to less current and temperature.
 Blowholes: After arc and gas welding small holes formed on the bead is known as
blowholes. They are formed due to excess current, improper arc length and technique.
 Less penetration: Depth of less fusion is known as less penetration. It is formed due to
low current, less temperature and improper root gap.

Spatter Blowhole
s

Crater
Welding bead

Job No. : 5

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Aim of the Job: To make a butt joint by arc welding.

Materials Used: Mild steel Flat (101 x 19 x 5) 2pcs and mild steel Electrode (3.15 mm dia.)
1pc
Tools and Equipment Used:
 Steel rule
 Scriber
 Try square
 Bench vice
 Hacksaw
 Odd leg callipers
 Rough file
 Leather apron
 Hand glove
 Hand shield
 Tong
 Chipping hammer
 Chisel
 Ball peen hammer
 Wire brush
 Number punch
 Transformer with all accessories.
Procedure:
Measuring: First measure the size of the flat (length, width and thickness) by a steel rule as
per the nominal size (101 x 19 x 5) mm.
Marking: After measurement coat any one surface, of the MS flat with a chalk. Draw a line at
101 mm from one edge by using steel rule, try square and scriber.
Cutting: Set the MS flat in bench vice and cut the marking lines by using a hacksaw.
Edge preparation. Then mark a line from one end of the chalked surface to make it
perpendicular to the adjacent side by using a scriber and a try square. After that, draw another

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line at 100 mm parallel to the previous line drawn on the chalked surface, by using Jenney
callipers. Prepare the edges of the MS flat by using rough flat file and try square to obtain the
required dimension (100x19x5) mm for both the pieces.
Job setting: Set both the MS flat in the arc welding booth, keeping in flat position with a 1
mm root gap between them for butt joint.
Current setting: Set the current 90-120 ampere, by using a transformer according to the size
of the electrode (3.15 mm).
Welding: First produce the arc by the scratching method then tack weld on the job by using
medium arc length to weld the job in a slightly weaving motion.
Cooling: After welding, cool the job in normal atmospheric condition.
Chipping: Then remove the slag by the help of a chipping hammer.
Cleaning: After that remove the spatters by a chisel and hammer from both sides of the bead.
Then clean the both sides of the beads by the help of a wire brush and rough file.
Checking: After completing all operation, check all the dimensions by the steel rule to see
whether it meets the desire dimensions or not.
Submitting: After checking, punch the roll number and branch on the job by a number punch
and letter punch then submit it for evaluation.

Shown above is a butt joint by arc welding, completed as a

job in the manufacturing practices lab

Gas Welding
Introduction:

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Oxy-acetylene is commonly used for gas welding. It consists of the supply of oxygen and
acetylene under pressure in cylinders, pressure regulators, a torch, hoses and accessories like
goggles and a lighter. The oxygen and acetylene cylinders are connected to the torch through
pressure regulators and hoses. The regulator consists of two pressure gauges, one for indicating
the pressure within the cylinder and the other shows the pressure of the gas fed into the torch,
which may be regulated. The torch mixes the two gases and the flame may be controlled by
adjusting the oxygen and acetylene supply.

Note:
 In oxy-acetylene welding the flame must be supplied by a correct balance of oxygen and
acetylene so that it is neither oxidizing nor carburizing, since either of these flames would
weaken the weld
 Oxygen regulators have “Right-hand” threads with plain nuts and acetylene regulators
have “Left-hand” threads with notched hexagonal nuts so that there is no confusion for
identification. The regulator is closed by unscrewing the regulating screw
 Apart from oxygen and acetylene gases, there are other combinations of gases used to
obtain a hot flame. They are can be a mixture of oxygen and hydrogen, air and acetylene
or oxygen and propane. However, the combination of oxygen and acetylene is the most
commonly used, as the heat produced is maximum in this case

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Goggles
Goggles with coloured glasses are used to protect the eyes
from glare and flying bits of hot metal. A welding table with
a top of fire bricks is recommended for oxy-acetylene
welding.

Types of Flames
The correct adjustment of the flame is important for efficient welding.
When oxygen and acetylene are supplied to the torch in nearly equal volumes, a neutral flame
is produced having maximum temperature of 3200 0C. The neutral flame is widely used for
welding steel, stainless steel, cast iron, copper, aluminium, etc. Carburizing flame, having a
maximum temperature of 3100 0C produced with an excess of acetylene, is need for welding
lead. Oxidizing flame, having a maximum temperature of 3300 0C with excess of oxygen is

used for welding brass.

Depending upon the thickness of the job, a different torch nozzle size is used. The pressure of
the gases and the flame size vary depending upon the size of the nozzle tip.
Filler Rods
For oxy-acetylene gas welding, filler rods are not coated with flux; however, they are applied
separately. Mild steel welding rods are usually copper coated to prevent rusting. Cast iron rods
are square shaped. Brazing rods are made of brass or bronze. They are usually one meter long.
Filler rod size increases as the metal thickness to be joined increases. 1.5mm diameter filler rod
is recommended for18 SWG sheet and 2 to 3mm diameter for 3mm thick sheet and so on.
Note:
Except for mild steel, every metal requires a good quality of flux for better welding.
Sometimes, borax powder may be used as a flux for gas welding of mild steel. In general, the
flux should be of such a quality that, it can dissolve impurities in molten metal and light in
weight, so that they can float above the welding metal in molten condition.

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Technique of Welding
Adjusting the equipment and lighting the torch, the recommended stages for adjusting the
gas welding equipment and lighting the torch are as follows:

 Select the proper size of tip for the job and insert it carefully into the torch.
 Check the valves on the torch to assure that they are turned-off (clockwise)
 Open the acetylene cylinder valve slightly, quarter to half turn.
 Open the oxygen cylinder valve slowly, till it is fully open.
 Open the acetylene valve on the torch and turn the acetylene regulator screw clockwise,
until the gauge reads 0.5 to 1 kg/cm2 of pressure. Then close the valve on the torch.
 Open the oxygen valve on the torch to check the flow and close it.
 Put-on the welding goggles, gloves and apron.
 Open the acetylene valve on the torch by quarter turn. Light the torch with a lighter,
keeping its tip away from the cylinders and your body.
 Adjust the acetylene valve on the torch until the flame extends slightly form the end of
the tip.
 Open and adjust the oxygen valve on the torch until the desired flame is obtained.
Welding Process
The following are the steps involved in a gas welding work.
 Prepare the work pieces to be welded and place them in proper position on the welding
table.
 Wear goggles, gloves and apron.
 Select the proper size tip for the job and fixit to the torch.
 Select the filler rod of recommended size.
 Adjust the welding equipment and light the torch.
 Adjust the torch for neutral flame.
 Hold the torch; with the inner cone about 3mm away from the metal and tack-weld the
workpieces at either end.
 Starting from one end, weld along the edge with a zigzag torch movement. Add the filler
metal to the joint as welding progresses.

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The two techniques of gas welding used are leftward and rightward welding. In leftward
welding most of the heat is absorbed by filler material and hence it is preferred in welding of
thin sheets up to 6mm thickness. In rightward welding most of the heat is absorbed by the base
metal and so it is preferred in welding of thick sheets of 6 to 25mm. During the leftward
technique the angle between the base metal and filler rod is 30-40 degree and the angle between
base metal and blow pipe is 60-70 degree. During the rightward technique the angle between
the base metal and filler rod is 30-40 degree and the angle between base metal and blow pipe
is 40-50 degree.
Note:
Do not touch the torch tip with the rod or molten metal. If the torch tip is too close to the melt,
it will form small blow holes in the weld and the torch may backfire. Practice the rhythm of
torch and rod movement for achieving good results.
Shutting off the equipment: After completing the gas welding operation, the following
procedure must be followed for shutting off the equipment;
 First close of the acetylene valve and then the oxygen valve of the torch.
 Close the acetylene cylinder valve first and then the oxygen cylinder valve.
 Drain the gas from the regulator and hose by opening the torch acetylene valve.
 Drain the oxygen from the regulator and hose by opening the torch oxygen valve.
 Open the regulator screws on each regulator and remove the pressure from the
diaphragms of the regulators.
 Hang up the hose and torch.
Tools and equipment used in gas welding
Steel rule, scriber, try square, odd leg callipers, shearing machine, chisel, file, hammer, bench
vice, tong, spanner, cylinder key, spark lighter, wire brush, hand glove, safety boot, apron,
goggles.
Advantages of Gas Welding
 It can be used for a wide variety of manufacturing processes and repairs
 As the source of heat and filler metal are different, the welder can have control over filler
metal deposition rates.
Disadvantages of Gas Welding
 It is not economical to join heavy sections.
 Flame temperature is less than the temperature of the arc welding.
 Fluxes used, produce fumes that are irritating in nature.

53 | Dept. of Basic Sciences and Humanities

Job No. : 6
Aim of the Job: To make a lap joint by gas welding.

Materials Used: Mild steel sheet (101 x 31 x 1) mm 2 pcs and mild steel copper coated filler
rod (1.6mm diameter) 1 pc
Tools and Equipment:
 Steel rule
 Scriber
 Try square
 Odd leg callipers
 Bench vice
 Shearing machine
 Rough file
 Ball peen hammer
 Tong
 Cylinder key
 Spark lighter
 Wire brush
 Hand glove
 Leather apron
 Goggles
 Oxy-acetylene cylinder with all accessories.
Procedure:
Measuring: At first measure the size of the MS sheet (length, width and thickness) by steel
rule as per the nominal size (101 x 31 x 1) mm.
Marking: After measurement coat any one surface, of the MS sheet with a chalk. Draw two
lines at 101 mm and 31 mm for the length and breadth respectively by using steel rule, try
square and scriber
Cuting: Cut the MS sheet as per the marking lines by using shearing machine.

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Edge preparation: After cutting coat the four sides of any one surface, of the MS sheet with
a chalk. Then mark a line from one end of the chalked surface to make it perpendicular to the
adjacent side by using scriber and try square. Similarly mark the other two adjacent sides to
get the desired length and breadth (100x30) mm by using Jenney calliper. Prepare the edges of
MS sheet by using rough file and try square to obtain the required dimensions.
Job setting: Set the both the MS sheet on the gas welding table in such a way that, one will
overlap half portion of the other for lap joint.
Flame setting: Adjust the acetylene and oxygen valve to get the neutral flame.
Welding: Tack weld both the workpieces by a neutral flame; during tacking, the tip of the
nozzle and filler rod to be maintained at a distance of approximately 3mm. Then use leftward
technique to weld both the workpieces.
Cooling: After welding, cool the job in atmospheric condition.
Cleaning: Then clean the job by a rough file and a wire brush.
Checking: After completing all operation, check all the dimensions by the steel rule to see
whether it meets the desire dimensions or not.
Submitting: After checking, punch the roll number and branch on the job by a number punch
and letter punch then submit it for evaluation.

Shown above is a lap joint by gas welding, completed as a

job in the manufacturing practices lab

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 Sheet Metal
Introduction:
Sheet metal is metal formed by an industrial process into thin, flat pieces. Sheet metal is one
of the fundamental forms used in metalworking, and it can be cut and bent into a variety of
shapes. Sheets are specified by standard gauge number. Greater the gauge number, thinner the
sheet. It has its own significance as a useful trade in engineering works also for our day to day
requirements. Common examples of sheet metal works are, hoopers, guards, covers, pipes,
hoods, funnels, boxes, dust pan etc. In sheet metal work, the sheet metals used are mild steel,
galvanised iron, stainless steel, copper, brass, aluminium and tin. The basic tools used in sheet
metal work are: steel rule, Vernier callipers, micrometre, measuring tape, wire gauge, folding
rule, straight edge, steel square, scriber, divider, punches, chisel, snip, shearing machine, plier,
hammers, mallet, stakes, rivet set, rivet gun, anvil.
Folding rule: This is very useful in measuring and laying out larger
work, the accuracy being 0.5 mm.

Steel Square: It is a L-shaped piece of hardened steel with marks

graduated on the edges for measuring. The narrow arm of the square
is called tongue and the wide part is known as the body. It is used for
marking in the perpendicular direction to any base line.

Wire Gauge: This is a notched plate having a series of gauged slots.

These are numbered according to the sizes of wire and sheet metal. It
is used for measuring the diameter of wire. The number of the slot in
which the wire or sheet fits properly, is its gauge.

Straight Edge: This is a flat graduated bar of steel with one

longitudinal edge bevelled. These are available in length ranging from
1 to 3 meter. It is useful for scribing long straight lines.

Snip: It is used for cutting thin metal sheets, before or after

marking according to the job. It looks like a pair of scissors. Its
edges are grinded at 80 degree angle and hardened and tempered.
These are of two types - straight snips are used for cutting the sheet
in a straight line, and bent snips are used for cutting circular cuts
and curved cuts.

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Hand shearing machine: It is fixed on the work bench with a nut and bolt. The
lower part is the base and on the upper side a handle is fixed. Two blades are
fitted between them. The lower blade is stationary and the upper blade moves
up and down by the handle. It is used for cutting the thin sheets and is specified
according to the length of the blade.

Mallet: These are made of wood. These are used in carpentry work
and for making plane metal sheets or to turn or bend them.

Stake: In different kind of jobs along with hand tools some special
anvils are also used for sheet bending, grooving, riveting and hollowing etc.
These anvils are called stakes. Different types of stakes are used for different
types of work.

Rivet set: This is a hardened steel tool with one hollow end.
It is used to shape the end of a rivet into a round, smooth
head. In order to join the jobs made of sheets or plates, rivets
are used. It is used for making trunks and buckets etc. Rivets
are made of mild steel, aluminium, copper, and brass.

Rivet gun: It is also used for the purpose of riveting. Different types of rivet guns are used for
different types of work.

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Job No. : 7
Aim of the Job: To make a Dust Pan.

Material Used: Galvanised iron (GI) sheet (325 X 300 X 1) mm.

Tools and Equipment Used
 Measuring tape
 Steel rule
 Straight edge
 Steel square
 Scriber
 Shearing machine
 Snip
 Hand drilling machine
 Hammer
 Mallet
 Stake
 Pop rivet gun and pop rivet.
Procedure
Measuring: At first measure the GI sheet (325 x 300 x 1) mm using steel rule to check whether
it is as per the nominal size or nominal thickness.
Marking: After measurement, mark the lines as per
the figure using scriber and steel square.
Cutting: Then cut the marking lines as per figure
using a snip.
Bending: According to the figure bend the sheet using
stakes and mallet.
Riveting: After bending drill both the joining parts
using the drilling machine and rivet both bending parts
using pop rivets and a pop rivet gun.
Submitting: After complete the job, submit for
evaluation. Shown above is a dust pan, completed as a
job in the manufacturing practices lab

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