Machining is a manufacturing process used

to produce products, parts, and designs

by removing layers from a workpiece.

There are three main kinds of

machining: turning, milling, and
drilling.
Lathe is one of the most important machine tools in
the metal working industry.

A lathe operates on the principle of a rotating work

piece and reciprocating cutting tool.

Lathe is a machine, which is used to remove metal

from the work piece to required shape and size.
1. Engine Lathe
2. Capstan & Turret Lathe
3. Special Purpose Lathe
4. Bench Lathe
5. Speed Lathe
6. Tool Room Lathe
7. Duplicating Lathe
8. CNC Lathe
 It is a general-purpose lathe and is widely used in
workshops.
 The main parts of engine lathe are the bed, headstock,
tailstock, carriage, lead screw, and feed change gearbox.
 The cutting tool may be feed both in cross and longitudinal
direction concerning the lathe axis with the help of a carriage.
 The engine lathe, depending upon the design of the
headstock for receiving power, may be classified as belt-driven
lathe, motor-driven lathe, and geared head lathe.
 In Belt driven lathe, power from the motor is transmitted to
the spindle by belt drive, In Geared head lathe power from the
motor is transmitted to the spindle by the gear drive.
 The speed changes in belt drive are obtained by
shifting the belt to different steps of a cone pulley.

 In geared-Head lathe the gear ratio (Spindle speed to

motor speed) is changed by Speed- Lever.

 Usage: It is used for producing cylindrical

components. By using the attachments and accessories,
other operations such as taper turning, Drilling,
milling, and grinding may also be performed.
 The bench lathe is so small that it can be mounted
on a bench.
 All the types of operation can be performed on this
lathe that may be done on an ordinary speed or
engine lathe.


Thisis used for small work usually requiring

considerable accuracy such as in the production of
gauges, punches, and beds for press tools.
In general, jewelers and watchmakers
use this machine a lot for their
machining needs.
3. Tracer Lathe:
A lathe that can follow a template to
copy a shape or contour.
 CAPSTAN AND TURRET LATHE

 The lathes which have multiple tools mounted on

turret either attached to the tailstock or the
cross-slide, which allows for quick changes in
tooling and cutting operations.

 The capstan and turret lathes are the

modification of engine lathe and is
particularly used for mass production of
identical parts in a minimum time.

 These lathes are semiautomatic and are fitted

with multi-tool holding devices, called capstan
and turret heads.

 The advantage of capstan and turret lathe is

that several different types of operation can
be performed on a workpiece without resetting
of the work or tools.
 SPECIAL PURPOSE LATHE
The works, which cannot be conveniently
accommodated or machined on a standard lathe, the
special purpose lathes are used.

The gap bed lathe which has a removable section in

the bed in front of the headstock tom provide a
space or gab is used to swing extra large diameter
jobs.

a) Crankshaft lathe: is especially used for

turning crankshafts.
b) Wheel lathe: is which is of large design, is
especially used for finishing the journal and
for turning the locomotive driving wheels.
c) Axle lathe: is used for turning car axles.
d) Precision Lathe: The precision turning of
previously rough-turned workpieces.
e) Facing Lathe: Used to machine the end faces
f) Vertical lathe: It is used for turning and
boring very large and heavy rotating parts that
cannot be supported on other types of lathes.
 SPEED LATHE

It is driven by power and consists of a bed, a headstock, a

tailstock, and an adjustable slide for supporting the tool.

It has no gearbox, lead Screw, and Carriage. Headstock may

have a step-cone pulley arrangement or may be equipped with a
Variable Speed Motor.

Various speeds are obtained by Cone pulley. Since the tool is

fed into the work by hand and cuts are very small, therefore this
type of lathe is driven at high speeds usually from 1200 to 3600
rpm.

Usage: It is mainly used for woodworking, centering, metal

spinning, polishing, etc.
It is the simplest type lathe. It is mainly used
for metal spinning, polishing etc
 TOOL ROOM LATHE

The tool room lathe is similar to an engine lathe and is equipped

with all the accessories needed for accurate tool work.

It has an individually driven-geared headstock with a wide range

of spindle speeds.

Since this lathe is used for precision work on tools, gauges,

dies, jigs, and other small parts, therefore greater skill is needed
to operate the lathe.
 SPECIAL PURPOSE & TOOL ROOM LATHE

•These lathes are It is used for production

modification of engine lathes of small tools, gauges,
developed for machining fixtures and accurate
special types of work pieces. parts in tool room
 A highly automated lathe, where both cutting,
loading, tool changing, and part unloading are
automatically controlled by computer coding
 CLASSIFICATION OF LATHES / TYPES OF
LATHE MACHINE
According to configuration:
 Horizontal – Most common for ergonomic conveniences.
 Vertical – Occupies less floor space, only some large
lathes are of this type.
According to the purpose of use:
 General-purpose – Very versatile where almost all
possible types of operations are carried out on wide
ranges of size, shape, and materials of jobs; e.g.: center
lathes.
 Single-purpose – Only one (occasionally two) type of
operation is done on limited ranges of size and material of
jobs; e.g.: facing lathe, roll turning lathe, etc.
 Special purpose – Where a definite number and type of
operations are done repeatedly over a long time on a
specific type of blank; e.g.: capstan lathe, turret lathe,
gear blanking lathe, etc.
According to size or capacity:
 Small (low duty) – In such light duty lathes (up to 1.1 kW), only
small and medium-size jobs of generally soft and easily
machinable materials are machined.
 Medium (medium duty) – These lathes of power nearly up to
11 kW are most versatile and commonly used.
 Large (heavy-duty)
 Mini or micro lathe – These are tiny table-top lathes used for
extremely small size jobs and precision work; e.g.: Swiss-type
automatic lathe.

According to the configuration of the jobs being handled:

 Bar type – Slender rod-like jobs being held in collets.
 Chucking type – Disc type jobs being held in chucks.
 Housing type – Odd shape jobs, being held in the faceplate.

According to precision:
 Ordinary
 Precision (lathes) – These sophisticated lathes meant for high
accuracy and finish and are relatively more expensive.
According to the number of spindles:
 Single spindle – Common.
 Multi-spindle (2, 4, 6, or 8 spindles) – Such uncommon lathes
are suitably used for fast and mass production of small size
and simple shaped jobs.

According to the type of automation:

 Fixed automation – Conventional; e.g.: single spindle
automat & Swiss-type automatic lathe
 Flexible automation – Modern; e.g.: CNC lathe, turning
center, etc.
PARTS OF LATHE MACHINE
1. Bed:
The bed is a heavy, rugged casting and it carries the headstock
and tailstock for supporting the workpiece and provides a base for
the movement of the carriage assembly, which carries the tool.

2. Headstock:
The headstock is provided on the left-hand side of the bed and it
serves as housing for the driving pulleys, back gears, headstock
spindle, live center, and the feed reverse gear. The headstock
spindle is a hollow cylindrical shaft that provides a drive from the
motor to work holding devices.

3. Gear Box:
The quick-change gearbox is placed below the headstock and
contains several different sized gears.
4. Carriage:
The carriage is located between the headstock and tailstock and
serves the purpose of supporting, guiding, and feeding the tool
against the job during operation.

The main parts of carriage are:

a) The saddle is an H-shaped casting mounted on the top of lathe
ways. It provides support to the cross-slide, compound rest, and
tool post.
b) The cross slide is mounted on the top of the saddle, and it
provides a mounted or automatic cross-movement for the cutting
tool.
c) The compound rest is fitted on the top of the cross slide and is
used to support the tool post and the cutting tool.
d) The tool post is mounted on the compound rest, and it rigidly
clamps the cutting tool or tool holder at the proper height relative
to the work centerline.
e) The apron is fastened to the saddle and it houses the gears,
clutches, and levers required to move the carriage or cross slide.
The engagement of split nut lever and the automatic feed lever at
the same time is prevented she carriage along the lathe bed.
5. Tailstock:
The tailstock is a movable casting located opposite the
headstock on the ways of the bed. The tailstock can slide along
the bed to accommodate different lengths of the workpiece
between the centers. A tailstock clamp is provided to lock the
tailstock at any desired position.
The saddle is mounted on the bed and slides along the
ways.
The cross slide and tool post are mounted on the
saddle.
The movement of the saddle is parallel along the axis
of the lathe, it is also known as feed.
APRON
It is also known as foot stock.
It used to apply support to the longitudinal rotary axis
of a work piece.
The tailstock is mounted on the right hand side of the
lathe bed.
The function of the tailstock is to support the work
piece, and to accommodate different tools like drill,
reaming, boring and tapping, etc.
Thetailstock moves on the guide ways over the bed, to
accommodate for different length of work piece.
• Tailstock is known as dead center.

6. Lead screw:
A lead screw also known as a power screw is a screw,
moves the carriage by a precise increment for every
rotation of the screw. The lead screw is made with
square, acme, or buttress type threads.
 LATHE SPECIFICATIONS
 Distance between centers (c)
 Swing over the bed (d)
 Swing over the cross slide
 Horsepower of the motor
 Number of speeds
 Feed Given
 LATHE SPECIFICATIONS

1. The height of the centres measured from the lathe bed. (r )

2. The swing diameter over bed. This is the largest diameter of
work that will revolve without touching the bed and is twice the
height of the centre measured from the bed of the lathe. (d)
3. The length between centres. This is the maximum length of
work that can be mounted between the lathe centres. (C)
4. The swing diameter over carriage. This is the largest diameter
of work that will revolve over the lathe saddle, and is always less
than the swing diameter over bed.
5. The maximum bar diameter. This is the maximum diameter of
bar stock that will pass through hole of the headstock spindle.
6. The length of bed. This indicates the approximate floor space
occupied by the lathe. (b)
 LATHE MACHINE OPERATION

 Facing
 Centering
 Rough and finish turning
 Chamfering, shouldering, grooving, recessing, etc
 Axial drilling and reaming
 Taper turning
 Boring (internal turning); straight and taper
 Forming; external and internal
 Cutting helical threads; external and internal
 Parting off
 Knurling
Operations, which can be performed in a lathe either by
holding the workpiece between centers or by a chuck are

1. Straight turning 8. Forming

2. Shoulder turning 9. Filing
3. Taper turning 10. Polishing
4. Chamfering 11. Grooving
5. Eccentric turning 12. Knurling
6. Thread cutting 13. Spinning
7. Facing 14. Spring winding
Operations which are performed by holding the work by a
chuck or a faceplate or an angle plate are

1. Undercutting
2. Parting-off
3. Internal thread cutting
4. Drilling
5. Reaming
6. Boring
7. Counter boring
8. Taper boring
9. Tapping

Operations which are performed by using special lathe

attachments are

1. Milling
2. Grinding
3. Slotting
Lathe operations
 TYPES OF CHIPS FORMED IN THE MACHINING
PROCESS

Different types of chips of various shape, size, color, etc. are

produced by machining depending upon:

Type of cut, i.e., continuous (turning, boring etc.) or intermittent

cut (milling).
Work material (brittle or ductile etc.).
Cutting tool geometry (rake, cutting angles etc.).
Levels of the cutting velocity and feed (low, medium, or high).
Cutting fluid (type of fluid and method of application).

1. Discontinuous chips:
2. Continuous chips.
3. Continuous chips with build-up edge (BUE).
4. Non-homogeneous chip
i) High rake angle: Continuous chips
(ii) High cutting speed: Continuous chips
(iii) Small depth of cut: Continuous chips
(iv) Low cutting speed: Continuous chips with built-up edge
(v) Large depth of cut: Continuous chips with built-up edge
(vi) Low rake angle: Continuous chips with built-up edge
SPEED, DEPTH OF CUT, FEED, MACHINING TIME
Cuttingspeed: The cutting speed (v) of a tool is the speed at which the metal is
removed by the tool from the work piece.In a lathe it the peripheral speed of
the work past the cutting tool expressed in meters per minute.

Cutting speed=m/min

Where, d is the diameter of the work in mm and n is the r.p.m. of the work.

Example: A steel shaft of 20m.m diameter is turned at a cutting speed of 40

m/min. Find the r.p.m of the shaft.
Feed: The feed of a cutting tool in a lath work is the distance the
tool advance for each revolution of the work. Feed is expressed in
millimeters per revolution.
Increased feed reduces cutting time. But increased feed greatly
reduces the tool life. Coarser feeds are used for roughing and
finer feed for finished cuts.
 Feed of the cutting tool can be defined as the distance it
travels along or in to the work-piece for each pass of its point
through a perpendicular position in unit time.

 In turning operation of lathe, it is equal to the advancement of

the tool corresponding to each revolution of work.

 In milling work, the feed is considered per tooth of the cutter.

The cutting speed and feed of a cutting tool is largely influenced
by the following factors:

1. Material being machined.

2. Material of the cutting tool.
3. Geometry of the cutting tool.
4. Required degree of surface finish.
5. Rigidity of the machine tool being used
6. Type of coolant being used
Depth of cut:
cut: It is indicative of the penetration of the cutting edge
of the tool in to the workpiece material in each pass, measured
perpendicular to the machined surface i.e. it determines the
thickness of metal layer removed by the cutting tool in one pass.

Example: In turning operation on a lathe it is given by

Depth of cut = (d1-
(d1-d2)/2
Where d1 = Original diameter of the work-piece in mm
d2 = Diameter obtained after turning in mm in one pass.

Depth of cut: The depth of cut is the perpendicular distance measured

form the machined surface to the uncut surface of the work piece. In a
lathe the depth of cut is expressed as following:
Machining time: The machining time in a lath work can be calculated for
particular operation if the speed of the job, feed and length of the job is
known.
If is the feed of the job per revolution expressed in mm per revolution and l
the length of the job in mm the number of revolutions of the job required for
a complete cut will be:
SPEED, DEPTH OF CUT, FEED, MACHINING TIME
Cutting speed of a tool can be defined as the rate at which its
cutting edge passes over the surface of the work-piece in unit
time. It is normally expressed in terms of surface speed in meters
per minute.

Feed of the cutting tool can be defined as the distance it travels along
or in to the
work-piece for each pass of its point through a perpendicular position
in unit time. In turning
operation of lathe, it is equal to the advancement of the tool
corresponding to each revolution
of work. In planning it is the work, which is fed and not the tool. In
milling work, the feed is
considered per tooth of the cutter.

Cutting speed, feed, depth of cut and machining time are the
terms which are used in cutting operation.

Study of all these terms is necessary to calculate the machining

cost.
The proper cutting speed for a given job depends upon the
hardness of the material being machined, the material of the
tool bit, and how much feed and depth of cut is required.

Cutting speeds for metal are usually expressed in surface feet

per minute, measured on the circumference of the work.
Cutting speed depends upon the following factors:

i. Tool material.
ii. Work material.
iii. Depth of cut.
iv. Tool geometry.
v. Type of machine tool.
vi. Surface quality required.
 FEED RATE
 Feed is the displacement of the tool along the workpiece for
each revolution of the work. It is expressed in millimeter per
revolution.

 Feed rate is defined as the distance the tool travels during one
revolution of the part.

 Cutting speed and feed determines the surface finish, power

requirements, and material removal rate.

 The primary factor in choosing feed and speed is the material

to be cut.

 However, one should also consider the material of the tool,

rigidity of the workpiece, size and condition of the lathe, and
depth of cut.

 For most Aluminum alloys, on a roughing cut (.010 to .020

inches depth of cut) run at 600 fpm. On a finishing cut (.002 to
.010 depth of cut) run at 1000 fpm.
 DEPTH OF CUT
It is the perpendicular distance measured from the machined
surface to the uncut surface of the workpiece. For lathe the depth
of cut is expressed as follow.
Depth of cut = (D − d ) /2 mm
where D = dia of job in mm, and
d = finished dia in mm (in single cut)

The depth of cut is the distance that the tool bit moves into the
work. Usually measured in thousandths of an inch or millimeters.

General machine practice is to use a depth of cut up to five times

the rate of feed, such as rough cutting stainless steel using a feed
of 0.020 inches per revolution and a depth of cut of 0.100 inch.
which would reduce the diameter by 0.200 inch.
 DEPTH OF CUT
If chatter marks or machine noise develops, reduce the depth of
cut.
It is the total amount of metal removed per pass of the cutting tool.
It is expressed in mm.
It can vary and depend upon the type of tool and work material.
Mathematically, it is half of the difference of diameters.

Depth of cut (t) = D-d/2 mm

where, D = outer diameter, (mm)
d = Inner diameter (mm)
 MACHINING TIME

In lathe work, if the speed of job, feed of tool and the length of job
are given, we can calculate the machining time by the following
formula

Machining Time for a Complete Cut minute = l / (S * N)

where l = length of job to be cut in mm,

S = feed in mm / revolution, and
N = rpm (revolution per minute).
 ACCESSORIES
Chucks : Mandrels :
 Three jaw chuck  Plain mandrel
 Four jaw chuck
 Stepped mandrel
 Collet chuck
 Collared
 Magnetic chuck
mandrel
 Hydraulic chuck
Centers:  Screwed mandrel
 Live centre
 Dead centre
 THE DIFFERENT TYPES OF CHUCKS

1. Four jaw independent chuck

2. Three jaw universal chuck
3. Combination chuck
4. Magnetic chuck
5. Air or hydraulic operated chuck
6. Collet chuck
7. Drill chuck
Collet chuck:

Collet chuck are used for holding bar stock in production work where quick
setting and accurate centering is needed.
Parts of lathe machine
To determine the RPM of the lathe while performing procedures on
it:
Formula: RPM = (CuttingSpeed x 4) / Diameter
We first must find what the recommended cutting speed is for the
material we are going to machine.
Learn to use the Machinery’s Handbook and other related sources
to obtain the information you need.
EXAMPLE: How fast should a 3/8 inch drill be turning when drilling
mild steel?
From our recommended cutting speed from our class handouts, use
a cutting speed of 100 for mild steel.
(100 x 4) / .375 = 1066 RPM
What would the RPM be if we were turning a .375 diameter
workpiece made out of mild steel on the lathe?
RPM = 100 X4 / 1.00 = 400 RPM
Recommended Cutting Speeds for Six Materials in RPM

These charts are for HSS tools. If using carbide, the rates may be
increased.
This is heavy rugged casting made
to support the working parts of
lathe and also guide and align
major parts of lathe.
This is heavy rugged casting made to
support the working parts of lathe and
also guide and align major parts of
lathe.
The bed material should have high
compressive strength and high wear
resistance.
Cast iron alloyed with nickel chromium
forms a good material for bed.
The headstock houses the main spindle ,
speed change mechanism, and change gears.

The headstock is required to be made as

robust as possible due to the cutting
forces involved, which can distort a
lightly built housing.

Induce harmonic vibrations that will

transfer through the work piece, reducing
the quality of the finished work piece.
Headstock is mounted on the left hand
side of the lathe bed.
The head stock accommodates gear box,
which helps to vary the spindle speed.
The gear box also transmits the power to
other parts like feed rod and lead screw.
The chuck or face plate is attached to
the spindle which provides mechanical
means clutching and rotating the work
piece.
Head stock is also known as live center
Head stock
Carriage
The carriage is mounted on the lathe bed,
which slides on the
guide ways of the bed.
• The carriage has various other parts
like, cross slide,
compound rest, and tool post.