INTRODUCTION TO THE
LATHE MACHINE
Module -3
Module Objectives
 Describe how a lathe operates.
 Identify the various parts and attachments of a
lathe and their function.
 Describe how the cutting tools cut materials.
 Implement and describe the safety rules for
machining using a lathe.
 Select the correct cutting speed, feed, and depth of
cut during machining.
What is a Centre Lathe Machine?
 It is a power-driven, general-
purpose machine tool used for
producing cylindrical workpieces.
 As the piece of metal to be
machined is rotated in the lathe,
a single-point cutting tool is
advanced radically into the workpiece at specified depth and
moved longitudinally along the
axis of the work-piece, to remove
the metal in form of chips in
order to make the required shape.
Major parts of a lathe Machine
Cross-Slide
Tool holder
Compound rest
Tailstock
Headstock
Feed levers
Lead screw
Bed
Quick-change
Gearbox
Feed rod
Base
Carriage hand
wheel
Split-Nut
lever
Carriage
The most important parts of a lathe
1.
Headstock


Head stock provides the
driving power to control
the rotation of the part
(workpiece)
being
machined.
The headstock contains
the spindle to which the
various work-holding
attachments are fitted.
The most important parts of a lathe
2. Bed

Its function is to
provide main frame
for the support of the
work-piece and tool
during machining.
The most important parts of a lathe
Carriage
3.


Controls and supports
Cross-slide
the cutting tool, and
composed of a number Saddle
of parts.
Power is transmitted to
the carriage through
the feed mechanism.
This
regulates
the
amount of tool travel
per revolution of the
spindle (Feed).
Apron
Tool rest
Compound rest
The most important parts of a lathe
3. Carriage Parts
The saddle is fitted to the ways of the bed and slides
along them (Z axis for CNC machines).
2. The apron contains a drive mechanism to move the
carriage along the ways, using hand or power feed.
3. The cross-slide allows the tool to move in and out
(toward or away from the operator), (X axis for CNC
machines).
4. The compound rest allows the tool to move at an
angle. (move in X and Z axes at the same time)
5. The tool rest is used to mount the cutting tool.
1.
The most important parts of a lathe
4. Lead screw


Lead
screw
transmits
power to the carriage
through a gearing and
clutch arrangement in the
carriage apron.
The power feed lever is
located on the carriage
apron. The power feed
lever activates either the
longitudinal power feed of
the carriage or the cross
feed of the cross slide
Lead screw
The most important parts of a lathe
5. Split-nut (Half nut) lever
Half-nut lever is placed on
the apron and engaged for
thread cutting.
 Thread cutting is the process
of cutting screws and helical
shapes.
 The power feed lever must
be in neutral position when
the half-nut is needed to be
engaged.

The most important parts of a lathe
Tailstock
6.



The function of the
tailstock is to support long
work-pieces
during
machining, and to hold
some tools.
Turning the hand wheel of
the tailstock clockwise
advances
the
spindle
(which holds the cutting
tools or center) toward the
workpiece.
E.g. the drill bit and boring
bar, during drilling or
boring operations.
(Boring is the process of
enlarging a hole).
Lathe attachments
 An attachment is a device mounted on the lathe so
that a wider range of operations could be
performed.
Workpiece holding devices
 There are different lathe attachments used to hold
and support different shapes (round, hexagon, or
irregular) and different sizes of workpieces.
1. Three-jaw universal chuck
The three-jaw universal
chuck holds cylindrical
or hexagonal work. All
three
jaws
move
together to bring the
work on center.
Workpiece holding devices
 Two
sets
of
interchangeable jaws
are provided as the
jaws are not reversible,
these are called inside
and outside jaws. One
set is used to grip the
work inside while the
other is used to grip the
work on the outside.
Workpiece holding devices
2. Four-jaw independent chuck
The four jaws are reversible
and can hold work of different
sizes and shapes. Each jaw
may be moved independently.
3. Collet chucks
Collet chucks are used to grip
small-diameter
workpieces.
Collets are made in sets, to fit
different sizes.
Workpiece holding devices
4. Faceplate
A faceplate is one of the workpiece
holding devices. It contains more
open slots or T slots so that bolts or
T bolts may be used to clamp the
workpiece to the face of the plate.
Many types of work that can not be
held in chucks may be machined
conveniently when mounted on a
face plate.
5. Centers
Support the workpiece between
the headstock and the tailstock.
Workpiece holding devices
6. Follower rest
Is used to support long
cylindrical workpieces. It is
attached to the carriage when in
use, and is moved as the tool and
carriage move.
Follower rest
7. Steady rest
Is used to support long cylindrical
workpieces. It is attached directly
to the machine bed.
Steady
rest