National Institute of Textile Engineering and Research (NITER)

Department of Textile Engineering

Level 1 Term 1
Course Code: IPE 1102 Course Title: Engineering Workshop Practices
Experiment no : 1
Name of the Experiment: Study of Different Parts of an Engine Lathe Machine

Introduction: Lathe is one of the most versatile and widely used machine tools all over the
world. It is commonly known as the mother of all other machine tool. The main function of a
lathe is to remove metal from a job to give it the required shape and size. The job is secure1y and
rigidly held in the chuck or in between centers on the lathe machine and then turn it against a
single point cutting tool which will remove metal from the job in the form of chips.
An engine lathe is the most basic and simplest form of the lathe. It derives its name from the
early lathes, which obtained their power from engines. The main function of a lathe is to remove
metal from a piece of work to give it the required shape and size by holding the work securely
and rigidly on the machine and then turning it against cutting tool which will remove metal from
the work in the form of chips. Besides the simple turning operation as described above, lathe can
be used to carry out other operations also, such as drilling, reaming, boring, taper turning,
knurling, screw thread cutting, grinding etc.

Engine Lathe: The term “engine” is associated with this lathe due to the fact that in the very
early days of its development it was driven by steam engine. This lathe is the important member
of the lathe family and is the most widely used. Similar to the speed lathe, the engine lathe has
all the basic parts, e.g., bed, headstock, and tailstock. But its headstock is much more robust in
construction and contains additional mechanism for driving the lathe spindle at multiple speeds.
Unlike the speed lathe, the engine lathe can feed the cutting tool both in cross and longitudinal
direction with reference to the lathe axis with the help of a carriage, feed rod and lead screw.
Centre lathes or engine lathes are classified according to methods of transmitting power to the
machine. The power may be transmitted by means of belt, electric motor or through gears.

Construction of Lathe Machine: A simple lathe comprises of a bed made of grey cast iron on
which headstock, tailstock, carriage and other components of lathe are mounted. The figure
shows the different parts of engine lathe or central lathe. The major parts of lathe machine are
given as under:
1. Bed
2. Headstock
3. Tailstock
4. Carriage
5. Tool post
6. Chuck
7. Feed rod
8. Lead screw

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 Figure: Engine Lathe

Bed: The bed of a lathe machine is the base on which all other parts of lathe are mounted. It is
massive and rigid single piece casting made to support other active parts of lathe. On left end of
the bed, headstock of lathe machine is located while on right side tailstock is located. The
carriage of the machine rests over the bed and slides on it. On the top of the bed there are two
sets of guide ways-inner ways and outer ways.

Head Stock: The headstock is located at the end of the lathe bed, to the operator's left. It is
clamped solidly on the inner ways and supports and houses the spindle and the means for turning
the spindle. The main function of headstock is to transmit power to the different parts of a lathe.
It comprises of the headstock casting to accommodate all the parts within it. The main spindle is
adjusted in it, which possesses live centre to which the work can be attached. It supports the
work and revolves with the work, fitted into the main spindle of the headstock produce different
velocity ratio required for thread cutting.

Carriage: Carriage is mounted on the outer guide ways of lathe bed and it can move in a
direction parallel to the spindle axis. It comprises of important parts such as apron, cross-slide,
saddle, compound rest, and tool post. The lower part of the carriage is termed the apron in which
there are gears to constitute apron mechanism for adjusting the direction of the feed using clutch
mechanism and the split half nut for automatic feed. The cross-slide is basically mounted on the
carriage, which generally travels at right angles to the spindle axis. On the cross-slide, a saddle is

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mounted in which the compound rest is adjusted which can rotate and fix to any desired angle.
The compound rest slide is actuated by a screw, which rotates in a nut fixed to the saddle.

The tool post is an important part of carriage, which fits in a tee-slot in the compound rest and
holds the tool holder in place by the tool post screw

Tail Stock: The tail stock of central lathe is commonly used for the objective of primarily giving
an outer bearing and support the circular job being turned on centers. Tailstock can be easily set
or adjusted for alignment or non-alignment with respect to the spindle centre and carries a centre
called dead centre for supporting one end of the work. Both live and dead centers have 60°
conical points to fit centre holes in the circular job, the other end tapering to allow for good
fitting into the spindles

Chucks: Chuck is one of the most important devices for holding and rotating a job in a lathe. It
is basically attached to the headstock spindle of the lathe. The internal threads in the chuck fit on
to the external threads on the spindle nose. Short, cylindrical, hol1ow objects or those of
irregular shapes, which cannot be conveniently mounted between centers, are easily and rigidly
held in a chuck. Jobs of short length and large diameter or of irregular shape, which cannot be
conveniently mounted between centers, are held quickly and rigidly in a chuck.

There are a number of types of lathe chucks, e.g.

(1) Three jaws or universal
(2) Four jaw independent chuck
(3) Magnetic chuck
(4) Collet chuck
(5) Air or hydraulic chuck operated chuck
(6) Combination chuck
(7) Drill chuck.

Feed Rod: Feed rod is a power transmission mechanism used for precise linear movement of the
carriage along the longitudinal axis of the lathe. Such lathe machines generally have a lead screw
as well for thread cutting

Lead Screw: The lead-screw should be used only when cutting threads. For all other
operations, motion is transmitted through the feed-rod. This practice is to preserve the accuracy
of the lead-screw.

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Specification of Lathe:
The size of a lathe is generally specified by the following means:
(a) Swing or maximum diameter that can be rotated over the bed ways
(b) Maximum length of the job that can be held between head stock and tail stock
Centers
(c) Bed length, which may include head stock length also
(d) Maximum diameter of the bar that can pass through spindle or collect chuck of
capstan lathe.