A lathe is a machine tool which is
used to remove metals from a work piece to give a desired shape and size.It is
one of the most important machine tool in the metal industry which operates on
the principle of a rotating work piece and a fixed cutting tool.
Working Principle:
The lathe is a machine tool which
holds the work piece between two rigid and strong supports called centers or in
a chuck or face plate which revolves. The cutting tool is rigidly held and
supported in a tool post which is fed against the revolving work. The normal
cutting operations are performed with the cutting tool fed either parallel or
at right angles to the axis of the work. The cutting tool may also be fed at an
angle relative to the axis f work for machining tapers and angles. The simple
operation of a Lathe machine is shown in Fig 1 and Fig 2 shows the different
parts of a universal lathe machine.
Fig 1 Working principle of a
simple Lathe machine
Fig
2 Universal Lathe Machine
Construction
The main parts of the lathe are the bed,
head stock, quick changing gear box, carriage and tail stock.
1.
Bed: The bed is a heavy,
rugged casting in which are mounted the working parts of the lathe. It carries
the head stock and tail stock for supporting the work piece and provides a base
for the movement of carriage assembly which carries the tool.
2.
Legs: The legs carry the
entire load of machine and are firmly secured to floor by foundation bolts.
3.
Head stock: The head stock is
clamped on the left hand side of the bed and it serves as housing for the
driving pulleys, back gears, head stock spindle, live centre and the feed
reverse gear. The head stock spindle is a hollow cylindrical shaft that provides
a drive from the motor to work holding devices.
4.
Gear Box: The
quick-change gear-box is placed below the head stock and contains a number of
different sized gears.
5.
Carriage: The carriage is
located between the head stock and tail stock 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 cross slide, compound rest and tool post.
b).
The cross slide is mounted on the top of saddle, and it provides a mounted or
automatic cross movement for the cutting tool.
c).
The compound rest is fitted on the top of 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 center
line.
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.
6.
Tailstock: The tail stock is a
movable casting located opposite the head stock on the ways of the bed. The
tail stock can slide along the bed to accommodate different lengths of work piece
between the centres. A tailstock clamp is provided to lock the tail stock at any
desired position. The tail stock spindle has an internal taper to hold the dead
centre and the tapered shank tools such as reamers and drills.
