LATHE MACHINE
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 of work for machining tapers and
angles.
Construction: The main parts of
the lathe are the bed, headstock,
quick changing gear box, carriage
and tailstock.
1. Bed: The bed is a heavy, rugged casting
in which are mounted the working parts of
the lathe. It carries the headstock and tail
stock for supporting the workpiece 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. Headstock: The headstock is clamped on
the left hand side of the bed and it serves as
housing for the driving pulleys, back gears,
headstock spindle, live centre and the feed
reverse gear. The headstock 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 headstock and contains a
number of different sized gears.
5. 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 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 centre 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 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 workpiece between the centers. A
tailstock clamp is provided to lock the
tailstock at any desired position. The
tailstock spindle has an internal taper to hold
the dead centre and the tapered shank tools
such as reamers and drills.
LATHE OPERATIONS
The engine lathe is an accurate and versatile machine on which many operations can be
performed. These operations are:
1. Plain Turning and Step
5. Reaming
10. Forming
Turning
6. Boring
11. Chamfering
2. Facing
7. Knurling
12. Filling and Polishing
3. Parting
8. Grooving
13. Taper Turning
4. Drilling
9. Threading
TYPES OF LATHE MACHINE
Engine Lathe
Bench Lathe
Copy Lathe
Automatic lathe
Origin of Lathe:
The origins of lathe can be traced back to
Ancient Egypt and ancient Greece. In ancient
Egypt, two-person lathes were extensively
used. In a two-person lathe, one person
would turn the wood (work piece) and the
other person would cut the wood with a
single point cutting tool. Cutting operation in
this lathe, involved a lot of manual labour
and consumed a large amount of time.
Turret Lathe
Computer controlled lathe
In Ancient Rome, the Egyptian Design was
modified. A turning bow was used to turn the
workpiece.
In the medieval period, pedals were used to
turn and cut the workpiece. The pedals were
operated by human legs.
The origin of modern lathe can be traced
back to the time when the Industrial
Revolution took place. The Industrial
Revolution brought a lot of changes to the
world of machines. During that golden
period, a number of mechanisms were
introduced to lathe. These mechanisms
enabled humans to operate lathe semiautomatically. Power generated from steam
engines were used to drive lathes.
The introduction of Numerical Control (NC)
and Computer Numerical Control (CNC) in
the twentieth century, made lathe a
versatile, automatically functioning machine
tool.
Today, lathe is one of the basic machine tools
widely used in industries.
