Lathe Machine
Lathe
machine is probably the oldest machine tool know to mankind. Its first use date
back to 1300 BC in Egypt. The first lathe was a simple Lathe which is now
called a two-person lathe. In this one person would turn the wood workpiece
using rope and the other person would shape the workpiece using a sharp tool.
One
of the oldest machine tools is a lathe machine. In 1797, an Englishman, Henry
Maudslay, designed the first screw-cutting lathe which is the forerunner of the
present day high speed, heavy duty production lathe.
Definition - A lathe machine is a machine
tool which removes the undesired material from a rotating workpiece in the form of chips with the help of a tool which is
traversed across the work and can be feed deep into the work.
Functions
of the Lathe : - The main function of a lathe is
to remove metal from a piece of work to give it the required shape and size. This
accomplished by hold the work piece securely and rigidly on the machine and
then turning to regain the cutting tool. It remove the workpiece in the form of
chip.
Types
of Lathe –
Lathe are available in large
variety of types and sizes. It is difficult to classify them into categories.
There is a fairly large variation in their design, construction and use.
However, according to their construction and design we can classify the lathes
as follows:
1.
Bench Lathe: It is a very small lathe and is mounted on a separately prepared bench
or cabinet. It is used for small and precision work since it is very accurate.
It is usually provided with all the attachments, which a larger lathe carries, and
is capable of performing almost all the operations which a larger lathe can do.
2. Speed Lathes:
These lathes may be of bench type
or they may have the supporting legs cast and fitted to the bed. These lathes
have most of the attachments which the other types of lathe carry but have no
provision for power feed. They have no gear box, carriage and the lead screw.
With the result, the tool is fed and actuated by hand. Usually the tool is
either mounted on a tool post or supported on a T-shaped support. Such lathes
are usually employed for wood turning, polishing, centering and metal spinning,
etc. Thus, they can be considered as merely of a theoretical value so far as
the modern machine shops are concerned. They are named so because of the very
high speed at which the spindle rotates.
3. Engine Lathe:
It is probably the most widely
used type of lathe. The name Engine Lathe is a little confusing in modern
practice as all these lathes are now made to have an individual motor drive.
However, it carries a great historical significance that in the very early days
of its development it was driven by a steam engine. From this, it derived the
name which is popular even today.
Although it practically resembles
a speed lathe in most of its features, but its construction is relatively more
robust. Its headstock is bigger in size and more robust, incorporating suitable
mechanism for providing multiple speeds to the lathe spindle. The headstock
spindle may receive power, from a lathe shaft or an individual motor, through belts.
In that case, it will have a cone pulley with back gears in the headstock to
provide different speeds to the spindle. It carries a combination of gears,
instead of the cone pulley and back gears combination, the lathe is known as
geared head lathe and the headstock as all geared head stock.
4. Tool Room Lathe:
It is nothing but the same engine
lathe but equipped with some extra attachments to make it suitable for a
relatively more accurate angle of speeds and feeds. The usual attachments
provided on a tool room lathe are taper turning attachment, follower rest,
collets, chucks, etc. This lathe is made to have a comparatively smaller bed
length than the usual engine lathe. The most commonly used lengths are 135 to
180 cm.
5. Capstan and Turret Lathe:
These lathes form as very
important and useful group and are vastly used in mass production. These
machines are actually of semi-automatic type and a very wide range of
operations can be performed on them. In operating these machines, a very wide
range of operations can be performed on them. In operating these machines, a
very little skill is required of the operator. Whatever skill is needed of the
operator is only in the setting of tools in the turret or capstan head, and
once this setting has been successfully accomplished further operation of these
machines is more or less automatic. They carry special mechanisms for indexing
of their tool heads.
6. Automatic Lathe:
These lathes help a long way in
enhancing the quality as well as the quantity of production. They are so
designed that all the working and job handling movements of the complete
manufacturing process for a job are done automatically. No participation of the
operator is required during the operation. Another variety of this type of
lathes includes the semi-automatic lathes, in which the mounting and removal of
work is done by operator whereas all the operations are performed by the
machine automatically. Automatic lathes are available having single or multi
spindles. They fall in the category of heavy duty, high speed lathes mainly
employed in mass production.
7. Special Purpose Lathes:
A large number of lathes are
designed to suit a definite class of work and to perform certain specified
operations only. They prove to be more efficient and effective as compared to
the common engine lathe so far as this specified class of work is concerned. A
brief description of these machines will be given in the following table.
Description
of lathe parts :
The Bed : -The lathe bed forms the base of
the machine, the headstock and tailstock are located at either end of the bed
and the carriage rests over the lathe bed and slides over it.
The lathe bed is the
guiding member of the lathe machine so it needs to satisfy the following
condition.
Ø It should be
sufficiently rigid to prevent deflection
Ø It must be massive
with sufficient depth and width to absorb vibration
Ø It must resist the
twisting
Ø To avoid distortion
For this point of
view, the bed material should have a high compressive strength, should be wear
resistant and absorb vibration.
Cast iron alloyed with
nickel and chromium forms a good material suitable for lathe bed.
Headstock : -
The headstock is
secured permanently on the inner ways at the left-hand end of the lathe bed.It
comprises essentially a hollow spindle and mechanism for driving and altering
the spindle speed.
Tailstock:-
The tailstock is
located on the inner ways at the right-hand end of the bed.
This has two main use:
Ø It supports the other
end of the work
Ø It holds a tool for
performing an operation such as drilling, reaming, tapping etc.
Carriage:-
The carriage of a
lathe machine has various parts which serve to support, move and control the
cutting tool. Parts are following -
Ø Saddle - The saddle is
an H-shaped casting that fits over the bed and slides along the ways. It
carried the cross-slide and tool post.
Ø Cross-slide - The
cross-slide consists a casting, machined on the underside for attachment to the
saddle and carries location on the upper face for the tool post or compound
rest.
Ø Compound slide - The
compound rest is mounted on the top of the cross-slide which is used for
obtaining angular cuts and short taper.
Ø Apron - The apron is
fastened to the saddle and hangs over the front of the bed. Apron contains
gears, clutches, and levers for operating the carriage by hand and power feeds.
Ø Tool post - The tool post
located on the top of the compound rest to hold the tool and to enable it to be
adjusted to a working position.
Type of tool post :
Ø Single screw tool post
Ø Four bolt tool post
Ø Open side tool post
Ø Four way tool post
Feed Mechanism:-
Feed is the movement
of the tool relative to the work. A lathe tool may have
three types of feed :
Ø Longitudinal
Ø Cross
Ø Angular
Lathe machine working :-
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. In a tool post which
is fed against the revolving work, the cutting tool is rigidly held and
supported. With the cutting tool fed either parallel or at right angles to the work
axis, the normal cutting operations are performed.
Operation performed in Lathe Machine:-
Ø Straight turning
Ø Shoulder turning
Ø Chamfering
Ø Thread cutting
Ø Facing
Ø Knurling
Ø Filling
Ø Undercutting
Ø Taper turning
Ø Eccentric turning
Ø Polishing
Ø Grooving
Ø Spinning
Ø Spring winding
Ø Boring
Ø Parting
Safety precautions in Lathe
machine:-
During operation of
lathe machine safety & precaution must be needed to avoid an accident. When
we work on a lathe, the following things you need to remember.
Ø Do not support the
work piece by hand use work holding device.
Ø Instead of using hand
use brush to clean the chip.
Ø No adjustment while
machine is operating.
Ø Do not measure to
attempt revolving parts.
Ø Make sure that all
parts are secure tightly in the lathe before starting the operation.
Ø Never place tools on
the drilling table.
Ø Wear safety goggles.
Ø Don’t hold a chuck
handle attached by the chuck and it flies at the moment of turning a lathe.
Ø Don’t touch the byte
table into the rotating chuck and chance of damage not only a byte but the
table also.
A lathe is one of the
most versatile machine tools used by industries today. It is an important
machine tool in manufacturing industries due to its versatility. A number of
profiles can be made on a workpiece using a lathe.
Limitation of Lathe Machine:-
Ø Setting time for
holding job is very high.
Ø Only one tool can be
used generally at a time.
Ø Idle time in between
the operation is high.
Ø Preciseness of the job
depends highly on the skills of operator.
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