lathe machine

1. GEC , PATAN
NAME : DATANIYA ARUNKUMAR MANUBHAI
ENROLLMENT NO. : 190220119012
SEMESTER : 4TH SUBJECT : MANUFACTURING PROCESS
DEPARTMENT : MECHANICAL BATCH : B1
TOPIC : LATHE MACHINE
UNIT NO . 2 : METAL CUTTING LATHES
FACULTY NAME : PRO. M.G.P SIR

2. LATHE MACHINE
Contents
1. Introduction and working principle of lathe
2. Types of lathe
3. Construction and parts of lathe machine
4. Capstan and turret lathe
5. Lathe accessories and attachements
6. Operation on lathe
7.Lathe parameters

3. INTRODUCTION AND WORKING PRINCIPLE OF
LATHE
• 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 securely 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. Figure shows the working principle of
lathe. 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.
Besides the simple turning operation as

4. TYPES OF LATHE
1. Speed lathe
2. Center lathe or engine lathe
3. Bench lathe
4. Tool room lathe
5. Capstan and turret lathe
6. Special purpose lathes
7. Automatic lathes
8. Computer-controlled lathes

5. 1.SPEED LATHE
• Speed lathe is simplest of all types of lathes in
construction and operation. The important parts of
speed lathe are following-
1) Bed
2) Headstock
3) Tailstock
4) Tool post mounted on an adjustable slide
• It has no feed box, leadscrew or conventional type
of carriage.
• The tool is mounted on the adjustable slide and is
fed into the work by hand control .
• The speed lathe finds applications where cutting
force is least such as in wood working , spinning,
centering , polishing, winding, buffing etc.
• This lathe has been so named because of the very
high speed of the headstock spindle .

6. 2. CENTRE LATHE OR 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
transmitting power to the machine . the power may
be transmitted by means of belt , electric motor or

7. 3. BENCH LATHE
• This is a small lathe usually
mounted on a bench. It has
practically all the parts of an
engine lathe or speed lathe
and it performs almost all the
operation. This is used for
small and precision work.

8. 4. TOOL ROOM LATHE
• This lathe has features similar to an
engine lathe but it is much more
accurately built. It has a wide
range of spindle speeds ranging
from a very low to a quite high
speed up to 2500 rpm. This lathe
is mainly used for precision work
on tools, dies , gauges and in
machining work where accuracy is
needed.

9. 5. CAPSTAN AND TURRET LATHE
• The development of these lathes results
from the technological advancement of
the engine lathe and these are vastly
used for mass production work.
• The distinguishing feature of this type of
lathe is that the tailstock of an engine
lathe is replaced by a hexagonal turret,
on the face of which multiple tools may
be fitted and fed into the work in proper
sequence.
• Due to this arrangement, several different
types of operations can be done on a job
without resetting of work or tools, and a
number of identical parts can be
produced in the minimum time.

10. 6. SPECIAL PURPOSE LATHES
• These lathes are constructed for special
purposes and for jobs, which cannot be
accommodated or conveniently machined
on a standard lathe.
• The wheel lathe is made for finishing the
journals and turning the thread on
railroad car and locomotive wheels.
• The gap bed lathe, in which a section of
the bed adjacent to the headstock is
removable, is used to swing extra-
diameter pieces. The t-lathe is used for
machining of rotors for jet engines.
• The bed of this lathe has t-shape.
Duplicating lathe is one for duplicating
the shape of a flat or round template on
to the job.

11. 6. AUTOMATIC LATHES
• These lathes are so designed
that all the working and job
handling movements of the
complete manufacturing
process for a job are done
automatically. These are high
speed. Heavy duty. Mass
production lathes with
complete automatic control.

12. 8. COMPUTER- CONTROLLED LATHES
• In the most advanced lathes,
movement and control of the machine
tool and its components are achieved
by computer numerical control (cnc).
• These lathes generally are equipped
with one or more turrets, and each
turret is equipped with a variety of
tools and performs several
operations on different surfaces of the
workpieces to take advantage of new
cutting – tool materials, computer –
controlled lathes are designed to
operate faster and have higher power
available compared with other lathes.

13. CONSTRUCTION AND PARTS OF LATHE
MACHINE
• In the year 1797 henry maudslay, an
englishman, designed the first screw cutting
lathe machine.
• Lathe operates on the principle of a rotating
work piece and a fixed cutting tool.
• The lathe can be defined as a machine tool
which holds the work between two rigid and
strong centers, or in chuck or face plate
while the tool cuts material from the work.
Parts of lathe machine :
Headstock carriage
Bed lead screw
Cross slide leg
Tail stock thread cutting mechanism

14. 1. BED
• The lathe bed is the base of the machine, which is a solid
structure. It should be provided strictly under heavy
pressure. On top of the bed, has the v-type of guideways
include the angle of 90’.
• There are two guideways provided, inner ways and outer
ways, which are accurately machined to make them parallel
to the axis. The lathe should take up the varies vibration ,
which are causing due to different types of force. The
guideways provide sliding surfaces to the carriage and
the tailstock.
• The lathe bed must resist stresses due to the results of
two important forces,
1. The downward cutting force on the tool

15. 2. HEADSTOCK
• It is located on the left – hand side of the lathe bed. It
has a hollow spindle and the different types of
mechanism for driving and changing the speed of the
spindle.
• In this case, the speed increases when the belt is shifted
from larger to smaller diameter pulleys. The spindle is
made up of nickel , chrome and carbon steel. The front
end of the spindle hole is taper for holding the centres
perfectly.

16. 3. TAILSTOCK
• The tailstock is located on the right- hand side of the lathe bed. The tailstock
supports the other end of the workpiece when it is machining between two
centres.
• It holds the tool rigidly and perfectly for performing operations such as
drilling , reaming, tapping, and boring. It can move along the guideways and
can clamp in any position on the bed.
• The tailstock is consist of the dead centre , spindle , adjusting screw, hand
wheel ,etc. the spindle can move forward and backward of the body called
barrel by means of a hand wheel. The keyway is provided on the inside surface
of the barrel to hold the dead centre.

17. 4. CARRIAGE
• the carriage is one of the most important parts of the lathe tool and it will serve
as supporting, moving and controlling part of the cutting tool.
• It consists of the following parts :
1. Saddle
2. Cross slide
3. Compound rest
4. Tool post

18. 5. FEED MECHANISM
• the amount of the tools relative to the workpiece is called ‘feed’.
• A lathe tool has 3 types of feed
1. Longitudinal feed : here the tool moves parallel to the lathe axis. It is
affected by means of the carriage movement.
2. Crossfeed : here the tool moves at right angles to the axis.
3. Angular feed: by adjusting the compound slide and swivelling it to the
required angle to the lathe axis.
• Cross and longitudinal feeds are both hand and power operated , but angular is
only hand operated.

19. 6. SCREW OR THREAD CUTTING MECHANISM
• the lathe is important to the machine tool, which is used to cut the required
type of threads on a given work. The rotation of the screw is used to move the
tool along the workpiece to produce the screw threads. The half-nut mechanism
is used in the lathe.

20. 7. FEED ROD
• It is a long shaft having a keyway extends from the feed box across and in
front of the bed. The power is transmitted from the lathe spindle to the
apron gears through the feed rod.
• The feed rod is mainly using to move the carriage or cross slide for the
operation such as turning, boring, facing and all other considering the thread
cutting operation.

21. 8. LEADSCREW
• it is a long thread shaft used for only thread cutting operation. The lead screw
is in arranged position in all operation from the gearbox. It may also be used to
give the motion for turning, boring, etc., in the lathes which are equipped with a
feed rod.

22. CAPSTAN AND TURRET LATHE

23. LATHE ACCESSORIES AND ATTACHEMENTS
• the devices employed for handling and supporting the work and the tool on
the lathe are called its accessories.
• Function : to hold work piece of different sizes and holding dif. Tools for
different types of operations
• 2 types : standard and special
• Chucks : 3 jaw , 4 jaw
• Live centers
• Dead centers

24. 3 JAW AND 4 JAW CHUCKS

26. LATHE MANDRELS
• A “mandrels” can be described as a solid steel shaft or spindle which is used for
holding bored parts for machining their outside surfaces on lathe. They are also
known as arbors.
• Mandrels are usually employed for those jobs ( relatively small ) which have a
finished hole which is concentric with the outer surface that is to be machined.
• The common types of mandrels are : solid or plain, collar , expanding and
double cone mandrels.

27. COLLET
• Collet is an essential component of a spindle because it held the spindle in a
machine tool.
• Collet is a cone shaped sleeve generally used for holding circular or rod like piece in
so many machines typically in lathe.
• It is generally cylindrical inside and a conical outside and has edges along its length to
permit it to expand and contract.
• Collet is an adjustable metal part that is used to tightly grip a tool or any workpiece.

32. OPERATION ON LATHE
• Turning : to remove material from the outside diameter of a work piece to
obtain a finished surface and produce straight, conical , curved , or grooved
workpieces
• Facing : to produce a flat surface at the end of the part or for making face
grooves.
• Boring : to enlarge a hole or cylindrical cavity made by a previous process or
to produce circular internal grooves.
• Drilling : it is an operation of producing a cylindrical hole in a workpiece . For
this operation, the work is held in a suitable device. Such as chuck or face plate,
as usual , and the drill is held in the sleeve or barrel of the tailstock. The drill
is fed by hand by rotating the hand wheel of the tailstock.
• Reaming : reaming is the operation which usually follows the earlier operation
of drilling in case of those holes in which a very high grade of surface finish
and dimensional accuracy is needed. the tool used is called the reamer. The
reamer is held on the tailstock spindle and is held stationary while the work

33. • Threading : threading is an operation of cutting helical grooves on the external
cylindrical surface of the w/p . In this operation the work is held in a chuck or between
centres and the threading tool is longitudinally to the revolving work. Thread of any pitch
, shape and size can be cut on lathe machine using single point cutting tool. The cutting
tool must travel a distance equal to the pitch as the work piece completes a revolution.
The definite relative rotary and linear motion between job and cutting tool is achieved by
locking or engaging a carriage motion with lead screw and nut mechanism and also
fixing the gear ratio between head stock spindle and lead screw.
• Knurling : it is an operation of embossing a diamond shaped pattern on the surface of a
w/p. the purpose of knurling is to provide an effective gripping surface on a w/p. to
prevent it from slipping when operated by hand . The operation is performed by a special
knurling tool which consists of 1 set of hardened steel rollers in a holder with the teeth
cut on their surface in a definite pattern. The tool is held rigidly on the tool post and the
rollers are pressed against the revolving w/p.

35. GRINDING OPERATION
• It is also called as tool post grinder. It is mounded on the compound rest in
place of tool post.
• This attachment consists of a base plate, grinding wheel and a motor. The job
is held in a chuck or between centres. It is extensively used for grinding lathe
centres in position.
• With this attachment many other grinding operation can be performed on the
lathe. It is a useful attachment, which can be mounted on any lathe.
• It can grind hardened work and ensures a fine finish.
• Internal grinding can also be done with this grinder.

37. LATHE PARAMETERS
• Cutting speed (v) :
• It is the speed at which the metal is removed by the cutting tool from the
workpiece in case of lathe machine cutting speed is the peripheral speed of the
work past the cutting tool. It is expressed in meter/min.
• Cutting speed (v) =DN/60  1000 mm/min
• Where D = diameter of the work piece (mm)
• N = rpm of the work piece
• Cutting speed depends upon the following factors :
1. Tool material.
2. Work material.
3. Depth of cut.
4. Tool geometry.
5. Type of machine tool.

38. • feed (f) :
• It is the relative motion of tool in one revolution of workpiece. It is expressed in
mm/rev.
• Depth of cut (t) :
• It is the total amount of metal removed per pass of the cutting tool. It is
expressed in mm. it can vary and depending upon the type of tool and work
material. Mathematically. It is half of difference of diameters.
• Depth of cut (t) = D-d/2 mm
• Where , D = outer diameter. (mm)
d=inner diameter (mm)

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