Lathe Machine

Maintenance Of Lathe Machine
Government Polytechnic, Khamgaon Page 1
INTRODUCTION
A lathe is a machine tool that rotates the workpiece on its axis to perform various
operations such as cutting, sanding, knurling, drilling, or deformation, facing,
turning, with tools that are applied to the workpiece to create an object with
symmetry about an axis of rotation.
Lathe are used in woodturning, metalworking, metal spinning, thermal spraying ,
parts reclamation, and glassworking. Lathes can be used to shape pottery, the
best known design being the potters wheel. Most suitably equipped metalworking
lathe can also be used to produce most solids of revolution, plain surfaces and
screw threads and helices. Ornamental lathes can produce three dimensional
solids of incredible complexity. The workpiece is usually held in place by either
one or two centres, at least one of which can typically be moved horizontally to
accommodate varying workpiece lengths. Other work-holding methods include
clamping the work about the axis of rotation using a chuck or collet, or to a
faceplate, using clamps or dogs.
Fig no.1 Lathe machine

HISTORY
Lathes were developed as early as the 15th century and were known as "bow"
lathes. The operator rotated the workpiece by drawing a bow back and forth,
either by hand or with the use of a foot treadle. Next came Bessons lathe in
1568, which was driven by a cord passing over a pulley above the machine. This
in turn drove two other pulleys on the same shaft which rotated the workpiece
and a crude, wooden lead screw, which in turn allowed the operator to remove
metal from the piece being machined. The screw cutting lathe originates in the
17th century. Development and advancements have continued and today we
have sophisticated computerized controlled lathes.
Lathes have allowed man to reshape, machine and manufacture many precision
cylindrical components made of various types of metal, wood, plastics, and other
materials. Without the lathe, man would still be trying to produce cylindrical
components in some crude fashion or another. However, because of advanced
technology, the lathe has allowed man to become an important asset in
developing and machining many precision components needed to operate and
function in many areas of our industrial complex.
Fig no 2. Olden Type of Lathe Machine

TYPES OF LATHE
1) Engine Lathes
These are probably the most popular among the lathe machines. In fact, no
machine soft is seen without this type of lathe. The good thing about engine lathe
is that it can be used in various materials, asides from metal. Moreover, the setup
of these machines is so simple that they are easier to use. Its main components
include the bed, headstock and tailstock. These engine lathes can be adjusted to
variable speed for the accommodation of a wide scope of work. In addition, these
lathe come in various sizes.
2) Turret Lathes
These types of lathes are used for machining single workpieces sequentially.
This means that several operations are needed to be performed on a single
workpiece. With thw turret lathes, sequential operations can be done on the
workpiece, eliminating errors in work alignment. With this setup, machining is
done more efficiently. Correspondingly, time is saved because there is no need to
remove and transfer the workpiece to another machine anymore.
3) Special Purpose Lathes
As name implies, these lathes are used for special purpose such as heavy duty
production of identical parts. In addition, these lathe also perform specific
functions that cannot be performed by the standard lathes. Some examples of
special purpose lathes include the bench type jeweler’s lathes, automatic lathes,
crank shaft lathes, duplicating lathes, multispindle lathes, breakdrum lathes and
production lathes among others.

BASIC PARTS OF LATHE
1) Bed and Ways.
The bed is the base for the working parts of the lathe. The main feature of the
bed is the ways which are formed on the bed's upper surface and which run the
full length of the lathe. The tailstock and carriage slide on the ways in alignment
with the headstock. The headstock is normally permanently bolted at one end (at
the operator's left). The ways are accurately machined parallel to the axis of the
spindle and to each other. The V-ways are guides that allow the carriage and the
tailstock to move over them only in their longitudinal direction. The flat way takes
most of the downward thrust. The carriage slides on the outboard V-ways which,
because they are parallel to the V-ways, keep the carriage in alignment with the
headstock and tailstock at all times. This is an absolute necessity if accurate
lathe work is to be done. Some lathe beds have two V-ways and two flat ways,
while others have four V-ways. For satisfactory performance of a lathe, the ways
must be kept in good condition. A common fault of careless machinists is to use
the bed as an anvil for driving arbors or as a shelf for hammers, wrenches, and
chucks. Never allow anything to strike the ways or damage their finished surfaces
in any way. Keep them free of chips. Wipe them off daily with an oiled cloth to
help preserve their polished surface.
Fig no. 3 Bed and guide ways of Lathe machine

2) Headstock
The headstock carries the head spindle and the mechanism for driving it. In the
belt-driven type headstock, the driving mechanism consists merely of a cone
pulley that drives the spindle directly or through the back gears. When the spindle
is driven directly, it rotates the cone pulley. When the spindle is driven through
the back gears, it rotates more slowly than the cone pulley, which in this case
turns freely on the spindle. Thus two speeds are available with each position of
the belt on the cone; if the cone pulley has four steps, eight spindle speeds are
available. The geared headstock shown in figure is more complicated but more
convenient to operate, because the speed is changed by changing or by shifting
the gears. This headstock is similar to an automobile transmission except that it
has more gear-shift combinations and, therefore, has a greater number of speed
changes. A speed index plate, attached to the headstock, indicates the lever
positions for the different spindle speeds. To avoid damage to the gear teeth, the
lathe is always stopped before the gears are shifted.
Figure shows the interior of a typical geared headstock that has 16 different
spindle speeds. The driving pulley at the left is driven at a constant speed by a
motor located under the headstock. Various combinations of gears in the
headstock transmit power from the drive shaft to the spindle through an
intermediate shaft.
Fig no. 4 Headstock

3) Tailstock
The primary purpose of the tailstock is to hold the dead center to support one end
of the work being machined between centers. However, it can also be used to
hold live centers, tapered shank drills, reamers, and drill chucks. The tailstock
moves on the ways along the length of the bed to accommodate work of varying
lengths. It can be clamped in the desired position by the tailstock clamping nut.
The dead center is held in a tapered hole (bored to a Morse taper) in the tailstock
spindle. The spindle is moved back and forth in the tailstock barrel for longitudinal
adjustment. The handwheel is turned which turns the spindle-adjusting screw in a
tapped hole in the spindle. The spindle is kept from revolving by a key that fits a
spline, or keyway, cut along the bottom of the spindle. The tailstock body is made
in two parts. The bottom, or base, is fitted to the ways; the top can move laterally
on its base. The lateral movement can be closely adjusted by setscrews. Zero
marks inscribed on the base and top indicate the center position and provide a
way to measure set over for taper turning. Before inserting a dead center, a drill,
or a reamer into the spindle, carefully clean the tapered shank and wipe out the
tapered hole of the spindle. After a drill or reamer is placed into the tapered hole
of the spindle, make sure that the tool will not turn or revolve. If the tool is allowed
to revolve, it will score the tapered hole and destroy its accuracy. The spindle of
the tailstock is engraved with graduations which help in determining the depth of
a cut when a piece is drilled or reamed.
Fig no. 5 Tailstock

4) Carriage
The carriage carries the crossfeed slide and the compound rest whichin turn
carries the cutting tool in the toolpost. The carriage slides on the ways along the
bed. The wings of the H-shaped saddle contain the bearing surfaces which are
fitted to the Vways of the bed. The cross piece is machined to form a dovetail for
the crossfeed slide. The crossfeed slide is closely fitted to the dovetail and has a
tapered gib which fits between the carriage. dovetail and the matching dovetail of
the cross feed slide. The gib permits small adjustments to remove any looseness
between the two parts. The slide is securely bolted to the crossfeed nut which
moves back and forth when the crossfeed screw is turned by the handle. The
micrometer dial on the crossfeed handle is graduated to permit accurate feed.
Depending on the manufacturer of the lathe, the dial may be graduated so that
each division represents a 1 to 1 ratio. The compound rest is mounted on top of
the crossfeed slide. The carriage has T-slots or tapped holes for clamping work
for boring or milling operations. When the lathe is used in this manner, the
carriage movement feeds the work to the cutting tool which is revolved by the
headstock spindle. The carriage can be locked in any position on the bed by
tightening the carriage clamp screw. The clamp screw is to be used only when
doing work for which longitudinal feed is not required, such as facing or cutting off
stock. Normally, the carriage clamp is kept in the released position. The carriage
is always moved by hand to make sure that it is free before the automatic feed is
applied. The carriage consists of the tool post which carries the tool used in lathe
machine.
Fig no. 6 Carriage

5) Lead screw
The lead screw is used for thread cutting. Along its length are accurately cut
Acme threads which engage the threads of the half-nuts in the apron when the
half-nuts are clamped over it. When the lead screw turns inside the closed half-
nuts, the carriage moves along the ways a distance equal to the lead of the
thread in each revolution of the lead screw. Since the lead screw is connected to
the spindle through a gear train the lead screw rotates with the spindle.
Whenever the half-nuts are engaged, the longitudinal movement of the carriage
is directly controlled by the spindle rotation. The cutting tool is moved a definite
distance along the work for each revolution of the spindle. The ratio of the
threads per inch of the thread being cut and the thread of the lead screw is the
same as the ratio of the speeds of the spindle and the lead screw. For example: If
the lead screw and spindle turn at the same speed, the number of threads per
inch being cut is the same as the number of threads per inch of the lead screw. If
the spindle turns twice as fast as the lead screw, the number of threads being cut
is twice the number of threads per inch of the lead screw. The ratio of the threads
per inch of the thread being cut and the thread of the lead screw is the same as
the ratio of the speeds of the spindle and the lead screw. For example: If the lead
screw and spindle turn at the same speed, the number of threads per inch being
cut is the same as the number of threads per inch of the lead screw. If the spindle
turns twice as fast as the lead screw, the number of threads being cut is twice the
number of threads per inch of the lead screw.
Fig no 7 Lead screw

6) Quick Change GearMechanism
To do away with the inconvenience and loss of time involved in removing and
replacing change gears, most modern lathes have a selfcontained change gear
mechanism, commonly called a "quick-change gear box."
There are a number of types used on different types of lathes, but they are all
similar in principle. The quick-change gear box mechanism consists of a cone-
shaped group of change gears. One can instantly connect any single gear in the
gear train by a sliding tumbler gear controlled by a lever. The cone of gears is
keyed to a shaft which drives the lead screw (or feed rod) directly or through an
intermediate shaft. Each gear in the cluster has a different number of teeth and
hence produces a different ratio when connected in the train. Sliding gears also
produce other changes in the gear train to increase the number of different ratios
one can get with the cone of change gears. All changes are made by shifting the
appropriate levers or knobs. An index plate or chart mounted on the gear box
indicates the position in which to place the levers to obtain the necessary gear
ratio to cut the threads or produce the feed desired. Figure depicts the rear view
of one type of gear box. The splined shaft turns with gear G, which is driven by
the spindle through the main gear train mounted on the end of the lathe. Shaft F
in turn drives shaft H through the tumbler gear T, which can be engaged with any
one of the cluster of eight different size gears on shaft H by means of the lever C.
Shaft H drives shaft J through a double-clutch gear, which takes the drive through
one of three gears, depending on the position of lever B (right, center or left).
Shaft J drives the lead screw through gear L. Either the lead screw or the feed
rod can he connected to the final driveshaft of the gear box by engaging the
appropriate gears. The lathe gear box shown in figure has no feed rod. Twenty-
four different gear ratios are provided by the quick-change gear box. The lower
lever has eight positions, each of which places a different gear in the gear train
and hence produces eight different gear ratios. The three positions of the upper
level produce three different gear ratios for each of the 8 changes obtained with
the lower lever, thus making 24 combinations in the box alone. This range can be
doubled by using the sliding compound gear which provides a high- and low-gear
ratio in the main gear train. This gives two ratios for every combination obtainable
in the box, 48 combinations in all.

LATHE ACCESSORIES
The lathe machines are provided with different accessories. Lathe accessories
are used for holding and supporting the work and holding the tool. The following
are the accessories employed with the lathe.
1) Centre
The lathe centres are used for supporting the work during turning operations.
There are two centres i.e. live centre and dead centre. The workpiece is held
between these two centres.
2) Chuck
A chuck is one of the most important devices for holding and rotating the piece of
the work on lathe. It is attached to the headstock spindle by the means of bolts
with back plates and set scews on the spindle nose.
Types of chucks:
 Three jaw chuck.
 Four jaw chuck.
 Combination chuck.
 Collect chuck.
 Spindle chuck.
 Magnetic chuck.
 Air operated chuck.
3) Face plates
It is a cast iron circular disc, having a threaded hole a its centre so that it can be
screwed on the threaded nose of the spindle. There are number of holes and
slots provided on this plate. It is used for holding the work, which cannot be held
between centres or on the chuck. The work is held with the help of clamping
plates and bolts.

4) Driving plate or catch plate
A catch plate is plane disc made up of cast iron or steel. It has a central boss and
catch pin projecting from it. It is screwed on the threaded nose of headstock
spindle. It is used for driving the work with the help of projecting pin on it, with the
dog or carries clamp to work while turning the work between the centres.
5) Angle plate
Angle plate is a “L” shaped cast iron plate. Two faces of the plates are at right
angle and having slots for clamping face plate on its surface. It is used for holding
the work, which is not possible to mount directly on the face plate.
6) Mandrel
Mandrel is a device used for holding a hollow workpiece that has been previously
drilled or bored. It is the solid shaft made up of high carbon steel. It is mounted
between centres and work revolves with it. It is driven by the driving plate and
carrier.
Different types of mandrel are:
 Plain mandrel.
 Collar mandrel.
 Cone mandrel.
 Expansion mandrel.
 Step mandrel.
7) Rest
It is the device which is used to support long slender jobs at an intermediate point
to prevent it from bending, due to its own weight and vibration caused by cutting
force acting on it. Rest will be used when length of workpiece is more than 12
times its diameter.
Common types of rest used are:
 Steady rest.
 Follower rest.

OPERATIONS PERFORMED ON LATHE MACHINE
1) Facing
Facing is the square finishing of the ends of the workpiece and is often used to
bring the piece to a specified length. In facing operations, the cutter bit does not
traverse laterally (left or right) but cuts inward or outward from the axis of the
piece. Facing of the ends is usually performed before turning operations.
2) Straight turning
Straight turning may he performed upon a workpiece supported in a chuck, but
the majority of workpieces turned on an engine lathe are turned between centers.
Turning is the removal of metal from the external surface of cylindrical
workpieces using various types of cutter toolbits.
3) Finish turning
When the workpiece has been rough turned to within about 1/32 inch of the
finished size, take a finishing cut. A fine feed, the proper lubricant, and above all
a keen-edged toolbit are necessary to produce a smooth finish. Measure carefully
to be sure that the workpiece is being machined to the proper dimension. The
lathe should be stopped whenever measurements are to be made.
4) Parting
One of the methods of cutting off a piece of stock while it is held in a lathe is a
process called parting. This process uses a specially shaped tool with a cutting
edge similar to that of a square nose cutting tool. The parting tool is fed into the
rotating workpiece, perpendicular to its axis, cutting a progressively deeper
groove as the workpiece rotates. When the cutting edge of the tool gets to the
center of the workpiece being parted, the workpiece drops off. Parting is used to
cut off parts that have already been machined in the lathe, or to cut tubing and
bar stock to their required lengths.

5) Taper turning
In ordinary straight turning, the cutting tool moves along a line parallel to the axis
of the work, causing the finished job to be the same diameter throughout.
However, when cutting a taper, the tool moves at an angle to the axis of the work,
producing a taper. Therefore, to turn a taper, the work must either be mounted in
a lathe so that the axis upon which it turns is at an angle to the axis of the lathe,
or cause the cutting tool to move at an angle to the axis of the lathe.
6) Chamfering
Chamfering is operation of producing a bevel shape finish at the end of
workpiece. Chamfering is done for removing burrs and for protecting the end from
getting damaged. Chamfering is essential after thread cutting operation. It may
be performed after turning, knurling, boring, drilling etc.
7) Knurling
Knurling is the operation of producing a diomand shaped pattern on the surface
of the workpiece. The purpose of knurling is to provide an effective gripping
surface on a workpiece to prevent it from slipping when operated by hand.
Knurling is provided on handle of the machine and gauges. It is done by the
knurling tool, which consists of hardened steel rollers in a holder. The rollers have
a teeth cut in a definite pattern on their surface. Knurling is done at very low
speed. The feed during knurling varies from 1mm to 2 mm per revolution.
8) Drilling
Drilling is the operation of producing a cylindrical hole by removing metal by the
rotating edge of the cutting tool called as drill. The workpiece is held in chuck and
drill tool is fitted in tailstock barrel. The drill is fed to workpiece by rotating hand
wheel of tailstock. The speed of feed during drilling is 25% less than normal
speed.

CUTTING TOOL USED IN LATHE MACHINE
The main function of the cutting tool is to remove the unwanted material from the
work piece in form of chips to give it desire shape and size. In metal cutting
process chip can be removed either by cutting having cutting edges or by
abrasive i.e. gringing wheel.
The cutting tools can be classified as:
1) On the basis of cutting edges.
 Single point cutting tool.
 Multi-point cutting tool.
2) On the basis of motion of tool.
 Linear motion tool.
 Rotary motion tool.
 Linear and rotary motion tool.
Single point cutting tool
(1) Shank:- The shank is the main body of the tool.
(2) Nose:- The nose is the part of the cutter bit which is shaped to produce the
cutting edges.
(3) Face :- The face of the cutter bit is the surface at the upper side of the cutting
edge on which the chip strikes as it is separated from the workpiece.
(4) Side :- The side of the cutter bit is the near-vertical surface which, with the
end of the bit, forms the profile of the bit. The side is the leading surface of the
cutter bit used when cutting stock.
(5) Base :- The base is the bottom surface of the shank of the cutter bit.

(6) End :- The end of the cutter bit is the near-vertical surface which, with the
side of the bit, forms the profile of the bit. The end is the trailing surface of the
cutter bit when cutting.
(7) Heel :- The heel is the portion of the cutter bit base immediately below and
supporting the face.
Fig no 8 Single point cutting tool.

SIZE AND SPECIFICATION OF LATHE MACHINE
1) Size Of Lathe Machine
 The height of the centre over the bed.
 The length between the centres : It is the maximum length of the
workpiece that can be held in between the lathe centres.
 The swing diameter over the bed : It is the maximum length diameter of
the workpiece that can be revolving without touching the bed. It is twice
the height of the centres.
 The swing diameter over the carriage : It is the maximum diameter of
the workpiece that can swing over the carriage. It is always less than
the swing diameter over bed.
 The maximum bar diameter : It is the maximum diameter of the bar
stock that will pass through the hollow headstock spindle.
 Length of the bed.
2) SpecificationOf Lathe Machine
 Floor space occupied:- ( 175 x 45 x 115 ) cm
 Bed:- ( 115 x 25 ) cm
 Carriage:- ( 35 x 30 ) cm
 Speed ( chuck) :- 224 – 1200 rpm
 Motor used :- 1.5 HP
 Maximum bar diameter:- 60mm

TOOLKIT
1) Hex key :
A hex key or allen key of hexagonal cross section used to drive the bolts and the
screws that have a hexagonal socket in the head.
2) Open End Wrench :
It is solid nonadjustable wrenches with opening either on one or both ends called
open-end wrenches.
3) Spanner :
Spanner is the tool used to provide grip and mechanical advantage in applying
torque to turn the object.

4) Screw Driver :
A screw driver is one of the most basic operating hand tool. It is most frequently
used hand too of all.
5) Hammer :
Hammers are mostly used by the people who work with metal or around the
machinery. Hammer mostly used for press fitting or making sheets.
6) Box Wrenches :
Box wrenches are safer than opened end wrenches.
7) Plier :
Pliers are the hand tool used to hold the object firmly, possibly developed from
tongs.

TROUBLE SHOOTINGS
Problem Checklist/Remedy
1) There was no free
movement of the carriage,
tool-post.
We clean the guide ways, and oiled it
properly for the free movement.
2) The internal gearing of the
lathe machine was
damaged.
We replaced the gears to run the
machine properly.
3) The tailstock of the lathe
machine had no movement.
We maintained the tailstock with proper
lubrication to function properly.
4) The coolant system of the
lathe machine was damaged
completely.
We replaced the motor of the coolant
system, removed the rust inside the
tank.
5) The lathe machine had the
stopper problem. The
alignment of the stopper was
disturbed.
We aligned the stopper properly to work
well.
Table no 1 Trouble shooting

MAINTENANCE CHART
Maintenance chart for lathe machine for three months
Sr.no
Name of
month
Maintenance done
1. January
1) Clean the entire machine.
2) Made the parts of the machine to work
smoothly.
3) Replaced the internal gears.
2. February 1) Stopper problem of the machine.
2) Coolant system
3. March
1) Lubrication to parts of machine.
2) Final touch to the machine.
Table no 2 Maintenance Chart

SAFETY
1) In machining operations, there is one sequence of events that one must
always follow: safety first, accuracy second, and speed last. With this in
mind, let's look at some of the more important safety precautions that
should be observed before and during lathe operations.
2) Lathe accidents are usually caused by:
 Loose clothing snagging on the revolving workpiece, the chuck, or
the work piece.
 Flying chips entering the eye when turning cast iron or nonferrous
metals.
 Contact of the hands or arms with the lathe dog, chuck or
workpiece.
3) The operator should prepare himself by rolling up his shirt sleeves and
removing watches, rings, and other jewelry that might become caught
while he is operating the machine.
4) The operator should be sure to wear safety glasses or a face shield of the
approved type at all times when operating a lathe or when in the area of
lathes that are in operation.
5) The operator should be sure that the work area is clear of obstructions
that one might fall over or trip on.
6) On turret lathes, care must be taken not to catch loose or torn clothing on
a stock that is supported in the collet with chucks and extends beyond the
headstock of the lathe.
7) If a coolant or cutting oil is used, the operator should take care when
adjusting the splash pans to prevent the liquid from splashing on the floor.
The cutting oil or coolant can make the floor beneath the lathe slippery and
cause the operator to lose his balance and suffer injury.
8) The operator will keep the floor around the machine clear of oil or grease
to prevent anyone from slipping and falling into the machine.
9) The operator should use assistance when handling heavy or awkward
parts, stock, or machine accessories. Never remove chips with your bare
hands.

COST ESTIMATION
MATERIALS QUANTITY COST (Rs)
Gears 3 nos 7500
Machine oil 3000ml 330
Kerosene 2000 ml 80
Oil Paint 200 ml 90
Motor 1 nos 150
Wire, Plug 7 feets 90
Other Cost - 100
Total 8340
Table no. 3 Cost Estimation

CONCLUSION :-
In this project we have studied about Lathe machine and get knowledge about all
parts of the machine. We had repaired the machine and remove the faulty parts
from it and did the maintenance chart.
While doing this maintenance we face many difficulties and their remedies. We
get the knowledge about the various parts of the Lathe machine. We expect that
our maintenance will helpful for the workshop department in future period.
In this way we maintained the lathe machine.

REFERENCES
 Maintenance engineering and management .Author :- Sushil Kumar Srivastava
 Lathe machine manual. Author: - CMT COMEX.
 SJ 2060 Manual Lathe.
 Lathe operations and maintenance. Author: - John G. Edwards
 Manufacturing processes. :- nirali prakashan
 http:/en.m.wikipedia.org/wiki/lathe.(machine)
 http:/m.wikihow.com/set-up-a-lathe-machine
 http:/www.thomasnet.com/about/lathe-machine-51276103.html
 http:/www.sciencedirect.com

SNAPSHOTS
1) Machine before maintenance.
2) Machine under maintenance.

3) Maintenance of gears.

4) Maintenance of carriage.
5) Maintenance of tailstock.

6) Maintenance of coolant tank.

7) Machine after maintenance

Lathe Machine

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