2. SYLLABUS
Centre lathe, constructional features,
specification, operations – taper turning
methods, thread cutting methods, special
attachments, machining time and power
estimation. Capstan and turret lathes- tool
layout – automatic lathes: semi automatic
– single spindle: Swiss type, automatic
screw type – multi spindle: cutting off,
bar type.
3. INTRODUCTION
• Lathe is the most important machine used in any
work shop. like from small scale industry to large
scale industry.
• A Lathe removes metal from rotating the workpiece
by using single point cutting tool.
• The parts to machined can be held b/w two rigid
supports called live and dead centre's.
• The tool is moved perpendicular to work piece axis to
produce a flat surface.
• The tool is moved at an angle to work piece axis to
produce tapered surface.
4. VARIOUS OPERATIONS
The following operations can be done
by using lathe. There are: turning,
taper turning, eccentric turning,
chamfering, facing, drilling, boring,
reaming, tapping, knurling, forming,
grooving, polishing, spinning and
thread cutting.
8. PARTS OF A LATHE
• BED
• HEAD STOCK
• TAIL STOCK
• CARRIAGE
• FEED MECHANISM
9. LATHE BED
Its the base of the
machine.
Its made up of
cast iron alloyed
with nickel and
chromium.
It has v and
dovetail guide
ways.
10. Lathe bed
Accurately machined
slideways
Slideways guide carriage
& tailstock
Headstock on upper end
of the lathe bed
11. Head stock
Headstock
Holds lathe spindle
and gears
Chuck is fitted to
spindle
Spindle is hollow for
long bars
Its having driving and
speed changing
mechanism
A live centre is
attached to the spindle
in the head stock.
So its called live centre
12. Tailstock
Can be moved along
slideways
Can be clamped
in any location
Inside tapered
to hold drill chuck
16. .
• Feed shaft
Used to move the
Carriage
automatically
• Lead screw
Used when screw
cutting on the
lathe
17. Cross slide
Fitted on the Saddle
Moves cutting tool at
right angles to lathe
bed
18. Top Slide (Compound slide)
Fitted to top of Cross slide
Carries toolpost and cutting
tool
Can rotate to any angle
Is used to turn tapers
19. Chucks
• Three Jaw Chuck
Self centring
Holds round and
hexagonal work
3 jaws are connected
Jaws are stamped 1,2 & 3
and fitted in order
Chuck key used to open
20. Tool post
Fitted on top slide and
carries the cutting tool
or the cutting tool
holder
Can adjust the height
on some types
Can carry 4 different
tool holders
26. SPECIFICATION
The size of the lathe
specified as follows
•Length of bed
•Distance b/w centers
•Height of centers from bed
•Swing over the bed
•Width of the bed
•Spindle bore
•Spindle speed
•Swing over the cross slide
29. 1. SPEED LATHE
It’s a simplest lathe.
It consist of head stock , bed ,tailstock and
adjustable slides.
It can be operated at various speeds.
The speed range is from 1200 – 3600 rpm.
Used for wood working, spinning and
polishing
31. ENGINE LATHE
• In earlier days it was driven by steam engine
and hence its called engine lathe
• It has lead screw , feed rod , head stock ,
speed change gears and everything provided.
• Its used for turning, taper turning , threading,
drilling, knurling, reaming and forming.
33. 3. BENCH LATHE
Its mounted on a bench
It’s a small size lathe for small and accurate machining operations.
34. 4.TOOL ROOM LATHE
It consist of all necessary attachments
required for precision and accurate
machining.
It has more variety of speed and feed
ranges
It has taper turning attachments, quick
change gear mechanism, steady rest,
coolant pump, micrometer stop… etc
This lathe is costly due to its high
precision and accuracy in operation.
35. 5.SEMI AUTOMATIC LATHE
Some operations done
manually and some
operations done
automatically
Example : capstan and turret
lathe
Its mainly used for mass production
It has heavier head stock, more speed and feed
For certain usage they removed the tail stock and mounted a turret head
For mass production– they using two tool post along with turret head
36. Automatic lathe
All the operations are done automatically
( Loading ,unloading and tool changing )
It has a cam shaft with number of cams
used to change the feed , speed and tool
in the operation.
Its mainly used in mass production.
Initial setting only done by worker. So one
operator can work more than one
machine at a time.
So machining time is less.
37. SPECIAL PURPOSE LATHE
• For doing some special type of products in
operations we need some extra set up in the
lathe. That kind of special set up lathe is called
special purpose lathe.
38. COPYING LATHE
• The tool in the lathe follows a template through a tracer.
• The tracer is connected to the cutting tool through cutting devices.
• According to the tracer movement, the tool moves to machine the job.
40. 1. Back geared mechanism
For having slow speed running in spindle in tread cutting and knurling
we go for back geared mechanism
41. Working of back geared head stock
• For normal operation the bull gear is locked with
pulley
• For having slow speed the lock is released and the
lever L is pulled to connect B1 with pulley pinon.
• So now the power moves from P1 to B1 and then B2
to P2
• Like wise the speed is reduced.
43. ALL GEARED HEAD STOCK
•It give wide range of speeds
•Its more efficient and compact than cone pulley mechanism
•Power available at the tool is almost constant for all spindle speeds
•Belt shifted is eliminated.
•The vibration in the spindle is reduced
•More power can be transmitted.
44. FEED MECHANISM
• Feed is defined as the movement of tool
relative to the work
• This feed mechanism used to transmit power
from spindle to the carriage.
• It convert rotary motion of spindle in to linear
motion of table
45. Types of feeds
• Longitudinal feed : Tool movement parallel to lathe axis
This is for moving carriage
• Cross feed : The movement of tool perpendicular to lathe
axis
This is for movement of cross slide
• Angular feed : The tool movement at an angle to lathe axis
This is for the movement of compound rest
47. working
• It has three lever position in its arrangements.
the gear A and B are in a bracket.
• By changing the position of lever the gear A or B
going to connect with the spindle gear.
• If gear A connected with spindle gear means , the
rotational power moves from spindle gear c - A – D –
E – F of lead screw. Here the lead screw rotates same
to spindle direction. So the carriage will move from
left to right.
• If the gear B connects with spindle gear c then the
rotational power transmitted from C- B –A –D-E-F .
Here the lead screw rotates opposite to spindle
direction. So the carriage will move from right to left
99. Tumbler gear quick change gear box
• It’s the simplest form of quick gear box
• The different speed of the driving shaft
obtained by tumbler gear and cone gear
arrangement.
• The driving shaft has many cone gears and the
driven shaft has sliding gears.
• The sliding gears are keyed to driven shaft
which is connected to lead screw or feed rod.
• By sliding the gears through tumbler gear we
get different speeds.
103. working
• The lead screw and feed rod get power from spindle.
• Power transmitted from feed rod to the worm wheel through
gears A,B,C,D and worm
• A splined shaft is attached to the worm wheel. This shaft
always engaged with gear F and G which is keyed to feed
check shaft.
104. WORK HOLDING DEVICES
• CHUCKS
• CENTRES
• FACE PLATE
• ANGLE PLATE
• MANDRELS
• STEADY AND FOLLOWER REST
105. WORK HOLDING DEVICES
- CHUCKS
• Its used to hold work piece of small length and
large diameters (L< 4D)
• Its also used to hold irregular jobs
• The chuck is attached to the headstock spindle
of the lathe.
• Types - 3 jaw – self centering
- 4 jaw – independent centering
- Magnetic chuck
106. 3 jaw chuck
• It’s a self centering type of internal
mechanism chuck.
• All the three jaws moves at a same time to
hold cylindrical jobs.
107. 4 jaw chuck
• Each jaws moves separately
• It has a slot at the back, when the key is
turned the jaw move separately.
• So we can easily hold the irregular jobs
• These jobs also used to hold the hollow
work pieces by reversing its position
108. Magnetic chuck
• It’s a easiest way of catching the work piece in
the chuck.
• The plates are electro magnetized during the
process.
• So its only used for Magnetic material only
109. WORK HOLDING DEVICES
- CENTRES
• The long shafts can be held between the
centers.
• Catch plate and dog carrier is used to hold the
job between centers.
• The live center in the head stock and dead
center in the tail stock are used to hold the
work piece.
• A small drill is made in the work piece ends for
having perfect contact of centers with work
piece.
111. • It’s a circular cast iron disc with 4 T- Slots and
number of plain radial slots.
• These slots used to holt the w/p by clamps
and bolts.
• Its highly efficient to hold asymmetrical work
of complex and irregular shape work piece.
• When the spindle rotates, the face plate will
also be rotated and the work will rotate.
WORK HOLDING DEVICES
- FACE PLATE
113. • Its a perfectly machined faces right angled to
each other, made up of cast iron block.
• It has slots and holes in the faces.
• So one of the face is mounted on face plate
and the work piece is mounted on other face.
• Counter weights are fixed to balance the
weight of the w/p , when its fixed eccentrically
as shown in figure.
• Its mainly used to hold the elbow pieces.
WORK HOLDING DEVICES
- ANGLE PLATE
115. • Its used to hold the hollow pieces
• The inside diameter of the w/p is equal to the
outside diameter of the w/p.
• The work mounted with the mandrel is held
between the centers.
WORK HOLDING DEVICES
- MANDRELS
117. • Its fixed in the bed of the lathe by clamp and
bolts
• The w/p is supported by 3 jaws of the
arrangement.
• The longer work pieces are machined using
this type of arrangements.
• We can fix the steady rest any where in the
lathe bed according to the length of the job.
WORK HOLDING DEVICES
- STEADY REST
119. • Its mounted on the saddle.
• So when the carriage with the tool moves ,
the set up also moving along the w/p.
• So it give continuous support to the work
piece.
WORK HOLDING DEVICES
- FOLLOWER REST
125. Parting off
• If the workers wants to cut
off the part they have
turned, they can use the
hacksaw and a vice or use
the parting off tool on the
lathe.
126. Screw-cutting on the lathe
• Lathes are also used
to cut threads in
round bars
• These threads take up
different profiles e.g
iso (60°) ACME etc.
• These threads can be
seen on bench vices,
lathes etc.
