capstan and turret lathes

1. Semi – Automatic lathes
Aditya College of Engineering. Madanapalle
By:
Amar Gandhi
Faculty ,Dept. of Mechanical Engineering

2. Capstan lathe
Capstan lathe is one of the types of semi-automatic
lathe.
In semi-automatic lathes machining operations are
done automatically.
Turret head is mounted on a slide called ram which
is mounted on the saddle.
The saddle is locked at a particular point and the
ram is moved to provide feed to the tool.
Lightweight machine and Suitable for bar work.
Functions other than machining like loading and
unloading of job, positioning of tools coolant
operations are done manually.

3. Capstan lathe

4. CAPSTAN LATHE

5. .
WORKING PRINCIPLE
 Work piece is held in collet or chucks which is
actuated hydraulically or pneumatically.
 All the needed tools are held in the respective holes on
the turret head.
 According to the sequence of operation the tool is
moved with the help of turret head.
 · Drilling, boring, turning, reaming, threading tools are
mounted on the turret head.
 · Forming, chamfering, knurling tools are mounted on
the front end of the turret.
 · Parting tool is mounted in inverted position on the
rear end of the turret.
 After completing each operation the turret head is
moved back to its initial position which indexes the
tools automatically

6. ADVANTAGES
 · Rate of production is higher.
 · Different ranges of speeds are obtained.
 · More number of tools can be accommodated.
 · Chucking of larger work pieces can be done.
 · Operators of less skill is required hence lowers the
labour cost.
 · Higher rigidity so can withstand heavy loads.

7. The Turret or Saddle Type Lathe
 The turret lathe is another type of lathe machine.
 It is used for repetitive production of same duplicate
parts, which by the nature of their cutting process are
usually replaceable.
 The hexagonal turret as shown in the figure.
 It is mounted directly on a saddle and the whole unit
moves back and forth on the bed-ways to apply feed.
 This type of turret lathe machine is heavier in
construction.
 It is particularly adapted for larger diameter bar work
and chucking work.
 The machine can take in longer work pieces than that
in a capstan lathe.

8. TURRET LATHE

9. Turret Lathe

10. The main parts of a capstan and turret lathe:
1. Bed.
2. Headstock.
3. Cross slide and saddle.
4. The turret saddle and auxiliary slide.

11. 1. Bed
The bed is a long box like casting provided with accurate
guide ways upon which are mounted the carriage and
turret saddle. The bed is designed to ensure strength,
rigidity and permanency of alignment under heavy duty
services.
2. Headstock
The headstock is a made up of large casting. It is located at
the left-hand end of the bed. The different types of
headstocks in capstan and turret lathe are as follows:
Step cone pulley driven headstock.
Direct electric motor driven headstock.
All geared headstock.
Pre-optive or pre-selective headstock.

12. 3. Cross-Slide and Saddle
In small capstan lathes, hand-operated cross slide is used
which are clamped on the lathe bed at the required
position.
The larger lathes and heavy-duty turret lathes are equipped
with usually two designs of the carriage.
1. Conventional type carriage
2. Side hung type carriage

13. 4. The Turret Saddle and Auxiliary Slide
In a capstan lathe, the turret saddle bridges the gap
between two bed-ways.
And the top face is accurately machined to provide a
bearing surface for the auxiliary slide.
The saddle is adjusted on lathe bed-ways and clamped at
the desired position.
The hexagonal turret is mounted on the auxiliary slide.
In a turret is directly mounted on the top of the saddle and
any movement of the turret is affected by the movement
of the saddle.
The movement of the turret may be effected by hand or
power.
The turret is a hexagonally shaped tool holder intended for
holding six or more tools.

14. Hexagonal Turret

15. Differences between Capstan & Turret lathes
Capstan lathe
 1. It is a light duty semi
automatic lathe
 2 . The turret lathe head is
mounted on a ram . The ram
slides on a saddle . The saddle is
clamped at the required position
on the bed ways
 3 . It has non rigid construction .
Hence only light cuts can be
taken
 4 . The ram with the head can be
moved to small distance .(It is
limited by the lathe travel of the
ram of saddle )
Turret lathe
 1 . It is heavy duty automatic
lathe
 2 . The turret head is mounted
on a saddle .The saddle slides
directly on the bed-ways , while
on machining.
 3 . The construction provides
rigidity to the tool while cutting.
Hence heavier cuts can be taken.
 4 .The saddle with turret can be
moved over the entire length of
the bed , while machining

16. -
 5 . Only shorter pieces can be
machined .
 6 . This is suitable for
machining small components
for a bar stock . collects are
used for holding
 7 . The turret head fitting on a
ram can be easily moved over
saddle .
 8 . It is used for machining
and small jobs up to 60 mm
dia.
 5 . Longer pieces can be
machined .
 6 . This is suitable for heavy
work , which are held in
chucks.
 7 . It is difficult to move the
turret head with saddle
manually on the bed.
 8 . It is used for machining
large and heavier work
pieces up to 200 mm.

17. Differences Between semi-automatic And Engine
Lathe
CAPSTAN AND TURRET
LATHE
 1 . The head stock is similar
to that of engine lathe but
posses wider range of
speeds and heavier in
construction
 2 . Power consumption will
be up to 15 H.P
 3 . Rate of production is high
 4 . The tool post mounted
on cross slide is a four way
tool post ,which holds 4
tools and may be indexed at
900.
ENGINE LATHE / CENTRE
LATHE
 1 . The head stock is light in
construction , posses smaller
range of speeds.
 2 .Engine lathe requires 3 H.P.
 3 . Rate of production is low.
 4. In engine lathe , it is usual
practice to hold only one tool on
the tool post .

18. -
 5 . In turret lathe , tail stock is
replaced by a hexagonal turret
, which carrys 6 more tools .
 6 . In turret lathe ,
combination of cuts can be
taken .Two or more tools can
be mounted on the same face
of turret .
 7 . Labour cost to operate
capstan and turret lathe is less .
 8 . A semi skilled operator can
operate
 9. capstan and Turret lathes
are fundamentally production
machine , capable of machining
large number of identical
pieces.
 5. In engine lathe no such turret
head to fix extra tools.
 6. This facility is quite un common.
 7. Labour cost is more
 8. A skilled operator may be
required
 9. It is suitable for odd jobs having
shapes and sizes .

19. WORK HOLDING DEVICES
1. COLLET CHUCKS :-
 A collet is a cylindrical steel bush having three or four
equally speed slits along the length .
 These slit give the spring action .
 The collet nose is made thicker to from the jaws ,
 The outer surface of nose fits in the taper hole of the hood .
 The bore of collet may be circular hexagonal etc , depending
upon the shape of work .
 Collets chucks are used for holding the bar stock quick
setting and accurate centering is done using collet chucks .
 Different types of collets chucks used in the capstan lathe
are :-
1. Draw back collet 2. Push out collet 3. Dead weight collet

20. Collets

21. 2. JAW CHUCKS
 The jaw chucks are used in capstan lathes having two or
three or four jaws depending upon the shape of the work.
 The jaws are used to support odd sized jobs or jobs having
larger diameter , which cannot be introduced though the
head stock spindle and gripped by collet chucks .
Different types of chuck used are :-
 Self centering chuck
 Independent chuck
 Combination chuck
 Air operated chuck
 Soft jaws chuck

22. Chucks

23. 3. FIXTURES
 A fixture may be described as a special chuck built for the
purpose of holding ,locating and machining a large
number of identical pieces , which cannot be easily held
number of identical pieces , which cannot be easily held
by conventional gripping devices .
 Fixtures also serve the purpose of accurately locating the
machining surface
The main function of a fixture are as follows :-
 They accurately locate the work .
 They grip the work properly , preventing it from bending
or slipping during macching operations .
 They permit rapid loading and un loading workpieces.

24. Turning Fixtures

25. TOOL HOLDING DEVICES
 The wide variety of work performed in a capstan or Turret
lathe in mass production .
 Different types of tool holders are used for holding tools
for typical operations .
 These tools are held in the six faces of the turret , on the
four position of the front tool post and in the rear tool
post .
 Special tool holders are also sometimes designed for
special purpose .

26. The important and widely used for tool holders
are listed below:-
 1. Straight cutter holder
 2. Multiple cutter holder
 3. Adjustable angle cutter holder
 4. Offset cutter holder
 5. Sliding tool holder
 6. Knee tool holder
 7 . Box tool holder
 8. Bar ending tool holder
 9 . From tool holder
 10.Tap holder
 11. Die holder
 12 .V –steady box tool holder
 13 Roller steady box tool holder
 14 . Balanced tool holder

27. TOOL HOLDING DEVICES

28. Tool and Tool-Layout
 Tools for capstan and turret lathe are similar in
construction to those of centre lathe tools, except
material.
 The tools used are made of H.S.S. or tungsten carbide
because the machines are more rigid and also operated at
higher cutting speeds.
 The tools mounted on cross-slide are used for tuning,
facing, necking, parting etc. and those mounted on the
turret head are used for drilling, boring reaming, etc.

29. Tool Layout
 The tool layout for a job constitutes the pre-
determined plan for machining operation of a
particular component.
 The layout is dependent upon the number of pieces to
be manufactured, i.e. lot size.
 As a general rule, standard tools should be used as
much as possible and also for small batches of work,
the layout should be simple.

30. For large quantities and long run special tools should be
used as they minimize machining time and retain their
cutting qualities for the maximum period.
The accuracy and cost of component largely depends
upon the tool layout.
For preparation of the tool layout, it is necessary to have
the finished drawing of the part to be machined and if it
is a forging or casting, the forged, or cast blank will
determine how much machining has to be done on
various faces.

31. Tool Layout for Hex. Headed bolt

32. The sequence of operation to be done for the
manufacture of hexagonal bolt is illustrated as below :-
•Hexagonal bar stock is used in the turret faces bar stop ,box
turning tool and forming tool and self opening dia. head
mounted
•For each tool position the length of travel of the turret is set
by feed stop screws
•Chamfering tool is held in the front tool post and the parting
off tool is held in the rare tool post .
•Bar stop in the turret face is brought position
•The coller opens and bar stock is pulled out by the bar feeding
mechanism till it butt against the bar stop collar closes.
•Turret goes back and is indexed.

33. -Box turning tool comes into position .The turret head moves
towards the head stock. The bar is turned down to 16mm dia.
for a length of 50mm.
-The turret returns to starting position and is indexed. End
forming tool comes into position. The turret moves forward. The
end forming tool, machines the bolt end.
-The turret returns to starting positions and is indexed. The self
opening die head comes into position. The turret moves
forward.
- The end forming thread is cut for 37mm length. The
die opens our. The turret goes back the starting position.
-The chamfering tool in the front slide moves forward and
chamfer is machined. The front slide is withdrawn to original
position.
-The parting off tool post moves forward and cuts off the
component. The cycle is repeated.