Understanding Center Lathe and its Operations

By
ARUL R
Assistant Professor
Mechanical Engineering Department
arulsivagiri.r@gmail.com
08-10-2021
1

08-10-2021
3
CENTER LATHE
Working Principle: The lathe is a machine tool which
holds the workpiece between two rigid and strong
supports called centers or in a chuck or face plate
which revolves. The cutting tool is rigidly held and
supported in a tool post which is fed against the
revolving work. The normal cutting operations are
performed with the cutting tool fed either parallel or
at right angles to the axis of the work.
The cutting tool may also be fed at an angle relative to
the axis of work for machining tapers and angles.

08-10-2021
4
Construction of Centre lathe
The main parts of the lathe are the bed, headstock, quick
changing gear box, carriage and tailstock.

08-10-2021
5
1. Bed: The bed is a heavy, rugged casting in which are mounted
the working parts of the lathe. It carries the headstock and tail
stock for supporting the workpiece and provides a base for the
movement of carriage assembly which carries the tool.
2. Legs: The legs carry the entire load of machine and are firmly
secured to floor by foundation bolts.
3. Headstock: The headstock is clamped on the left hand side of
the bed and it serves as housing for the driving pulleys, back
gears, headstock spindle, live centre and the feed reverse gear.
The headstock spindle is a hollow cylindrical shaft that provides a
drive from the motor to work holding devices.
4. Gear Box: The quick-change gear-box is placed below the
headstock and contains a number of different sized gears.

08-10-2021
6
5. Carriage: The carriage is located between the headstock and
tailstock and serves the purpose of supporting, guiding and
feeding the tool against the job during operation. The main parts
of carriage are:
a). The saddle is an H-shaped casting mounted on the top of lathe
ways. It provides support to cross-slide, compound rest and tool
post.
b). The cross slide is mounted on the top of saddle, and it provides
a mounted or automatic cross movement for the cutting tool.
c). The compound rest is fitted on the top of cross slide and is
used to support the tool post and the cutting tool.
d). The tool post is mounted on the compound rest, and it rigidly
clamps the cutting tool or tool holder at the proper height relative
to the work centre line.
e). The apron is fastened to the saddle and it houses the gears,
clutches and levers required to move the carriage or cross slide.
The engagement of split nut lever and the automatic feed lever at
the same time is prevented she carriage along the lathe bed.

08-10-2021
7
6. Tailstock: The tailstock is a movable casting located opposite
the headstock on the ways of the bed. The tailstock can slide
along the bed to accommodate different lengths of workpiece
between the centers. A tailstock clamp is provided to lock the
tailstock at any desired position. The tailstock spindle has an
internal taper to hold the dead centre and the tapered shank
tools such as reamers and drills.

08-10-2021
8
LATHE OPERATIONS
1. Plain Turning: Plain turning is the operation of removing excess
amount of material from the surface of a cylindrical job.
2. Step Turning: Step turning produces various steps of different
diameters.

08-10-2021
9
Facing:The facing is a machining operation by which the end surface of the
work piece is made flat by removing metal from it.
Parting:The parting or cutting off is the operation of cutting away a
desired length of the workpiece, i.e., dividing the workpiece in two or more
parts.

08-10-2021
10
Drilling: Drilling is the operation of producing a cylindrical hole
in the workpiece.
Reaming: The holes that are produced by drilling are rarely
straight and cylindrical in form. The reaming operation finishes
and sizes the hole already drilled into the workpiece.

08-10-2021
11
Boring: The boring operation is the process of enlarging a hole
already produced by drilling.
Knurling: The knurling is a process of embossing (impressing) a
diamond-shaped or straight-line pattern into the surface of
workpiece. Knurling is essentially a roughening of the surface and
is done to provide a better gripping surface.

08-10-2021
12
Grooving: Grooving is the act of making grooves of reduced
diameter in the workpiece.
Threading: Threading is the act of cutting of the required form of
threads on the internal or external cylindrical surfaces.

08-10-2021
13
Forming: The forming is an operation that produces a convex,
concave or any irregular profile on the workpiece.
Chamfering: Chamfering removes the burrs and sharp edges,
and thus makes the handling safe. Chamfering can be done by
a form tool having angle equal to chamfer which is generally
kept at 45°.

08-10-2021
14
Filing and Polishing: The filing is the finishing operation that
removes burrs, sharp corners and feed marks from the
the surface quality is the workpiece is improved by the polishing
with the help of emery cloth of fine grades.
Taper Turning: The taper turning is an operation of producing a
conical surface by gradual reduction in the diameter of a cylindrical
workpiece.

A capstan and turret lathe is used to manufacture any number of
identical workpieces in the less time.
These lathes are the development of engine lathes. For the first
time in 1860, Pratt and Whitney developed the capstan lathe..
INTRODUCTION TO CAPSTAN AND TURRET LATHE
08-10-2021
17

 Before understanding difference between capstan and turret
lathe let us first understand what a lathe is? and how it is
different from the capstan and turret lathe.
 Lathe is a machine used to done various operations such as
drilling, boring, knurling, thread cutting, facing etc. on the work
piece to make it a value added product.
 In classical lathe machine such as in center lathe there is only one
tool post and only one tool fitted in the tailstock, which usually
takes time while changing tools for different operations.
INTRODUCTION
08-10-2021
18

There are certain difficulties that cannot be overcome by center
lathes such as:
1) The large time involvement while setting and movement of tool
between the machining processes
2) Unsuitable for mass production
3) Less number of speeds
4) One tool fixation in the tailstock etc..,
INTRODUCTION
08-10-2021
19

 Thus the center lathe is modified to turret and capstan lathe to
overcome all these difficulties.
 Capstan and Turret lathes are the advancement of the Engine
lathes and center lathe, wherein the tailstock is replaced by a
hexagonal turret tool head, having 6 different tools in the turret,
where turret tool is rotate in each operation according to process
requirement.
 These are used to produce large number of identical parts in
minimum time and are used for mass productions in less time
with maximum accuracy and precision.
INTRODUCTION
08-10-2021
20

 These are the semi-automatic lathes which mean that all the
machining process such as boring, drilling, thread cutting, facing,
turning etc., without changing of tools, are to be done
automatically and other functions like setting of tools, clamping
of work piece, cooling process are to be done manually.
 These machines can be used to machine from small to large work
piece and are costlier than engine lathe because of having
complex construction.
INTRODUCTION
08-10-2021
21

The conventional general purpose automated lathes can be
classified as,
Semiautomatic
1. Capstan lathe (ram type turret lathe)
2. Turret lathe
3. Multiple spindle turret lathes
4. Copying (hydraulic) lathe
Automatic
1. Automatic cutting off lathe
2. Single spindle automatic lathe
3. Swiss type automatic lathe
4. Multiple spindle automatic lathes
INTRODUCTION
08-10-2021
22

The characteristic features of semiautomatic lathes are;
1. Some major auxiliary motions and handling operations like bar
feeding, speed change, tool change etc. are done quickly and
consistently with lesser human involvement
2. The operators need lesser skill and putting lesser effort and
attention
3. Suitable for batch or small lot production
4. Costlier than centre lathes of same capacity
INTRODUCTION
08-10-2021
23

 The capstan and turret lathe is a form of metalworking lathe that
is used for repetitive production of duplicate parts, which by the
nature of their cutting process are usually interchangeable.
 It evolved from earlier lathes with the addition of the turret,
which is an indexable tool holder that allows multiple cutting
operations to be performed, each with a different cutting tool in
easy, rapid succession, with no need for the operator to perform
set-up tasks in between, such as installing or uninstalling tools.
INTRODUCTION
08-10-2021
24

 Capstan and Turret lathes are one of the types of semi-automatic
lathe.
 In semi-automatic lathes machining operations are done
automatically.
 Functions other than machining like loading and unloading of job,
positioning of tools coolant operations are done manually.
 The semiautomatic lathes, capstan lathe and turret lathe are very
similar in construction, operation and application.
 Capstan and turret lathes are production lathes used for
production of large number of identical parts in minimum time.
CONSTRUCTION
08-10-2021
25

These lathes are different from the engine lathe because
of following aspects:
1. They do not have tail stock.
2. The work piece is supported at the head stock and
alone.
3. They carry a much larger number and variety of tools
than the engine lathe.
4. More than one tool may be set to operate
simultaneously.
CONSTRUCTION
08-10-2021
26

The main parts of capstan or turret lathe
1. Bed
2. Spindle
3. Head stock
4. Carriage
5. Rear tool post
6. Cross slide
7. Slide or ram
8. Hexagonal turret head
9. Square tool post on the cross slide
CONSTRUCTION
08-10-2021
27

1. BED
The base part of the lathe is the bed. It is made of
cast iron. Guide ways are provided on the top of the bed. Cross slide
and turret head are mounted on the guide ways. The bed should be
strong and rigid to withstand loads force and vibrations during
machining process.
2. HEAD STOCK
The headstock assembly is permanently fastened to
the left end of the bed. Headstock of capstan lathe is similar to that
of ordinary lathe. But it is heavier in construction. a powerful motor
of 30 to 2000rpm speed is fitted.
The four main types of headstocks are
 Step cone pulley driven headstock.
 Direct electric motor driven head stock
 All geared headstock.
 Pre-selective headstock.
CONSTRUCTION
08-10-2021
30

3. TURRET HEAD AND SADDLE
The turret head is mounted on the ram fitted with
turret slides longitudinally on the saddle. Turret head has a
hexagonal block having six faces with a bore for mounting six or
more than six tools at a time. The threaded holes on these faces are
used to hold the tools. The actuation of ram is done by hand or
power. An adjustable stopper is used to control the forward
movement of the ram. Ram is returned to its initial position in order
to index the cutting tool.
The tools are indexed to 60 by rotation of circular
plate which is indexed automatically along with the turret head. For
bringing the next tool into cutting position a mechanism called
Geneva mechanism is used. It is an H shaped component fitted
across the lathe bed. It moves along the guide way. It can be moved
anywhere along the bed and locked to the required position. In
capstan lathe the turret head is mounted upon the ram which slides
upon the saddle.
CONSTRUCTION
08-10-2021
31

4. CROSS SLIDE
There are two type of cross slides they are
1. Reach over type
2. Slide hung type
1. Slide hung type
This type of cross slide is entirely supported on the
front and has no rear tool post. This enables a greater swing capacity
to hold large diameter work piece.
2. Reach over type
The cross slide has two tool posts having totally four
faces of square turret for mounting the tools. Tools are indexed by
an angle of 90. While indexing, the motion of each tool is controlled
by stop bars.
CONSTRUCTION
08-10-2021
32

CAPSTAN LATHE
08-10-2021
35
Capstan Lathe
 The turret of the capstan lathe machine is mounted on a slide
or ram which can be moved longitudinally on the saddle for
feeding the tools.
 The saddle itself is mounted on the bed.
 The turret is generally hexagonal but may also be square or
round.
 This type of machine is lighter in construction and is suitable
for machining bars of up to 60 mm in diameter.
 More than one tool may be mounted on the same face on the
turret making it possible to machine more than one surface at
the same time.

TURRET LATHE
08-10-2021
36
Turret Lathe
 The tool turret is mounted directly on the saddle and the feed
is given by moving the entire unit.
 The turret lathe can thus operate under more serve condition
accommodating heavier work pieces with higher cutting
speeds, feeds and depth of cut.
 Turret lathes are capable of turning bars up to 200-600 mm
diameter using collets as well as handling irregular jobs like
castings and forgings with chucks.
 Some turret type’s lathes are equipped with crosswise
movement of the hexagonal tool turret by hand or power.
 Turret machines provided with so called side hung type of
carriage do not require any support from the rear slide of the
bed.

WORKING PRINCIPLE
08-10-2021
37
 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.

WORKING PRINCIPLE
08-10-2021
38
 All 6 faces of the turret can hold 6 or more number of different
tools. The turret can be automatically indexed and each tool
brought in line with the lathe axis in a regular sequence. The
workpieces are held in collets or in chucks.
 The longitudinal and crossfeed movement of the turret saddle
and cross slide are regulated by adjustable stops
 These stops enable different tools set at different stations to
move by a fixed amount for performing different operations
on repetitive workpieces without measuring the length or
diameter of the machined surface in each case.

08-10-2021
39
These special characteristics of a capstan and turret lathe
enable it to perform a series of operations such as:
1. Turning.
2. Drilling.
3. Boring.
4. Thread cutting.
5. Reaming.
6. Necking.
7. Chamfering.
8. Cutting-off.
And many other operations in a regular sequence to produce a
large number of identical pieces in a less amount of time.

TOOLS HOLDERS FOR CAPSTAN AND TURRET LATHES
08-10-2021
40
1. Box tool holder
2. Flanged tool holders
3. Slide tool holders
4. Adjustable turning head
5. Threading die head
6. Quick acting slide tool holder

08-10-2021
41

WORK HOLDING DEVICES FOR CAPSTAN AND TURRET LATHES
08-10-2021
42
WORK HOLDING DEVICES IN A CAPSTAN OR TURRET LATHE
1. Collets
2. Self-Centring Chuck
3. Four Jaw Independent Chuck
4. Combination Chuck
5. Air Operated Chuck
6. Soft Jaw Chuck

08-10-2021
43

08-10-2021
45
S.NO CAPSTAN LATHE TURRET LATHE
1 It is a Light weight machine. It is a heavy weight machine.
2 In capstan lathe the turret tool head is
mounted over the ram and that is
mounted over the saddle.
In turret lathe the turret tool head is
mounted over the saddle like a single unit
3 For providing feed to the tool, ram is
moved.
For providing feed to the tool, saddle is
moved.
4 Because of no saddle displacement,
Movement of turret tool head over the
longitudinal direction of bed is small
along with the ram.
Turret tool head move along with the saddle
over the entire bed in the longitudinal
direction.
5 Used for shorter work piece because of
limited ram movement.
Used for longer work piece because of
saddle movement along the bed.
6 Its working operations are fast because of
lighter in constructions.
Its working operations are slower because
of heavier in constructions.

08-10-2021
46
S.NO CAPSTAN LATHE TURRET LATHE
7 Heavy cuts on the work piece cannot be given
because of non-rigid construction.
Heavy cuts on the work piece
can be given because of rigid
construction of machine.
8 For indexing turret tool head, the hand wheel of the
ram is reversed and turret tool index automatically.
For indexing turret tool head,
turret is rotated manually after
releasing clamping lever.
9 The turret head cannot be moved in the lateral
direction of the bed.
The turret head can be moved
crosswise i.e. in the lateral
direction of bed in some turret
lathe.
10 In capstan lathe, Collet is used to grip the Job. In turret lathe, power Jaw chuck
is used to grip the Job.
11 Used for machining work piece up to 60 mm
diameter.
Used for machining work piece
up to 120 mm diameter.
12 These are usually horizontal lathes. Turret lathes are available in

08-10-2021
49
Taper Turning
Cutting the metal on a lathe machine in such a way that,
its surface makes an angle with the axis of the metal is
called taper turning.
The following are the various methods to which taper can
represent.
•According to the top angle of the taper.
•mm Per meter (mm / m).
•According to the diameter of each end of the taper and
the length of the taper.
•By any ratio.

08-10-2021
50
Types of Taper Turning Methods
•The following are the different types of taper turning methods
on lathe machine.
•Tailstock Set Over Method
•Compound Rest Method
• Taper Turning Attachment Method
• Form Tool Method
• Combining Feeds Method

08-10-2021
51
Tailstock Set Over Method
This taper turning methods is
used only for taper turning of small top angles.
Only external tapers can be machined by this method.
In these types of taper turning methods, tailstock is set out of
alignment according to the size of the turning taper.
The clamping mechanism is loosened for
offsetting, adjusting the upper part of the tailstock as required,
and adjusting screws are tightened which is shown in figure.

08-10-2021
52
This method is also called as Offsetting Tailstock method.
For performing this method ball center type work holding device is used in a tailstock.
The amount of offset is calculated in the following way,
O = (Taper × L)/2000
Where,
0 = Offset, in mm.
Taper = millimeter/meter
L = Length of workpiece in mm

08-10-2021
53
Compound Rest Method
These types of taper turning methods on lathe machine is used for turning small and steep
tapers.
See in figure compound rest method on lathe machine which is described in below.
In this method firstly compound rest is set at a particular angle corresponding to the center
line of the workpiece or a job, It is then locked into this position.
After then cutting tool is set exactly at the center and brought into position by carriage
movement.
The carriage is then locked and then taper turning of the job is done by turning the handle of
the compound rest by hand.

08-10-2021
54
Compound rest angle can be calculated by formula,
Tan θ = D-d/2L
θ = tan-1 (D-d/2L)
Where,
D = Larger diameter of the taper
d = Smaller diameter of the taper
L = Length of the taper

08-10-2021
55
Taper Turning Attachment Method
The taper turning attachment is an accessory that is provided with the modern lathes.
It is mounted behind the carriage.
It is used for taper turning or boring without tailstock offsetting.
In this taper turning methods, job is held in between center or a chuck.
If the job is held between the centers, only the outer taper turning can be done.
Show in figure taper turning attachment method,

08-10-2021
56
The taper turning attachment consists of a frame that attaches to the rear end of the lathe
and a guide bar that is pivoted at the center.
The guide bar can be swiveled in either side at a 10° angle and it can be clamped to the
position by two bolts.
The taper turning workpiece is mounted parallel to the lathe bed (between the centers as
shown in a figure).
Taper turning attachment forces the tool to move at a fixed angle.

08-10-2021
57
Form Tool Method
In this types of taper turning methods a straight form tool with a taper angle is set with
a taper cutting edge.
Show in figure,
It is given a direct feed on the job so that it creates a definite form on the job.
The drawback of this method is that more force is not generated because more area
comes in contact between the cutting edge and the workpiece.
Due to the reality of taper turning, this form tool method is only used for short length
tapers.

08-10-2021
58
Combining Feeds Method
In such a method, longitudinal and cross feeds are performed simultaneously, so that the
tool moves along the diagonal path.

08-10-2021
59
Methods of Measuring Tapers
•There are six methods of measuring tapers in
precision.
By comparing the newly turned taper with a
known taper.
• Using plug gauge for internal taper and ring gauge for
the external taper.
• Using the taper test gauge.
•Using gauge blocks, test mandrel.
•Using sign bars and gauge blocks.
•Using a micrometer.

08-10-2021
60
THREAD CUTTING METHODS
Types of Machining Threads
Internal Threads
An internal machining thread is a screw thread on a concave
surface. These types of threads are machined with a single-lip
threading tool. Some internal threads make use of the
traditional threading tap. A tap is a metal tool used for cutting
internal threads on CNC machining parts.
Calculate the diameter for tapping using the formula below:
Core hole diameter = Tap diameter – Thread pitch.

08-10-2021
61
External Threads
An external thread is also referred to as a screw thread. The common
external threads include screws, plug gage, bolts, or studs. For parts that
qualify for turning, an external thread can extend through the length of the
parts.
Machining Thread
Milling
This method involves the use of a revolving milling cutter. The cutter’s
shape conforms to the desired shape of the thread. Manufacturers make
use of either single or multiple cutters. For single cutters, every one of the
cutting edges is present in one plane. On the other hand, there are several
rows of annular cutting teeth on the multiple cutters.
It is also possible to use a hob to cut the threads. In this case, the cutter’s
teeth will lie along a helix. Milling can be used to make internal or external
threads. Threads cut using the milling method come with a high level of
accuracy.

08-10-2021
62
Threading on a Lathe
The process produces a helical ridge on a workpiece. The helical ridge
has a uniform section on the part. Threading on a lathe involves
successive cuts using a threading toolkit.
A tap handle is one of the most common methods for tapping with a
lathe machine. The machinist clamps the workpiece in the lathe chuck.
Then, a spring loader center or a dead center is used for smaller and
larger taps, respectively—either of these equipment clamps to the
tailstock.
Die-Cutting
The die-cutting method is most popular for cutting external threads.
Die-cutting relatively produces parts rapidly. Therefore, they are
economical ways for cutting threads. This method has a moderate
level of accuracy and quality.

08-10-2021
63
There are generally two types of threading dies. They are:
1. Bottom or Round Split Dies: The design of these dies makes
them suitable for hand use. However, they may also be
employed in machines. They are round with a screw closing
their radial cuts. This enables their adjustments for both loose
and tight fits.
2. Adjustable Dies: In this case, there are two pieces of dies
mounted in a die stock. The dies may also be held in a collet. A
taper arrangement also allows the movement towards the
center or away from it. This provides different degrees of fit.
Adjustable dies are great for hand use.

AUTOMATIC LATHES
 Machine tools in which components are machined automatically.
 The working cycle is fully automatic that is repeated to produce duplicate parts with
out participation of operator.
 All movements of cutting tools, their sequence of operations, applications, feeding of
raw material, parting off, un loading of finished parts all are done on machine.
 All working & idle operations are performed in definite sequence by control system
adopted in automatic which is set up to suit a given work.
 Only operation reqd to be performed manually is loading of bar stock/ individual
casting/ forged blanks.
 These machines are used when production requirements are too high for turret lathes
to produce economically.

AutomaticLathes
 Manual machine controls replaced by various mechanisms
 Parts are fed and removed automatically
 May have single or multiple spindles
 Automatic lathes uses servo motor
 Automatic lathes Limited ranges of variety and sizes

Automatic LatheFeatures
 Minimum man power utilized
 Meant for mass production
 Manual machine controls replaced by various mechanisms
 To eliminate the amount of skilled labour.
 Mechanisms enable to follow certain prescribed frequency
 Parts are fed and removed automatically
 Minimizing the loading and unloading time
 May have single or multiple spindles
 Tool set up may be permanent
 May have horizontal or vertical spindles
 More accuracy can be obtained

Advantages
 Greater production over a given period.
 More economy in floor space.
 Improvement in accuracy.
 Floor space maintenance and inventory requirements are reduced.
 More consistently accurate work than turrets.
 More constant flow of production.
 Scrap loss is reduced by reducing operator error.
 During machine operation operator is free to operate another machine/can
inspect completed parts.

CLASSIFICATION OF AUTOMATICLATHES
 Depending up on type of work machined these machines are classified as:
1. Magazine loadedAutomatics:
 Machines used for producing components from separateblanks.
 Also called as automatic checking machines.
2. Automatic Bar Machines:
 designed for machining components from bar/ pipe stock.
 M/c’s are used for manufacture of high quality fasteners (screws, nuts),
bushings, shafts, rings, rollers, handles which are usually made of bar / pipe
stock.

 Depending upon number of work spindles, automatic lathes are classified as:
1. Single SpindleAutomatics.
2. Multi SpindleAutomatics.
 Depending upon purpose & arrangement of spindle also automatics are
classified as:
1. Purpose General & single purposem/c.
2. Arrangement of spindle Horizontal & vertical

I) Type of Single SpindleAutomatics:
a) Automatic Cutting Off Machine:

These machines produce short w/p’s of simple form by means of cross sliding
tools. Machines are simple in design.
Head stock with spindle is mounted on bed.
2 cross slides are located on bed at front end of spindle.
CAMS on cam shaft actuate movements of cross slide through system of levers.
Operation:
 The reqd length of work(stock) is fed out with a cam mechanism, up to stock
stop which is automatically advanced in line with spindle axis at each end of
cycle.
 Stock is held in collet chuck of rotating spindle.
 Machining is done by tolls that are held in slides operating only in cross wise
direction.
 Typical simple parts (3 to 20 mm dia) machined on such a machine is shown in
fig.

b) Single spindle Automatic Screwm/c:

 Used for producing small screws(12.7 to 60 mm dia) generally, but also in
production of all sorts of small turned parts.
 These are completely automatic bar type turret lathes, designed for machining
complex internal & external surfaces on parts made of bar stock/separateblanks.
 Up to 10 different cutting tools can be employed at one time in tooling of this kind
of screw machine.
 2 cross slides(front & rear) are employed for cross feedingtools.
 Vertical tool slides for parting off operation may also be provided.
 Head stock is stationary & houses the spindle.
 Bar stock is held in collet chuck & advanced after each piece is finished & cutoff.
 All movements of machine units are actuated by cams mounted on cam shaft.

 Bar stock is pushed through stock tube in a bracket & its leading endis
clamped in rotating spindle by means of collet chuck.
 By stock feeding mechanism bar is fed out for nextpart.
 Machining of central hole is done by tools that are mounted on turretslide.
 Parting off/ Cutting off, form tools are mounted on crossslide.
 At end of each cut turret slide is with drawn automatically & indexedto
bring next tool to position.

c) Swiss type automaticscrew/Sliding headscrew:

 As name implies in this m/c head stock is movable & tools are fixed.
 These machines are used for machining long accurate parts of small diameter.(2 to
25mm).
 Bar stock is held in rotating collet in head stock & all longitudinal feedsare
obtained by cam which moves entire head stock as unit.
 Rotating bar stock is fed through hard bushing in centre of toolhead.
 Tool head consists of 5 single point tools is placed radially aroundbushing.
 Mostly diameter turning is done by 2 horizontal slides, other 3 slides usedfor
operations such as knurling, chamfering, cutoff.
 Tools are controlled & positioned by cams that bring tool in as needed toturn,
face, form, cutoff w/p from bar as it emerges from bushing. Close tolerances
0.005 to 0.00125 mm are obtained.

II) Multi SpindleAutomatics:
 These are fastest type of production machines and are made in a variety of
models with 2,4,5,6,8 spindles.
 In contrast with single spindle m/c where one turret face at a time is
working on one spindle, in multi spindle m/c all turret faces works on all
spindles at same time.
 Production capacity is higher, machining accuracy is lower compared to
single spindle.
 Because of longer set up time, increased tooling cost this machines are
less economical than other on short runs, more economical for longer
runs.

a)Parallel Action Automatics/ Multiple Flow m/c:

 In this type of machine same operation is performed on each spindle, w/p is
finished in each spindle in one workingcycle.
 It means that No. of components being machined== No. of spindles inmachine.
 Rate of production is high & machine can be used to machine simple parts only
since all the machining processes are done at one position.
 These machines are usually automatic cutting off bar type machines, used to
perform same work as single spindle automatic cut offmachines.
 Machine consists of frame with head stock at rightend.
 Horizontal work spindles that are arranged one above the another are housedin
this head stock.
 Cross slides are located at right & left hand sides of spindles & carry cross
feeding tools. All working & auxiliary motions of machine unit are obtainedfrom
CAM mounted on cam shaft.

b) Six Spindle Progressive ActionMultiSpindle:

 In this design of machine, the w/p is machined in states & progressively in station
after station.
 Head stock is mounted on left end of base of machine.
 It carries spindle carrier which rotates about a horizontal axis through centreof
machine.
 Working spindles are mounted on this spindle carriers.
 Spindles carry collets & bars from which w/p’s are machined.
 Bar stock is fed through each spindle from rear side.
 On face of spindle carrier support are mounted cross slides which carry toolsfor
operations such as cutoff, turning, facing, forming,chamfering.

 No. of slides === No. of spindles.
 Main tool slide (end tool slide) extends from middle of thissupport.
 Fed of each tool, both cross slide & end tool slides is controlled by itsown
individual cams.
 In this diagram spindle carrier indexes on its own axis by 60° at each cuttingtool
retraction.
 As spindle carrier indexes, it carries work from one station to anotherstation
where different tolls operate on work.
 Stock moves round the circle in counter clock wise direction & returns to station
no. 6 for cutting off.

Toollayout
schematically showing the type and configuration of A
typical tool layout for a particular job being machined in a
single spindle automatic lathe is schematically shown in Fig.

Tool layout and camdesign
 Pre determined plan for order and method off machining
operations necessary to produce it . Following steps are
recommended for lay out for an automatic lathe.

» SHAPING MACHINE
08-10-2021
88

 The shaper machine is a reciprocating type of machine
basically used for producing the horizontal, vertical or flat
surfaces.
 The shaper holds the single point cutting tool in a ram and
work piece is fixed in the table.
 During the forward stroke, the ram is holding the tool is
reciprocating over the work piece to cut into the required
shape. During the return stroke, No metal is cutting.
 In the shaper machine, the rotary motion of the drive is
converted into reciprocating motion of ram holding the tool.
 Therefore in order to reduce the total machine time, It
allows the ram holding the tool should move slower during
forwarding cutting stroke and it comes faster in return
stroke.
 This can be achieved by a mechanism called as quick return
mechanism.
INTRODUCTION
08-10-2021
89

 The shaper process can be defined as a process for removing
metal from the surface in horizontal, vertical and angular planes
by the use of a single point cutting tool held in a ram that
reciprocates the tool in a linear direction across the work piece
held on the table of the machine.
 The work is fed at right angles to the direction of the ram in small
increments, at the end of the return stroke.
SHAPER MACHINE PRINCIPLE
08-10-2021
90

SHAPER MACHINE CONSTRUCTION
08-10-2021
91

08-10-2021
92

BASE
 The base is the necessary bed or support required for
all machines tools.
 The base is hollow casting made of cast iron to resist
vibration and on which all parts of the shaper are
mounted.
 It is so designed that is can take up the entire load of
the machine and the forces set up by cutting tool over
the work.
08-10-2021
94

COLUMN
 This is made of cast iron, which is a box-like and is
mounted on the base.
 Two accurately machined guide ways are provided on
the top of the column on which the ram reciprocates.
 The column acts as a cover to the drive mechanism and
also supports the reciprocating ram and the worktable.
08-10-2021
95

CROSS-RAIL
 Cross rail is mounted on the front vertical surface of the
column on which saddle is mounted.
 The vertical movement is given to the table by raising
or lowering the cross rail using the elevating screw.
 The horizontal movement is given to the table by
moving the saddle using the cross feed screw.
08-10-2021
96

TABLE
 The table is bolted to the saddle and receives crosswise and
vertical movements from saddle cross rail.
 T-bolts are used for clamping on top and sides.
 The table can be swiveled at any required angle.
 In a universal shaper, the table may be swiveled on a horizontal
axis and the upper part of the table may be fitted up or down.
 In heavier type shaper the table clamped with table support to
make it more rigid.
08-10-2021
97

RAM
 The ram reciprocates on the column guide ways and
carries tool head with a single point cutting tool.
 the tool head is in the clapper box, which causes
cutting action only in forward stroke of the ram and
sliding movement of the tool in the reverse stroke of
the ram.
 the depth of cut or feed of the tool is given by down
feed screw.
 The tool head has swivel base degree graduations,
which helps to move the tool head to any desired
inclination for machining inclined surfaces on the work
pieces.
08-10-2021
98

The shaper is a machine tool used primarily for:
• Machining Horizontal Surfaces
• Machining Vertical Surfaces
• Machining Angular Surfaces
• Cutting Slots, Grooves & Key ways
• Machining irregular surfaces
• Machining Splines / Cutting Gears
SHAPER MACHINE FUNCTIONS/OPERATIONS
08-10-2021
10
2

 Based on the type of driving mechanism types of shaper
machines.
1. Crank type shaper.
2. Geared type shaper.
3. Hydraulic type shaper.
 Based on ram travel types of shaper machines.
1. Horizontal shaper
2. Vertical shaper.
 Based on the table design types of shaper machines.
1. Standard shaper.
2. Universal shaper.
 Based on cutting stroke types of shaper machines.
1. Push cut type
2. Draw cut type
TYPES OF SHAPER MACHINE
08-10-2021
10
5

08-10-2021
10
6
BASED ON THE TYPE OF DRIVING MECHANISM TYPES
OF SHAPER MACHINES

1. CRANK AND SLOTTED QUICK RETURN MECHANISM
08-10-2021
10
8

1. CRANK AND SLOTTED QUICK RETURN MECHANISM
08-10-2021
10
9

2. WHITWORTH QUICK RETURN MECHANISM
08-10-2021
11
0

08-10-2021
11
1
3. HYDRAULIC TYPE SHAPER.

2. HYDRAULIC DRIVE MECHANISM
08-10-2021
11
2

» PLANNER MACHINE
08-10-2021
11
3

Planer is machine that use to generate
accurate flatsurfaces and cutting slots.
It is similar toa shaper, but it is larger than
shaper machine.
and with the entire workpiecemoving
beneath thecutter,
The work table is moved back and forth on
the bed beneath the cutting head either by
mechanical means, such as a rack and pinion
gear, or by a hydraulicsystem.

PLANING MACHINE PARTS
 BED
 TABLE
 COLUMN
 CROSS RAIL
 TOOL HEAD

BED
 Bed of a planer is large insize and heavy inweight
 Itsupports the columnand all other moving partsof
machine
 It is made slightly longer than twice the length of the
table so that thefull length of the table may bemoved
on it.
 There is av shaped wayson the bed which help to
reciprocateor back and forth motion tothe table.
 Smooth movement need to properoil on tableand bed
v shape surfacesooil is provided byoil reservior.

TABLE or platen
 Table supports thework and reciprocates along the
bed
 Table is made from good quality castiron
 The top faceof the table is accurately finished in
order to locate thework correctly
 T-slotsare provided on theentire length of the tableso
that the work and work holding devices may be bolted
upon it.

COLUMN
 These are rigid box likevertical structureplaced on
each side of the bed andtable.
 Theyare heavilyribbed to trace upsevere forcedue to
cutting.
 It also facilitate tool headmechanism.
 The cross rail may be madetoslide up and downfor
accommodating different heights ofwork

CROSS RAIL
 It is rigid box- likecasting connecting the twocolumns
 It may be raised or lowered on the faceof housing and
can be clamped at a desired position by manual or
electrical clampingdevices
 It should remainabsolutely parallel to the topsurface
of the table

TOOLHEAD
 According toconstruction it is similar to the shaper
machine tool head.
 Tool heads are mounted on thecross rail bysaddle
 The saddle may be made to move transverselyon the
crossrail to give crossfeed.
 The clapperblock is hinged at hinge pins to theclapper
block and it holds the tool post in which the tool is
clamped bystraps

CLASSIFICATION OF PLANER
Planeraregenerallydivided into 2 types
 Double housing planer.
 Opens sideplaner.
 Divide typeplaner.

DOUBLE HOUSING PLANER
 It is very old systemmachine.
 Massive bed on which worktablereciprocates
 A planer having two housings tosupport thecross rail,
with two heads on thecross rail.
 Twovertical columnson which two tool head slides
 Cross rail fitted between twocolumnsand carries one
or two heads slides horizontally.

OPEN SIDE PLANER
 It consistof onevertical column may be mounted on
the crossrail
 column and cross railconsistof single anddouble
tool head
 Used for the machining of wide workpieces

DIVIDE TYPE PLANER
 it also called tandemplaner.
 Consist of twoworktable.
 Used for continuous mass production.
 On one table the workpiece is being machined and
on the other tablework piece is on standby.
 Twotableare also join together whenneeded.

PLANNING OPERATION
 Operation that isperformed in planer are similar to
thatof a shaper. The onlydifference is thata planer is
speciallydesigned forplanning largework, whereas a
shaper can machineonly small work . The common
typesof work machined in a plannerare bases and
table of all kinds of machine tools ,large structure,
frames of different engines and identical pieces of
work which may be small in size but large in number.

OPERATION ON PLANER
 PLANING FLAT HORIZONTAL SURFACES.
 PLANNING VERTICAL SURFACES

PLANNING HORIZANTAL SURFACES
 While machining horizontal surface, the work isgiven
a reciprocating movement along with the table and
tool is fed crosswise to complete the cut. Both the
railheads may be used forsimultaneousremoval of the
metal from two cuttingedges.

PLANNING VERTIAL SURFACE
 The vertical surfaces of a work is planed by adjusting
the saddle horizontallyalong the cross rail until the
tool is in a position to give the required depth of cut.
The vertical slide is adjusted perpendicular to the
planertableand theapron is swivied in adirection so
that the tool will swing clear out of the machined
surface during the returnstroke.

TOOLS
Theyaregeneral similar in shapesand tool angles to
thoseused on a latheand shaping machine
 As a planer toolhas to take up heavy cut and coarse
feed during a long cutting stroke , the toolsare made
heavier and larger in crosssection.

 Planers tools may be forged type or bittype.
 Bitsare madeof high speed steel, satellite or
cemented carbide and they may bebrazed.
 Cemented carbide tipped toolsare used forproduction
work.
 A planertool mayalso beclassified as right hand or
left hand and roughing orfinishing.

Difference b/w planer and shaper
Shaper machine Planer machine
In shaper ram moves in
reciprocating and backand
fourth
Platen/table reciprocates moves
and also moves back andfourth
In shaper cutting toolmoves
back and forth
In planer work piece moves in
back and forth
Used for the machining ofsmall
jobs
Used for the machining of large
jobs
Each stroke of cutting tool
,gives the feed in crosswise.
In Each stroke of Platen or work
piece feed are given by feed
screw.
For the adjustment of Ram
stroke crank mechanism are
used
For the adjustment of platen
gears and rack mechanismare
used
Only one tool areused Two or more tools areused
In shaper cutting speed ,feed
range are in widerange
In planer machine cutting
speed , cutting feed are limited

Understanding Center Lathe and its Operations

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Understanding Center Lathe and its Operations

Similar to Understanding Center Lathe and its Operations (20)

Recently uploaded

Recently uploaded (20)

Understanding Center Lathe and its Operations