Unit 3 - Other Machine Tools Guide

Unit 3 - OTHER MACHINE TOOLS
G.Ravisankar, Asst Prof , Mechanical, Sri
Eshwar college of Engineering , Coimbatore .

UNIT III - OTHER MACHINE TOOLS
2
Shaper - Types of operations. Drilling, reaming,
boring, Tapping. Milling operations-types of milling
cutter. Gear cutting – forming and generation
principle and construction of gear milling, hobbing
and gear shaping processes –finishing of gears.
1. Hajra Choudhury, "Elements of Workshop Technology", Vol.II., Media
Promoters.
2. Rao. P.N “Manufacturing Technology - Metal Cutting and Machine Tools",
Tata McGraw-Hill, New Delhi, 2003

SHAPER MACHINE
Introduction
• Shaper is a reciprocating type of machine tool in which
the ram moves the cutting tool backwards and forwards
in a straight line.
The shaper is a machine tool used primarily for:
1. Producing a flat or plane surface which may be in a
horizontal, a vertical or an angular plane.
2. Making slots, grooves and keyways
3. Producing contour of concave/convex or a combination
of these
4

• The job is rigidly fixed on the machine table.
• The single point cutting tool held properly in the tool post is mounted
on a reciprocating ram.
• The reciprocating motion of the ram is obtained by a quick return
motion mechanism.
• As the ram reciprocates, the tool cuts the material during its forward
stroke. During return, there is no cutting action and this stroke is called
the idle stroke.
• The forward and return strokes constitute one operating cycle of the
shaper.
SHAPER MACHINE
Working Principle
5

SHAPER MACHINE
Working Principle
6

SHAPER MACHINE
Working Principle
7

SHAPER MACHINE
Working Principle
8

The main parts of the Shaper machine is
 Base,
 Body (Pillar, Frame, Column),
 Cross rail,
 Ram and tool head (Tool Post, Tool Slide, Clamper
Box Block).
SHAPER MACHINE
Construction
9

Base:
• The base is a heavy cast iron casting which is fixed to the
shop floor.
• It supports the body frame and the entire load of the
machine.
• The base absorbs and withstands vibrations and other
forces which are likely to be induced during the shaping
operations.
SHAPER MACHINE
Construction
10

Body (Pillar, Frame, Column):
• It is mounted on the base and houses the drive mechanism
compressing the main drives, the gear box and the quick
return mechanism for the ram movement.
• The top of the body provides guide ways for the ram and
its front provides the guide ways for the cross rail.
SHAPER MACHINE
Construction
11

Cross rail:
• The cross rail is mounted on the front of the body
frame and can be moved up and down.
• The vertical movement of the cross rail permits jobs of
different heights to be accommodated below the tool.
• Sliding along the cross rail is a saddle which carries
the work table.
SHAPER MACHINE
Construction
12

Ram and tool head:
• The ram is driven back and forth in its slides by the slotted
link mechanism.
• The back and forth movement of ram is called stroke and it
can be adjusted according to the length of the workpiece to
be-machined
SHAPER MACHINE
Construction
13

SHAPER MACHINE
Job Surface Generated
15

SHAPER MACHINE
Clapper Box Function
16

• The size of a shaper is specified by the maximum
length of stroke or cut it can make.
• Usually the size of shaper ranges from 175 to 900 mm.
Besides the length of stroke,
• other particulars, such as
▫ Type of drive
(belt drive or individual motor drive),
▫ floor space required,
▫ weight of the machine,
▫ cutting to return stroke ratio,
▫ number and amount of feed,
▫ power input etc.
SHAPER MACHINE - SPECIFICATION OF A SHAPER
17

A shaper is a machine tool primarily designed to
generate a flat surface by a single point cutting tool.
The different operations, which a shaper can
perform, are as follows:
1. Machining horizontal surface
2. Machining vertical surface
3. Machining angular surface
4. Slot cutting
5. Key ways cutting
6. Machining irregular surface
7. Machining splines and cutting gears
SHAPER MACHINE - SHAPER OPERATIONS
18

19

20

21

Classification of Shapers
• According to the type of driving mechanism
▫ Crank drive type
▫ Whit worth
▫ Hydraulic drive
• According to the position of ram
• horizontal,
• Vertical,
• Travelling head
• According to the table design
• Standard or Plain
• Universal
• According to the cutting Stroke
• Push out
• Draw back
38-22

• In a shaper, rotary motion of the drive is converted into
reciprocating motion of the ram by the mechanism
housed within the column or the machine.
• In a standard shaper metal is removed in the forward
cutting stroke, while the return stroke goes idle and no
metal is removed during this period
(1) Crank and slotted link mechanism
(2) Whitworth quick return mechanism, and
(3) Hydraulic shaper mechanism
SHAPER MACHINE - Shaper Mechanism
23

• In crank and slotted link mechanism , the pinion receives its
motion from an individual motor or overhead line shaft and
transmits the motion or power to the bull gear.
• Bull gear is a large gear mounted within the column. Speed
of the bull gear may be changed by different combination of
gearing or by simply shifting the belt on the step cone
pulley.
• A radial slide is bolted to the centre of the bull gear. This
radial slide carries a sliding block into which the crank pin
is fitted.
• Rotation of the bull gear will cause the bush pin to revolve at
a uniform speed. Sliding block, which is mounted upon the
crank pin is fitted within the slotted link.
Shaper Mechanism - Crank and slotted link mechanism
24

• This slotted link is also known as the rocker arm. It is
pivoted at its bottom end attached to the frame of the
column.
• The upper end of the rocker arm is forked and connected to
the ram block by a pin.
• With the rotation of bull gear, crank pin will rotate on the
crank pin circle, and simultaneously move up and down the
slot in the slotted link giving it a rocking movement, which
is communicated to the ram.
• Thus the rotary motion of the bull gear is converted to
reciprocating motion of the ram.
25

26

27

• This mechanism is mainly used in shaping and slotting
machines.
• In this mechanism Link CD (L-2) forming the turning pair is
fixed.
• The driving crank CA (L-3) rotates at a uniform angular speed.
• The slider (L-4) attached to the crank pin at A slides along the
slotted bar PA (L-1).
• Slotted bar oscillates at a pivoted point D.
• The connecting rod PR carries the ram at R to which cutting
tool is fixed.
• The motion of the tool is constrained along the line RD
produced. i.e.-along the line passing through D and
perpendicular to CD.
Shaper Mechanism - Whitworth quick return mechanism
28

29
http://gipsy-prashant.blogspot.in/2013_03_01_archive.html

• When the driving crank CA moves from the
position CA1 to CA2 (or the link DP from DP1 to DP2 )
through an angle α (alfa) in clockwise direction ,
the tool moves from left to right. i. e. cutting stroke
• And when the driving crank moves from the
position CA2 to CA1 (DP2 to DP1) through an angle β
(Beta) in clockwise direction the tool moves back i.
e. return stroke.
30

• Time taken for cutting stroke = time taken by CA1
to CA2
• Time taken for return stroke = time taken by CA2 to
CA1
• Since the crank link CA rotates in uniform angular
velocity, therefore, time taken during the cutting
stroke is more than time taken during return
stroke. i.e. the mean speed of ram during cutting stroke
is less than that of the return stroke..
31

Shaper Mechanism – Hydraulic Mechanism
32
http://shopswarf.orconhosting.net.nz/b/shd.html

Feed Mechanism
• Hand feed
• Automatic table feed
▫ Paul and ratchet mechanism
38-34

Paul and Ratchet Mechanism
38-35

Work Holding Devices
38-37
1.Vise

40
PLANER MACHINE- Not in syllabus

DIFFERENCE BETWEEN SHAPER AND PLANER
41

38-42
Drilling Machines
• Principle of rotating tool to make hole
• One of most common and useful machines in
industry
• Come in several types and sizes
▫ From hand-fed to computer-controlled

38-43
Standard Operations
• Drilling
▫ Operation of producing hole by
removing metal from solid mass
using twist drill
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
• Countersinking
– Operation of producing tapered
or cone-shaped enlargement
to end of hole

38-44
Standard Operations
• Reaming
▫ Operation of sizing and producing
smooth, round hole from previously
drilled or bored hole
• Boring
• Truing and enlarging hole by
means of single-point cutting tool

38-45
Standard Operations
• Tapping
▫ Cutting internal threads in hole
with cutting tool called tap
• Counterboring
– Enlarging top of previously
drilled hole to given depth
to provide square shoulder for
head of bolt or capscrew

38-46
Standard Operations
• Spot Facing
• Smoothing and squaring surface around hole
to provide seat for head of cap screw or nut
▫ Boring bar fitted with
double-edged cutting
tool
 Pilot section on end
to fit into existing hole

38-47
Principal Types of Drilling Machines
• Wide variety of drilling machines
• Size of drill press may be designated in different
ways by different companies
▫ Some state size as distance from center of spindle
to column of machine
▫ Others state size by diameter of largest circular
piece that can be drilled in center

38-48
Portable drilling Machine
• Only hand feed
mechanism, Manual
operated machine
• Hand drilling machine

38-49
Sensitive Drill
Press Parts
• Only hand feed
mechanism
▫ Control downfeed
pressure
• Manufactured in bench
and floor model
• Four main parts
▫ Base, column, table
and drilling head

38-50
Radial
Drilling
Machine

39-51
Tool-Holding Devices
• Drill press spindle provides means of holding
and driving cutting tool
• End may be tapered or threaded for mounting
drill chuck
• Most common
▫ Drill chucks
▫ Drill sleeves
▫ Drill sockets

39-52
Drill Chucks
• Most common devices used for holding
straight-shank cutting tools
• Most contain three jaws that move
simultaneously when outer sleeve turned
▫ Hold straight shank of cutting tool securely
• Two common types
▫ Key
▫ Keyless

39-53
Chucks
• Hold straight-shank drills
• Mounted on drill press spindle
▫ Taper
– Threads
• Held in spindle by self-holding
taper in larger machines
• Four types of drill chucks

39-54
Types of Drill Chucks
• Key-type
▫ Most common
▫ Three jaws move simultaneously
when outer sleeve turned
 Tighten with key
• Keyless
▫ Chuck loosened or tightened by
hand without key
• Precision keyless
▫ Holds smaller drills accurately

39-55
Types of Drill Chucks
• Jacobs impact keyless chuck
▫ Hold small or large drills
accurately using
Rubber-Flex
collets
▫ Gripped or released
quickly and easily by
means of built-in
impact device in chuck

39-56
Drill Sleeves and Sockets
• Drill Sleeves
▫ Used to adapt cutting
tool shank to machine
spindle if taper on tool is
smaller than tapered hole in spindle
• Drill Socket
▫ Used when hole in spindle of drill press to small
for taper shank of drill
▫ Used also as
extension sockets

39-57
Drill Drift
• Used to remove tapered-shank drills or
accessories from drill press spindle
• Always place rounded edge up so this edge will
bear against round slot in spindle
• Use hammer to tap drill drift and loosen
tapered drill shank
• Use board or piece of masonite to protect table

39-58
Work-Holding Devices
• Angle vise
▫ Angular adjustment on base to allow operator to
drill holes at an angle without tilting table
• Drill vise
▫ Used to hold
round, square
or odd-shaped
rectangular, pieces
▫ Bolt vise to table for stability

39-59
• Contour vise
▫ Has special movable jaws that automatically
adjust to shape of odd-shaped workpiece
• V-blocks
▫ Made of cast iron or hardened steel
▫ Used in pairs to support round work for drilling
• Step blocks
▫ Used to provide support for outer end of strap
clamps
▫ Various sizes and steps

39-60
• Angle plate
▫ L-shaped piece of cast iron or hardened steel
machined to accurate 90º
▫ May be bolted or clamped to table
▫ Variety of sizes
• Drill jigs
▫ Used in production for drilling holes in large
number of identical parts
▫ Eliminate need for laying out a hole location

39-61
• Clamps or straps
▫ Used to fasten work to drill table or an angle plate
for drilling
▫ Various sizes
▫ Usually supported at
end by step block and
bolted to table by T-bolt
that fits into table T-slot
• Modifications are double-
finger and gooseneck clamps
Finger clamp
U-clamp
Straight clamp

39-62
Clamping Stresses
• Don’t want stresses to cause springing or
distortion of workpiece
• Clamping pressures should be applied to work,
not step block
▫ Step block should be
slightly higher than
work
▫ Bolt close to work

40-63
Twist Drill Parts
• Most made of high-speed steel
▫ Replaced carbon-steel drills for two reasons
 Can be operated at double the cutting speed
 Cutting edge lasts longer
▫ Stamped with letters H.S or H.S.S.
• Carbide-tipped drills
▫ Speeds for production have increased up to
300% over high-speed drills

40-64
Three Main Parts
of a Drill
Shank
Body
Point

40-65
Shank
• Straight-shank drills
▫ Held in drill chuck
▫ Up to ½ in.
in diameter
• Tapered-shank drills
– Fit into internal taper of drill press spindle
– Tang provided on end to prevent drill from
slipping

40-66
Body
• Portion of drill between shank and point
• Consists of number of parts for cutting
• Flutes
▫ Two or more helical grooves cut around body of
drill
▫ Form cutting edges, admit cutting fluid, allow
chips to escape hole
• Body Clearance
▫ Undercut portion of body between margin and
flutes

40-67
Body, cont.
• Margin
▫ Narrow, raised section on body of drill
▫ Next to flutes and extends entire length of flutes
▫ Provides full size to drill body and cutting edges
• Web
▫ Thin partition in center
of drill, extends full length of flutes
▫ Forms chisel edge at cutting end of drill

40-69
Lip Clearance
• Is the relief ground on point of drill extending
from cutting lips back to the heel

40-70
Drill Point Characteristics
1. Control size, quality and straightness of
drilled hole
2. Control size, shape and formation of chip
3. Control chip flow up flutes
The use of various point angles and lip
clearances, in conjunction with thinning
of the drill web, will allow:

40-71
4. Increase strength of drill's cutting edges
5. Reduce rate of wear at cutting edges
6. Reduce amount of drilling pressure required
7. Control amount of burr produced
8. Reduce amount of heat generated
9. Permit use of various speeds and feeds for
more efficient drilling

40-72
Types of Drills
• Wide variety manufactured to suit specific
drilling operations and materials
• Design of drills vary
▫ Number and width of flutes
▫ Amount of helix or rake angle of flutes
▫ Shape of land or margin
▫ Shape of flute: straight or helical
▫ Whether helix is right-hand or left-hand

40-73
Twist Drills
• Manufactured from three main materials
▫ Carbon-steel drills
 Used in hobby shops not for machine shop work
 Cutting edges wear down quickly
▫ High-speed steel drills
 Used in machine shop work
 Cutting edges withstand more heat and wear
▫ Cemented-carbide drills
 Operated at high speeds, withstand higher heat,
and can drill hard materials

40-74
General-Purpose Drill
• Has two Helical flutes
• Designed to perform well on wide variety of
materials, equipment and job conditions
• Can be made to suit different conditions and
materials by varying point angle, speeds and
feeds
• Straight-shank drills called general-purpose
jobbers length drills

40-75
Oil Hole Drills
• Have one or two oil holes running from shank
to cutting point
▫ Compressed air, oil, or cutting fluid can be forced
through when deep holes being drilled
• Used on turret lathes and screw machines
• Cutting fluid cools drill's cutting edges and
flushes chips out of hole

40-76
Step Drills
• Used to drill and countersink or drill and
counterbore different sizes of holes in one
operation
• May have two or more diameters ground
• Each size or step separated by square or
angular shoulder

40-77
Saw-Type Hole Cutter
• Cylindrical-diameter cutter with twist drill in
center to provide guide for cutting teeth on
hole cutter
• Made in various diameters
• Used for drilling
holes in thin materials
• Little burr produced

40-78
Drilling Facts and Problems
• Excessive speed
• Excessive clearance
• Excessive feed
• Insufficient clearance
• Cutting lips with unequal angles
• Cutting lips with unequal in length
• Loading and galling

40-79
Loading and galling is
caused by poor chip
removal with insufficient
dissipation of heat so that
material anneals itself to
the cutting edge and flute.
This condition frequently
results from using wrong
drills for the job or
inadequate cutting fluid
application.

43-81
Reamer Parts
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Three main parts
1. Shank
2. Body
3. Angle of chamfer

44-82
Set of Hand Taps
Taper
Plug
Bottoming

44-83
Types of Machine Taps
Gun
Stub-flute
Spiral-flute

Boring Machine
• Boring is the
process of
enlarging and
location
Previously
drilled Hole
with a single
point cutting
tool

Types of boring machine
• Horizontal boring machine
▫ Table Type
▫ Floor Type
▫ Planer Type
▫ Multiple head Type
• Vertical boring machine
• Precision boring machine
• Jig boring machine
38-85

MILLING MACHINE
Introduction
• Milling is the cutting operation that removes metal by
feeding the work against a rotating, cutter having single
or multiple cutting edges.
• Flat or curved surfaces of many shapes can be
machined by milling with good finish and accuracy.
• A milling machine may also be used for drilling, slotting,
making a circular profile and gear cutting by having
suitable attachments.
87

• The work piece is holding on the worktable of the machine.
• The table movement controls the feed of work piece against
the rotating cutter.
• The cutter is mounted on a spindle or arbor and revolves at
high speed.
• Except for rotation the cutter has no other motion.
• As the work piece advances, the cutter teeth remove the metal
from the surface of work piece and the desired shape is
produced.
MILLING MACHINE
Working Principle
88

MILLING MACHINE
Introduction
89
MILLING METHODS
• There are two distinct methods of milling classified as
follows:
1. Up-milling or conventional milling, and
2. Down milling or climb milling.

UP-Milling or Conventional Milling Procedure
90
• In the up-milling or conventional milling, the metal is
removed in form of small chips by a cutter rotating against
the direction of travel of the workpiece.
• In this type of milling, the chip thickness is minimum at the
start of the cut and maximum at the end of cut.

Down-Milling or Climb Milling
91
• Down milling is also known as climb milling.
• In this method, the metal is removed by a cutter rotating in
the same direction of feed of the workpiece.
• The effect of this is that the teeth cut downward instead of
upwards.
• Chip thickness is maximum at the start of the cut and
minimum in the end.

The main part of machine is
 Base,
 Column,
 Knee,
 Saddle,
 Table,
 Overarm,
 Arbor Support and Elevating Screw.
MILLING MACHINE
Horizontal Milling Machine Construction
92

Base:
• It gives support and rigidity to the machine and also acts as a
reservoir for the cutting fluids.
Column:
• The column is the main supporting frame mounted vertically
on the base.
• The column is box shaped, heavily ribbed inside and houses
all the driving mechanisms for the spindle and table feed.
MILLING MACHINE
Construction
94

Knee:
• The knee is a rigid casting mounted on the front face of
the column.
• The knee moves vertically along the guide ways and this
movement enables to adjust the distance between the
cutter and the job mounted on the table.
• The adjustment is obtained manually or automatically by
operating the elevating screw provided below the knee.
MILLING MACHINE
Construction
95

Saddle:
• The saddle rests on the knee and constitutes the
intermediate part between the knee and the table.
• The saddle moves transversely, i.e., crosswise (in or out)
on guide ways provided on the knee.
MILLING MACHINE
Construction
96

Overarm:
• The Overarm is mounted at the top of the column and is guided in perfect
alignment by the machined surfaces. The Overarm is the support for the
arbor.
Arbor support:
• The arbor support is fitted to the Overarm and can be clamped at any
location on the Overarm. Its function is to align and support various
arbors. The arbor is a machined shaft that holds and drives the cutters.
Elevating screw:
• The upward and downward movement to the knee and the table is given
by the elevating screw that is operated by hand or an automatic feed.
MILLING MACHINE
Construction
97

Table:
• The table rests on guide ways in the saddle and
provides support to the work.
• The table is made of cast iron, its top surface is
accurately machined and carriers T-slots which
accommodate the clamping bolt for fixing the work.
• The worktable and hence the job fitted on it is given
motions in three directions:
MILLING MACHINE
Construction
98

• According to general design, the distinctive types of milling
machines are
1. Column and knee type milling machines
(a) Hand milling machine
(b) Horizontal milling machine
(c) Universal milling machine
(d) Vertical milling machine
2. Planer milling machine
3. Fixed-bed type milling machine
(a) Simplex milling machine.
(b) Duplex milling machine.
(c) Triplex milling machine.
TYPES OF MILLING MACHINES
99

• According to general design, the distinctive types of milling
machines are,
4. Machining center machines
5. Special types of milling machines
(a) Rotary table milling machine.
(b) Planetary milling machine.
(c) Profiling machine.
(d) Duplicating machine.
(e) Pantograph milling machine.
(f) Continuous milling machine.
(g) Drum milling machine
(h) Profiling and tracer controlled milling machine
100

Column and knee type milling machines
Vertical milling machine Horizontal milling machine
101

Horizontal Milling Machine
38-102

Vertical Milling Machine
38-103

Omniversal Milling Machine
38-104

Fixed Bed Type Milling Machine
38-105

Duplex Head Milling Machine
38-106

Plano type Milling Machine
38-107

Special Purpose Milling Machine
1.Rotary Milling Machine
38-108

Drum Type Milling Machine 38-109

Work holding devices
• T bolt and clamps
• Angle plates
• V blocks
• Machine vices
• Milling fixture
• Dividing heads ( Indexing Head)
38-110

Tool (or) cutter holding Devices
• Arbors
 Standard arbor
 Stub arbor
• Adaptors.
• collets
38-112

Arbor
 Standard arbor  Stub arbor
38-113

CNC Vertical Mill
Spindle Speed
Saddle Table
Knee
ColumnHead

CNC Vertical Mill: Axes & Tools
Spindle
+ Z-axis
+ X-axis
– Y-axis
Tool Holder
Cutter
Alternate
Tools (in
quick-
change
magazine)
Air Vise

Milling Parameters Illustrated
Two forms of milling: (a) peripheral milling, and (b) face milling

Slab / Plain Milling
The basic form of
peripheral milling in
which the cutter width
extends beyond the
workpiece on both sides
slab milling
OPERATIONS PERFORMED ON MILLING MACHINE

Slotting
Width of cutter is less
than workpiece width,
creating a slot in the
work
slotting

Conventional Face Milling
Cutter overhangs work
on both sides
conventional face milling

End Milling
Cutter diameter is
less than work
width, so a slot is
cut into part
End milling

Profile Milling
A form of end
milling in which the
outside periphery
of a flat part is cut
Profile milling

Pocket Milling
Another form of
end milling used
to mill shallow
pockets into flat
parts
Pocket milling

Surface Contouring
Ball-nose cutter is fed
back and forth across the
work along a curvilinear
path at close intervals to
create a three
dimensional surface form
Surface contouring

MILLING MACHINE - TYPES OF MILLING CUTTERS
127

Plain Milling Cutters
• Most widely used
• Cylinder of high-speed steel with teeth cut on periphery
• Used to produce flat surface
Several types
• Light-duty
• Light-duty helical
• Heavy-duty
• High-helix

Light-Duty Plain Milling Cutter
• Less than ¾ in. wide, straight
teeth
• Used for light milling
operations
• Those over ¾ in have helix
angle of 25°
• Too many teeth to permit chip
clearance

Heavy-Duty Plain Milling Cutters
• Have fewer teeth than light-duty type
• Provide for better chip clearance
• Helix angle varies up to 45°
• Produces smoother surface because of shearing action and reduced
chatter
• Less power required

High-Helix Plain Milling Cutters
• Have helix angles from 45° to over 60 °
• Suited to milling of wide and intermittent surfaces
on contour and profile milling
• Usually mounted on milling machine arbor
• Sometimes shank-mounted with pilot on end and
used for milling and gated slots.

Standard Shank-Type Helical Milling Cutters
• Also called as arbor-type cutters
Used for
• Milling forms from solid metal
• Removing inner sections from solids
• Inserted through previously drilled hole and
supported at outer end with type A arbor support

Side Milling Cutters
• Comparatively narrow cylindrical milling cutters with
teeth on each side and on periphery
• Used for cutting slots and
for face and straddle milling
operations
• Free cutting action at high
speeds and feeds
• Suited for milling deep, narrow slots
Straight
Staggered

Half-Side Milling Cutters
• Used when only one side of cutter required
• Also make with interlocking faces so two cutter
may be placed side by side for slot milling
• Have considerable rake
• Able to take heavy cuts.

Face Milling Cutters
• Generally over 6 in. in diameter
• Have inserted teeth made of high-speed
steel held in place by wedging device
• Most cutting action occurs
at beveled corners and
periphery of cutter
• Makes roughing and finishing cuts in
one pass

Shell End Mills
• Face milling cutters under 6 in.
• Solid, multiple-tooth cutters
with teeth on face and
periphery
• Held on stub arbor
• May be threaded or use key in
shank to drive cutter

Angular Cutters
Single-angle
▫Teeth on angular surface
▫May or may not have teeth on flat
▫45° or 60°
Double-angle
▫Two intersecting angular surfaces
with cutting teeth on both
▫Equal angles on both side of line
at right angle to axis

Types of Formed Cutters
Concave Convex Gear Tooth

T-Slot Cutter
• Used to cut wide horizontal groove at bottom of T-
slot
• After narrow vertical groove machined with end mill or side
milling cutter
• Consists of small side milling cutter with teeth on
both sides and integral shank for mounting

Dovetail Cutter
• Similar to single-angle milling cutter with integral
shank
• Used to form sides of dovetail after tongue or groove
machined
• Obtained with 45º, 50º, 55º, or 60º angles

Woodruff Key seat Cutter
• Similar in design to plain and side milling cutters
• Small (up to 2 in) solid shank, straight teeth
• Large mounted on arbor with staggered teeth
• Used for milling semi cylindrical key seats in
shafts
• Designated by number system

68-144
Index Head Parts
• Headstock with index plates
• Headstock change gears
• Quadrant
• Universal chuck
• Footstock
• Center rest

A – large index
plate
B - crank
C – small index
plate
D - crank
G – gear housing

Machining Calculations: Milling
• Spindle Speed - N (rpm)
 v = cutting speed
 D = cutter diameter
• Feed Rate - fr (mm/min -or- in/min)
 f = feed per tooth
 nt = number of teeth
Dπ
v
N 
fnNf tr 

Machining Calculations: Milling
• Machining Time - Tm (min)
▫ Slab Milling:
 L = length of cut
 d = depth of cut
▫ Face Milling:
 w = width of cut
 2nd form is multi-pass
• Material Removal Rate - MRR
(mm3/min -or- in3/min)
r
m
f
DL
T


 
r
m
f
dDdL
T
-

 
r
m
f
wDwL
T
-2

-or-
r
w d fMRR 

GEAR GENERATION AND FINISHING
OPERATIONS
148

INTRODUCTION
• Gear is one of the important machine tool
elements which is an integral and inevitable part
of power transmission system.
• A gear is a round blank having teeth along its
periphery.
• Gears are used to transfer power or torque from
prime mover to the place where it is to be used.
• Along with the transmission of power gears also
transfer the accurate velocity ratio between two
shafts.
149

INTRODUCTION
• Power Transfer between Driver and Driven
Gears
150

METHOD OF GEAR MANUFACTURING
• In broader sense the gears can be manufactured by
the following three methods.
(a) Casting
(b) Plastic Moulding
(c) Machining
Gear Forming
Gears Shaping
(a) Gear cutting by gear shaper.
(b) Rack planning process.
(c) Hobbing process
151

152
Gear forming- where the profile of the teeth are
obtained as the replica of the form of the cutting tool
(edge); e.g., milling, broaching etc.
Gear generation- where the complicated tooth profile
are provided by much simpler form cutting tool (edges)
through rolling type, tool – work
motions, e.g., hobbing, gear shaping etc

153
Gear forming- where the profile of the teeth are
obtained as the replica of the form of the cutting tool
(edge); e.g., milling, broaching etc.
Gear generation- where the complicated tooth profile
are provided by much simpler form cutting tool (edges)
through rolling type, tool – work
motions, e.g., hobbing, gear shaping etc

154
Gear forming- Milling

Gear Shaping :
1.Gear Cutting by Gear Shaper
• Process of Gear Cutting by Shaper Cutter
155

Gear Cutting by Gear Shaper
• Setup for Gear Shaping Machine
156

Advantages of Gear Shaping Process
• Shorter product cycle time and suitable for making
medium and large sized gears in mass production.
• Different types of gears can be made except worm
and worm wheels.
• Close tolerance in gear cutting can be maintained.
• Accuracy and repeatability of gear tooth profile can
be maintained comfortably.
• For same value of gear tooth module a single type
of cutter can be used irrespective of number of
teeth in the gear.
157

Limitations of Gear Shaping Process
• It cannot be used to make worm and work wheel
which is a particular type of gear.
• There is no cutting in the return stroke of the gear
cutter, so there is a need to make return stroke
faster than the cutting stroke.
• In case of cutting of helical gears, a specially
designed guide containing a particular helix and
helix angle, corresponding to the teeth to be made,
is always needed on urgent basis.
158

2. Gear Shaping by Rack Shaped Cutter
• Gear Cutting by Rack Shaped Cutter
159

2. Gear Shaping by Rack Shaped Cutter
• Rack Planning Process
• This process is used for shaping of spur and helical
gear teeth with the help of a rack type cutter.
160

3. Gear Hobbing Process
• Setup for Gear Hobbing Machine
163

3. Gear Hobbing Process
Advantages of gear hobbing process
• Gear hobbing is a fast and continuous process so it
is realized as economical process as compared to
other gear generation processes.
• Lower production cycle time, i.e. faster production
rate.
• Hob is multipoint cutting tool having multi cutting
teeth or edges at a time few number of cutting
edges work so lots of time is available to dissipate
the generated heat. There is no over heating and
cutting tool.
164

GEAR FINISHING OPERATIONS
• Surface of gear teeth produced by any of the
generating process is not accurate and of good
quality (smooth).
• Commonly used gear finishing operations are
described below.
▫ Gear Shaving
▫ Roll Finishing of Gear Tooth
▫ Gear Burnishing
▫ Gear Honning
165

Gear Shaving
• Gear shaving is a process of finishing of gear tooth
by running it at very high rpm in mesh with a gear
shaving tool.
• A gear shaving tool is of a type of rack or pinion
having hardened teeth provided with serrations.
• These serrations serve as cutting edges which do a
scrapping operation on the mating faces of gear to
be finished.
166

Gear shaving tool with serrated teeth is explained by
illustration in Figure
167

Roll Finishing of Gear Tooth
• This process involves use of two hardened rolling dies
containing very accurate tooth profile of the gear to be
finished.
• The gear to be finished is et in between the two dies as
shown in Figure and all three are revalued about their
axis.
168

Gear Burnishing
• The gear to be finished is mounted on a vertical
reciprocating shaft and it is kept in mesh with three
hardened burnishing compatible gears.
Gear Grinding
▫ In this operation abrasive grinding wheel of a particular
shape and geometry are used for finishing of gear teeth
169

Gear Burnishing
Lapping of a Gear
▫ The process of lapping is used to improve surface
finish of already made teeth.
▫ In this process the gear to be lapped is run under
load in mesh with cast iron toothed laps.
▫ Abrasive paste is introduced between the teeth.
▫ It is mixed with oil and made to flow through the
teeth. One of the mating members (either gear or
lapping tool) is reciprocated axially along with the
revaluations.
170

Gear Burnishing
171

GEAR HONING
• It is used for super finishing of the generated gear
teeth.
• Honing machines are generally used for this operation.
• The hones are rubbed against the profile generated on
the gear tooth.
172

Unit 3 - Other Machine Tools Guide

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