MILLING

1. Introduction
• Milling is the basic process of progressive chip
removal to produce a surface.
• Mill cutters have single or multiple teeth that rotate
about an axis, removing material.
• Often the desired surface in obtained in a single pass
of cutter or work piece with very good surface finish.
• Milling is particularly well suited and widely used for
mass production.
• More flat surfaces are produced by milling than by
any other machining processes.
• Preferred for small and medium job

2. Methods of Milling
• The relative motion between the work piece and
the cutter can be in any direction based on which
is classified as up milling or down milling

3. UP & DOWN MILLING

4. UP MILLING

5. DOWN MILLING

6. Direction of Feed: Conventional
(UP MILLING)
• Most common method
is to feed work
against rotation
direction of cutter
60-6

7. Direction of Feed: Climbing
(DOWN MILLING)
• When cutter and
work piece going
in same direction
• Can increase cutter
life up to 50%
60-7

8. UP MILLING DOWN MILLING
The workpiece is fed in the direction
opposite to that of the cutter
The workpiece is fed in the same
direction as that of the cutter
The thickness of the chip is minimum at
the beginning of cut and reaches to
maximum when the cut ends
The thickness of the chip is maximum at
the beginning of cut and reaches to the
minimum when the cut ends
The cutting force is directed upwards
and hence tends to lift the workpiece
from the worktable (greater clamping
force required)
The cutting force is directed downwards
and hence tends to keep the workpiece
firmly on the worktable ( lesser
clamping forces required)
The chip gets accumulated at the cutting
zones, hence impairs the surface finish
of workpiece
The chips do not interfere with the
revolving cutter, hence no damage to
the surface finish of workpiece
Difficulty in efficient circulation of
coolant (cutter carries away coolant)
Efficient cooling of tool & workpiece
achieved (coolant reaches cutting zone)
Preferred for rough cuts especially for
castings & forgings
Used for finishing operations and small
work like cutting slots, grooves, etc.

9. Classification of Milling Machines
1.Column and knee milling machines
a) Horizontal milling machine
b) Vertical milling machine
c) Universal milling machine
d) Omniversal milling machine
2. Manufacturing or Fixed type milling machine
a) simplex milling machine
b) Duplex milling machine
c) Triplex milling machine
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10. 3.Planer type milling machine
4.Special purpose milling machine
a) Tracer controlled milling machine
b) Rotary table milling machine
c) Drum type milling machine
5. Thread milling machine
6. CNC Milling machine
7. Key way milling machine
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Classification of Milling Machines

11. Main parts of milling machine
• Base
• Work table
• Saddle
• Knee
• Over arm
• Spindle
• Column
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12. Main parts of milling machine
The basic components of these machines are as follows:
• Base: it is heavy casting on which column and other parts are
mounted.
• Worktable: on which the work piece is clamped using T-slots. The
table moves longitudinally relative to the saddle.
• Saddle: supports the table and can move in the transverse direction.
• Knee: supports the saddle and gives the table vertical movement so
that the depth of cut can be adjusted and work pieces with various
heights can be accommodated.
• Over arm: used on horizontal machines; it is adjustable to
accommodate different arbor lengths.

13. Main parts of milling machine
• Spindle; it gets power from gear, belt drives to drive
the motor. It has provision to add or remove milling
cutter on to the arbor.
• Column; there are guide ways on the front face of the
column on which the slide. It house power
transmission units such as gears, belt drives pulleys to
give rotary motion to the arbor
• Head: contains the spindle and cutter holders. In
vertical machines, the head may be fixed or can be
adjusted vertically, and it can be swiveled in a vertical
plane on the column for cutting tapered surfaces.
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14. Horizontal – spindle column and knee type milling machine

16. Vertical- spindle column and knee type milling machine

17. Column-and-Knee Type Milling Machines
(a) a horizontal-spindle column-and-knee type milling machine and (b) vertical-spindle column-and-
knee type milling machine.

18. Universal milling machine
• The Universal milling machine differs from
the plain horizontal types in that table can be
swiveled to helical grooves to be milled.
• Saddle is in two part so that the table can be
horizontally rotated.
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19. Basic difference between a universal and
horizontal milling machine
• Horizontal milling
• plain horizontal milling machine
table is mounted on the saddle.
• Longitudinal, cross and vertical.
• No such auxiliaries.
• Helical milling is not possible
• Plain horizontal milling machine
table is very rigid and heavier
• Universal milling machine
• The addition of a table swivel
housing between the table and the
saddle of the universal machine.
• Longitudinal, cross ,vertical and
addition swiveling up to 45 degree.
• indexing fixture, rotary table,
slotting and rack cutting
attachments.
• Helical milling can processed
• The universal machine table is
mounted on swivel housing hence
not rigid
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20. Duplex type fixed bed milling machine
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21. Planer milling machine
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22. Milling Operations
• Plain or Slab milling
• Face milling
• End milling
• Slot milling
• Angular milling
• Form milling
• Straddle milling
• Gang milling

23. Milling operations
Two forms of milling: (a) peripheral milling, and (b) face milling

24. Milling Operations
Plain or slab milling Angular milling Slot milling

25. Form milling

26. Straddle milling Gang milling

27. Face milling End milling

28. Slot milling

29. T-Slot Cutting

30. Face-Milling
Face-milling cutter with indexable inserts.

31. Face-Milling
• The Face milling is the operation of performed
by a face milling cutter rotated about an axis
perpendicular to the work surface. The
operation carried in a plain milling machine,
and cutter mounted on a stub arbor to produce
a flat surface

32. ANGULAR MILLING CUTTER

33. Types of Cutters
Figure 24.11 Cutters for (a) straddle milling, (b) form milling,
(c) slotting, and (d) slitting with a milling cutter.
Straddle milling: more
cutters are used to machine
two parallel surfaces on the
workpiece
Form milling produces
curved profiles using cutters
that have specially shaped
teeth
Slotting and slitting operations
are performed with circular
cutters. [T-slot cutters ]

34. ANGULAR MILLING CUTTER

35. Form milling cutter
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36. Pocket Milling
Another form of
end milling used
to mill shallow
pockets into flat
parts.

37. 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 .

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

39. Keyway milling

40. Milling cutter
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41. MILLING CUTTER NOMENCLATURE
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42. MILLING CUTTER NOMENCLATURE
There are following parameters by which we can define milling
cutter nomenclature which are following
Pitch: The pitch refers to the angular distance between like parts
on the adjacent teeth. The pitch is determined by the number of
teeth.
Face of Tooth: The tooth face is the forward facing surface of the
tooth which forms the cutting edge.
Cutting Edge: The cutting edge is the angle on each tooth which
performs the cutting.
Land: The land is the narrow surface behind the cutting edge of
each tooth.
Rake Angle: The rake angle is the angle formed between the face of
the tooth and the centerline of the cutter. The rake angle defines
the cutting edge and provides a path for chips that are cut from
the work piece

43. MILLING CUTTER NOMENCLATURE
Primary Clearance Angle (Relief angle): The primary
clearance angle is the angle of the land of each tooth,
measured from a line tangent to the centerline of the cutter
at the cutting edge. This angle prevents each tooth from
rubbing against the work piece after it makes its cut.
Secondary Clearance Angle : The secondary clearance angle
defines the land of each tooth and provides additional
clearance for the passage of cutting oil and the chips.
Flute: Flute is the part of milling cutter between the back of
one tooth and the face of following tooth.
Hole Diameter : The hole diameter determines the size of
arbor that is necessary to mount the milling cutter.
Keyway : A keyway is present on all arbor-mounting cutters
for locking the cutter to the Arbor.

44. MILLING CUTTER NOMENCLATURE
Radial rake angle: It is the angle between diametric plane and
tooth face. Its value might be positive, negative or zero.
Helical rake angle: It is the angle between cutting edge of the
cutter and cutter axis when we look radially at intersection
point. This angle is only present in helical cutters. If in any
cutter, it is not present than the rake angle is called axial rake
angle.
Gash depth: It is the distance between outside diameter to the
fillet radius.
Fillet radius: Fillet radius is in the form of curved surface and is
present at the flute bottom.
Types of Teeth : The teeth of milling cutters are either right-hand
or left-hand, viewed from the back of the machine. Right-
hand milling cutters cut when rotated clockwise; left-hand
milling cutters cut when rotated counterclockwise.

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46. INDEXING
• Indexing is the operation of dividing the periphery of a
work piece into any number of equal parts.
• In cutting spur gear, equal spacing of teeth on gear
blank is performed by indexing.
• Indexing also can be adapted for producing hexagonal
and square headed bolts, cutting on shafts, fluting drills,
taps and reamers and many other jobs.
• All requiring the periphery of the work piece to be
divided equally and accurately. Indexing is
accomplished by using a special attachment know as
dividing head or indexing head.

47. Universal Dividing Head
• It is most popular and common type of
indexing arrangement.
• As indicated by its name “universal”, it can be
used to do all types of indexing on a milling
machine.
• Universal dividing head can set the workpiece
in vertical, horizontal, or in inclined position
relative to the worktable.

48. Universal Dividing Head
Working principle :
The worm gear has 40 teeth and the worm has simple thread.
Crank is directly attached with the worm.
If we revolve crank by 40 revolutions the spindle attached
with worm gear will revolve by only one revolution and one
complete turn of the crank will revolve the spindle only by
1/40th revolution (turn).
In order to turn the crank precisely a fraction of a revolution,
an indexing plate is used.
An indexing plate is like a circular disc having concentric
rings of different number (diameter) of equally spaced holes.
Normally indexing plate is kept stationary by a lock pin. A
spring loaded pin is fixed to the Gear cutting Milling cutter.
Gear blank crank which can be fixed into any hole of
indexing plate. The turning movement of the workpiece is
controlled by the movement of crank.

49. Universal Dividing Head Parts
• Headstock with index plates
• Headstock change gears
• Quadrant
*Universal chuck
*Footstock
*Center rest

50. Universal Dividing Head Parts
• Swiveling block
– Mounted in base enables headstock to be tilted
from 5º to 10º.
• Spindle
– Mounted in swiveling block with 40-tooth worm
wheel, meshes with worm.
• Worm
– Right angle to spindle, connected to index crank.
• Direct indexing plate
– Engaged by pin and attached to front of spindle.

51. Universal Dividing Head Parts

52. INDEXING METHODS
There are different indexing methods in
popularity. These are :
(a) Direct indexing (Rapid)
(b) Simple indexing
(c) Compound indexing
(d) Differential indexing
(e) Angular indexing

53. Direct indexing
It is also named as rapid indexing. For this plate
is used which has 24 equally spaced holes in a
circle. It is possible to divide the surface of
workpiece into any number of equal divisions
out of 2, 3, 4, 5,6, 8, 12, 24 parts. These all
numbers are the factors of 24.

54. Direct indexing

55. Direct indexing
If we want to divide the surface into 6 parts then
number of holes by which pin is to be moved =24/N
for 6 parts
N = 6.
So number of holes =24/6=4 holes that is after
completing one pair of milling whole surface of
workpiece we have to move the pin by 4 holes
before next milling operation, that is to be done for
5 number of times for making hexagonal bolt.

56. Simple Indexing
• Work positioned by means of crank,
index plate, and sector arms.
• Worm attached to crank must be
engaged with worm wheel on dividing
head spindle,
• 40 teeth on worm wheel.
• One complete turn on index crank cause
spindle and work to rotate one-fortieth of
a turn (ratio of 40:1).

57. Simple Indexing
Plate No. 1 15 16 17 18 19 20
Plate No. 2 21 22 23 24 25 26
Plate No. 3 27 28 29 30 31 32
Three indexing plates are used (M/S Brown &
Sharpe). These plates have on concentric circles of
holes with
their different numbers as described below :

58. Simple Indexing

59. Simple Indexing
• Calculating the indexing or number of turns of
crank for most divisions, simply divide 40 by
number of divisions to be cut.
• N=Number of divisions to be cut.
40
Indexing =
N

60. Compound Indexing
This indexing method is employed when the
number of divisions required is outside the range
that cannot be obtained by simple indexing.
For Compound Indexing, the movement of the
crank and the index plate can be determined by the
expression.

61. Compound Indexing

62. Differential Indexing

63. Differential Indexing

64. Angular Indexing
• Setup for simple indexing may be used
– Must calculate indexing with angular distance
between divisions instead number of divisions.
• One complete turn of index crank turns work
1/40 of a turn
– 1/40 of 3600 = 9 degrees
9
required
degrees
of
no.
degrees
in
Indexing 