MILLING – Cutting parameters, machine time calculation Milling operation – Plain milling, side & face milling, form milling, gang milling, end milling, face milling, T slot milling, slitting GEAR CUTTING – Gear cutting on milling machine – dividing head and indexing method, gear hobbing, principle of operation, advantages & limitation, hobbing tech, gear shaping, gear finishing process

1. Milling & Gear Cutting
1
Mr. KONAL SINGHMr. KONAL SINGH
Director and Founder of
ProBotiZ Group, NagpurProBotiZ Group, Nagpur
(W) - Probotizgroup.com (M) - 8862098889, 9423632068 (E) - probotizinfo@gmail.com

2. Syllabus
• Milling – Cutting parameters, machine time
calculation
• Milling operation – Plain milling, side & face
milling, form milling, gang milling, end milling,
face milling, T slot milling, slitting
• Gear Cutting – Gear cutting on milling
machine – dividing head and indexing method,
gear hobbing, principle of operation, advantages
& limitation, hobbing tech, gear shaping, gear
finishing process
2

3. Learning Objective
• Details of milling machine, understand the
various process used and different function etc.
• Understand the gear tooth specification, gear
generating process, gear finishing process etc.
3

4. Milling Machine
• Milling machine: It is machine made up with the
different attachment like base, column, head /
overram, arbor (tool attachment), table, saddle,
Knee etc.
• Principle of operation: In this machine the work
piece is stationary & it is hold in a table whereas
the tool/ cutter are to be rotated about it own
axis and simultaneously the work piece are feed
against rotating cutter
4

5. Milling Machine
• Classification of milling machine:
a. Horizontal cutter axis type milling machine
b. Vertical cutter axis type milling machine
5

6. Milling machine
• Types of milling machine:
1.Column & knee type
2.Hand milling
3.Plain milling machine
4.Vertical, universal, general purpose, planner
5.Fixed bed type milling machine
6.Special type milling machine
6

7. Milling machine
• Types of work done on milling machine
7

8. Milling machine
• Milling Operation:
(a) Schematic illustration of conventional (up) milling and
climb milling (down). (b) lab-milling operation showing depth-
of-cut, d; feed per tooth, f; chip depth-of-cut, tc; and workpiece
speed, v. (c) Schematic illustration of cutter travel distance,
lc, to reach full depth-of-cut.
8

9. Milling machine
• Milling process
1.Milling is one of the basic
machining processes.
2.Milling is a very versatile
process capable of
producing simple two
dimensional flat shapes to
complex three
dimensional interlaced
surface configurations.
9

10. Milling machine
Milling Process
• Typically uses a multi-tooth
cutter
• Work is fed into the rotating
cutter
• Capable of high MRR
• Well suited for mass
production applications
• Cutting tools for this process
are called milling cutters
10

11. Milling machine
Plain milling machine
• It’s a more rigid m/c than
hand milling
Application
• It is used for Gang milling,
form milling, slotting,
keyways etc.
11

12. Milling machine
Vertical Milling machine
• It derives its name from the
vertical position of the
spindle
• Cutter used in this type are
End mill type
• Spindle head can be
swiveled to any desire
angle for machining
angular surfaces
12

13. Milling machine
Vertical Milling machine
Application
• It is used for profile cutting die
sinking
• Also useful for milling various
irregular shape
• In this m/c drilling boring
reaming and facing operation
can also be performed
13

14. Milling machine
Universal milling machine
• It is similar to plain
milling machine expect
here the table can be
swiveled horizontally
and can be fed angle to
the milling machine
spindle.
14

15. Milling machine
Universal milling machine
Application
• Accurate work can be
done in this tool room
m/c
• Milling cutter, twist drill
& straight and taper
work
15

16. Milling machine
Progressive milling
When two or more similar
or different operation are
to be performed either
simultaneous or
successively on
separate work piece
progressively moved
from one fixture to next
until all operation are
performed.
16

17. Milling machine
Angular milling
• This process is used to produce
angular surface on the work
piece
• The angle of cutting is other than
right angle
• The cutter used may be single or
double angle type
Application
• V block used in work shop
17

18. Milling machine
Planer (Plano – miller)
• It’s a largest size m/c
• It is used to machine
the flat surface
• it consist of a long
table having only a
longitudinal
movement
• It has a two vertical
column
18

19. Milling machine
Planetary milling
• In this m/c the work is held stationary while the
revolving cutter moves in circular path to machine
the surface
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• At the start of the job the
rotating cutter is in centre
• It is fed radially to the
proper depth & than given
a planetary motion inside
or outside the work

20. Milling machine
Gang Milling
• If more than two cutter
are used together on the
arbor of milling machine
• The distance between
cutter is adjusted by
spacing of coller
20

21. Milling machine
T – Slot milling
Open slot – It can be produce by same cutter with
special attachment
Closed slot – It can be produced by End mill type
cutter
21

22. Milling machine
• Some other
milling processes
are
22

23. Milling machine
Straddle milling
• In this a pair of side milling are
used for machining two parallel
vertical surface on the work piece
simultaneously.
• It is a special form of gang milling
• Distance between two cutter are
adjusted by spacing collar
• It has its teeth on side and
periphery
23

24. Milling machine
Up Milling : It is based on direction of feeding work
piece and rotation of milling cutter
• In this milling process the cutter is rotated in a
direction opposite to the direction of travel of the
work piece
Down Milling : In this cutter is rotated in the same
direction as that of the travel of the work piece
24

25. Milling Cutter
Milling cutter can be classified as
1.plain milling
2.side milling
3.End milling
4.Metal slitting cutter
5.Face milling cutter
6.Angle milling cutter
7.Form milling cutter
8.Fly cutter
25

26. Milling Cutter
Elements of plain milling cutter
26

27. Milling Cutter
Cutter Angles
Milling cutter is provided with Rake angle,
Clearance angle, Lip angle similar to SPCT
1. Rake angle (Gama): It is the angle measured in
the diametric plane between the face of the
tooth and radial line passing through the tooth
cutting edge
27

28. Milling Cutter
Cutter Angles
2. Relief angle (Alpha): the angle in a plane
perpendicular to the axis, which is the angle
between the land of the tooth and the tangent to
the outside diameter of cutter at the cutting edge
of that tooth
3. Lip angle (Beta): the angle between the face
and land of the cutter tooth is called lip angle
28

29. Milling Cutter
What is negative rack milling
• If the face of milling cutter lies along a
radius of the cutter, it is said to have zero
rake.
• If the face of the cutter lies along either
line, on either side of the radius of the
tooth, it is a Positive rack.
• If the face of the cutter lies along either
line, on opposite side of the radius of the
tooth, it is a Negative rack.
29

30. Milling Cutter
Advantages of Negative rack angle
• It gives better finish
• Improved tool life by increased tip angle and it
can withstand shock load better way
• Negative rake strengthens the cutting edge and
produces higher force and requires more power
and is used in carbide cutter
• It causes the cutting force to fall with in the body
of the cutter
30

31. Milling Cutter
Plain milling Cutter
• Once 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
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32. Milling Cutter
Face milling cutter
• 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
32

33. Milling Cutter
Shell End milling cutter
• In this cutting edge are
provided at the end and the
periphery of the cutter
• In this type teeth of the
cutter may be helical or
straight
• These cutter are used in
face milling operation
33

34. Milling Cutter
Slab milling cutter
• These cutter are cylindrical in
shape and have teeth on the
circumferential surface only
• The cutter are used to
produced flat surfaces parallel
to axis of spindle
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Work

35. Milling Attachment
• Vertical milling attachment
• Universal milling attachment
• High speed milling attachment
• Rotary milling attachment
• Slotting attachment
• Dividing head attachment
35

36. Indexing Method
Universal dividing head
• It is a device used for indexing
the work
• A worm is attached to a main
spindle. The worm gear has 40
teeth & worm is single threaded,
so that 40 turn of crank will
rotate the spindle through one
complete revolution
• Index plate is fixed on the
spindle with locking pin and
connected to the crank
36

37. Indexing Method
• It’s used to obtain greater
number of divisions that can not
be obtained by direct indexing.
• It’s carried out using 40:1 ratio of
the worm and worm mechanism.
• Two sector arms fit on the face
of the indexing plate.
• The arms can be set a part to
cover a required number of
holes between them
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38. Indexing
38

39. ELEMENTS OF GEAR
• Pitch circle.
• Circular pitch.
• Pitch circle diameter.
• Addendum circle.
• Root circle.
• Addendum.
• Dedendum .
• Hand.
• Clearance.
• Working depth.
• Flank of tooth.
39

40. ELEMENTS OF GEAR
• Addendum circle: The circle which limits the top
of the gear teeth & represent its maximum
diameter
• Addendum: It is the radial height of tooth above
the pitch circle
• Dedendum: It is the radial depth below pitch
circle and root circle
• Basic circle: It is the circle from which the
involutes curve of tooth profile is generated
• Pressure angle: It is a angle between tooth
profile and radial line and at its pitch point
• Pitch point: It is the point of contact between the
pitch circle of two mating gear
• Face: It is the side surface of tooth lying
between the pitch circle and addendum circle 40

41. ELEMENTS OF GEAR
• Flank: It is side surface of the tooth
lying between pitch circle and root
circle
• Module: It represent the ratio of the
pitch circle diameter to the number
of teeth on the gear
• M = (D / N)
• Diametrical pitch: It is the
number of teeth on the gear
per unit diameter of the pitch
circle
Diametric Pitch = Number of
teeth / Diameter of pitch circle 41

42. Gear Cutting Process
• In gear cutting process, the
cutter is formed according to the
shape of the tooth.
• The space to be removed
between two adjacent teeth by
FORM milling cutter
• The cutter is attached on the
mandrel and connected to
dividing head.
• The selection of cutter is depend
upon the size of gear tooth and
number of teeth 42

43. Roll of coolant in milling
• To remove chip, dirt, dust or any abrasive
particles from the work piece
• To reduce the heat generated during cutting
operation on and over the work piece
• Protect the distortion of work piece from any
affect of heat.
• Protect the work surface from corrosion
43

44. Cutting parameter of m/c
• Cutting speed: It is the peripheral speed of the
cutter and denoted by (V) = ΠDN / 1000 m/min
• Feed: The rate at which the work piece
advances under the cutter. It may also defined
as (feed per tooth, feed per cutter revolution,
feed per minute)
• Depth of cut: It is defined as the thickness of the
material removed in one pass in mm.
44

45. Machine time calculation
• It is a time required for one pass of width of cut
for milling a surface; it is given by
T = L /(F * N)
T = Time required to complete one cut
F = feed rate m, mm / min, N = Speed of cutter in rpm
• Approach distance for plain milling is given by
A = √(d(D-d))
A= Approach distance, d= depth of cut, D=
diameter of cutter mm
45

46. Gear manufacturing method
• Casting (sand, die casting), hot rolling,
stamping, powder metallurgy, extruding
• Machining method: are given below
46
A. Form Cutting
method
1.Form disc cutter
2.End mill cutter
3.Broaching gear
teeth
B. Gear generating
method
1.Gear hobbing
2.Gear shaping
3.Gear planing
C. Template Method

47. Gear manufacturing
Gear hobbing:
• It is a process of generating gears by means of
rotating cutter called HOB
• It is a continuous indexing method in which both
tool & work piece is rotating
• Hob may be of single or double start thread
• Feed rate of hob is 0.05 to 0.375 mm per rev of
gear blank
47

48. Gear manufacturing
Gear hobbing
48

49. Gear manufacturing
Advantages of gear hobbing process:
• Hobbing is the continuous cutting process,
therefore it is faster than any other gear
generating process
• The set up is simple in construction
• High accuracy can be maintained
• Long shaft and splines can be easily
accommodated on hobbing machine
• Gap type herring bone gear made by this
process only
49

50. Gear manufacturing
Gear Shaping
• In this process the gear blank is driven by a gear
train connected to the cutter drive and the cutter
can be given translatory feed motion.
Gear shaping are two types
• Rack cutter generating process
• Pinion cutter generation process
50

51. Gear manufacturing
Gear shaping process
Rack cutter shaping: In this process the cutter is
mounted in a ram and perform the vertical
cutting motion. Its action is similar to a shaper
• The cutter reciprocates with the required cutting
speed to moves the material from the gear
blank. The gear blank is rotates about it axis
slowly
• Material removes in cutting stroke only
51

52. Gear manufacturing
Gear shaping process
Rack cutter shaping: Advantages
• It is suitable for cutting internal
gears
• Gear produce would be accurate
and fast
• This process is suitable for
cutting various type of gear like
spur, herringbone, sprockets,
internal gears and cluster gears
etc. 52

53. Gear manufacturing
Gear shaping process
Rack cutter shaping: Limitation
• The cutting takes place during forward stroke
only and the return stroke is idle
• The cutting process is interrupted by the index.
The blank has to be brought back to its starting
position, this reduces the rate of production.
53

54. Gear manufacturing
Gear shaping process
Pinion cutter generating process
• In this process cutter takes the form of pinion
and generates the tooth profile by removing
metal from the blank
• Its eliminate the necessity of indexing the blank
• The gear blank is mounted on the vertical
spindle
• The cutter is given reciprocating motion parallel
to its axis & slowly rotary motion of the work
54

55. Gear manufacturing
Gear shaping process
Pinion cutter generating process:
Advantages
• This process is more accurate &
faster than gear hobbing
process
• Internal gear can also be cut
through this process. Other gear
are spur, herringbone, sprocket
and cluster gear
55

56. Gear manufacturing
Gear Planing Process
• This process is also known as Sundarland or
Magg process.
56

57. Gear manufacturing
Gear Planing Process
• In this a rack cutter is used instead of rotary tool
• The cutter is reciprocate across the width of gear
blank and at the same time moved toward the
gear blank
• The cutter teeth generates the tooth profile
• During the cutting stroke action the blank is kept
stationary
57

58. Gear manufacturing
Gear cutting by multi point tool
• In this method number of form tools equal to the
number of teeth are fixed in shaping cutter head
58
• It is arranged radially along
the gear blank
• All tools are fed radially
inward simultaneously
• In this process involves the
production of all teeth on a
gear simultaneously by using
gear shaping cutter head

59. Gear manufacturing
Gear cutting by multi point tool: Advantages
• Since all the teeth are cut at the same time the
rate of production is high
• This process is very rapid for producing internal
as well as external gear, splines, ratches wheel,
and tooth clutches.
59

60. Gear manufacturing
Gear cutting by form disc cutter
• Spur gear are usually cut by
the form disc cutter
• By using universal indexing
mechanism all types of gear
can be cut on horizontal or
vertical milling machine, but
commonly used horizontal
type
60

61. Gear manufacturing
Gear cutting by form disc cutter
• In this process the gear blank
is indexed by indexing
mechanism and the revolving
form disc cutter are fed
toward gear blank for cutting
action
61

62. Gear manufacturing
Gear cutting by using end mill
• This process is similar to the
disc form rotary milling cutter
expect that the axis of rotation
is differently situated
• The cutting process is very
slow as one tooth is cut at a
tine
62

63. Gear Grinding or Finishing
• Gear grinding is the
most accurate
method of gear
finishing
• It is used to remove
the considerable
amount of material
after heat treatment
to obtained the
desired quality gear
63

64. Gear Finishing
Types of gear finishing method:
• Gear shaving, Gear grinding, Gear lapping, Gear
burnishing
Gear shaving:
• In this process the gear shave tool is used for
finishing the gear
• This tool is in the form of rack & pinion
• In this process very thin chip is removed from
the tooth profile
64

65. Gear Finishing
Gear shaving:
• The meshing gear and shaving cutter are
rubbed each other
• In this process the gear to be finished and
shaving tool is mounted on shaving machine
and gear rotated at very high speed in mesh with
the gear shaving tool
• Shaving tool caring a little inclined teeth so that
the axis can be crossed as the two comes in
contact
65

66. Gear Finishing
Gear shaving: Disadvantage
• After shaving, the gear should be finished by
gear grinding to get high quality surface finish on
the tooth profile
• It is time consuming process.
66

67. Gear Finishing
Gear lapping:
• It is a gear finishing process in which the gear are
run together in pairs under load.
• An abrasive paste or compound is being introduce
between the teeth to remove small irregularities
from hardened gear
• In this process the gear to be lapped is run under
load in mesh with one or more cast iron toothed laps
• During lapping abrasive paste or fine abrasive
powder mixed in this process is used for cutting
action
67

68. Gear Finishing
Generating type grinding:
• In generation grinding
generally two wheels are used
• Both the wheel are rotated
around their axis and they are
also traversed around the
work piece as it in mesh
• The production rate is low and
expensive process and skilled
labor are required
68

69. Gear Finishing
Under cutting occurred in gear generating process,
why?
• It is a defect, this is due to the action of corner of
teeth of generating cutter on the profile of the
gear teeth mismatch.
Preventive action
• To increase the pressure angle so as to move
the interference point to word the centre of the
gear
69

70. Gear Finishing
Broaching process:
• It is highly accurate method with an
excelent surface finish of internal
gear
• It is highly productive method and is
suitable only for high volume of
production
• Gear can be made in one pass by a
circular broach having a facing
teeth
• Separate broach is used for each
size of gear
70

71. Summary
• From this topic we understood the various
important part of milling machine, its operation
etc.
• We also understood the details of milling
machine, understand the various process used
and different function etc.
• Understand the gear tooth specification, gear
generating process, gear finishing process etc
71

72. References
• Books: R.K. Jain – Production Technology
• Book: Workshop technology – Hajra
Chaudhri
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