This document provides information about various grinding processes and concepts. It begins by classifying grinding machines and describing different types of surface grinders based on spindle position. It then discusses centerless grinding and cylindrical grinding. The document outlines factors to consider when selecting a grinding wheel, such as abrasive type and grain size. It defines terms like grain, grade, and bond type. Finally, it covers topics like truing, dressing, glazing, and wheel wear.

1. Grinding
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
• Grinding – Classification of machine, grinding
wheel composition, types and shape,
designation
• Grinding operation
2

3. Learning Objective
• Details of grinder, understand the various
process used and different function etc.
• Understand the grinding wheel specification,
grinding process, important parameter etc.
3

4. Grinding
Classification of grinding machine:
According to the quality surface finish:
1. Rough grinder (Floor and bench, swing frame,
portable, abrasive belt grinder),
2. Precision grinder (Cylindrical, surface, internal,
tool cutter, disc, thread, cam shaft grinder
4

5. Grinding
Surface Grinder:
• It is employed to finish plain or flat surfaces by
means of a revolving abrasive wheel
• According to the shape of table, its movement it
is divided into: 1. Rotary table type, reciprocating
table type
• Angular, form irregular surfaces and curved
surfaces can also be ground
• It is further classified depending on spindle poss.
5

6. Rotary table & reciprocating
table type grinding
6
Rotary Table Reciprocating Table

7. Grinding
As per the position of
spindle it is classified
into
• Horizontal spindle
rotary table
• Horizontal spindle
reciprocating table
• Vertical spindle rotary
table
• Vertical spindle
reciprocating table
7

8. Grinding
Horizontal spindle rotary table or (Ring) grinder:
• The face of the wheel is used for grinding
• It is generally used for precision work
• The work is mounted on a revolving horizontal
table
• The area of contact is small and the speed is
uniform through out the process
8

9. Grinding
Horizontal spindle reciprocating table grinder:
• It consist of the horizontal spindle which carry’s
the straight grinding wheel
• These grinder grinders are used for flat surfaces
and light precision work in tool room and gauge
making
9

10. Grinding
Center-less Grinding:
• It is used for cylindrical jobs
• In this the work is not supported in centre but is
held against the face of the wheel by combined
action of a work rest and regulating wheel
• Regulating wheel controls the speed of rotation
of the work piece as well as feeding movement
• It was developed for mass production of
cylindrical or taper job
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11. Center-less Grinding
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12. Grinding
Center-less Grinding: Application
• It is used for circular job like pins,
piston rod, pipe, round casting, tubes etc.
Center-less Grinding: Advantages
• Idle time is almost zero
• It is very suitable for long job without deflection
• Heavy cut can be possible with this grinder
• Very little maintenance
• It is suitable for external and internal grinding
12

13. Grinding
Methods of job feeding in center-less grinding:
Through feed:
• it is used for straight cylindrical work
• In this the work is goes from one side of
machine and comes out from other side
• If there is a head on then work piece than this
method is not suitable
13

14. Methods of job feeding in
center-less grinding
14

15. Grinding
Methods of job feeding in center-less grinding:
In-feed feed:
• This method is used for stepped cylindrical work
piece which cannot be through feed
• In this method the work is placed on the work
rest against an end stop and then regulating
wheel with the work and work rest are advance
to the grinding wheel to reduce the diameter to
required size
15

16. Grinding
• Methods of job feeding in center-less grinding
16

17. Grinding
Methods of job feeding in center-less grinding:
End feed:
• This method is similar to form grinding
• Here both the wheels (regulating and grinding)
are trued to the required shape and work is fed
longitudinally from the side of the wheel to an
end stop
• It is used for taper cylindrical surfaces
17

18. Grinding
Types of internal grinders:
It is divided into three groups, depending on the
manner in which the work is held and method of
operation used
• Work rotating type
• Planetary type
• Center-less internal type
18

19. Grinding
Types of internal grinders: Work rotating type
• It is used in tool room 7 it is also called as
chucking grinder
• In this type the job is chucked and rotated about
it axis to bring surface to be grounded in contact
with the grinding wheel
19

20. Grinding
Types of internal grinders: Planetary type
• It is used to grind the large, irregular shaped and
heavy work piece which cannot be easily held
and rotated by a chuck
• In this type the work piece remain stationary &
grinding wheel spindle is given rotary well as
planetary motion to grind large holes of varying
diameter
20

21. Grinding
Types of internal grinders: Center-less internal type
• In this the work is supported by the three rolls
• 1. Regulating, 2. Supporting roll, 3. pressure roll
• The pressure roll holds the work piece firmly
against the supporting and regulating wheel
• Grinding wheel and work piece rotates in
opposite direction while all three rolls rotates in
same direction
21

22. Grinding
• Center-less internal type
22

23. Grinding
Plain centre type cylindrical grinder:
• It is used for external grinding
• These are a heavy duty machine
• In this type work piece is held between centre
• Rotating work piece is passed across the
rotating grinding wheel
• Grinding wheel moves toward the work piece
23

24. Grinding
• Plain centre type cylindrical grinder:
24

25. Grinding
Universal cylindrical grinder:
It is similar to the plain type but having some
special feature
• Head stock has both revolving or dead centre
spindle drive
• Contains swivel mechanism to swivel the wheel
up to 100 deg. For taper job
25

26. Grinding
Factor for grinding wheel selection:
To achieve better result in grinding operation the
following factors are to be consider.
The factor are classified in to two groups
1.Constant factor
a. Material to be ground
b. Amount of stock to be removed
c. Area of contact
d. Type of grinding (nature of work)
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27. Grinding
Factor for grinding wheel selection
2. Variable factor
a. Wheel speed
b. work speed
c. Condition of machine
d. personal factor
27

28. Grinding
Factor for grinding wheel selection
1. Constant factor
a.Material to be ground: Its affect the selection of
grinding wheel which influence the selection of
• Abrasive: aluminium oxide for high tensile
strength material (steel and steel alloys)
• Grain size: Medium grains are used for
operation where the stock removal and finish
both are required
• Grade: Hard wheel for soft material & vice versa
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29. Grinding
Factor for grinding wheel selection
1.Constant factor
b. Amount of stock to be removed: Coarse grain
are used for fast removal of material & fine grain
for finishing
c. Area of contact: For long contact are coarser
grain and soft grades of grinding wheels are
used and for small contact area finer and hard
wheels are used.
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30. Grinding
Factor for grinding wheel selection
1.Constant factor
d. Type of grinding machine: Light machine is
subjected to vibration.
For harder grinding wheel the poor condition
machine would be ok
For soft grinding wheel the heavy rigidly
constructed and well maintained machine
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31. Grinding
Factor for grinding wheel selection
1.Variable factor
a.Wheel speed: It is influenced by Grade & Bond,
High wheel speed for soft grinding wheel
b.Work Speed: Harder wheel for high speed work
in relation with wheel speed
c. Condition of grinding machine: heavy rigid
machine required softer wheel
d. Personal Factor: Skilled operator can worked with
softer wheel & achieve optimum production
31

32. Grinding
What do you mean by:
1.Grain or Grit:
• it indicates the size of the abrasive particles
used in making a wheel
• It is denoted by a number which is based on
sleeve size used
• Grain size are classified as Coarse, Medium,
Fine
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33. Grinding
What do you mean by:
2. Structure:
• It denotes the spacing & relative arrangement of
grain, bond, pores in a unit volume of grinding
wheel
• The primary purpose of structure is to provide
chip clearance
• It may be dense or open, it is denoted by
number (1 – 14), lower number indicates open
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34. Grinding
What do you mean by:
Grade:
• Grade means degree of hardness of the grinding
wheel
• The grade of grinding wheel is generally
considered as the degree of STRENGTH which
the bond holds the abrasive grain with in the
wheel
• The grade is depends on hardness of material
• It is denoted by a letter A to Z (soft to hard)
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35. Grinding
Grade:
The commercial wheel are denoted as
Soft A B C D E F G H
Medium I J K L M N O P
Hard Q R S T U V W X Y Z
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36. Grinding
General type of grinding wheels:
• Tapered wheel: It has taper on both side and it is
used principally for snagging operation
• Straight cut wheel : It is used for grinding on
horizontal & vertical spindle machine.
• Cylindrical wheel : It is used for surface grinding
on both horizontal & vertical spindle machine
• Dish wheel : Thickness of the dish wheel permits
the insertion of the grinding edge of the wheel
into narrow gaps
36

37. Grinding
• General
type of
grinding
wheels:
37

38. Grinding
Abrasives:
• An abrasives is hard substance used for
grinding and polishing operation. It has many
sharp edges and used to cut or wear away the
other materials
• It may be classified as:
a.Natural abrasive: Quartz, Energy, Corundum,
Diamond & Garnet
b.Artificial abrasive: Aluminium oxides, silicon
carbide, Boron carbide, Cubic boron carbide,
Diamond
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39. 39
What affects Abrasive Decision?
Ferrous Materials
Production Numbers
Fatigue Concerns
(Potential thermal damage)
Non-Ferrous Materials
Dimensional Tolerances
Process Controls
Grinding

40. 40
Aluminum Oxide
Cubic Boron Nitride
(CBN)
Diamond
Silicon Carbide
Ferrous Materials Non-Ferrous Materials
Abrasive Selection
Grinding

41. Properties of Grinding
41
For Grinding
Ferrous Materials
Hardness on Knoop Scale
(kg/mm2
) = 1400 - 2100
Thermal Conductivity
(W/m
O
K) = 29
Aluminum Oxide (Al2O3)

42. 42
For Grinding
Non-Ferrous Materials
Hardness on Knoop Scale
(kg/mm2
) = 2700
Thermal Conductivity
(W/m
O
K) = 400
Silicon Carbide (Si,C)
Properties of Grinding

43. 43
Properties of Grinding
For Grinding
Ferrous Materials
Thermal Conductivity
(W/m
O
K) = 1300
Hardness on Knoop Scale
(kg/mm2
) = 4500
Cubic Boron Nitride (CBN) (B,N)

44. 44
Properties of Grinding
For Grinding
Non-Ferrous Materials
Hardness on Knoop Scale
(kg/mm2
) = 8000
Thermal Conductivity
(W/m
O
K) = 2000
Diamond (C)

45. 45
Properties of Grinding
The Puzzle
Why Not Diamond?
REACTIONDiamond + Ferrous Material + Heat =
Note: Silicon Carbide has similar reaction

46. Grinding
What are Superabrasives
• Diamond
• Cubic Boron Nitride (CBN) Borazon
What makes Superabrasives Super?
• Hardness (Resistance to wear)
• Thermal Conductivity (The ability to absorb heat)
• Flexibility (one wheel for many applications)
• Wheel Life (100 + times Conventional Abrasives)
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47. 47
Some Advantages
(For Superabrasives)
Decreased Cycle Time
Reduced Dressing
Reduced Gaging
Reduced Time for Wheel Changes
Reduced Coolant Changes
Reduced Filter Changes
Less Swarf Contamination
Reduced Coolant Disposal Costs
More Consistent Parts (Less Scrap)

48. Types of Bond
48
Conventional Abrasives Construction
Conventional Layer = full area of wheel
Wheel
Vitrified Bond
Resin Bond
Rubber Bond
Shellac Bond

49. Superabrasive Construction
Superabrasive Layer = 3mm (1/8”) to 6mm (1/4”)
Wheel
Core Resin Bond
Metal Bond
Vitrified Bond
Types of Bond
49

50. BONDSBONDS
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51. Grinding Matrix Vitrified
Wheel
Grain
Bond
Pore
Chip
51

52. Grinding Wheel Bond
Systems
Resin ,, Metal & Bonds Sintered Vitrified
Abrasive + Bond = Wheel
52

53. Grinding Wheel Bond Systems
Open Structure (Low fired) Vitrified Bonds
Abrasive + Bond + Pores = Wheel
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54. Grinding Wheel Bond
Systems
Plated Wheels (Single Layer)
Wheel body
Cathode (-)
Abrasive
Anode (+)
Electrolyte
(Nickle Solution)
Plated Wheel
Cut-A-Way 54

55. Abrasive wear
Fracture
wear
Chip
Bond
Abrasive
Cut a way of
wheel
55

56. Abrasive wear
Attritious
wear
(Rubbing)
Work
Piece
Conventional
Abrasive (one
grain)
56

57. Abrasive wear
Fracture
wear
Work Piece
Conventional
Abrasive (one
grain)
57

58. Abrasive wear
Fracture
wear
Work Piece
Conventional
Abrasive (one
grain)
58

59. Abrasive wear
Attritious
wear
Work Piece
CBN
Abrasive (one
grain)
59

60. Standard Markings
Conventional Abrasives
Abrasive
Type
Abrasive
Size
Abrasive
(combina
tion)
Hardness
(Grade)
Structure
(Pore)
Bond
A
C
SG30
A
60
120
80
24
1
2
J
K
L
R
6
12
10
V
V
V
B
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61. Standard Markings
Superabrasives
Abrasive Type Abrasive Size Hardness
(Grade)
Concentration Bond
BN
D
BN
140
240
120
J
k
L
100
75
150
B
M
V
• Superabrasives are always combinations 120/140,
80/100 etc.
• Calculating concentration take number and divide by
4
• Example 100 ÷ 4 = 25% by volume of abrasive in
wheel
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62. Identify Standard
62

63. Identify Standard
Q. On a grinding wheel it is printed as 200X25X25 W A 36 N 3 V
23. What does each letter and number indicates
Answer
200 – Wheel diameter
25 – Thickness of wheel
25 – Bore diameter
W - Manufacturer’s prefix for abrasive
A – Type of abrasive (Aluminium oxide)
36 – Grain (medium)
N – Grade (medium)
3 – Wheel structure (Dense)
V – Type of bond (Vitrified)
23 – Manufactures number for wheel identification
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64. Coolant Flow
Coolant Velocity =
W
heel Velocity
64

65. TRUING & DRESSINGTRUING & DRESSING
&&
Glazing & LoadingGlazing & Loading
65
Run-Out Out of Balance

66. Truing & Dressing
Truing:
• It is a operation to give the true geometric shape
as it become worn from an original shape
Dressing:
• It is a process of clearing and opening up of the
face of a grinding wheel
• It remove worn out grains from the face of the
wheel
Note: Both operation can be done by same tool but not for same
purpose
66

67. Glazing & Loading
Glazing:
• It is a condition in which the face or cutting edge
takes a glass like appearance and is caused by
the abrasive grain wearing away faster than the
bond
• It causes decrease in cutting capacity
Loading:
• When the work piece chips adhere in the cutting
face of the wheel, the loading occurs
• It is caused due to slow work speed & wheel is to hard
67

68. The Difference Between
Truing & Dressing
68

69. Truing
Resin & Metal Bonds
69

70. Dressing
Resin & Metal Bonds
70

71. Truing & Dressing Vitrified Bonded
(CBN Wheels)
71

72. Examples of Rotary
Dressers
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73. Truing & Dressing
(Depth or In-Feed)
• Conventional Abrasives – Aluminum Oxide
• ≤ 0.0178mm (0.0007”) per pass
• Ceramic Abrasives – Seeded Gel (SG)
• ≤ 0.005mm (0.0002”) per pass
• CBN Abrasives
• ≤ 0.0025mm (0.0001”) per pass
73

74. Truing & Dressing
(Traverse Rate)
• Starting Parameters
• 0.1mm (0.004”) per revolution of wheel
Assuming 0.5mm (0.020”) radius dresser
Faster traverse rate creates rougher finish
Slower traverse rate creates finer finish
74

75. CBN vs. Conventional
(Surface Finish – plunge grinding only)
• Conventional Grinding Surface Finish = Grit Size
• CBN Grinding: Surface Finish = Diamond
Overlap
75

76. Thread Grinder
76

77. Thread Grinder
• It is used for grinding external and internal
threads very accurately
• The wheel is shaped as per the thread profile
• It is selected when high accuracy, high
precision, high surface quality is required (e.g.
Tab, Thread plug etc.)
• Selection of grinding wheel depends on the job
material, pitch required and profile of the thread
• Al oxide wheel is mostly preferred
77

78. Summary
From this chapter you all understand the..
• Details of grinder, understand the various
process used and different function etc.
• Understand the grinding wheel specification,
grinding process, important parameter etc.
78

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