The document provides a comprehensive overview of abrasive processes, particularly focusing on grinding and broaching techniques. It covers the types and specifications of grinding wheels, the properties and classifications of abrasives, and various grinding machine types and operations including cylindrical, internal, and surface grinding. Additionally, it discusses the principles and specifications of broaching machines, outlining different types of broaching methods and their applications.

1. RAMCO INSTITUTE OF TECHNOLOGY
Mr.M.LAKSHMANAN
Assistant Professor (Senior Grade)
Department of Mechanical Engineering

2. UNIT IV
ABRASIVE PROCESS AND
BROACHING

3. UNIT -IV ABRASIVE PROCESS AND BROACHING -
Syllabus
Abrasive processes: grinding wheel – specifications and
selection, types of grinding process– cylindrical
grinding, surface grinding, centre less grinding and
internal grinding- Typical applications – concepts of
surface integrity, broaching machines: broach
construction – push, pull surface and continuous
broaching machines.

4. Grinding
Grinding is one of the abrasive processes. It’s a
metal cutting process in which the metal is
removed with the help of rotating grinding
wheel. This process removes comparatively
little material usually from 0.25mm to 0.5mm.
It is a metal cutting operation performed by
means of a rotating abrasive tool, called
Grinding wheel.
Such wheels are made of fine grains of
abrasive materials held together by a bonding
materials called a bond.

5. Grinding Wheel
Grinding wheels are made up of small abrasive
particles held together by bonding materials.
Thus it forms a multi edge cutter.
Grinding Wheel Abrasives:
Abrasive is a hard material. Its used to cut or
wear away other materials. Small sizes of
abrasives particles are used in grinding
wheels. They are called Abrasive Grains.

6. Types of Abrasive Materials
1.Natural abrasives
2.Artificial abrasives
1. Natural abrasives:
These are produced by uncontrolled forces of nature.
These are obtained from mines.
• Solid quartz(sio2)
• Emery (mixture of 50-60% Alumina + iron
oxide)coated paper
• Corundum (75-90% Crystalline Al2o3 + iron oxide)
• Diamond
Natural abrasives lack of uniformity of properties and the
reliability has largely been replaced by Artificial
abrasive.

7. 2. Artificial abrasives:
Its manufactured under controlled conditions in
closed electric furnace in order to avoid the
introduction of impurities and to achieve the
necessary temperature for the chemical reaction
to take place. These abrasives have better cutting
properties and higher efficiency than natural
abrasives. The various manufactured abrasives
are:
• Silicon carbide
• Aluminum oxide
• Boron carbide
• Cubic boron nitride

8. Silicon carbide (SiC):
• Silica sand+ petroleum coke + salt mixed
• 2000°c to 4000°c for 34 hours
• Brittle
• Used for low tensile strength such as cast iron,
brass, copper, aluminum.
SiO2 + 3C = SiC + 2CO

9. Aluminum oxide (Al2O3):
• Very hard and tough grains having sharp
cutting edges.
• Bauxide + Coke + Iron scrap
• Electric furnace
• Tough, less brittle and high tensile strength
• Used for high speed steel, malleable cast iron,
wrought iron etc.

10. Boron Carbide (B4C):
• It is harder than silicon carbide but not as hard as
diamond
• Coke + boric acid
• Electric furnace
• Used for grinding and lapping very hard metals,
hard alloys, glass and jewels.
Cubic Boron Nitride (CBN):
• It is harder than Aluminum oxide
• Boron + Nitrogen
• Nitrogen atoms
• Thermal resistance
• Grinding HSS cutters, tool steels, punch press dies,
hardenable stainless steels

11. BOND
Bond is an adhesive substance which holds the
abrasive grains together to form the grinding
wheel. The bonds must sufficiently be strong to
withstand the stresses of high speed rotating
grinding wheel.
Types of Bonds:
1. Organic Bonds
 Resinoid
 Rubber
 Shellac
 Oxychloride
2. Non Organic Bonds
 Vitrified
 Silicate

12. Non Organic Bonds
Vitrified bond (V):
• Clay+ Abrasive grains mixed with water
• 715°c
• Very strong
• Acids and alkalis not affected
• Brittleness
• Long time

13. Silicate bond (S):
• Abrasive grains + silicate of soda
• 270°c for 20 to 80 hours.
• Water proof
• Wear quickly
• Blades, grinding cutter
• Large wheels upto 1500mm diameter can
easily be produced.

14. Organic Bonds
Resinoid / Bakelite bond (B):
• Abrasive grains+ mixed with natural resin
• 210°c to250°
• Grinding Cams
• High finish on the work piece
• Speed upto 300m/min
• Used in grinding of steel, cast iron,
Malleable iron castings.

15. Rubber bond (R):
• Abrasive grains+ Pure rubber and Sulphur
• Sulphur vulcanizing agent
• High class surface finish (Centreless Grinding)
• Wheel thick upto125mm
• Very strong and tough and close grained
Shellac bond (E):
• Abrasive grains+ coated with shellac
• Elastic bonded wheel
• 160°c to 200°c
• Very thin wheels can be produced (for Cutting off
operation)
• Cam shaft and Mill Rolls

16. Oxychloride bond (O):
• Abrasive grains+ mixed with Oxide and
Chloride of magnesium
• Disc shaped wheels.
• Less brittle
• Less sensitive to side loads as compared to
vitrified bond wheel
• Grinding in dry condition (Cool cutting action)

17. Specification of Grinding Wheel
• Grit Number and Grain Size
• Grade
• Structure of Wheels

18. Specification of Grinding Wheel

19. Grit Number and Grain Size
• It refers to the actual size of the abrasive
particles. The grain size is denoted by the grit
number. Grid Number is equal to the number
of meshes in 254 mm of a sieve through which
the grains can pass through.
• Larger is the grit number, smaller will be the
grain size (fine Grit) and vice versa.
• For rough machining, coarse grained wheels
(Smaller grit number) are used.
• For finishing, fine grained wheels (large grit
number) are used.

20. Grain size used for Grinding Operation
Grit
The size of the abrasive grains are indicated by
grit number or grain number.
Grinding Operation Grit number
Coarse 10 12 14 16 20 24 -
Medium 30 36 46 54 60 - -
Fine 80 100 120 150 180 - -
Very fine 220 240 280 320 400 500 600

21. GRADE
• The term grade refers to the bond strength.
• This is the strength with the bond holds the
abrasive grains in place.
• Grade or Hardness indicates the strength with
which the bonding material holds the abrasive
grains in the grinding wheel.
• It does not refer the hardness of abrasive
grains.

22. The degrees of hardness are specified by the
use of letters of the Alphabet. “A” indicates
the softest Grade whereas “Z” indicates the
hardest Grade.
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

23. Structure of Wheels
• This term denotes the spacing between abrasive
grains or in other words the density of the wheel.
• The abrasive grains in the grinding wheel are
distributed through the bond.
• The relative spacing of abrasive is referred as
structure.
• When the spacing is small, the structure is called
Dense structure.
• When the spacing is wide, the structure is called
open structure. Structure Symbol
Dense 1 2 3 4 5 6 7 8
Open 9 10 11 12 13 14 15 or higher

24. Designation of Grinding Wheel
An Indian Standard Institution (IS:551 – 1954) has
specified a standard system of marking the
grinding wheels.
Elements:
• Type of abrasives
• Grain size or grit number
• Grade of the wheel
• Structure
• Type of bond
• Manufacturer’s code

26. Selection of grinding wheels
The following factor are to be considered.
1.Constant factor:
• Physical properties of Material to be ground
• Amount and rate of stock to be removed
• Contact area
• Type of grinding machine

27. 2. Variable factors
• Work speed
• Wheel speed
• Condition of the grinding machine(Dry/Wet)
• Personal factors

28. 1. Constant factor:
• The material to be ground
Abrasive
Grain size
Grade
structure
-Aluminum oxide wheel
-Coarse grain wheel
-hard grade wheel
-open structure wheel
For soft, ductile and
high tensile material
Abrasive
Grain size
Grade
structure
-silicon carbide wheel
-fine grain wheel
-soft grade wheel
-dense structure wheel
For hard and brittle
the material

29. • The grit and grade range for various class of
work
Class of work Grit size Grade
Rough work 14-30 Q-S
Cylindrical work 35-150 J-N
Centre less and
crankshaft
46-80 J-N
Surface grinding 20-36 G-M
Tool grinding 30-80 M-Q
Internal grinding 46-60 H-N

30. • Amount and rate of stock to be removed
-Coarse grain and wide spacing are used for fast
cutting.
-Fine grain and close spacing are used for fine
finish.
• Contact area
-When the contact area is small, fine grain and
close spacing
-When the contact area is large coarse grain and
wide spacing

31. • Type of grinding machine
-Heavy rigid machine
-Light rigid machine
2. Variable factor:
a) Work speed
-Hard wheel
-Soft wheel

32. b) Wheel speed
-Soft wheel
-Hard wheel
c) Condition of the grinding machine
-Dry conditions
-Wet conditions
d) Personal factor
-Skilled worker
-Unskilled worker

33. Reconditioning of Grinding Wheel
During grinding operation, the grinding of the wheel
are subjected to wear and the wheel loses its
cutting capacity. Grinding wheels are dressed to
restore their cutting capacity which is lost by the
phenomenon of loading and Glazing.
During the operation the chips formed get entrapped
in the inner granular space of abrasive particles.
Its called Loading.
When the bond of the abrasive is very hard, it does
not dislodge an abrasive particle. Therefore the
surface of the wheel becomes smooth and gets a
glassy like appearance. Its known as Glazing of the
wheel.

34. DRESSING
It’s the process of loading and breaking away the
glazed surface so that new sharp abrasive particles
are again present to work for efficient cutting is
called Dressing. The dressing is done using the tool
called Dresser.
Types of Dressing Tools:
• Star Wheel Dressing Tool
• Abrasive Stick
• Diamond Dressing Tool

36. Abrasive Stick

39. TRUING
Truing is the process of trimming the cutting
surface of the wheel to run true with the axis. By
truing the cutting surface of the worn out wheel
can be shaped to the original form.
Its also used to produce the required contour for
form grinding. Truing is done with a Diamond
Truing tool. Tis process is similar to dressing.

41. • The grinding face of the wheel may become
irregular.
• Hence it loses its original shape
• Truing is done to bring back the original of the
wheel.

42. Shapes of Grinding Wheel

43. Standard Shapes of Grinding Wheel Faces

44. Classification of Grinding Machine
• According to type of operation
 Tool Grinders
 Cut off Grinders
• According to the quality of surface finish
 Precision Grinders
 Rough Grinders
• According to the type of surface generated
 Cylindrical Grinders
 Internal Grinders
 Surface Grinders
 Tool Grinders
 Special purpose Grinding Machines
 Surface finishing Grinders

45. 1. cylindrical grinders
 Plain cylindrical grinder
Universal cylindrical grinder
Centreless grinder
2. Internal grinders
 Plain internal grinder
Centreless internal grinder
Chucking internal grinder
Universal internal grinder

46. 3.Surface grinder
(i) Reciprocating table
(a) Horizontal spindle
(b) Vertical spindle
(ii) Rotating table
(a) Horizontal spindle
(b) Vertical spindle
4. Tool and cutter grinder
(a) Universal
(b) Special

47. Rough Grinders
Its used for removing large amount of metal
from the workpiece. It is used for removing
projections such as sprue pins from casting,
projections in forging, finishing the
weldments, sharpening of hand tools.

48. Bench Grinder

49. Portable Grinder

50. Abrasive Belt Grinder

51. Swing Frame Grinder

52. Precision Grinders
Its used to manufacture parts of accurate
dimensions and good surface finish. The
workpiece and the grinding wheel are rigidly
mounted but they are adjustable according to
the requirement of the machining methods.
It is used for cylinder bores, gauges, tools,
cutters, machine guide ways, threads, gears,
cams etc.

53. 1. Cylindrical Grinders

54. 1.1 Plain Centre Type Cylindrical Grinding
Machine

55. 1.2 Centre Type Universal Grinder Machine

56. 2. Surface Grinders
• Horizontal Spindle Reciprocating Table Surface
Grinder
• Horizontal Spindle Rotary Table Surface
Grinder
• Vertical Spindle Reciprocating Table Surface
Grinder
• Vertical Spindle Rotary Table Surface Grinder

57. 2.1 Horizontal Spindle Reciprocating Table
Surface Grinder

60. 2.2 Horizontal Spindle Rotary Table Surface
Grinder

61. 2.3 Vertical Spindle Reciprocating Table
Surface Grinder

63. 2.4 Vertical Spindle Rotary Table Surface
Grinder

66. 3. Centreless Grinding
Centreless grinding differs from centered grinding
operations in such a way that no spindle or
fixture is used to locate and secure the workpiece.
The workpiece is secured between two rotary
wheels and speed of their rotation relative to
each other determines the rate at which the
material is removed from the workpiece.
Its performed on cylindrical workpieces such as
pistons, Valves, rings, tubes, balls, drills, shafts,
etc. it can be done on both external and internal
surfaces.

67. Principle of Centreless Grinding

68. Centreless Grinding Machine

69. Centreless Grinding Machine

70. Methods of External Centreless Grinding
 Through Feed
 In Feed
 End Feed

71. 1. Through Feed:
Its used for straight cylindrical workpiece such
as long shafts or bars, roller pins etc. In this
method regulating wheel is tilted at small
angle. It makes the work to move axially
through the space between grinding wheel
and regulating wheel. The guides are
provided at the ends of the wheel and guide
the movement of the workpiece.
The machine usually removes 0.2mm of stock in
one pass on the diameter of the work.

72. Through Feed

73. 2. In Feed:
Its similar to plunge grinding. The work is placed
on the work rest against an end stop. It
prevents the axial movement of the workpiece.
The regulating wheel and work rest with the
workpieces are moved towards the grinding
wheel by hand feed. Its used to grind shoulders
and formed surfaces.

74. 3. End Feed:
In this method, both grinding and regulating
wheels are tapered and thus, it produces
tapered workpieces. The workpiece is fed
lengthwise between wheels and its ground
as it advances until it reaches the end stop.

75. Internal Grinding
• Chucking Type
• Planetary Type
• Centreless Type

76. 1. Chucking Type Internal Grinders
The workpiece is mounted in a chuck and
rotated about its axis. The workpiece is
mounted at the left side of the machine. The
grinding wheel (wheel head) is mounted at
the right end of the machine.
The grinding wheel is rotated and at the same
time, it reciprocates back and forth through
the length of the hole.

78. 2. Planetary Type Internal Grinders
In this grinders, the work remains stationary
and the rotation of wheel spindle gives an
eccentric motion according to the diameter of
the hole to be ground.
Therefore in this operation, the motion of the
grinding wheel is in the form of the planet and
hence, its called planetary grinding.

79. 3. Centreless Internal Grinding

80. In this centreless internal grinding, the work
is supported by three rolls.
One is the regulating wheel,
The second one is a supporting roll and the
last one is a pressure roll.
The pressure roll is used to hold the
workpiece against the support and
regulating rolls.

82. Advantages of Centreless Grinding
• Small diameter and long length work pieces can
be ground without any deflection as the work
piece.
• Size of job can be controlled easily and accurately.
• Suitable for mass production.
• Work holding devices like,chucks,dogs are not
possible.
Disadvantages
• It is not used for large diameter work piece
• Jobs having flat surface on cylindrical can not be
ground.

83. Size and specification of grinding machines
• The largest work piece which can be held on
a grinder
• The normal capacity of the grinder
• The width of the table
• The maximum traverse of the table
• Wheel diameter
• Height of the grinding head

84. Grinding Ratio
G= volume of material required
volume of wheel wear

85. Applications of Grinding Wheel
• Forming
• Gear Teeth Grinding
• Thread Grinding
• Cam Grinding
• Tool and Cutter Grinding

87. Surface Integrity
Surface integrity is the surface condition of a
workpiece after completing a particular
manufacturing process.
The concentrated energy consumption at the
contact region of a machining process can be
divided into Mechanical, Thermal and Chemical
effects which lead to differing intensities of
surface property alterations.
Types of Surface integrity characteristics:
Topography Characteristics – surface roughness,
waviness, errors of forms and flaws.
Surface layer Characteristics – Plastic deformation,
residual stresses, cracks, hardness, phase change,
recrystallization, etc.

88. Factors influence workpiece Surface Topographies
in Grinding
• Workpiece material – Harder materials allow finer
finishes
• Type of wheel – Fine Grains yield finer finishes
• Dressing procedure – Improperly dressed wheels will
damage the work surface.
• Feed rate – Finer finishes are obtained with
slower feed rates
• Machine rigidity – Older, worn machines yield a poor
quality finish
• Wheel condition – Clogged wheels cannot produce a
good finish
• Lubricant cleanliness – Coolant filtration removes waste that
could damage workpiece surface.

89. BROACHING
Broaching is a process of machining a surface
with a special multipoint cutting tool called
Broach which has successively higher cutting
edges in a fixed path.
It is faster and cheaper method of machining but
depth of removed material is limited to 6mm or
less. External and Internal surfaces can be
machined by broaching.
It is used to machine key ways,splines,square,
rectangular and polygon holes, internal gear
etc.

90. External Broaching

92. Internal Broaching

94. Specification of Broaching Machine
Main Specifications:
• Maximum length of the stroke in mm
• Maximum force developed by the slide in
Tonnes.
Minor Specifications:
• Power rating of electrical motor in H.P
• Speed and feed Range
• Weight of thee machine in Tonnes
• Floor space required in square meter.

95. Types of Broaching Machine
• According to the direction of the cutter
1.Horizontal 2. Vertical
• According to the method of cutting
1.Pull type 2.Push type 3. Continuous type
• According to the type of drive
1.Mechanical drive 2. Hydraulic drive
• According to the number of pull heads
1.single head 2. multiple pull head
• According to the type of operation
1.External type 2. Internal type

96. Horizontal Broaching Machines
1.Horizontal type Internal Broaching Machine

97. All Horizontal broaching machines are of pull
type and provided with either hydraulic or an
electric drive. Its operated at a low speed of 2
to 15m per minute.
Its used for small and medium sized works like
keyways and internal gears, etc.

99. 2. Horizontal Type Surface Broaching Machine
The broach is pulled over the top surface of the
workpiece. The cutting speed ranges from 3 to
12 mpm with a return speed up to 30mpm.

100. Vertical Broaching Machine
1. Push Down Type
2. Pull Down Type
3. Pull Up Type
1. Push Down Type Vertical Broaching Machine
The push type vertical broaching machine is
used in the surface broaching operation. It
consists of a box shaped column, slide and
drive mechanism. The slide is provided with
a quick return mechanism.

103. 2. Pull Down Type Vertical Broaching Machine
These machines are
mostly used for internal
broaching operations. Its
pulled through the job.
The tail end of the
broach is automatically
engaged by a pulling
mechanism and it is
pulled down through the
job.

104. Pull Down Type Vertical Broaching Machine

105. 3. Pull Up Type Vertical Broaching Machine
In this type, the ram slides
on the vertical column of
the machine.
The ram carries the pulling
head at its bottom. The
broach is pulled upward.

106. Continuous Broaching Machines
Its used for high production rate of small
parts.
Types:
• Horizontal Type
• Vertical Type
• Rotary Type

107. 1. Horizontal Type Continuous Broaching Machine
It is one type of surface broaching machine. It has a
driving unit which consists of two sprockets. They are
connected by an endless chain. Fixtures are mounted
at intervals on the chain for loading and holding
workpieces.
The broach is horizontally fixed in the frame of the
machine. The rigid guiding member is arranged
under the chain in the zone where the workpiece
passes under the broach. The work is automatically
clamped before it reaches the Tool.

109. 2. Vertical Type Continuous Broaching Machine
When the axes of two sprockets are vertical. Its
called Vertical Broaching Machining. The
broach is vertically placed on the frame of the
machine.

110. 3. Rotary Type Continuous Broaching Machine
The machine has a rotary table and vertical
column. In vertical column the broach is
horizontally fitted above the table. A series of
fixtures are mounted on the rotary table for
locating and holding workpieces.

111. Broach Nomenclature
The broach is composed of a series of teeth. Each
tooth is standing slightly higher than the
previous one. This rise per tooth is the feed per
tooth and it determines the material removed
by the tool.

113. Types of Broaching Tools
• Push Broach
• Pull Broach
• Progressive Broach
• Push Broach:

114. • Pull Broach:

115. • Progressive Broach:

116. Broaching Tool Materials
• High speed tool steel such as alloy steel and
stainless steel
• TiN Coated carbides
• Aluminium
• Brass
• 12L14

117. Applications of Broaching Machines
• Straight and helical slots
• External surfaces of various shape
• External and internal toothed gears
• Holes of cross sectional shape

118. HONING
Honing is an abrasive machining process that
produces a precision surface on a metal
workpiece by scrubbing an abrasive stone
against it along a controlled path. Honing is
primarily used to improve the geometric form
of a surface, but may also improve the surface
texture.