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GRINDING WHEEL INFORMATION
GB
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GB
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Getting started
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Getting started
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TTB521GRB by
TITAN
TTB521GRB by
TITAN
Care and maintenance
Care and maintenance
GB
IE
In more detail...
GB
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In more detail...
The following information is a guide only on the different types of grinding wheels
and their uses.
TYPES OF ABRASIVE GRAIN
Grinding wheels are made of four main types of abrasive grain: aluminum oxide,
silicon carbide, CBN (cubic boron nitride) and diamond. In the home workshop you
will probably only use wheels of aluminum oxide or silicon carbide. Both types are
available from your tool stockiest. Grain size is separated into four main categories:
course, medium, fine and very fine. Table 1 shows the breakdown of grain size in
each category. For most work a medium or fine wheel is recommended.
TABLE 1
The four main categories of abrasive grains
Coarse
Medium
Fine
Very Fine
12
46
70
150
14
60
80
180
16
90
220
20
100
240
24
120
30
36
TYPES OF BOND
There are five main kinds of bonding agents namely, ceramic (vitrified), phonetic
resin, rubber, shellac and metal. The abrasive can be bonded with its particles close
together or with spaces between each grain particle. Bond material creates a link
between each grain. The spaces between the grains will determine how dense the
wheel is, large spaces will give an open wheel and smaller spaces will give a close
or dense wheel.
The structure is measured on a scale of 0-14 with 0 being very close and 14 being
very open with wide spacing between the grains.
WHEEL HARDNESS OR GRADE
Grade or hardness is the strength of bonding between the abrasive grains. Wheel
hardness is graded alphabetically, in increasing order of hardness; letters A through
D represent very soft wheels, and letters V through Z represent very hard ones.
Letter K in the illustration below represents a soft to medium wheel.
9A – 46 – K5 – V 22
Kind of
Abrasive
9A
Grain
Size
46
Grade
K
Destiny
5
Bond
Type
V
Manufacturers
Symbol
22
The number shown in the above illustration is an example of a grinding wheel
description. 9A means that the abrasive is aluminum oxide46 means that the
grain size is medium, K means that the wheel is soft, 5 means that the wheel
is dense, V stands for vitrified bonding and 22 is the manufacturer’s symbol.
Wheels supplied with bench grinders are generally “N” on the hardness scale,
which is considered hard. Do not try to sharpen carbide tools, knives, scissors
or high-speed tools (router bits, wood turning tools) with this hard wheel. A
tandard wheel will not cut carbide. If you try, you will only create heat and glaze
over the wheel. Hard wheels will burn router bits and other high-speed tools.
Overheating the tools will destroy their hardness and render them ussels.
Soft wheels give themselves up while grinding. When grinding, only a small
amount of material is removed, and the wheel releases grains a little at a time,
presenting new cutting edges. This releasing activity helps to keep the tool from
heating up and gives a finer grinding result.
Table 2 shows wheel hardness and uses.
Wheel Hardness (Grade) Uses for designated hardness
Description of hardness
A B C D
E F G H I J K L
M N O P Q R S T
U
V W X Y Z
Not used very often
Use these soft wheels to sharpen high -speed
-steel tools, such as router bits,drills, and tool bits.
Use these wheels for rough grinding on
soft materials.
This hard grade is used for dressing sticks
to dress grinding wheels.
Not used very often
Very soft
Soft to medium
Medium to hard
Hard
Very hard
TABLE 2
The following table 3 should help you to select the correct grinding wheel for the
job. New bench grinders are supplied with grey wheels. All other types of grinding
wheel are available from your tool stockiest.
TABLE 3
Type of tool
Drill bits
Spade boring bits
Masonry drill bits
Lathe tool bits
Chisels
Router bits
High-speed steel carbide tipped
Rotary lawnmower blade
Scissors & snips
Tool material
High-speed steel
High-speed steel
Cutting edge is carbide
High-speed steel
High-speed steel
High-speed steel
Cutting edge is carbide
Non heat-treated steel
Hard steel (but not file hard)
Recommended wheel type
Aluminum oxide (grey)
Aluminum oxide (grey)
Silicon carbide (green)
Soft aluminum oxide(Pink or white)
Soft aluminum oxide(Pink or white)
Soft aluminum oxide(Pink or white)
Silicon carbide (green)
Aluminum oxide(grey)
Aluminum oxide (Pink or white)
