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Fittting the new linishing belt is a reversal of the removal
procedure described above.
LINISHING BELT TRACKING
After changing the belt it may be necessary to adjust the tracking
of linishing belt to ensure that it runs centrally on the rollers. The
belt tracking is adjustable by means of the belt tracking screw
(Pic. 12). By turning the screw counter-clockwise the belt moves
to the left and by turning the screw counter clockwise the belt
moves to the right. Adjust the tracking only while turning the belt
by hand (never with the machine running), ensure the belt is
running centrally before switching the machine on.
ADJUSTING THE LINISHING BELT TENSION (PIC.13)
The belt tension can be increased or decreased by adjusting the
belt tension spring (Pic. 13) This is achieved by moving the large
nut located at the bottom of the spring up it's thread to increase
tension, or down it's thread to decrease tension.
Ensure that the smaller lock nut is secured once you have
adjusted the belt tension.
Do not over tension the linishing belt as this will reduce the life
of their belt and put undue stain on the rollers and bearings
reducing the life of the machine.
GRINDING WHEEL INFORMATION
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:
aluminium oxide, silicon carbide, CBN (cubic boron nitride and
diamond. In the home workshop you will probably only use
wheels of aluminium oxide or silicon carbide. Both types are
available from your tool stockist.
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.
9A
Kind of Abrasive
Grain Size
The number shown in the above illustration is an example of
a grinding wheel description. 9A means that the abrasive is
aluminum oxide 46 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
9A – 46 – K5 – V 22
46
K
Grade
You will probably never need a coarse wheel. For most work a
medium or fine wheel is recommended.
TABLE1
The four main categories of abrasive grains
COARSE
MEDIUM
12
30
14
36
16
46
20
60
24
TYPES OF BOND
There are five main kinds of bonding agents namely, ceramic
(vitrified), phenolic 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.
5
V
Density
Bond Type
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 standard 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
22
FINE
VERY FINE
70
150
80
180
90
220
100
240
120
22
Manufacturers Symbol
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