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4.9 Installing Tool Rests
Refer to Figure 4.
Note:
There is a
left
and a
right
tool rest. Refer to
Figure 4 to ensure that you install them correctly.
(The beveled edge of tool rest faces the wheel.)
1. Install the left tool rest bracket (Q) by
threading two 5/16 x 3/4 hex cap screws (H)
through two 5/16 flat washers (J) and the tool
rest bracket (Q) into the wheel housing.
2. Place the tool rest (O) over the bracket (Q) so
that the scale is seen through the cutout.
Secure with knob (S).
3. Install the right tool rest in the same manner.
The tool rests must not contact the grinding wheel
but should ideally be adjusted to within 1/16” of
the wheel, depending upon the type of tool being
ground. As a wheel wears down, the tool rest
should be readjusted to maintain this clearance.
Figure 4: Completion of Assembly
4.10 Grinding Wheel Selection
Abrasive wheels are generally designed around
five characteristics: material, wheel grade, grain
size, grain spacing, and type of bond. These
codes will usually be listed on a wheel’s label.
General-use
silicon-carbide
(carborundum)
wheels can overheat and ruin the temper of high-
quality tool steel. For sharpening woodworking
tools, an
aluminum oxide
wheel is recommended.
Always inspect an abrasive wheel before
mounting. (See
section 4.11, Ring test
.) A wheel
that is cracked or damaged in any way must
not
be used. Maximum operating speed – listed on
the abrasive wheel label – must meet or exceed
1725 RPM (grinder spindle speed).
4.11 Ring Test
An internal defect, such as a crack or void, may
not be apparent by visual inspection alone.
Before installing a grinding wheel, check its
internal integrity by performing a simple “ring
test”.
1. Suspend wheel from the hole by a small pin
or finger.
2. Gently tap the flat side of the wheel with a
non-metallic object, such as a wood dowel or
the handle of a screwdriver. Tap about 45° to
each side of vertical center line, and about 1”
to 2” from the periphery. Then rotate wheel
45° and repeat.
3. A good wheel will "ring"; a defective wheel will
"thud", indicating cracks or other internal
compromise. Discard any wheel that does
not "ring".
A cracked or otherwise
damaged grinding wheel can break apart and,
if unguarded, exit grinder at high velocity
causing injury. Regularly inspect wheels for
damage, and make sure all guards are in
position.
