USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 2/TASK 1
(1) Bench Grinder and Grindstone. Wear goggles when using a bench-
type grinder and the grindstone. Use the rest (figure 62 on the previous
page) provided on the grinder frames to support the work. Hold the tools
that are being shaped so that they will not catch in the abrasive wheel;
otherwise, they will slip and injure the operator, or wear the wheel
To grind specific tools, refer to instructions covered in
pertinent sections of the technical manual on the particular tool you desire
to grind or sharpen. Never use a cracked wheel. Before using a wheel, tap
it lightly with a mallet.
A ringing sound indicates that the wheel is
satisfactory; a dull sound indicates that the wheel may be cracked.
(2) Valve Grinder.
A hand valve grinder (figure 62) is used for
grinding or lapping a valve.
By applying a small amount of grinding
compound around the valve face and rotating the valve in its seat with the
grinder, a perfect lap can be made.
The grinder is geared so that the
attached blade rotates quickly. One complete revolution of the crank handle
advances the blade several revolutions.
Check the grinding operation by
removing the valve and applying a thin coat of prussian blue on the face of
the valve. Reinsert the valve and, with hand pressure on the valve head,
rotate the valve about one-quarter turn on its seat. Remove and inspect the
impression made on the prussian blue.
The impression will indicate the
accuracy of the seating.
Continue to lap grind the valve face until the
entire circumference of the valve seat, without a gap, indicates contact
with the valve face on 90 percent of its area. The grinder shaft mounts a
suction cup to hold those valves that have no recessed holes or slots.
e. Using Sharpening Stones and Oilstones.
Sharpening stones and
oilstones (figure 63 on the previous page) are used with a fine oil,
sometimes with kerosene, and in some cases are used dry. When a tool has
been sharpened on a grinder or grindstone, there is usually a wire edge or a
feather edge left by the coarse wheel. The sharpening stones and oilstones
are used to hone this wire or feather edge off the cutting edge of the tool.
Do not attempt to do a honing job with the wrong stone.