Using Grinders

Use And Care Of Handtools And Measuring Tools
Page Navigation
85

d. Using Grinders.

(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

excessively.

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.