Figure 10-17.--A. Tooth rest blade in a plain holder. B. Tooth rest blade in a universal holder.
grind the primary clearance angle) varies according to
rest all in the same plane and then raise or lower the
the size of the cutter. Primary land widths range from
wheelhead the proper distance to give the desired
0.0005 to 0.015 inch for a small cutter to 0.030 to 0.062
inch for a large cutter. You should grind the lands very
When you use the straight wheel, use a centering
carefully. A land that is too narrow will allow the cutting
edge to chip or wear rapidly. A land that is too wide will
of the wheel and the center of the work into the same
cause the trailing side (heel) of the land to rub the work.
plane. Then, fasten the tooth rest to the machine table
When the width of the primary land becomes
and adjust the tooth rest to the same height as the center
excessive due to repeated grindings, you must grind the
secondary clearance angle to reduce it. The secondary
clearance angle is normally 3° to 5° greater than the pri-
mary clearance angle.
You get the desired clearance angle by the
positioning of the grinding wheel, the cutter, and the
tooth rest. The general procedure is to position the
center of the wheel, the center of the work, and the tooth
Figure 10-18.--Cutter clearance angles.
Figure 10-19.--Centering gauge.