Table 9-3.--Rake Angles for Single-Flute Cutters
cutter in your hands at the proper inclination from the
can readily see it after grinding the cone, and the point
grinding wheel face and touch the cutter very lightly
side of view B. To correct this, grind the flat to center
against the wheel. You also may dress it with an
as in the right side of view B.
3°; this angle causes the cutter to bite into the work like
GRINDING THE CHIP CLEARANCE.--The
a drill when it is fed down. Angle B (fig. 9-25) varies,
cutter now has the correct angle and a cutting edge, but
depending on the material to be engraved. Use table 9-3
has no chip clearance. This must be provided to keep
as a guide to determine angle B.
the back side of the cutter from rubbing against the work
and heating excessively, and to allow the hot chips to
fly off readily. The amount of clearance varies with the
angle of the cutter. Use the following procedure to grind
A properly ground square-nose single-flute cutter
In the first step, gently feed the cutter into the face
of the wheel. Do not rotate the cutter. Hold the back
(round side) of the conical point against the wheel. Rock
square-nose cutters are ground, they should be tipped
the cutter continuously across the wheel's face, without
off in the same manner as described in connection with
turning it, until you grind a flat that runs out exactly at
peripheral clearances ground back of the cutting edge.
with a magnifying glass if necessary, to be sure you
After grinding the flat to center (easily checked with a
have reached the point with this flat. Be extremely
micrometer), grind the clearance by feeding the cutter
careful not to go beyond the point.
in the required amount toward the wheel and turning the
In the next step, grind away the rest of the stock on
cutter until you have removed all stock from the back
the back of the conical side to the angle of the flat, up
to the cutting edge. Rotate the conical side against the
face of the wheel and remove the stock, as shown in
the cutter too far and grind away part of the cutting edge.
Clean up all chatter marks. Be careful of the point; this
is where the cutting is done. If this point is incorrectly
ground, the cutter will not work.
TIPPING OFF THE CUTTER POINT.--To
engrave hairline letters up to 0.0005 inch in depth, you
should not flatten, or TIP OFF, the cutter point. For
ordinary work, however, you should flatten this point
as much as the work will permit. Otherwise, it is very
difficult to retain a keen edge with such a tine point, and
when the point wears down, the cutter will immediately
fail to cut cleanly. The usual way to tip off is to hold the
Figure 9-26.--Square-nose cutter with a properly ground tip.