Figure 2-38.--Broaching a keyway on a gear.
keyway broach requires a bushing that will fit snugly
around the hole to be broached is perpendicular on
both the entry and exit sides.
in the hole of the part and has a rectangular slot in it to
slide the broach through. Shims of different
You will need a considerable amount of pressure
thicknesses are placed behind the broach to adjust the
to broach, so be sure the setup is rigid and all safety
precautions are strictly observed. Use a slow, even
pressure to push the broach through the part. That
A broach is a relatively expensive cutting tool and
will produce the most accurate and most safe results
is easily rendered useless if it is not used and handled
with the least damage to the broach. Do not bring the
properly. Like all other cutting tools, store it so no
broach back up through the hole, push it on through
and catch it with a soft cushion of some type. Use a
cutting edge is in contact with any object that could
lubricant to broach most metals. They help to cool the
chip or dull it. Preparation of the part to be broached
tool, wash away chips, and prevent particles from
is as important as the broaching operation itself.
galling or sticking to the teeth.
Make the size of the hole so the beginning pilot
section enters freely but does not allow the broach to
fall freely past the first cutting edge or tooth. If the
SCREW THREAD INSERTS
hole to be broached has flat sides opposite each other,
you need only to measure across them and allow for
A screw thread insert (called inserts for the
some error from drilling. The broach will sometimes
remainder of this section) is a helically wound coil
have the drill size printed on it. Be sure the area
designed to screw into an internally threaded hole and
2-20