SECTION 5.9

One of the most common occurrences which causes a need for reconditioning broach cutting tools is galling, or metal pick-up on the broach tool. Gall appears as a dull spotting on the sides of broach teeth when viewed under a bright light. Galling is usually caused by an inferior grade of part material, or contaminated coolant. If left unchecked, galling can compound until part quality suffers, or broach splines and/or teeth become welded together.

Galling is usually removed by hand and, although a tedious job, it is very critical process. First, a coarse stone is used to remove the heavy gall. One side at a time, front to back, the entire broach must be gone over and stoned. (When degalling, care must be taken with the hard stone so the cutting corners of the tooth are not rounded.) Second, a rubberized emery is used to clean and polish the sides of the teeth. The rubber takes the shape of a spline tooth form so that both sides can be completed at the same time. All the existing gall must be removed or else the broach tool will immediately begin to pick up new gall!