SECTION 5.8

In most cases, it is important to remove sharpening burrs. This can most easily be accomplished with a wire brush wheel. The wire wheel should be about 3" in diameter with 0.008" diameter wires. The wheel should then be loaded onto a hand-held pneumatic tool and operated at around 17,000 RPM. The operator should begin deburring from the back end of the broach and then proceed toward the front. The rotation of the wire wheel should be such that the bristles pass over the teeth from the back side. This prevents the dulling or damaging of the cutting edge. After deburring, the broach should be washed in mineral spirits to remove all loose burrs and grinding grit.

With the arrival of new high-speed metallurgies (especially particle metal), grinding burrs are increasingly more difficult to remove with the conventional brushing method. The malleability of the steel causes the burr to be pushed over the cutting edge by the wire brush, only to be pushed back after a part has been broached. If the burrs cause streaks or tearing in the part, the broach may have to be sent back to the sharpener for a repeat of the polishing operation, this time using a fine mist to quench the burr as it is formed. The burr will then become brittle, thus making it easier to be removed by the wire brush. A light application with a fine grit Arkansas stone may also help remove the burrs.

Another method of removing sharpening or grinding burrs is vapor blasting. With this process a very fine granular mixture of abrasives is blasted on the back side of the broach teeth. Vapor blasting is the most effective way of removing burrs. However, blasting also removes the acute sharpness of the cutting teeth. The broach should be placed between centers and rotated at 10 to 15 RPM to allow a uniform blasting. The broach must be cleaned with a light oil or mineral spirits to remove the blast grit and powder.