Correct broach horn design

Insures Good Keyways and Longer Broach Life

Quality broaches, such as those produced by Colonial, are the first requirement for complete success in keyway broaching. However, no broach will perform at its best unless it is used with a properly designed broach horn. The few simple principles of correct horn design given bellow will, if carefully followed, give you the greatest output from your Colonial keyway broaches.

The function of the horn is to locate the part in relation to the broach and to support the broach. Broaching pressures are restricted to the part. Equal and opposite pressures are generated in the broach itself. Because of this, it is most important to provide adequate support for the bottom of the broach at the point where the teeth enter the cut. Figure-1 shows the results of incorrect horn design; varying keyway depth, and as the broach dulls, tool breakage.

Figure-2 shows a method of determining the proper length of support required in front of the part to eliminate broach flexing during the cutting stroke. Note that this portion of the horn can be reduced in diameter to provide a pilot for easier part loading.

Using the parameters given here, the design of adequate broach horns for keyway broaching should present no problem. Colonial also designs and builds broach horns of various types to suit customer requirements. In addition, Colonial can provide threaded type broach pullers to give you a single source for all your keyway broaching requirements.

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