Use of Individual Push-Type Keyways Broaches or Keyways Broaches from a Broach Set requires the use of a Bushing and Shim(s). The Bushing size and Style are determined by the bore diameter of the workpiece as well as the Style of Broach to be used. “A” Style Broaches are used with “A” Style Bushings, “B” Style Broaches with “B” Style Bushings, etc. The smallest Broaches cut in one pass and require no Shim. Multiple pass Keyway Broaches are furnished with all necessary Shim(s) unless otherwise noted. A Shim is required to compensate for the thickness removed following a Keyway Broach’s cutting pass. The addition of a Shim to the bottom of the bushing’s slot serves to move the Broach forward towards its standard finished cutting depth. Subsequent passes require the stacking of Shims. To insure proper support the length of cut must never exceed the length of the bushing being used. All individual stock Broaches have recommended Minimum and Maximum Length of Cut guidelines which should be followed. Workpieces may be stacked to establish the Minimum Length of Cut, or to improve the efficiency of the operation as long as the Maximum Length of Cut is not exceeded. Proper nesting and clamping of stacked parts is vital when this approach is taken. The workpiece must be solidly fixed or nested perfectly square with the baseplate and ram face. Make sure all square and parallel surfaces on the face of the ram and baseplate remain true. It is essential to maintain a rigid set-up at all times and caution should be taken when stacking parts to maintain the integrity of the set-up. Never attempt to exceed the Broach’s specified Maximum Length of Cut. Do not use a dull Broach, this may result in poor finish or damage to part and increases the danger of breakage. At the beginning of a cut, be sure the Broach is centered under the ram. Proper alignment is important. After the Broach starts to cut, back off pressure on the ram allowing the Broach to center itself, providing for better alignment. If the Broach moves out of alignment after starting cut, back off the pressure on the ram and align the broach itself. Repeat this procedure during successive cuts. This will assure a perfectly straight broached hole.
- Select the right Bushing for the bore (sizes are plainly marked) and insert in the bore of workpiece.
- Insert Broach (which is also plainly marked for size) into the Bushing slot and check alignment.
- Place this assembly in the press, be sure the Broach is centered under the ram.
- Apply pressure to the Broach – back off pressure on the ram allowing the Broach to center itself, providing for better alignment. If the Broach moves out of alignment after starting cut, back off the pressure on the ram and align the broach itself – reapply pressure to push Broach through the work.
- Clean Broach using a stiff brush to remove chips from cutting section.
- Insert Shim and repeat steps 3 thru 6 as required to obtain exact keyway depth.