PART PREPARaTION GUIDE
INTERNAL BROACHING PART PREPARATION
Pre-Drill Hole Diameter:
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A pre-drill hole is required for internal broaching.
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The pre-drill hole must be at least equal to the minor diameter of the broach. It is strongly
recommended to open the hole diameter larger than the minor diameter.
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See below formulas for recommended pre-drill hole diameters of hex and square forms.
Pre-Drill Hole Depth:
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The depth of the pre-drill hole must be greater than the broaching depth to allow for chips to
accumulate and avoid excess packing.
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If chips must be removed after broaching, it can be done with a drill or boring tool. A recess at
the bottom of the pre-drill will allow the chips to break cleanly. The recess diameter should be
larger than the major diameter of the broach.
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It is recommended to have a pre-drill depth of 1.75 x depth of broached area.
Lead Chamfer:
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A 45° lead chamfer must be provided for successful internal rotary broaching, going from the
major diameter to the minor diameter of the form.
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