Pilot hole diameter: Pilot holes are required for internal broaching. The pilot hole diameter must be at least equal to the "Across Flats" dimension of the internal broach. Often, hexagon holes are not required to be "full form". In these cases, a larger pilot hole will reduce the required broaching pressure. Click here to see the chart for recommended pilot hole sizes for standard Slater Tool broaches.

Pilot hole depth: The pilot hole depth must be greater than the depth to be broached. It must be deep enough to allow for chips to accumulate without excessive packing. If the chips must be removed, this can be done after broaching with a drill or boring tool. A recess at the bottom of the pilot hole will allow the chips to break cleanly. The recess diameter should be larger than the "Across Corners" dimension of the broach.