Loading... Please wait...A high quality 7/16" drill bit for drilling the differential housing, prior to tapping a 1/4" BSPF (19 tpi) thread, for the air fitting needed when installing an air locker. This dril has three ground flats on the shank to prevent spinning in the drill chuck. The corresponding tap is Tap - 1/4" BSPF (19tpi) - Differential Casing (for air locker).