Drill a pilot hole and countersink or counterbore in one step. Precision machined out of thru-hardened alloy steel and heat-treated for long cutting life Our signature gold set screw securely holds the HSS twist drill without slippage and easily unscrews to adjust pilot depth or replace a dull bit. 1/4" hex power bit shank for use with Snappy Quick Change Chucks or any tool that accepts a 1/4" hex