Insty-bit 82611 11/64" Hex Shank Taper Drill Bit & Countersink for #8 Screws Drills Precise Tapered Holes In Wood Adjustable Smooth Cutting 4-Flute Countersink Tapered HSS Drill Bit 1/4" Hex Shank (can be used with Insty-Bit quick change chuck # IB80138, sold separately) Install Screws Flush or Recessed in 3/8" counterbore