3Pcs Countersink Drill Bits 5 Flute 90 Degree Chamfering Countersink Drill Bit Set with 1/4″ Hex Shank Woodworking Chamfer Drilling Tool Carbon Steel 12mm/16mm/19mm. With 1/4″ hex shank, This countersink drill bit fits most handheld and stationary drills.2.