Countersink Bit, 3-Flute, Non-Piloted, 100 Degree, 0.250" Diameter, 1.750" OAL, 0.187" Shank

Countersinks expand the top of an existing hole in a workpiece to allow countersinking screws to install flush with the surface of the workpiece. This helps prevent the workpiece material from swelling when a screw is inserted in the hole and tightened down. They can also be used to debur holes for a smooth finish.