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. Drill bit countersinks allow users to both drill a hole and countersink the top of the hole with one tool. Center drills have a pilot drill and a countersink and are used to create holes at the center of a piece of stock so it can be turned between centers on a lathe. The pilot drill creates a small hole in the stock and the countersink expands the hole, leaving a small gap at the bottom of the hole that helps protect the lathe's centers from damage when the stock is turned on it. The flute or tip style of the countersink or center drill can optimize the tool's performance in different materials or metalworking applications.