Countersinking is used to ensure screws and bolts lay flush with the surface.

Countersinking is the process of cutting a cone-shaped hole in a manufactured object. It is commonly used in the machining and manufacturing industries, for a variety of reasons. There are a number of different tools commonly employed to cut these holes.

Countersinking is often used for ensuring any screws, rivets, or bolts that are used become flush with the surface. This can be done for aerodynamic reasons, or strictly for aesthetic purposes. These holes are often made using specially formed drill bits.

Countersinking tools can also be used for other purposes. A cross-bore countersink cutter, for instance, is used for removing any burrs that might remain after the machining process. A fluted countersink cutter is often used to create a chamfer inside an existing hole.