A
countersink (symbol:
⌵) is a
conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt or screw, when placed in the hole, to sit flush with or below the surface of the surrounding material (by comparison, a
counterbore makes a flat-bottomed hole that might be used with a socket-head capscrew). A countersink may also be used to remove the
burr left from a drilling or
tapping operation thereby improving the finish of the product and removing any hazardous sharp edges.