A countersink is a cutter used to cut a conical hole into a manufactured object. It is commonly used to allow the head of a countersunk bolt, screw or rivet, when placed in the holes, 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 hence improve the finish of the product and remove any hazardous sharp edges. Countersinking is done to make the flat head screws sit flush to the workpiece.

Each of the indexable countersinks comes with a TiN coated carbide insert. The are TCMT32.51 triangle inserts and SCMT431 square inserts. When a cutting edge becomes dull, you just need to rotate the insert in the holder to use the sharp edge. When you buy the replacement inserts, be noted that the larger nose angles and larger tip radii enable a stronger cutting edge, but they result in increased vibration and a rougher finish.

Using the indexable countersinks with carbide inserts in the production environment, you can renew the cutting edge without removing the cutting tool by simply unclamping the insert and turning it (indexing) to a fresh cutting edge or removing the completely worn insert with a new one.

Comparison between Accusize countersinks