Machine Counterbore

An end cutting tool having two or more cutting edges with flutes or grooves for the passage of cuttings, an integral or removable holder designed for adaption to the end of a machine spindle. The flutes or grooves are usually helical to give a positive rake at the cutting edges. It is designed to form a flat-bottomed enlargement of the mouth of a previously formed cylindrical hole. For items requiring a holder but the holder is not included, use cutter, counterbore.