Abstract: A high-speed forming tap (1) for cutting and forming a female screw by cutting edges (E) of a screw portion (2) fed in synchronous with the rotation of a machine tool. The high-speed forming tap is characterized in that chamfers (CF) are provided at a bevel lead (2a) of the screw part (2). The chamfers (CF) start from the cutting edge (E) and are provided along ridgelines (R) between a crest face (2e) and flanks, or a following flank (2c) and a leading flank (2d). This structure enables the shape of the edges of the tap leading portion to be stably maintained and high-speed, smooth female screw cutting with high accuracy, and provides a tap with long life.

Abstract: A ceramic material for use as a cutting tool in the high speed machining of high temperature alloys and cast irons is provided with a composition of beta prime sialon (Si.sub.6-z Al.sub.z O.sub.z N.sub.8-2 ; where 1<Z<3) and intergranular phase. The material has high wear resistance and reliability when used in the high speed machining of high temperature alloys at speeds of 300 to 1500 surface feet per minute.