PURPOSE: To cut a chip apt to be long and continuous into fine pieces for efficient disposal to ensure smooth machining by forming on a cutting face a protruding shape chip breaker lifted up from this cutting face.

CONSTITUTION: On one peripheral surface 1B of mutually adjoining peripheral surfaces 1B, 1B of a tip main body 1 exhibiting a nearly equilateral triangular flat plate shape, a cutting face 3 continuous to a cross ridge line part with the other peripheral surface 1B is formed, while a flank 4 swelling in a chevron shape is formed on the other peripheral surface 1B. A triangular shape cutting edge 5 protruding to the outside of the tip main body 1 is formed on a cross ridge line part between the cutting face 3 and the flank 4. On this cutting face 3, a chip breaker 6 is formed at a position a little apart from the cutting edge 5, and a chip rubbing and passing on the cutting face 3 is curled small and cut into fine pieces by this chip breaker 6.