PURPOSE: To improve the ability to dispose chips on finishing work by improving the configuration of breakers for throw away chip.

CONSTITUTION: Convex projections 14 are extended from a central land area 13 in breaker grooves 11 and the width of breaker grooves 15 on R sections 12 at the noses are substantially reduced, thereby improving the ability to dispose the chips on finishing cutting work. The projections 14 are lower than the central land area 13 by W3. Cutting edges 21 are also made lower than the plane of the projections by W2=W4=0.05mm, because the chips can be better disposed when the cutting edges are slightly lower than the pojections, with the same width of breaker grooves.