To perform excellent finish cutting machining even when a tip mounting attitude deviates.
At the corner part 14 of a tip upper surface, a main cutting edge 13 is formed on one side of a corner blade 15 and an auxiliary cutting edge 16 on the other side. The corner blade 15 is parallel to a tip under surface, the clearance angle of a corner blade first flank 21 is varied and gradually changed such that a central part is negative and the angles at two ends are brought into 15°. The auxiliary blade 16 is gradually increased in height throughout a portion extending from a connection point (a) to the main cutting edge 13 to a connection point (d) to the corner blade 15, and formed approximately in an arcuate shape where a protrusion toward the outside is formed in a plan. An auxiliary cutting edge first flank has a clearance angle varied and gradually increased throughout a portion extending from the corner blade first flank 21 to the connection point (a) and forming a positive clearance angle. When a tip is mounted on a cutter, the auxiliary cutting blade 16 forms a face cutting edge.
NAGAYA HIDEHIKO
HAYASHIZAKI HIROAKI
