To fit a throw away chip for showing the sufficient breaker work even in case of a use in a drill main body having a remarkably narrow diameter by fitting a nearly elliptic throw away chip having two cutting blades at symmetrical positions in the circumferential direction to a peripheral side fitting seat.

This drill has fitting seats 10, 11 for respectively fitting throw away chips 1, 2 at two positions of a core side and a periphery side thereof. In such a drill main body 3, a nearly triangle throw away chip 1 having three cutting blades 1a-1c, which can be changed three times for use, in the circumferential direction with a constant space is fitted to the core side fitting seat 10. A nearly elliptic throw away chip 2 having two cutting blades 2a-2b at symmetrical positions in the circumferential direction is fitted to the periphery side fitting seat 11. Chip breakers 12a-12c, 13a-13b corresponding to each cutting blade 1a-1c, 2a-2b of both the throw away chips 1, 2 are provided.