Patent ID: 8197163

Claim:
A drill comprising: a drill body having at a tip thereof a plurality of installation points; and a plurality of the indexable inserts each comprising: a plurality of cutting edges provided at an upper face of the indexable insert; a chip breaker provided along each of the cutting edges; and at least one recess provided at the chip breaker, the recess extending from a portion of the chip breaker near the cutting edge toward a center hole of the insert, wherein the recess is retracted from an end of the chip breaker near the cutting edge toward the center of the insert by 0.2 mm or greater, or the recess communicates with or penetrates to the center hole of the insert, and wherein the recess is located in an area distant from an insert edge used as a peripheral cutting edge or as an inner cutting edge by 25% to 60% of an insert width, wherein the indexable inserts are respectively attached to the plurality of installation points with different installation distances to the drill center such that the upper faces with the chip breakers serve as rake faces, and wherein the indexable inserts share a cutting area extending from the drill center to the periphery of the drill to perform cutting.