| 摘要 |
An insert for a drill is provided which is capable of being detachably attached to an axial line (O) side and an outer circumferential side of a tip portion of a drill main body (11) rotated around an axial line (O), in which cutting edges (3) are formed on ridge portions of a polygonal face in a drill rotation direction of a polygonal flat plate-shaped insert body (1) such that rotation trajectories around the axial line (O) toward a tip side of the drill main body (11) overlap each other when viewed in an axial line (O) direction, and a land (8) is provided on each of the cutting edges (3). The insert is formed such that, when the insert is attached to the drill main body (11), a land angle of the land (8) gradually increases to a negative angle side from one end portion (3A) of the cutting edge (3) positioned on an outer circumferential side of the drill main body (11) toward the other end portion (3B) side of the cutting edge (3), and a land width of the land (8) gradually increases from the one end portion (3A) of the cutting edge (3) toward the other end portion (3B) side. |
