| 摘要 |
[Problem] To provide a drill having excellent chip evacuation performance even in a machining condition resulting in a large amount of discharge. [Resolution Means] The drill (1) is provided with a drill body (2) having a rotation center axis (O), two cutting edges (3) provided on the tip side of the drill body (2), and chip evacuation flutes (10) provided behind the two cutting edges (3) in the direction of rotation of the drill (1) from each of the cutting edges, the drill tip angle (±) being from 170 to 190°, the web thickness (d) being from 0.10 to 0.25 times the drill diameter (D), the opening angle (³) of the chip evacuation flutes (10) being from 85 to 110°, and the drill (1) comprising a curve having a radius of curvature that gradually decreases from the cutting edge side wall surface (14) to the heel side wall surface (15) of the chip evacuation flutes (10) in a cross-section orthogonal to the rotation center axis (O) at a position at which the chip evacuation flutes (10) are present. |
