| 摘要 |
Provided is a drill suitable for high-efficiency working. A cut debris discharge groove (2) is formed in the outer periphery of the front end section of a drill body (1) rotated about the axis (O), and a cutting edge is formed at the front end of the drill body (1). The wall surface (2A) of the cut debris discharge groove (2), which faces the rotational direction (T) of the drill, is formed to have a concave curve line shape in a cross-section perpendicular to the axis (O), the concave curve line shape extending along a first circular arc (C1). The bottom surface (2C) of the cut debris discharge groove (2), which continues to the wall surface (2A) and which faces the outer peripheral side of the drill body (1), is formed to have a concave curve line shape in a cross-section perpendicular to the axis (O), the concave curve line shape extending along a second circular arc (C2) circumscribing a core diameter circle (E) at the front end section of the drill body (1). The first circular arc (C1) has a greater radius than the second circular arc (C2) and is in contact with the second circular arc (C2) at a position closer to the leading edge (1A) side than the point (P) of contact between the second circular arc (C2) and the core diameter circle (E). |
