| 摘要 |
[Problem] To provide a drill which enables a great reduction in cutting resistance and easy performance of a drilling operation by human power using a hand drill, a drilling machine, or the like. [Solution] A drill has two cutting edges formed symmetrically with respect to a rotation axis, and is subjected to thinning at the tip thereof. The cutting edge is configured from a thinned cutting edge (1) which extends in a shape including a curved line from a chisel edge to the outer peripheral side of the drill, and a main cutting edge (2) which extends from the end of the thinned cutting edge to the outer peripheral end of the drill when viewed from the tip side of the drill, and a thinned surface formed by the thinned cutting edge is formed into an approximately parabolic shape inclined in a drill axis direction when viewed from the front side of the drill. |
