DRILL

摘要

[Problem] To provide a precise and inexpensive drill. [Solution] Instead of forming a chisel edge (11) on a tip end section (12), a polygonal pyramid shape (1) is formed in a manner such that an oblique angle (?1) defined from a drill centerline (CL) to edges (4) extending from a vertex (P) is greater than an angle (?2) which is 1/2 of a drill tip end angle (?0), so as to remove chisel stepping and thereby make stable machining possible and improve the precision of holes. In addition, since the polygonal pyramid shape (1) can be formed by grinding a tip end section of a conventional drill with a grinding plate, the polygonal pyramid shape (1) can be formed with lower costs.