| 摘要 |
A drill in which a rake surface is provided with a negative land, and ridgelines at which the negative land and a flank, the flank and a margin, and the negative land and the margin intersect configure a convex surface in a longitudinal rectangular cross-section, wherein the curvature radius of a second ridgeline convex surface positioned where the flank and the margin intersect is 0.8-1.5 times the curvature radius of a first ridgeline convex surface positioned where the flank and the negative land intersect, and the curvature radius of a fourth ridgeline convex surface positioned where the negative land and the margin intersect is 1.5-3.0 times the curvature radius of the first ridgeline convex surface. |
