| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill having improved straight advancement stability during drilling.SOLUTION: A drill 1 comprises a body part 20 and a cylindrical cutting part 10. The cutting part 10 includes a cutting edge 11 positioned at a tip part 10a, a flank 14 continuous to the cutting edge 11, and a groove 12 continuous to the cutting edge 11 at the opposite side of the flank 14 in tip view with reference to the cutting edge 11 and extending helically toward a rear end part 10b. The flank 14 includes an auxiliary flank 14c positioned at the opposite side of an end part 111 at an outer side of the cutting edge 11 in tip view with reference to a rotation axis O. A ridge line 14c1 at an outer circumferential side of the auxiliary flank 14c is a linear shape or a curved shape that is convex toward the tip side in side view. |
