| 摘要 |
PROBLEM TO BE SOLVED: To lengthen the service life due to abrasion by a diamond layer, and prevent breakage of a drilling tip rear end where a base material is exposed, while securing crushing performance of a drilling tip.SOLUTION: A gauge surface 2 inclining to the rear end side toward the outer peripheral side is formed on the tip part outer periphery of a bit body 1, and a face surface 3 turning to the tip side is formed on a tip surface of the bit body 1 on the inner peripheral side more than the gauge surface 2, and at least two-stage convex curved surface parts 9A and 9B forming a convex curved shape of becoming gradually small in a radius of curvature toward the tip side in a cross section along the tip center line C extending toward the tip side, are formed in a tip part projecting from the face surface 3 of the drilling tip 8 implanted in the face surface 3, and a diamond layer 10 harder than a base material 11 of the drilling tip 8, is formed on a surface of the convex curved surface part 9A of a stage on at least the forefront tip. |
