| 摘要 |
In the drill tip of the present invention, the tip body of the drill tip has a cylindrical or disc-shaped rear end part, an intermediate part having a smaller outside diameter than that of the rear end part, and a leading end part in which the outer diameter gradually decreases from the centerline of the tip toward the leading end. The tip body is covered by a hard layer from the surface of the leading end part of the tip body to the outer periphery of the intermediate part. The outside diameter of the hard layer at the intermediate part is equal to the outside diameter of the rear end part. |
