| 摘要 |
PURPOSE:To make it possible to drill a steel object by taking off a hard coating layer of a cutting face of a gun drill, which is made by forming a hard coating on the surface of a carbide tip, so as to make the cutting face to be a cemented carbide metal surface, and generating a moderate frictional resistance in a flow of chips. CONSTITUTION:A cutter which is formed of the inner edge 4a and the outer edge 4b, the margin 5, a pad 6, an oil hole 7, and a V-shaped groove 8 are formed in a carbide tip 3 which is connected to a shank 2. A hard coating layer 11 of such as TiN, TiCN, TiC, or Al2O3, is formed on the outer circumferential surface of the tip 3 except a cutting face 9, and on a front surface of relief 10, as to be about 5mu in thickness, in such as a PVD-method. After that, the coating on the cutting face 9 is taken off by polishing or in any other way, and the cutting face 9 is made to be a metal surface. |
