| 摘要 |
PURPOSE:To raise the dimensional precision in processing a hole and improve the abrasion resistance of a drill by forming a layer of hard coating with a specific thickness at least on the rake face of the groove face for the surface of a drill body except the major flank and the margin section. CONSTITUTION:A layer 4 of hard coating with a thickness of 0.3-20mum is formed at least on the inner rake face 1 of the groove face 8 for the surface of a drill body 6 except the major flank 2 and the margin section 3 in order to improve the abrasion resistance. According to this constitution, the margin section 3 of the drill is not coated, therefore, the dimensional precision such as the size of the drill outer diameter and the longitudinal clearance angle theta can be assured by grinding, and since the major flank 2 is also not coated, the sharpness of the cutting edge crossing the rake face 1 can be assured. |
