| 摘要 |
PURPOSE:To improve tool rigidity by allowing an intermediate tapered part to intervene in a tip body part made of super-hard alloy and welding it to a large diameter straight shank part. CONSTITUTION:A turncated cone end 8 having a diameter gradually increased is formed on the rear end of the tip body part 2 of a small diameter drill 1. Further, a flute 6 does not reach this end 8, and forms a interrupted groove extending near the conical end. A straight shank part 3 facing this turncated cone has a truncated cone end 9 formed on its end part. These turncated cone ends 8, 9 are integrated with ease by welding without deteriorating tool rigidity due to thermal effect. |
