| 摘要 |
PURPOSE:To permit stable cutting even with a small diameter tool by fixedly attaching a plurality of hard sintered tips such that the direction of thickness coincides with the radial direction of a main body and the circumferential surface is provided longitudinally of the main body with straight or torsional grooves to provide a cutting edges. CONSTITUTION:A round rod-like tool body 10 made of steel or sintered hard alloy is formed on the outer periphery of the end with grooves 11 having a certain pitch, and hard sintered tips 12 respectively insert one portions in the grooves 11 to make the direction of thickness coincide with the radial direction of the tool body and are fixedly attached to said body by soldering or the like. Also, the surface 12a of the tip 12 projecting from the outer periphery of the body is bent circumferentially to be concentric with the body. The end of the surface 12a is slanted forward downward to be smoothly introduced into an underhole. Further the tip 12 is provided on the surface with a plurality of torsional grooves 12b extending longitudinally of the tool body to provide cutting edges 12c in the intersection of the groove 12b, tip side and surface 12a. Thus, since the cutting edges and chip pockets are formed by the grooves, stable cutting can be provided even by a small diameter tool without any damages or the like. |
