| 摘要 |
PURPOSE:To heighten wear resistance and cutting efficiency, by embedding and fixing a very hard substance such as cubic boron nitride (CBN) and sintered polycrystalline diamond in a part of the cutting edge of a drill. CONSTITUTION:A straight drill 1 has a shank 2 and a cutting part 3 extending therefrom to the tip. A cutting edge 4 is provided on the tip of the cutting part 3. Two straight cutting edges 5 are provided on the peripheral surface of the cutting part 3 so that the straight cutting edges 5 extend to the tip of the part 3. A very hard substance 8, which is higher in hardness than a very hard alloy from which the cutting part 3 is made, is embedded and fixed in the cutting edge 4 on the tip and in a step 6 so that the outside surface of the very hard substance 8 is exposed. Since cutting is performed by the very hard substance 8 in the main, the lifetime of the drill 1 is long. |
