| 摘要 |
PCT No. PCT/SE88/00178 Sec. 371 Date Nov. 13, 1989 Sec. 102(e) Date Nov. 13, 1989 PCT Filed Apr. 8, 1988 PCT Pub. No. WO88/07905 PCT Pub. Date Oct. 20, 1988.A drill produced from a substantially rod-like blank containing high speed steel has at one end thereof a pointed tip which is intended to penetrate the material to be drilled. The drill is preferably a helical drill having edge parts which extend essentially from the outer part of the drill tip to the periphery of the drill cross-section, and further includes a radially open groove which extends helically along the drill, for the purpose of removing chippings from the drill. The drill is particularly characterized in that the blank, and therewith also the drill, in cross-section includes a central steel part, which is intended to exhibit high compressive stength, and which therewith forms the outer part of the drill tip, and a concentrical outer layer of high-speed steel which is intended to exhibit high thermal stability and which is applied with the aid of a casting technique. |
