| 摘要 |
1,161,863. Making twist drills and the like; extruding; drills. ROHDE & DÍRRENBERG. 23 April, 1968 [9 May, 1967], No. 19036/68. Headings B3A, B3C and B3P. A method of making twist drills or the like having internal liquid channels comprises providing a tool blank with at least one longitudinal bore traversing at least the intended cutter member, the bore being filled with a material whose melting temperature is higher than the deformation temperature of the tool blank material, heating the cutter member of the tool blank to deformation temperature and forming the cutter member in a non-cutting operation, removing the filler material and finishing the tool in a conventional manner. The tool blank may be made either in one piece or as a shank portion 2b welded to a cutter part 2a. Preferably the blank is made shorter and of greater diameter than the finished tool. The one piece blank (1) comprises cutter and shank portions and is drilled straight through, Fig. 1 (not shown). Alternatively blind bores may be drilled. The channels in the blank may be interconnected either by a recess at one end or by a transverse bore, the bore or bores in the shank member interconnecting therewith. The parts 2a, 2b are welded together after the bores have been filled with filler material. If the bores in the shank and cutter parts are continuous, then they may be made after the parts have been welded together. The cutting grooves in the case of a twist drill are formed by profiled rollers or in a die 10. For rolling, the open ends of the bores are first sealed, but when extruding, the ram of the die effectively seals the bores. The profiled blanks are hardened in known manner by insertion, cutter portion downwards, into a salt bath. The filler melts progressively upwardly, with consequent increase in pressure until still solid end portions are driven out. The end of the portion 2a is removed to expose the bores and a cutting edge is ground on to the tip. Alternatively the filler may be removed before or after hardening by a suitable solvent. |
