GB577249A - Method of producing dies by powdered metallurgy - Google Patents

Abstract

577,249. Sliding-clasp fastenings. PLASCO, Ltd. April 15, 1944, No. 6996. Convention date, March 24, 1943. [Class 44] [Also in Groups II and XXII] Dies for casting the links 11, Fig. 2, of sliding-clasp fasteners, are made from an original pattern die by die casting or pressing metal powder to form a negative of the impression surface thereof, and using this negative to form a pressed powdered-metal positive. The link 11 shown combines a male part 16 and corresponding female part 17 so that both sides are identical and the dies to form them comprise two identical parts 20, Fig. 1. Knobs 18 and corresponding holes or recesses may also be formed in the links, the latter by a core 19 inserted through recesses 25 of the dies 20, Fig. 3, and the former by projections 29. The surfaces 30, of the original pattern die are milled away to leave raised walls 27, 28 which are reproduced in the final dies, thus avoiding fins on the cast links 11. One of these original die parts 20 is mounted on a backing 31, Fig. 6, so that its impression face 21 forms part of a mould cavity into which zinc alloy, silicon bronze &c. 38 is cast. This casting may be brazed or otherwise fixed to a plunger 39, Fig. 8, of the same cross section which is then forced into a housing 40 containing metal powder 41 resting on an ejector 42. The separated pressing 41 is then sintered, hardened, and, if required, polished to form a final die. If 'the pressing is to be handled much the casting 38 is not fixed to the plunger 39 but is removed from the housing 40 with the pressing and placed in the sintering furnace where the part 38 melts as it has a lower melting point than the pressing 41. If the negative is formed from metal powder it may be done as in the case of the final die.