GB476781A - Apparatus for producing diamond boring bits or the like - Google Patents

Abstract

476,781. Making diamond tools. McCLINTOCK, R. S. Jan. 25, 1937, No. 2149. Convention date, June 16, 1936. [Classes 83 (i) and 83 (ii)] Casting composite articles; costing-machines ; moulds ; cores.-Diamonds D to be set in diamond cutting tools, particularly boring bits, are inserted in holes 11b, Fig. 2, pricked or punched in a pattern-holder 11, e.g. a mica disc supported upon a perforated plate 7 closing a vacuum chamber 2, and are retained in position by suction before and during the formation of the bit by pouring molten metal into the mould 13. The plate 7 is provided with a pin 9 for centring the mica pattern-holder and a carbon core 10 which forms a central passage in the finished bit B, Fig. 1, and rests on gasket material 6 in the countersunk top of the vacuum chamber. Upon the plate 7 are superposed annular portions 12 and 13 forming the mould, an annular cup 14, and a feed cup 15 with a perforated bottom to distribute uniformly the molten metal, all being countersunk and flanged as shown to engage one another. The casting may be sandblasted to expose the diamonds to a greater extent, and may be finished on a lathe. The mould may be modified, by the provision of co-operating passages in the carbon core and pin 9, and in the plate 7, mica disc 11, and ring 12, opening into the vacuum chamber 2 to produce a tubular bit with diamond cutters in the interior and exterior walls. The perforated plate 7 may have an annularly grooved or knurled upper surface, or radial grooves and a single annular groove may be provided. Alternatively, an annular depression 7b, Fig. 15, may be provided, small pieces 11c of mica retained by suction being used as pattern-holders. By using modified moulds, tools in the form of solid cylinders or rectangular prisms may be cast with diamonds in one end face, or a portion of a rotary saw in the form of a sector of a circular disc with diamonds set in its periphery.