| 摘要 |
<p>1,206,937. Polishing gems. SPECTRUM DIAMONDS (PTY) Ltd. 28 Nov., 1967 [20 Dec., 19661, No. 56979/66. Heading B3D. A method of faceting a bruted gem stone held in a pot provided with a surrounding guide ring comprises forming a plurality of facets by polishing on a polishing surface and terminating the polishing of each facet when the ring contacts the polishing surface. A bruted stone is inserted into a cavity at the front end of a metal press pot a, Fig. 5, the pot wall around the cavity being axially slit to provide radially sprung fingers b, c, d which grip the stone around its girdle section. The pot is pre-inserted in the front end of a holder e, the front end having a pot holding cavity f surrounded by an inner metal sleeve g, an insulating sleeve h and an outer metal sleeve j. A tight fitting axially slidable metal guide ring k is provided. A first half facet 1a is then polished; when portion m of the facet and portion n of the pot have been polished away, lip I of the ring k contacts the polishing wheel and polishing is then terminated. The process is repeated, until facets 1a to 16a on the stone and facets 1b to 16b on the pot have been formed. Polishing then commences e.g. along line B, Fig. 4, to produce a first main facet 17a, polishing being terminated upon contact with the polishing wheel of the peak A2 formed on the pot during polishing of the half facets. The process is repeated until all main facets 17a to 24a have been formed. The machine may have an electric control system including means for automatically lifting the chuck off the wheel when the outer ring (when polishing half facets) or pot (when polishing main facets) contacts the wheel, and means for indexing the chuck about its axis, through 22¢ degrees for half facets and 45 degrees for main facets, after which the chuck is lowered towards the wheel. Alternatively, the circuit may only indicate when the outer ring or pot contacts the wheel. Alternatively, faceting is effected by visual inspection.</p> |
