Gem faceting machine

Claim 1

A gem stone faceting machine having, in combination, a. a rotary lap whose active upper face is horizontally disposed, b. a stand alongside the lap, said stand including b1. an elevator and means for raising and lowering the elevator vertically, b2. a frame mounted on the elevator with freedom for limited rotary movement about a horizontal axis, b3. a rotatable gem supporting and facet spacing shaft mounted on the frame with its axis disposed at right angles to the frame axis, b4. a selectable settable gear-like member fast with the facet spacing shaft and having a number of equal tooth spaces, which number is suitable to provide all the forming positions required for faceting a particular gem or a multiple thereof, b5. a dop stick holder on the facet spacing shaft which is coaxial with the shaft, b6. means on the frame for fixing any selected tooth space of the gear-like member in a datum position for controlling orientation of the gem stone relative to the active face of the lap, b7. selectively usable circular index plates each constructed and arranged for securement on the facet spacing shaft in contact with a gear face, and each of a limited diameter which at least closely approches but does not exceed the diameter of a circle tangent to the bases of said tooth spaces, and each having a single simple marginal scale whose marks divide the plate circumferentially into equal parts sufficient in number to provide the facet positions actually required for the complete faceting of a particular gem stone, whether that number is equal to the number of index gear tooth spaces or a factor of the latter number, with the scale marks divided into identical groups of not more than four, by the large and clear consecutive numbering of marks at regular intervals, such that there will be a whole number of equal groups altogether, the intermediate marks of each group being varied in character according to a consistent plan, b8. means for removably securing the index plates individually upon the spacing shaft in fixed relation to the index gear as needed, c. a horizontal shaft forming a fixed part of the frame and mounted on the elevator with capacity for unrestricted rotary movement within a limited range, and which further includes c1. cooperative index means on the elevator and the scale plate for indicating, in a relatively coarse manner, the declination of the facet spacing shaft, and c2. an upwardly convex level, mounted on the shaft, of a high precision, tubular type of very large radius, having a bubble which can occupy any operative position stably, and means for fixing said cooperative index means and the level in any desired angular position relative to the shaft so that the grinding of a facet can be terminated with exactness when the bubble of the level reaches a predetermined position.