| After determining the desired shape of the cut stone (John Bailey’s Fast Bright Emerald cut) I ground a flat on the side of the stone where the table will be. After several attempts, the aluminum dop stick was centered on the flat side of the peridot, held with slowly cooling black dop wax. For reasons I do not understand, the use of foul language is apparently essential to success in this procedure. |
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| Setting the angle on the quill to 90 degrees, and the index at 96, I inserted the dop in the collet of the quill. Since the rough is already rectangular, I want to align the long sides with the long sides of the finished gem. At this point the dop is free to rotate within the collet.Sudden moves from this point on can knock the stone off the dop and force me to start over. Sudden moves should therefore be avoided. |
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| With great care, I use the Eyeball Mark 1 Semiprecision Measuring Device to get the stone aligned as near parallel to the surface of the lap as possible. When I am convinced that I can do no better, I tighten the collet to lock the dop in place.Time to start cutting. |
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| Being a beginner, I don’t trust myself to properly charge my own laps, so I use pre-charged aluminum laps. At this stage of the game, who needs the complication? Even though this is a small stone, the culet cuts will be removing a fair amount of material, so I am using a 600-grit lap to start. After starting the lap spinning at a fairly slow speed, I start the water drip and use a finger to evenly wet the lap. DO NOT press on the lap, it will grind your finger away! |
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| With this faceting machine, I can use a hard stop to set the cutting angle to within perhaps a quarter of a degree. Here it is set to 90 degrees, but I want about 40 degrees for the culet cuts. The brass stop puts me close, and a set screw gives me a fine adjustment spanning about 3 degrees. A simple and effective system, but I can not cut a pattern that requires precision to the nearest 1/100th degree. |
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| Adjusting the cutting height is equally simple. The quill assembly slides up and down a cylindrical mast. Its descent is stopped by a ring with a set screw to hold it in place. The ring has a nut threaded on it, which permits fine adjustments over a range of about 1 centimeter. The knurled ring I am holding in this picture is the fine adjustment nut. |
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| The actual cutting is a simple matter of setting the angle stop, the index, and the height, then gently lower the stone to the spinning lap. GENTLY press the stone into the lap until the quill meets the angle stop. It is best to start with the height adjusted a bit higher than you expect to finish. Then it is cut and look, then lower the height slightly and repeat until you have cut to the depth you want. |
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| Opposing facets of the same row are symmetrical, so I can simply flip the stone by changing to the opposite index (from 96 to 48, for example) and cut to the angle stop again. When I do this, I do not change the height or angle. This gives me two perfectly symmetrical facets for half the work. |
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| As I mentioned before, my machine does not allow extreme precision, so after cutting the culet and any other preforming, I like to switch to the prepolish grit to cut the rest of the facets. It takes a bit longer, but I don’t have to worry about trying to precisely match cutting angles, or leave room to recut with a finer grit. As I gain experience, I may change this practice. |
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| After cutting all of the pavilion facets in the recommended sequence, usually working from culet to girdle, the pavilion is ready to polish. |
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