| How To Make a Cabochon, page 5 by Paul W. Cinnamon Step #9: CUTTING THE DOME The first bevel cut should be at about a 45-degree angle around the top of the cabochon. Keep your cut even at all times by slowly rotating the cab as you cut, and visually inspecting it often. Cut until you have reached the top mark you made encircling the cab. A second even bevel is then cut at about 60 degrees around the top of the cab. Thus begins the domed top of the cabochon. Continue cutting until you have cut away most of the 45 degree cut. Next, cut another even bevel down to the center of the cab girdle at an approximate angle of 30-degrees. As you make this cut, adjust the angle appropriately and blend and round the edges of all the bevels until they are uniform and almost smoothly rounded toward what will become the center of the dome. As you do this you will note that you are continuously reducing the size of the crosshatch design that represents the flat area not yet domed. Your final bevel cut should be at a very slight angle, and should be smoothly and evenly rounded into the rounded top of the cab. Cut this slight bevel until you reach the line scribed approximately 1/4 of the way up from the bottom of the cab. Do not cut below this line, as doing so may cause the cab to be too loose in a standard mounting. Complete the doming the top of the cabochon with the coarse wheel until you have a smoothly rounded top with no flat place in the center. You will know when you have completed doming the top of the cab by watching the crosshatch pattern as it is gradually reduced in size. Continue to rotate the cab, gradually making the untouched portion smaller until all traces of the marks are removed. Inspect the cab and remove any marks or ridges that need to be removed. Also, be certain that all saw marks are removed from the center of the cab. A little extra time working on the center portion of the cab and smoothly blending it so that it uniformly rolls its curvature back toward the edges will save time later, because the deep scratches left from the saw are very difficult to see until the cab is almost completed. Step #10 FINISH GRINDING Change your water spray or drip to the next finer wheel, usually about a 220 grit, and completely go over the cab top and sides again leaving the area below the mark on the lower 1/4 of the cab untouched. Remove all the marks left by the coarse grit of the previous wheel. Complete removal of the deep furrows plowed by the coarse grit of the first cutting wheel will usually take more time than you think. Failure to properly perform this operation will come back to haunt you about the time when you get to the final sanding operation, or sometimes when you finish polishing and realize that a few light marks remain. STEP #11: SANDING THE CAB WITH 220 GRIT Moving to the next finer wheel, the cabochon is further smoothed and shaped by coarse sanding. This is usually done with about a 280 grit-sanding wheel. Be sure you uniformly cover the entire cab. At this step, I usually lightly sand off the line scribed about 1/4 of the way up from the bottom of the cab, uniformly blending and smoothing the entire top of the cab. STEP #12: SANDING WITH 600 GRIT Additional smoothing and close inspection for flaws and scratches is performed while sanding with the next wheel, usually a 600 grit. Usually a close inspection under magnification after 600-grit sanding will show any scratches left from insufficient sanding in the previous steps. Usually the only remedy is to go back and sand some more. Occasionally, you may have to go back to the 220-grinding wheel to remove the scratches, and repeat the entire interim sanding steps. STEP #13: SANDING WITH 1200 GRIT Next, sand with the 1200-grit wheel. Carefully inspect the cabochon for scratches left from previous wheels, and for uniform coverage of the sanding. STEP #14 PREPOLISHING THE CAB Pre-polish the cabochon by sanding with the 14,000-grit wheel. The cabochon should now appear virtually completed, however, for a super bright polish, one additional step can be performed. |