Cutting and Setting Cabochon
Stones
Cutting and Setting Cabochon
StonesA Cabochon is a round-top stone that is cut to rest in a bezel setting. It has no facets, though it is sometimes cut to have one smooth edge to accentuate the stone's assets. Cabochons are the most versatile of stone cuts as they can be either a common size and shape, such as round, oval, or square, or they can be cut freeform. Contemporary cuts can be added to cabochons to give them some uniqueness, such as: faceted or plane areas, channels, plateaus, dimples, convex or concave surfaces, and even frosting or rough faceting.
There are four basic steps to cutting a cabochon stone:
These are the steps used for cutting or "cabbing" the stones.
Before you even start cutting, however, you must take the raw stone material and slice it into "slabs". This requires a study of the basic rock to decide which cut would be the most adventageous to the assets and flaws of the stone. Once this is determined, you can take your slabbing saw and cut slice that are 1/4" to 3/8" in thickness. When you have a slab, take time to study the stone to look for flaws that will inhibit your ability to use this stone for jewelry. Does it have pits? Unhealed cracks? Pockets of air? Flaws that look like they might shatter?
Once you have determined that your slab is useable, set it aside and cut out a template that is the shape of the stone you wish to use. By using the template, you can look at the entire stone to decide which cut will be the most adventageous to your finished piece. It's always good to take advantage of striations, mineral deposits, and other unique characteristics of your stone. Remember that you will see something different every time you look at the stone, and others will see things that are different than you. Make your best judgement based on what you know from your sketches of the piece you're planning. Once you have found an area of the stone you feel best fits your piece, take your stylus and trace the shape from your template onto the stone.
With your shape now outlined
on your stone, take your stonecutting saw and carefully cut about half an inch
around the basic shape you've drawn.
This will allow room for mistakes or chips should that occur during sawing
or stonecutting. Once you have your basic stone cut, you can move to the
sanders.
The sanding wheels come in a variety of grits ranging from 180-220 up to 12000. "Grit" is the amount of sand or dust on the sandpaper per square inch. Begin with the largest grit of 180. (Be careful! If you're using a soft stone, this grit will chew right through it, so you may need to skip this largest of grits for softer stones!) Get your wheel spinning, and hold the large, flat sides of the stone so that the edge is at a 90 degree angle to the wheel. The first goal is to cut a flat-edged stone that is the same shape as your outline. Take your time to cut out this shape. It should be similar to a flat medallion when you've finished this step if you've done it right, all angles from the top to bottom being at 90 degrees.
Move to the next sanding wheel, which should be 400 grit (For softer stones, start here with the same steps as above). Now you're going to start taking off the top edge at 45 degree angles very carefully. You want to get the sharp corners off at this point, but you will not get a smooth, final surface with this rougher grit. Turning the stone with a consistant amount of pressure at all times, you will sand down the sharp corners on the top side of the stone until you're left with only a flat surface around the lower edge (about 1/16") and a small flat area on the top of the stone.
The next grit should be 600 grit sandpaper. Now you're going to work on smoothing out the surface of your cabochon. Gently rock the stone back and forth, sanding the entire surface from top to bottom, and then from side to side. Run your fingers over the stone to see if you're getting all the 'flats' out. You should end up with a nice, rounded dome on the top of your stone. Take a moment at this point to delicately sand down the flat edge of your stone with a very, very tiny 45 degree flat on the sharp edge of the underside of the stone. This will allow your stone to sit flat in the bezel setting later, allowing room for extra solder that will occur.
Now move to the 12000 grit
diamond dust paper. This is the first step in polishing and will work out any
final flaws in the cabochon if done
correctly. Resume the rocking motions with the stone, making sure that
all surfaces of the stone come in contact with the sanding wheel. The smooth,
slick surface of the stone is your goal. If you don't feel this, then keep going
until the surface is smooth and slick.
The final process is buffing.
This is done with a wheel covered in sueded leather. Take a small amount of
tin oxide, mix it with water, and paint this onto the spinning buffing wheel.
Keep water nearby to spray on the wheel if it dries out. Again put the domed
side of your stone against the wheel, working to get an even polish over the
stone with even pressure.
Make sure to polish the flat edges as they may show once your stone is set.
It is not necessary to polish the flat back of the stone unless your setting
will be showing that side of the cabochon. Your cabochon should shine in the
light as if it was wet when your polishing is done correctly.
References:
Written by Journeyman Essei, SouCon MUSH
Emblems are copyright of Anne McCaffrey and drawn by Belan.