Cabochons, also known as cabs, are flat-backed semi-precious or precious gemstones with rounded tops. These stones are cut to specific sizes and shapes, polished and fit into settings for pendants, bracelets, earrings, rings and other pieces of fine jewellery. The right tools can greatly simplify the process of cutting, shaping and polishing these stones.
A lapidary template resembles a stencil with different shapes and sizes of cabochons on it. It allows jewellers to calibrate their stones into standard setting shapes and sizes. Most lapidary templates feature other measurements as well, including millimetre and centimetre scales. The cabochon template cutouts range from 10 by 8 millimetres on the small end and 24 by 10mm on the larger end of the spectrum, though sizes may vary from template to template.
A trim saw uses a diamond blade lubricated with coolant to cut basic shapes in stone slabs. Such a saw will allow you to create the basic shape of your cabochon prior to smoothing and polishing. Run the coolant before you begin cutting, as this will keep the diamond blade free from any debris. An alternative to using a trim saw is a machine called a diamond band saw, which creates a similar rough or basic shape. Accurate cutting using one of these machines will minimise the amount of grinding necessary.
Grinders and Shapers
These machines smooth out rough edges to create the desired shape. They have a grid surface that you can place the cabochon on, and then you will slowly move the cabochon into the head of the grinding machine while it runs. Rub the cabochon back and forth to create a rounder, smoother shape than before. The cabochon should still be approximately 1/16 inches larger than the desired final product at this stage in the process.
DOP Pot and Stick
A DOP pot contains wax that you will bring to temperature, then use to secure a stick to the back of the cabochon. This creates a handle on the back of your cabochon that you can use for the remainder of the shaping and polishing process. The most common type of DOP stick is a 4- or 5-inch wooden dowel.
Flat Lap Machine
The flat lap machine is effective both for creating the "dome" shape of the cabochon and the basic polishing process. You begin with heavier grit diamond lap, and then slowly fine-tune the grit until you have the desired shape. How you hold and grind the cabochon on the machine will impact the finished shape. The grinding will be rough until you finish the polishing process, typically with a 325 grit lap. You may need to graduate to the 600 grid lap and the 1200 grit lap to get a completely smooth polish.
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