What Is a Cabbing Machine? | How It Shapes Cabochon Gems

A cabbing machine is a lapidary tool used to grind, shape, sand, and polish rough stone into smooth, domed cabochons for jewelry making.

If you have ever admired a smooth, rounded gemstone in a ring or pendant—with no sharp edges or faceted cuts—you were looking at a cabochon. The machine that creates it is called a cabbing machine (short for cabochon machine), the centerpiece of a lapidary workshop that turns jagged rock and stone slabs into finished gems. Unlike a faceting machine, which cuts precise geometric facets, a cabbing machine produces the soft, polished dome that gives cabochons their classic look.

What Does a Cabbing Machine Do?

A cabbing machine shapes rough or flat stone into a domed cabochon using a sequence of diamond grinding wheels and polishing laps. The operator moves the stone from a coarse wheel through progressively finer grits until smooth and glossy. Most machines use water cooling to prevent overheating and control dust. Beyond natural stone, many cabbing machines can polish glass, synthetic materials, and some metals; their primary job is turning raw rock into wearable gems for rings, pendants, earrings, and brooches.

A typical machine includes a motor, grinding wheels or laps at different grit levels, polishing wheels or pads, a water cooling system, and sometimes an arbor for accessories. Machines like the CabKing 6″ model operate at roughly 1725–1800 RPM on standard 110V household power, making them accessible for home workshops.

How a Cabbing Machine Works: The Step-by-Step Process

CabKing’s official how-to guide outlines the standard workflow, which follows the same basic progression for all cabbing projects.

1. Trim the stone. Use a trim saw to cut close to your template outline, cutting straight lines only—never curves. Leave about 1/16 inch of extra material around the template line.
2. Rough grinding. Start with a coarse diamond wheel (e.g., 80# grit), using the lower quarter and whole width for even wear. Do not grind too close to the template line yet.
3. Fine grinding. Move to a finer wheel (e.g., 220# grit) to refine the shape and remove scratches from the coarse wheel.
4. Polishing. Finish with a canvas pad charged with diamond paste—the pad does not come pre-loaded.
5. Optional back flattening. If the cabochon needs a flat back for a jewelry finding, grind it flat on a flat lap machine or cabbing machine that accepts one.

CabKing recommends mounting wheels left to right from coarser to finer grits to prevent contamination. The result is a smooth, domed cabochon ready for setting. For those exploring their first purchase, our roundup of the top cabbing machines compares leading models.

Common Mistakes to Avoid When Cabbing

• Wrong wheel order. Coarser wheels must go on the left, finer on the right; reversing can drag coarse grit across a nearly finished stone.
• Cutting curves with the trim saw. The saw blade is for straight cuts only—curves can bind the blade or break the stone.
• Grinding too close to the template line too early. Later stages remove more material, so leave that 1/16 inch margin.
• Skipping grit progression. Moving from coarse directly to fine polish leaves visible scratches; each step removes the previous ones.
• Not charging the canvas pad. The polishing pad must be loaded with diamond paste before use, or it won’t polish effectively.

FAQs

What is the difference between a cabbing machine and a faceting machine?

A cabbing machine produces smooth, domed cabochons using diamond wheels of decreasing grit. A faceting machine cuts precise flat facets at specific angles, creating the glitter of a faceted diamond. Both have a place in a lapidary shop but serve different stone shapes.

Can a cabbing machine polish materials other than stone?

Yes. Many can polish glass, synthetic materials like lab-created opals, and some softer metals. The same grit progression applies, though optimal speeds and pressure may vary. Test on a scrap piece first.

Do cabbing machines require water to operate?

Most rely on water cooling to prevent overheating and control stone dust. Running a cabbing machine dry for extended periods can damage both the diamond wheels and the stone.