What Is a Cabbing Machine? | Turning Stone Into Gems

A cabbing machine grinds and polishes rough rock into cabochons, the rounded dome-shaped gems used throughout jewelry.

Jewelry stones don’t come out of the ground looking like gems. Most start as rough slabs, and they only reach that glossy, dome-shaped finish after a careful run from a coarse grinding wheel down to a fine polish. That run happens on a cabbing machine.

In plain terms, a cabbing machine cuts cabochons, or “cabs” — the rounded stones with a flat back that sit flush in rings, pendants, and earrings. Lapidary guides commonly describe cabbing as the most popular form of gem cutting, and the machine is what makes the whole process practical outside a professional shop.

What Does A Cabbing Machine Do?

A cabbing machine shapes stone into finished cabochons with a row of spinning diamond wheels, each one cut for a different grit. You work the stone from the coarse end of the machine toward the fine end, then move to a polish wheel, while a water system keeps the cutting surface cool and clear.

The wheels mount on a single shaft, arranged coarse to fine from left to right. Because every wheel runs wet, the machine doubles as its own cooling system: water drips over the spinning surface, flushing away stone dust and preventing heat fractures in the rock.

Don’t confuse cabbing with faceting. A faceting machine cuts flat, angled facets into transparent stones like diamonds and sapphires. Cabbing produces the smooth, curved dome you see on agate, jade, opal, turquoise, and malachite, and it is not a general-purpose cutting tool — that job belongs to a rock saw.

How The Cabbing Process Works

The recipe is the same on every machine: remove material with a coarse wheel, then step down through progressively finer wheels, drying the stone between stages to check your work. A typical run looks like this:

1. Cut the rough shape. CabKing’s how-to guidance suggests starting on an 80# diamond wheel for the initial grind. Hold the stone against the lower quarter of the wheel and use its full width so the wheel wears evenly, easing the stone in gently instead of forcing it. CabKing’s official cabbing guide covers this first stage in detail.
2. Inspect between every stage. Dry the stone and look for scratches before moving to the next wheel. Scratches left behind get harder to remove as the grit gets finer, so this check is what keeps the finish clean.
3. Step through the grits, then polish. Move from the coarse wheel to each finer wheel in order, finishing on the polish wheel. The dome should look smooth and scratch-free by the time the last wheel is done.
4. Remove the dop stick. For stones mounted on a dop stick with wax, CabKing recommends freezing the cab and stick for 10–15 minutes, then peeling the wax off and scraping away any residue carefully with a clean, sharp knife.
5. Flatten the back if a setting needs it. If the cab will sit in a bezel, CabKing recommends flattening the back on a diamond lap, either on a flat-lap machine or a cabbing machine that can accept one.

Safety Rules And The Mistakes That Ruin A Cab

• Never run the wheels dry. Water is the only approved coolant, and running a dry wheel can overheat both the stone and the machine.
• Start coarse enough. A wheel that’s too fine won’t shape the stone properly, which is why the first wheel, not the last, does the rough removal.
• Let the diamond cut. Heavy pressure damages wheels and causes uneven wear; ease the workpiece against the wheel and let the abrasive do the work.
• Dress for the shop. Wear eye protection, skip loose clothing, gloves, neckties, and jewelry, tie back long hair, and never unplug the motor, lamp, or pump with wet hands.
• Know your rock. Some stones contain poisonous elements such as uranium, mercury, lead, and arsenic, so wet-grind and research the material before you start.
• Cut one piece at a time. Never start the machine with a wheel already touching the workpiece, and don’t grind more than one stone at once.

What A Cabbing Machine Costs Today

The price tracks the wheel size: 6-inch machines suit most home shops, while 8-inch units grind faster and handle bigger stones. These are current U.S. list prices from retail listings:

CabKing, a dedicated cabbing brand, sells its machines in both 6-inch and 8-inch sizes, so beginners and pros both have room to grow. Spec sheets and price tags only tell part of the story, though — wheel quality, water delivery, and build stability decide how enjoyable the machine is to run.

If you’re comparing models before spending, our tested picks for the best cabbing machines look at the leading 6-inch and 8-inch setups in depth.