Every kind of lapidary work follows the same pattern: cut the stone to rough size, shape it with a coarse abrasive, then remove the scratches with finer and finer abrasives until the surface takes a polish. Keep the stone and the abrasive wet the whole time, rinse between grits, and do not skip a grit. The tools change from branch to branch: diamond wheels for cabochons, loose grit in a tumbler, discs on a flat lap. The pattern does not.
The rules that apply to everything
| Rule | Why |
|---|---|
| Coarse to fine, in order | Each grit removes the scratches the one before it left |
| Do not skip a grit | The next grit has to work much harder to remove the deeper scratches, and wears out faster |
| Run wet | Water cools the stone and the abrasive and carries off the slurry. Our soft wheels must be used with water |
| Rinse between grits | One coarse particle carried to a fine wheel leaves a scratch the fine wheel cannot remove |
| Check before you move on | Rinse the stone and look at it dry under good light. Move on only when the previous grit's scratches are gone |
| Protect your eyes | Wear safety goggles at the saw and the wheels |
Running wet also keeps stone dust out of the air. With quartz stones such as agate and jasper, that dust is silica. Do not grind dry.
Making a cabochon
A cabochon is a stone with a domed, polished top and a flat back. Making one is the clearest example of the whole pattern, and it uses most of the tools in a lapidary shop.
Step 1. Get a slab. Rough stone is cut into slabs on a slab saw, which runs in oil: we sell mineral oil for slab saws. You can also start from a slab someone else has cut. A slab with flat, parallel faces gives you a flat back to start from.
Step 2. Mark the outline. Lay a gem template on the slab and trace the shape with an aluminum scribe. The templates come in oval and circle, square and rectangle, and assorted shapes, in aluminum or plastic; the sets of three include a scribe. Place the outline on the best part of the pattern and clear of cracks.
Gem templates, aluminum, with a scribe.
Step 3. Trim close to the line. On a trim saw, cut away the waste outside the line with straight cuts, then take the corners off with more straight cuts. Stay outside the line; the wheels take it the rest of the way. Our Rock-Rascal, made in our Orange, CA warehouse, is a 6" trim saw, sold complete as Model JM, or with a grinder as Model TM. For the blade, see Choosing a saw blade.
Step 4. Shape on the hard wheels. On an 80 grit hard wheel, grind the blank down to the marked line all the way round, keeping the edge square to the back. Then, if you dop the stone, do it now: warm the stone and set it on a dop stick in dop wax. Our green dop wax is rated 150°F and sold for cabbing, with an electric dop pot to melt it. Back on the 80, form the dome, working from the edge up to the top, and put a small bevel on the back edge. Then go to a 220 hard wheel to take out the 80's scratches and refine the shape.
| Hard wheel | Sizes | Grits |
|---|---|---|
| Nickel bond | 4", 6", 8" | 36 to 600, including 80 and 220 |
| Sintered | 6" and 8" x 1 1/2" | 30 to 600 |
Step 5. Smooth on the soft wheels. Move to the soft wheels in order: 280, 600, 1,200, 3,000. The soft wheel's flexible face follows the curve of the dome instead of grinding flats into it. At each wheel, work the whole dome evenly, rinse, check under light, and move on only when the last grit's scratches are gone.
SuperNova soft wheels are made in our Orange, CA warehouse in 4", 6" and 8", from 60 to 200,000 grit plus cerium, chrome and tin. 280, 600, 1,200 and 3,000 are our most popular grits. A new soft wheel needs breaking in before it is used on a good stone: see Breaking in a new soft wheel.
Step 6. Polish. After 3,000, polish on a finer soft wheel or disc, or with an oxide:
| Polish | Our products |
|---|---|
| Finer diamond | SuperNova wheels at 8,000, 14,000, 50,000 and up; the SuperNova disc, 5.5" with a 1/4"-20 screw back, 280 to 50,000, made in our Orange, CA warehouse |
| Oxide | Polishing powder, on a polishing pad. Cerium oxide is the standard polish for glass and quartz stones such as agate and jasper. Tin oxide gives a bright finish on many cabochon stones. Chrome oxide suits jade and other hard-to-polish stones |
| Oxide on a wheel | SuperNova wheels in cerium, chrome and tin |
Step 7. Finish the back. Warm the wax, take the stone off the dop and clean off the wax. Smooth the back on a fine wheel or a flat lap if it needs it.
For why the wheels run in this order, see Cabbing grit progression.
Tumbling
Tumbling follows the same coarse-to-fine pattern, with loose grit doing the work.
| Stage | Our silicon carbide grit |
|---|---|
| Coarse: knocks off sharp edges and rough spots | 46, 60, 60/90, 80 |
| Medium: removes the coarse scratches | 120, 120/220, 220 |
| Fine: readies the surface for polish | 400 to 1,200 |
| Polish | Polishing powder, including CPP tumbling polish |
Clean the stones and the barrel or bowl completely between stages, for the same reason you rinse between wheels. Tumbling media, such as plastic pellets, cushions delicate or soft stones in the polish stage.
Our Gy-Roc, made in our Orange, CA warehouse, is a vibratory tumbler in 3 lb., 10 lb. and 40 lb. sizes. Vibratory action smooths and polishes while keeping the natural shape of the stones.
Flat lapping
A flat lap does for a flat face what the wheels do for a dome. Work through diamond discs from coarse to fine, or loose silicon carbide grit on a lap plate, then polish.
| Disc | Grits |
|---|---|
| Nickel bond lapping discs, for the coarse steps | 30 to 3,000 |
| Resin bond lapping discs, made in our Orange, CA warehouse, for the fine steps | 100 to 50,000 |
For the machine, see our lapping machines, including Covington vibrating laps and the Lortone oscillating lap, which we resell.
Water
Every step above runs wet. If your arbor has no water feed, our water spray keeps the stone and wheel wet while you grind and polish. It is sold as a complete system, or as the brass geyser piece with tubing to replace a worn one.
Our water spray.
When a wheel wears out
Soft wheels wear. When a soft wheel's diamond face is worn but its core is intact, we can resurface it, whatever brand it is, for half the price of a new SuperNova at 4", 6" and 8". It comes back about a week after it reaches us, in the same grit or a different one. Hard wheels are not resurfaced. See Resurfaceable or scrap.
Fitting wheels to your machine
SuperNova, Diamond Pacific Nova and CabKing soft wheels are all made with a 1" bore. SuperNova wheels ship with bushings for 3/4", 5/8" and 1/2" shafts. See Arbor and bore sizes before you order.
Questions we get
What do I need to make a cabochon?
A slab, a template and scribe, a trim saw, hard diamond wheels at 80 and 220, soft diamond wheels at 280, 600, 1,200 and 3,000, a polish, and water on every wheel. Dop wax and a dop stick are optional.
What grit sequence do I use?
80 and 220 on hard wheels to shape. 280, 600, 1,200 and 3,000 on soft wheels to smooth. Then 14,000 or finer, or an oxide, to polish.
Do I have to dop the stone?
No. A dop stick gives you a grip on a small stone and keeps your fingers away from the wheel. Larger stones can be held by hand.
Why does my stone still show scratches after polishing?
A scratch from an earlier grit was not removed before you moved on, or a coarse particle was carried to a finer wheel. Go back to the grit that removes it and work forward again, rinsing between wheels.
Can I skip a grit to save time?
No. The next grit has to work much harder to remove the deeper scratches, and that wheel wears out faster.
Which polish do I use?
For agate, jasper and other quartz stones, cerium oxide. Tin oxide gives a bright finish on many cabochon stones. Chrome oxide suits jade and other hard-to-polish stones.
How is tumbling different?
A tumbler does the work in a barrel or bowl with loose grit, and the stones keep their natural shape. You do not choose the shape, so there is no sawing or marking.
Related: What is lapidary, Cabbing grit progression, Breaking in a new soft wheel, Resurfaceable or scrap.