Stone Cutting How-To and Adding Dimension to a Gem by Stone Carving with a Flex Shaft
Anytime I get a chance to share a stone cutting or jewelry project by Roger Halas, I take it! He’s a man of many talents and frequently shares them in Lapidary Journal Jewelry Artist magazine. This stone-cutting project is great for the lucky folks who know (or are learning) how to cut gems, and for those of us who want to but haven’t yet learned how, we can follow his shortcut idea start with stone carving. Read on and enjoy! –Tammy
Stone Cutting and Carving: Carved Quartz Cabochon
It’s easy to add dimension to a common form with a flex shaft.
by Roger Halas (originally published in the December 2010 issue of Lapidary Journal Jewelry Artist)
When you’re faced with a translucent gem material, the next step is to figure out what to do with it. The question usually is: Do you facet it, or do you cab it?
If you have the equipment, either of these may be a viable option, but there is also another option: stone carving. This typically evokes the image of an animal or other figure, or perhaps something geometric, but carving is a broad term encompassing much more than that. It can combine curves with facets, or it can look entirely organic. The point is it’s time to breach the limitations of the typical calibrated form.
Here, I show stone cutting with a piece of rutilated quartz, but what you’ll do is take a piece of translucent material, whatever you have on hand, cut it into a cabochon of sorts, and then add a design element that takes it to an entirely new level of optical splendor. And you’ll do this all with tools you may already have on hand.
I took my time on this, as it’s always difficult to maintain that girdle when working freehand, and even then it was only three hours.
An Easier Way: Purchase a transparent or nicely translucent finished cabochon of something, anything, and then skip the stone cutting and just focus on the flex shaft carving.
translucent cutting material (any size, preferably facet grade)
6mm onyx bead strand
1200-grit diamond compound
cerium oxide compound
Crystalube diamond extender
standard 6mm round diamond burs, 200- and 600-grit (for flex shaft)
1mm or smaller engraving bur (for flex shaft)
1. Cutting the Cabochon:
So, I had this piece of rutilated quartz. It looked close to facet grade, so it was perfect for this project. Clear or rutilated quartz is always cheaper than facet-grade amethyst or aquamarine, but if you have something like that on hand, don’t hesitate to use it.
2. Grind the material into a dome. I used an 80-grit turbine wheel on a modified Diamond Pacific unit I’ve had since high school. It works great and removes a lot of material fast. As you work the piece, keep dipping it in water and holding it up to the light. If you see any inclusions, you might have to grind them out–in effect losing material–which is always a judgment call, sometimes a painful one.
3. After deciding on the initial shaping, mark the piece around the perimeter to set the girdle. As you go through the successive grinding stages (280, 600, etc.), repeat marking the line to remind you not to deviate from it. For purposes of setting, the girdle must always remain straight–even if the top and bottom profiles of the stone are altered during the sanding stages.
4. My stone is roughly pillow shaped, at this point taken to the 600-grit sanding stage. Once again, I’ve marked the girdle because the 600 grit, though very fine, can remove material fairly quickly on a smaller stone such as this. One false move and that girdle can start to waver. But if it does, don’t worry; just straighten it out and don’t put so much pressure on it, as excess pressure is the typical cause for this error during stone cutting.
Cabochon or Beyond?
5. This is where you have to make a critical stone cutting decision. Because sanding wheels are often cushioned, most cabbing units aren’t designed to put a sharp edge on a stone. The Genie, for example, comes with a 1200- and 3000-grit prepolishing wheel that I don’t use; I replaced those wheels with one 6″ x 3″ expandable drum, which I use with 3M abrasive belts. This, coupled with the rotational force of the expandable drum, enables me to maintain a relatively sharp edge on a stone that is nearly as wide as the drum itself. This effect comes in particularly handy on the final stages. I used a 9-micron (1200-grit) belt to refine the girdle. Additionally, rather than using water, I usually run the belt dry and use the compound extender as coolant. Then, once this stage is complete, the entire stone can be finished with cerium oxide and extender on a resin belt, charged felt, leather, or even wood.
At this point, you have a nice cabochon ready for setting and could be done with this project. However . . .
6. Carving the Stone:
Mark the stone with any number of dots, spaced however seems appropriate. There is no right or wrong way to do this, so long as it looks right to you. Use the 200-grit diamond cutter, the fluid extender, and the flex shaft to start cutting divots into the back of the piece. The deeper you cut, the greater the optical effect. The best way to do this is to vary the depth of the cuts and keep looking at the stone from the other side until you like what you see. The 200-grit will cut fairly quickly, so switch to the 600-grit for refinement. If you see any obvious chips around the edges of the divots, keep sanding until they go away.
7. If you carve at all, you’ve probably noticed that 600-grit is as fine as grinding burs get. My solution to a finer grind is to use an onyx bead with 1200-grit paste. A 6mm bead is the same size as the grinding burs, with the bonus of a centered hole. Take a dulled 1mm engraving bur and jam it into the bead. If it doesn’t fit in the bead hole, snap off the head or use a smaller bur that does fit. Then, put a drop of Super Glue on this little contraption and you’re ready to go.
Fill in the divots with black marker, then go over them with the onyx bead and the 1200-grit (with extender) until the marker is gone, which means you’ve sanded those divots smooth. Since you’re dealing with such a small surface area, this takes no time at all–literally seconds. Inspect your work, and then proceed with another onyx bead and cerium oxide paste. When you’re done, you will have discovered that gem carving, though complex, is an endeavor well worth the effort.
The onyx ball bur applies to the 1200-grit prepolish, plus another onyx bur for 14,000 diamond, or tin, or cerium oxide final polish.
Want to learn more ways to use a flex shaft in your studio? Go beyond stone cutting, polishing and grinding with this versatile tool.
About the designer/author: Roger Halas is a self-taught lapidary, metalsmith, and jewelry designer in Southern California. When not making jewelry, he works as a professional photographer, martial arts instructor, and aspiring screenwriter and encourages others to explore their creativity. He’s a frequent contributor to Lapidary Journal Jewelry Artist magazine.