Easy Combination cutting MV
Combination cutting: a minimalist approach - Marco Voltolini
With the term "combination cutting" we basically mean those cuts where faceting and carving techniques are combined by the lapidarist.
In this tutorial I'll show how to cut such a stone with a minimal equipment (assuming you already have a faceting machine). Improved and more specialized equipment is of course used by the real pro's in the field. Anyway even with my simple approach it is possible to obtain very good results: I'll show you how I cut an aquamarine featuring "bubbles", "channels" and other features, to obtain a cut stone truly different from what you can usually find on the market.
Let's start with the rough: in my case it's an aquamarine. The piece is rather flat and has a couple of small surface cracks. Now, with combination cutting the depth required to cut a stone can be smaller that the one required by conventional facet designs, because it is usually not a problem to have open culets and/or carve that part of the stone. So combination cuts can offer a bonus when you have a nice, clean, big, but flat piece of rough. Also, surface flaws are not an issue: you can plan a "bubble" (or any other carved feature) strategically, in the position where those flaws are. I would suggest to use only clean pieces, since evident flaws can detract the attention from the carved features (unless you are dealing with some nice-looking included materials, tourmalinated quartz, for example)
Once you have selected your piece of rough, just dop it and start to facet the stone. Any design with few large facets should work well. If you want to have reflection (my advice is to do so) cut above the critical angle. I chose a cushion-ish shape and I cut all the pavilion facets at 42 degrees. I also cut a open culet. Don't waste your time cutting with fine grits here, since you'll have to recut the stone after carving. A finish using a 600 (or my very worn 260) plated lap is usually fine here. Look at the picture of my stone, where I've just finished this preforming stage.
Now it's time to cut the carved features on the pavilion. I quickly draw an outline on the stone using a marker. What I used at this stage:
- Dremel tool: you need such a tool (or better) for carving. A flex shaft sure will help, but mine was broken during this experiment. Using the Dermel alone is no big deal, just it's a little more uncomfortable for your wrist...
- Diamond carving burrs: I use either 600 or 1200 grit plated burrs. They can be found very cheap, but the quality is cheap as well. Anyway once you find what kind of burrs you use the most, you can upgrade those to good quality sintered burrs. Here I'm using cheap 600 grit plated burrs: a ball and a cylinder shaped ones.
- Bamboo skewers: for the sanding and polishing processes. The diameter of the skewer has to be compatible with the collet of your carving tool (i.e. ~ the same diameter of the shaft of your plated burrs).
- File for metal: if you want to shape your bamboo skewer tools. For example if you need a cone point, you just mount a piece of your skewer on the Dremel, you turn it on, and rub it at a proper angle on the file. Done. Usually the bamboo skewer will take the shape of the feature you are working into, so often this shaping process is unnecessary (es. I never do that when sanding/polishing "bubbles"). This file will be needed when you need to do some more "advanced" tools, such as small cutting disks out of nailheads (this kind of tools have not been used on this stone).
- Oil and water to use a s a lubricant. I use olive oil for diamonds and water for oxides. But when I cut with the plated burrs I use water.
- Diamond paste (I use 600, 1200, 3000 grit), Ce-oxide (since I'm cutting beryl)
- An old toothbrush is very helpful when cleaning the stone between different diamond grits. I use a disposable surface (old newspapers, old envelopes, etc) to work onto. Toilet paper for cleaning.
Now I use my plated burrs for carving the bubbles (ball) and the channels (cylinder). Be careful when you start cutting each feature not to slip with the burr. While cutting move the burr to avoid deep scratches: use an orbital motion for the bubbles and go forward-and-behind rather quickly when cutting the channels when you finish cutting them. Also, since you'll have to recut the stone after carving, go a little deeper than the outcome you have in mind. Pay attention not to chip too much the overlapped parts of the different carved features.
This picture is to see how my stone is after this first rough carving. Note the chipping where the bubbles meet the faceted surface. We will get rid of all those chips by recutting the stone, after finishing the carved features.
Next we need sanding. I started using my 600 grit diamond paste (using a hint of oil when needed). At this stage we need to smooth out all the scratches caused by cutting and to get rid of the chips where the different carved features are overlapping. There's no real need to smooth out the chips on the facets perfectly. Use the 1200 paste to smooth out the 600 grit surface. Clean again with the toothbrush. Pre-polish with the 3000 diamond paste.
For polishing I use a paste made of ceria and water, and I use again a piece of bamboo skewer. At this point it's rater easy to go dry and burn the wooden tool and overheat the stone. If things are getting dry and you feel your stone getting hot, stop immediately, wait a little (do NOT wet the stone to cool it down while it has a portion still hot: it could crack), and use more water/paste. Overheating is a problem since it will consume your tool and may cause cracking in your stone. So try to avoid it as much as you can; wet your stone frequently.
Notice how the carved features are well-polished, the facet-bubble junctions still have chipping, but the bubble overlaps have been sanded to obtain crisp and sharp arcs, without any chipping left.
I have then remounted the stone on the quill of my faceting machine and re-cut the stone with my plated 600 grit lap until I got rid of all the chips. Note how crisp are now those junctions.
After you got rid of all the chipping, simply proceed as usual for flat faceting: pre-polish and polish the facets. On this stone I left the culet and the girdle unpolished.
Then you have to cut the crown. There are many options available: faceted crown, buff-top, mixed, etc. In this case I decided to cut a simple step crown, leaving one step unpolished to create a "frame" effect. That, coupled with the pavilion facets and the shape of the culet, adds a further impression of "depth" in the stone to the viewer. In the figure I'm starting to cut the table, using my 45 deg adapter.
The stone off the dop and cleaned. It's pretty impressive for a stone cut using bamboo skewers, isn't it? My first stone of this kind sure wasn't as nice as this one, but with some practice the results will improve steadily. As you have seen, cutting this one was quite a lot of work, but results have been rewarding.
Different concepts & ideas
You don't necessarily need a faceting machine for this kind of cuts: this one features only curved surfaces (the "pavillion" is shaped like a boat) and a buff-top. "Bubbles have been carved on the "pavillion" to obtain this overall pleasing effect.
Of course it is possible to mix a variety of techniques: in this stone the pavillion is flat faceted and some "bubbles" have been carved. The crown is a buff-top with a very large table. Also in this case the overall effect is pleasant to the eye.
 Michael Dyber (2005) Lapidary Journal, August issue. Pp. 61-67.