Tumbling and the Cab Contest

I'm in the "purist" camp but first I agree with Rockindad : we have to define what a cab is before we can set any particular contest rules. I've noticed that these days almost any lapidary creation is classified as a cab, including carvings and beads. I don't agree with that. But I don't think any particular style of cabochon should be idealized either.

I've cut and set many a stone with no defined girdle beyond it being the outer perimeter of the stone with a very tiny angle. In bezel setting the slightest girdle angle, say 3 degrees, is sufficient to hold a stone very firmly. Prong settings offer even more setting options. When cutting fire agates, for instance, I used to bevel some stones' sides' inward so the top of the stone was flush with the surface of the jewelry piece. It was held in place tightly with small prongs. Of course those were custom-made pieces and not common -- but they were cabs. Wire wrapping has different requirements.

What's needed is some general agreement as to what a cab is and how it should be fashioned. Then a contest can be built around that definition. There are other issues as well: unequal cutting equipment and experience. I don't know how to overcome those problems.

I don't think a completely level playing field is possible or desirable. I like this place because of what I can soak up here being surrounded by people with more experience and better equipment than me. I know it only makes me better and I will reach their level, and perhaps exceed it, if I keep learning and practicing. If that means they kick my butt month after month in a friendly contest so be it. My day will come.

Al

Pfft! Wannabe!

Just kidding, I like your side boob stone!

Al

That's what I've been trying to find. When did the girdle come in?

Tuscarora Lapidary Society, Inc.

Skill
Improvement
Program


Rules

Regulations

Judging

Instructions



Tuscarora Lapidary Society

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610h490h5252 www.lapidary.org

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SKIP — The TLS Skill Improvement Program

Tuscarora’s Skill Improvement Program (SKIP) is dedicated to increasing enjoyment of our hobby by the

development of higher levels of craftsmanship. Each member is given the opportunity to have his/her work

evaluated in relationship to standards of workmanship. These standards become progressively more rigorous as

the member’s skill increases.

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CABOCHON DIVISION

Definitions

A cabochon is a polished stone with a domed surface (the top), cut freehand (not tumbled). The second surface (the

back) may be flat or domed. If domed, it may be of lesser height than the front dome. A cabochon is normally of a

size suitable to be worn as jewelry.

A standard cabochon is one whose girdle outline has at least one axis of symmetry. All patterns on the standard

templates satisfy this condition.

A free-form cabochon is one whose girdle outline has no symmetry.

The bezel angle is the slope that is cut on the side of a cabochon for a short distance above the girdle; it should

be uniform around the stone. Its purpose is to allow the bezel of a mounting to be rolled or pressed down against

the stone to secure it in the mount. It should be in the range of 10 to 15 degrees. The dome may meet the bezel

angle surface in a definite line, parallel to the girdle, or may blend in smoothly down to the girdle.

The chamfer or bevel is a narrow angled surface cut around the girdle of a cabochon toward the back to reduce

the likelihood of chipping. It should be about 45 degrees, of uniform width, not wider than 1mm except on very

large stones.

Note that cabochons with two domed surfaces have no chamfer, and that the angle at which the back surfaces

meet the girdle may be much larger than the bezel angle on the front. Ideally, the girdle in this case would be

sharp. Because of chipping, this is not practical and the girdle must be slightly and smoothly rounded.

The symmetry overall refers to the contour of the domed surfaces, not to the shape of the girdle.

Orientation refers to the shaping of the stone to make best use of its natural patterns, color distribution, and

inclusions to show chatoyancy, cat’s-eye, star, or to otherwise enhance the beauty of the finished piece.

Examples that illustrate the definitions

Material

A cabochon may be made of any suitable natural mineral or any synthetic mineral-like material, such as

goldstone. The quality of the material refers to color, pattern, freedom from cracks, pits, etc.


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Point Allocation for Evaluation

STANDARD CABOCHONS

Accuracy of girdle outline* 15

Symmetry overall (shaping of top & sides)

Top 10

Sides 10

Quality of polish

Top 10

Sides 10

Orientation 10

Quality of material 15

Bezel angle 10

Chamfer or bevel 5

Back 5

Perfection 100 points

*Free form cabochons: For accuracy of girdle outline, substitute complexity of form attempted.

Polished flats will not qualify in the Cabochon Division.

Judging

Accuracy of girdle outline: For traditional shapes — check by placing template over (or carefully tracing outline)

then placing template over traced outline, then cutting out and folding; freeform — shape that exhibits skill.

Symmetry overall: Make a light move over the stone. If the reflection changes shape or jumps, instead of

moving evenly over the top, then symmetry is off (flat spots).

Quality of polish: Check by looking at light reflection on stone (use a clear light bulb). Softer stones may not

take as high a polish, nor will stones of mixed minerals.

Quality of material: Take into consideration the quality for this particular material.

Bezel angle: The interface between the bezel and the top should be either smoothly rounded or have a nice

sharp edge.

Chamfer: Must be even all around — no chips.

Bottom: All stones submitted should be clean on the backs, with all saw marks, all aluminum pencil, or other

marks sanded off. Cabochons with two domes must have both polished. Clear or translucent material

cabochons must be polished on the back as well.

Judging will be done using 10X magnification.



Tuscarora’s Skill Improvement Program (SKIP) is dedicated to increasing enjoyment of our hobby by the

development of higher levels of craftsmanship.

SKIP program
Information on entry requirements and different levels of craftsmanship PDF HERE

I do enjoy the current contest. I don't cut cabs very often and this gives me motivation to get 1 done occasionally.

But I will admit I really enjoyed the previous contest as well. The point about level playing field is lost on me because back then I was just getting into this hobby and really enjoyed the challenge. You really had to step up to compete with the other entries. Of all the contests I entered I won one contest and was so excited! Most times I was lucky to get a vote.

So I have to say both contests have their merits.

Why mince words? What the hell exactly are you trying to say? I don't like your tone or insinuation... unless I took you wrong. I don't care WHO you are referring to, it just sounds shitty.

Jean, rockpickerforever The short lived technical skill cab contest rules were based on the first set of rules you found above. I guess anyone can make rules. We can for our purposes, too. I'm fine with the way the game is now, but the subject WAS brought up, so I chimed in. However, I do strongly disagree with a cab not being flat on the back. A jeweler can't really set a rocking cab.