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Post by invisibleuser on Oct 8, 2007 14:03:43 GMT -5
Is their a certain ratio between the depth of a cab and the length and width? For example- if you cut a cabochon 18mm long,13mm wide- what would be the proper thickness on something this size? How about a cab that was a 25mm x 25mm square?
Or is it just based on how durable the rough is?
invisibleuser
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rallyrocks
fully equipped rock polisher
Member since November 2005
Posts: 1,507
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Post by rallyrocks on Oct 8, 2007 14:10:32 GMT -5
I've seen cabs cut in any number of different aspects and dome heights.
As a general rule, thinner is usually better because it makes for a lighter weight piece in the end product, to a point- usually 5mm or so is as much dome as you need for many cases, but sometimes patterns or the cutters desire for a higher dome will outweigh that.
With material like fire agate and opal you are constrained by the material itself, you don't want to cut through and obliterate the color layers...
And as you mention, the strength of the material can also come into play, but usually if your slab is solid without cracks you can get away with cutting stuff pretty thin.
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stonesnbones
spending too much on rocks
Member since September 2007
Posts: 255
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Post by stonesnbones on Oct 8, 2007 14:53:53 GMT -5
I second everything Rally rocks said.Easily most of my cab size is dictated by color and pattern.Most solid color rough and petrified wood I do has a high dome.I rarely worry about the size,I more concern myself with appeal.The only size I stick to is the girdle,its always between 3 and 3.5 mm no matter cab size or dome hieght.
brad
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Post by Tweetiepy on Oct 9, 2007 7:26:01 GMT -5
Please note that if you are working a material that has some sort of flash or effect (like rainbow obsidian) I was told that a high dome is best to show off the color play
KD has high domes on hers, and they look amazing - I think it's a personal preference.
I find that if your piece is pretty big, you're better off with a higher dome (but that may just be me..)
(yeah I'm helpful aren't I?)
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Post by akansan on Oct 9, 2007 8:41:52 GMT -5
Yeah, personal preference does play into it. Most of my cabs end up with a 2-3mm dome with a 3mm girdle just because of the way I grind them. The few higher domed pieces I've cut have been bears to get even!
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Oct 9, 2007 20:10:30 GMT -5
And lets not forget the times that we plan on a cab having a high dome but due to error or maybe soft material it ends up being thin. You say oops! and continue cabbing your thin "low dome" cab. lol.
Shannon
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Post by larrywyland3 on Oct 11, 2007 19:30:20 GMT -5
I agree. The only two things I can add. 1) depending on how the stone will be made into jewelry dictates some of how it is cut. If you are doing a beaded bezel you will need to have about a 2 mm girdle with the dome at about 5 mm or more; also you will need to back bevel the bottom more so than any other setting meathod. If you are using a metal bezel you will need to be very concern with the evenness of the girdle all the way around and it can not be higher than the walls of the bezel. In this setting you drop the cab into the metal bezel and planish the tops of the walls over the girdle. If the girdle is to low it looks bad if it is too high the cab will fall out. If you are going to drill a hole through the side of the cab you will need it to be a little thicker as the hole will be about 1.5 - 2mm thick and this would be near the edge of the cab which is thinner than the dome so you need to make sure you have enough rock around the hole to keep it from breaking. 2) Some agates with plumes or other stuff in a clear semi clear agate look better cut a little thinner; maybe a mm or 1.5. I think most slabs are 5mm or 1/4 inch thick.
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