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Author Topic: Optimum Slab Thickness for Cabs  (Read 474 times)

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Michael

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Optimum Slab Thickness for Cabs
« on: September 27, 2018, 02:49:39 PM »

Ok, I need better opinions than my own.  The standard slab thickness for cabs that I have been using is in the range of 6 mm or about 1/4" thick.  That is. in order to get a good decent girdle and a proper dome.  I would like to know what others think. Does MOHS play a part in how you cut the stone for cabbing?

Other than trying to sell the most slabs out of a stone, what is the reason for the 1-3 mm slab sales you find at Quartzite, Tucson, and Rock Club sales?  Other than intarsia, or possibly doublets, there is limited use for these slabs as I can see.  I do see people buy them, though.  Any thoughts?

Mike
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rocks2dust

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Re: Optimum Slab Thickness for Cabs
« Reply #1 on: September 27, 2018, 04:23:57 PM »

What I see at shows averages around 5mm. Still, there isn't going to a "standard" that applies to all slabs.

For some agates, a thinner slab is going to be better (iris agate, dense plume and moss, some turtleback, etc.). Thinner slabs are also going to work better for jewel and lapidary items that will be kept lightweight (earrings, tablet-top gems, etc.). I've seen some high-domed cabs that were heavy enough to cut through earlobes or seriously dent the back of a neck in a necklace - weight can be a consideration for the final use. Some rarer and hard-to-source materials have always been cut thinner (3-5mm even in larger slabs) to maximize yield from expensive rough, and little choice but to cut low-dome cabs from those. Lighter is better for most jewelry, though.

Some materials (optical phenomena such as bull's eyes, cat's eyes, stars, labradorescence, etc.) often do need higher domes to show best, and something 6-7mm works really well for those. Large, collector-size cabochons can also be easier to cut with a bit of extra thickness. Slabs that may be intended for carving and similar lapidary work can be very thick indeed.

So, you get to decide :wink:
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r2d

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hummingbirdstones

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Re: Optimum Slab Thickness for Cabs
« Reply #2 on: September 27, 2018, 04:55:25 PM »

I personally despise thin slabs (unless it needs to be thin because of the stone -- what R2D mentioned).  When I started buying slabs, 7mm was pretty much the norm.  As rough prices started going up, slabs have gotten thinner.  That's why I prefer to buy rough so Vince can slab me what I like!  :icon_sunny:
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Robin

freeformcabs

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Re: Optimum Slab Thickness for Cabs
« Reply #3 on: September 27, 2018, 05:38:42 PM »

I prefer 7mm slabs but often find myself cutting finished 5mm cabs with a 2.5-3mm bezel height.  I was slabbing the other day in the club I belong to now and was cutting 5-6mm slabs out of the rough I had. This was based on yield only.  I find 7mm slabs to be common but I haven’t bought slabs in years. So that was 2008 sizes.
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~Shain

vitzitziltecpatl

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Re: Optimum Slab Thickness for Cabs
« Reply #4 on: September 27, 2018, 08:13:38 PM »

Only thing I'll add is in agreement with rocks2dust. For old-style high domes, or for cutting matched pairs, thicker slabs up to 9-10mm might be necessary. Otherwise I try to stay in the 6-7mm range.

finegemdesigns

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Re: Optimum Slab Thickness for Cabs
« Reply #5 on: September 30, 2018, 10:05:38 AM »

I think 5mm is optimum for most gems especially higher end materials.
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vitzitziltecpatl

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Re: Optimum Slab Thickness for Cabs
« Reply #6 on: September 30, 2018, 03:31:32 PM »

Definitely want to slab the good stuff thinner. 5mm is plenty for low to medium domes if the saw cuts are good and no internal flaws have to be ground out. Even opal cabs can be in the 2-3mm thickness range, so other stones being that thin is no problem.

Phishisgroovin

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Re: Optimum Slab Thickness for Cabs
« Reply #7 on: October 05, 2018, 09:29:08 PM »

all my slabs i cut are 4 USA pennies thick.
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vitzitziltecpatl

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Re: Optimum Slab Thickness for Cabs
« Reply #8 on: October 06, 2018, 08:24:47 AM »

...and our fearless leader adds his two cents worth. Twice.

Fun with numbers this early on a Saturday hurts my head, but that was a cool answer. Looked it up and found the answer to be 6.08mm / .239".

We use coinage as check weights for scales. Can be handy if buying or selling pricey rough. Even if they're worn it's still as close as the accuracy of most scales.

Nickel weighs 5 grams.
Five quarters weighs 28.35 grams. That's exactly 1 oz avoirdupois, so a roll of quarters weighs 1/2 lb.

Phishisgroovin

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Re: Optimum Slab Thickness for Cabs
« Reply #9 on: October 20, 2018, 09:04:26 AM »

...and our fearless leader adds his two cents worth. Twice.

Fun with numbers this early on a Saturday hurts my head, but that was a cool answer. Looked it up and found the answer to be 6.08mm / .239".

We use coinage as check weights for scales. Can be handy if buying or selling pricey rough. Even if they're worn it's still as close as the accuracy of most scales.

Nickel weighs 5 grams.
Five quarters weighs 28.35 grams. That's exactly 1 oz avoirdupois, so a roll of quarters weighs 1/2 lb.

four full cranks on my depth handle in the 20 inch saw is 4 pennies thick lol
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vitzitziltecpatl

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Re: Optimum Slab Thickness for Cabs
« Reply #10 on: October 20, 2018, 08:55:36 PM »

Maybe that could be the new standard - like nails. They are 8-penny, 10-penny, etc, right? So 4-penny slabs it is.

Just be careful how you crank your handle... .

olgguy

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Re: Optimum Slab Thickness for Cabs
« Reply #11 on: October 26, 2018, 10:53:49 AM »

I cut 5, 6,&7mm so the customer can choose what they like.
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