jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Nov 27, 2016 8:37:33 GMT -5
I would think 'hardness' and 'toughness' comes into play. Toughness would prevent shear and shattering for any reason. Silicon carbide totally brittle, opposite of tough. But that is it's mechanism of cutting, it never rounds, it only breaks into sharp cutting particles. Diamonds(synthetic anyway) are surely tough. Watch a 10,000 RPM diamond cup grinder with a man bearing down hard on it while grinding about any hard material. Lots of shock loading. I think the binding matrix wears and releases the diamonds. Doubt the diamond ever wears or shatters. Not to mention they were cast in metal at high temperatures. Maybe one day they will manufacture diamonds cheap enough for use in a tumbler. I haven't done an exhaustive search but the information I have found so far suggests that diamonds are indeed quite brittle (which is what I would expect given their hardness) and do have cleavage planes making them susceptible to shock. I believe that they would break down in a similar manner to SiC in a tumbler over time. It would be very interesting to actually do some experiments to see if that hypothesis is correct. Unfortunately for me I'm in a bit of a cash crunch and can't afford to buy diamonds to test it out. diamonds not created equally, see ballas and carbonado diamonds: Unlike hardness, which denotes only resistance to scratching, diamond's toughness or tenacity is only fair to good. Toughness relates to the ability to resist breakage from falls or impacts. Because of diamond's perfect and easy cleavage, it is vulnerable to breakage. A diamond will shatter if hit with an ordinary hammer. The toughness of natural diamond has been measured as 2.0 MPa m1/2, which is good compared to other gemstones, but poor compared to most engineering materials. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond has a cleavage plane and is therefore more fragile in some orientations than others. Diamond cutters use this attribute to cleave some stones, prior to faceting.[9][10] Ballas and carbonado diamond are exceptional, as they are polycrystalline and therefore much tougher than single-crystal diamond; they are used for deep-drilling bits and other demanding industrial applications.[11] Particular faceting shapes of diamonds are more prone to breakage and thus may be uninsurable by reputable insurance companies. The brilliant cut of gemstones is designed specifically to reduce the likelihood of breakage or splintering.[5] Solid foreign crystals are commonly present in diamond. They are mostly minerals, such as olivine, garnets, ruby, and many others.[12] These and other inclusions, such as internal fractures or "feathers", can compromise the structural integrity of a diamond. Cut diamonds that have been enhanced to improve their clarity via glass infilling of fractures or cavities are especially fragile, as the glass will not stand up to ultrasonic cleaning or the rigors of the jeweler's torch. Fracture-filled diamonds may shatter if treated improperly.[13]
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Nov 27, 2016 9:28:55 GMT -5
James, yes that pretty much agrees with what I have been reading. I suspect that diamond grit would last longer than SiC but the big question in my mind is how much longer and does one actually save money by going with diamond grit vs SiC.
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Post by trollfacetheman on Apr 12, 2017 14:36:28 GMT -5
Everyone keeps asking how you'd separate the Diamond Grit. This is actually much easier than everyone seems to think, you literally just pan the mud after it's done just like you would gold.
I did it for my course mud after a week grind and I was able to recover about a table spoon and a half of the original 4 tablespoons of SiC I added. (Should of been two Tbsp but that was my own fault.)
The Carbide had reduced to around the mesh of the medium grit but I didn't really care and I added it in with my next rough grind along with the standard amount.
Why not right..? It was recovered so no extra expenses, and the extra Carbide should only help cut or smooth the stones quicker than just the rough alone.
However the recovery process would not be perfect and you'd most likely lose a bit of diamond by washing it down the drain or having it trapped in rock crevices every time you switched batches.
And if you think a few grains of Carbide contamination is bad..? Just think about a few grains of diamonds getting carried over into the next stage...
No bueno...
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Post by grandpapatrick on Aug 19, 2017 15:50:35 GMT -5
Revisiting this idea... I'm not the expert that you guys and gals are but I would think that a centrifuge might give back near 100 percent of the diamonds. Am I right? I'm just guessing.
Since this thread stopped in April has anyone done any more experiments or do you all feel that it is not really practical.
Are gemstones tumbled industrially for jewelry? Or is all jewelry that needs tumbling done by experts like us (you) who sell it to the manufacturers?
Is there a thread where everyone tells what they do with their stones?
I'm a newbie with too many questions I know.
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Post by Jugglerguy on Aug 19, 2017 16:07:33 GMT -5
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Wooferhound
Cave Dweller
Lortone QT66 and 3A
Member since December 2016
Posts: 1,423
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Post by Wooferhound on Aug 19, 2017 16:22:57 GMT -5
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zekester55
starting to spend too much on rocks
Member since March 2017
Posts: 111
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Post by zekester55 on Aug 22, 2017 5:39:12 GMT -5
Everyone keeps asking how you'd separate the Diamond Grit. This is actually much easier than everyone seems to think, you literally just pan the mud after it's done just like you would gold. I did it for my course mud after a week grind and I was able to recover about a table spoon and a half of the original 4 tablespoons of SiC I added. (Should of been two Tbsp but that was my own fault.) The Carbide had reduced to around the mesh of the medium grit but I didn't really care and I added it in with my next rough grind along with the standard amount. Why not right..? It was recovered so no extra expenses, and the extra Carbide should only help cut or smooth the stones quicker than just the rough alone. However the recovery process would not be perfect and you'd most likely lose a bit of diamond by washing it down the drain or having it trapped in rock crevices every time you switched batches. And if you think a few grains of Carbide contamination is bad..? Just think about a few grains of diamonds getting carried over into the next stage... No bueno... I disagree with your statement of "recovered no extra expense." Time is definitely an expense.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Aug 23, 2017 8:07:07 GMT -5
Diamond grit being carried over is a concern. Thinking about a dozen missed 46 grit diamonds circulating in the vibe at polish...easy to happen. The addition of Borax may release it from mud packed voids in the rocks at the most inopportune time. Having SiC breakdown is a good thing. Diamond impregnated media may be safer. It too releases diamond particles though. Maybe using diamond for a first stage of coarse grind, then going to coarse SiC to help remove any jammed diamond particles. Diamond abrasive will be useless if it is not very sharp. Gotta have sharp in a tumbler due to low grinding pressure within. Sharp and hard his everything, not just hard. SiC meets those credentials. Starts out sharp, breaks down sharp. It is an excellent coarse grinding medium. Separating it with a good stream of fresh water in big enough settlement containers is an easy and fast process. My finding. Wash the whole load in a tray and continue pouring the top layer off. The dense abrasives have no choice but settle to the bottom. If you pour any thick slurry off before thinning it with water you may well be pouring off suspended diamond particles. Just treat the settlement as 'the crap at the bottom of the settlement tray'. Just pour and wash the whole mess back in the barrel. Add rocks and additives, roll away. Don't plan on getting much cutting action from the common form of diamond abrasive, octahedron crystals. Too dull: Maybe this form, what ever it is. Just saying, diamond abrasives are made in many shapes
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