ohthatspretty
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Post by ohthatspretty on Mar 16, 2018 4:44:26 GMT -5
I'm looking for some bulk course AO on eBay and I notice that the White AO seems more readily available and seems about 25% cheaper than the black version of the same grit.
The white is usually labeled as blasting media.
Is there any difference besides color on these?
Also where is the best place you folks have found to purchase AO online?
Best price I found so far is about $2/lb for 25 lbs for 60 grit delivered.
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Post by gmitch067 on Mar 16, 2018 6:33:58 GMT -5
Very good question Josh. Hold off on the purchase until more knowledgeable members chime in with their replies. I vaguely remember hearing that there is a distinct difference in AO products when it comes to rock tumbling... the type used for sand blasting might not be the same for rock tumbling.
I get my AO from the Rock Shed in South Dakota ( therockshed.com ). They only sell AO 500-grit, 1000-grit, and 14,000-grit (polish)
Glenn
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pizzano
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Post by pizzano on Mar 16, 2018 9:36:44 GMT -5
I'm looking for some bulk course AO on eBay and I notice that the White AO seems more readily available and seems about 25% cheaper than the black version of the same grit. The white is usually labeled as blasting media. Is there any difference besides color on these? Also where is the best place you folks have found to purchase AO online? Best price I found so far is about $2/lb for 25 lbs for 60 grit delivered.From what I understand, there are various types of AO used for both blasting and lapidary applications. The common AO types (color) are white, brown and black. Typically, white is finer grit with less impurities, brown more medium grit sizes and black very course material........For lapidary (tumble, vibe, lap grinding and polishing) AO is more commonly applied to "polishing stages".......and Silicon Carbide compounds for grinding stages........AO tends to be more expensive than Sic and may be the reason Sic is recommended for lapidary work.
Here's a link that does a pretty good job of explaining differences....:
sandblastingabrasives.com/sinterblast-100-sintered-bauxite-16-through-150-grits-492.html
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Fossilman
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Post by Fossilman on Mar 16, 2018 10:18:11 GMT -5
White AO, I use on most of my tumbling.....Black AO, you would use on the darker material, like Jade, dark marble, granite, etc (most of them are a harder material)...Yes there is a bit of course difference too...
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ohthatspretty
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Post by ohthatspretty on Mar 16, 2018 11:53:37 GMT -5
Grit ExplainedI've never really given any real thought as to how grit is measured. As a contractor my normal interaction with grit is on sandpaper and it is obvious that the higher the grit the finer the pattern is on your sandpaper. I guess I always sort of thought that the grit number on sandpaper had to do with how many particles would fit in a given area. Looks like I was thinking about it all wrong. That being said, if the material that is crushed is AO and it passes through the screen properly sized for 60 grit, I would think it's all the same stuff. You can buy sandpaper in every color in the rainbow and it's all basically the same stuff unless you are wet sanding. Not sure why the color would matter. I wonder if white/black/brown are broken in a different way as to create more/less sharp profiles on the grit. I'll keep digging, but so far I haven't found any real definitive answers. As far as buying specialty grit for the tumbling hobby...... I have immersed myself in a bunch of different fun hobbies through the years. It seems to me that when anything sold specifically for a hobby type activity the price goes waaaay up. Like ten fold. A good example would be lights for fish tanks. If you know what you are looking for, you can get good grow lights, with the proper brightness at the proper color spectrum for a fraction of the cost you would pay for anything labeled for fish tank use. That said, I would like to gear my purchases toward smaller purchases of materials intended for industrial purposes. Grit just seems ridiculously priced in small batches intended for tumbling. Am I making sense?
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Post by toiv0 on Mar 16, 2018 12:10:13 GMT -5
Just went through what you are talking about. Problem is always industrial people sell in volume.to keep price low. The cheapest I found was Kramer industry but by the time the shipped a 50 lbs bag ups (they wouldn't ship a flat rate mail) the cost was as much as a smaller amount. They said the difference in colors was the white is 99.5 pure and the darker has more oxides. They said a person wouldn't notice any difference in performance. I just bought some from the Abrasive Armory. Reasonable price and recommend by a couple members on here. It was here in 3 days.
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jamesp
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Post by jamesp on Mar 16, 2018 12:45:22 GMT -5
Abrasive Armory on Ebay
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jamesp
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Post by jamesp on Mar 16, 2018 12:52:25 GMT -5
I have tried about every color of AO and it all behaves the same. The only difference in expensive AO and cheap AO is the screening to a guaranteed tight particle size range for super high tolerances totally needed for tumbling. If you knew the range of allowable sizes you would be surprised.
Common AO 500 probably has 20% 300 and 20% 700. abrasive suppliers are allowed to market size with a large degree of size variation. if you buy AO +/_ 3 % particle size variation it may cost $50/ounce or way more if the size variation is tighter than that. Such as finishing the blades on jet engines where a 3 micron scratch may blow the engine from seeding out a stress fracture.
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ohthatspretty
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Post by ohthatspretty on Mar 16, 2018 13:37:31 GMT -5
That is exactly the info I was after. Thanks so much fellas!!
This forum is awesome!
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ohthatspretty
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Post by ohthatspretty on Mar 16, 2018 15:42:24 GMT -5
So I was looking at AO on the abrasive armory store in eBay.
According to them there is a significant difference between brown and white AO. They wrote that brown grit gets rounded as it is used And that the white will fracture creating new cutting edges.
I've read on this site about AO fracturing during vibe polishing to the point that you don't even need to change it to achieve some pretty awesome stones.
Eventually it will just turn to polish.
Any thoughts on if the forces created in a little tumbler would be enough to fracture say 25 white grit down to 50 then 100?
Seems like that would be a nice way to start on some harder stones.
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pizzano
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Post by pizzano on Mar 16, 2018 17:21:48 GMT -5
So I was looking at AO on the abrasive armory store in eBay. According to them there is a significant difference between brown and white AO. They wrote that brown grit gets rounded as it is used And that the white will fracture creating new cutting edges. I've read on this site about AO fracturing during vibe polishing to the point that you don't even need to change it to achieve some pretty awesome stones. Eventually it will just turn to polish. Any thoughts on if the forces created in a little tumbler would be enough to fracture say 25 white grit down to 50 then 100? Seems like that would be a nice way to start on some harder stones. I think the material (stone) you are breaking down will play a part in the process.......the grit is not only breaking down, but the residual material the stone is leaving in the mix will also interact with the grit......particularly harder stones.
Just out of curiosity........why the attraction to AO....?
The "standard" practice for most "hobby folks" is to use Sic for the grinding stages.......most likely due to the cost and availability........I may be out in left field with this notion, but the greatest amounts of grit (per application) are used in the 1st & 2nd & 3rd cycles.....be it 60/90 - 120/220 - 400 grades........AO is kind of expensive to routinely cycle through those stages, given the amount that is used......even if not re-charging during like cycles.....?
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ohthatspretty
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Post by ohthatspretty on Mar 16, 2018 19:36:10 GMT -5
I think the material (stone) you are breaking down will play a part in the process.......the grit is not only breaking down, but the residual material the stone is leaving in the mix will also interact with the grit......particularly harder stones.
Just out of curiosity........why the attraction to AO....?
The "standard" practice for most "hobby folks" is to use Sic for the grinding stages.......most likely due to the cost and availability........I may be out in left field with this notion, but the greatest amounts of grit (per application) are used in the 1st & 2nd & 3rd cycles.....be it 60/90 - 120/220 - 400 grades........AO is kind of expensive to routinely cycle through those stages, given the amount that is used......even if not re-charging during like cycles.....?
That's actually a good question........ Originally I ordered a pack of grit from some random seller on eBay that was labeled for a 3lb tumbler. I didn't realize it was a pack of grit good enough for one tumble in a three pound tumbler!! I have about 50lbs of Black Magic blasting media from Tractor Supply that I have left over from some other project I finished a while back. I ran a google search to see if I could use that in my first stage tumbles. I read somewhere (not sure where) that Aluminum Oxide is superior as it has a much sharper profile than SiC and that the blasting media wouldn't have the staying power for a good tumble without having to change out the grit every couple of days. That is before I found this site. I know that the next pack of tumbling media I bought from Amazon and all stages are listed as SiC with the exception of 1200 which is AO.
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jamesp
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Post by jamesp on Mar 16, 2018 19:52:46 GMT -5
So I was looking at AO on the abrasive armory store in eBay. According to them there is a significant difference between brown and white AO. They wrote that brown grit gets rounded as it is used And that the white will fracture creating new cutting edges. I've read on this site about AO fracturing during vibe polishing to the point that you don't even need to change it to achieve some pretty awesome stones. Eventually it will just turn to polish. Any thoughts on if the forces created in a little tumbler would be enough to fracture say 25 white grit down to 50 then 100? Seems like that would be a nice way to start on some harder stones. Fused white AO 22 from the Abrasive Armory after 3 days. The AO particles were still in the mix with the rocks but rounded. AO 22 is big, like bigger than sea salt.
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pizzano
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Post by pizzano on Mar 16, 2018 19:57:18 GMT -5
Well....I go with what the folks at Covington Engineering and the Yucaipa Gem & Mineral folks suggested to me for vibe and rotary tumbling.....I do not lap/cab or otherwise use more sophisticated methods of lapidary....and I know squat about Tractor Supply Black Magic......lol...Although, I do frequent there for pet supplies and outdoor gear.
I'm just reinforcing what I've learned and practiced....I'm still new at this as well.
I doubt there are many here that would not recommend Sic over AO for grinding stages, unless there was some specific reason for the AO application.......there are quite a few "Masters" here that we all can learn from.
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ohthatspretty
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Post by ohthatspretty on Mar 16, 2018 20:15:53 GMT -5
Fused white AO 22 from the Abrasive Armory after 3 days. The AO particles were still in the mix with the rocks but rounded. AO 22 is big, like bigger than sea salt. That's nuts!!! Did you put 22 grit in the vibe?
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jamesp
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Post by jamesp on Mar 17, 2018 3:43:39 GMT -5
Never noticed a difference in BFA/WFA in tumbling which is a whole different world than sand blasting. Pretty sure the Abrasive Armory's #1 customer is sand blasters and not tumblers. The white starts out aggressive enough to remove SiC 4 scratches and take your rocks to polish though. I never used the brown with SiC 4, only SiC 30 and it had no problem removing 30 scratches. My vibe never could crush AO 22, but one of them would crush AO 80 into oblivion. "Both main applications are: in refractory and abrasives products. Both Mohs hardness are: 9.0, Differences are below; BFA bulk density is (1.53~1.99g/cm3) and true density (3.90g/cm3). While WFA bulk density (1.75~1.95g/cm3) and true density (3.95~3.97g/cm3). Main raw material of BFA is bauxite, and main raw material of WFA is calcined alumina powder. BFA has Al2O3 content of 95% Min., WFA has Al2O3 Content of 99% Min. BFA has refractory temperature 1850 Celsius degree, WFA has refractory temperature 2100 Celsius degree. Although their Mohs hardness is 9.0,WFA is even harder than BFA, and BFA is more flexible than WFA. learn more info:brown fused alumina,white fused alumina,black silicon carbide,glass beads,garnet sand|J.L Group" www.quora.com/What-is-difference-between-white-fused-alumina-and-brown-fused-alumina
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jamesp
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Post by jamesp on Mar 17, 2018 3:45:58 GMT -5
A source of white AO:
"Calcined Kaolin Formula: Al2O3.2SiO2 Alternate Names: Cal Kaolin, Meta Kaolin
Oxide Analysis Formula Al2O3 45.90% 1.000 SiO2 54.10% 2.000 Oxide Weight 222.22 Formula Weight 222.22 If this formula is not unified correctly please contact us. GSPT - Frit Softening Point 2930F Calcined kaolin is a powdered white non-plastic material. It is raw kaolin that has been fired (in a rotary calcining kiln) high enough to remove the 12% (approx) crystal water. The material is a good example of how we can alter the mineralogy of a material to affect its working properties while maintaining the chemistry to maintain fired properties.
This material is often under-utilized in traditional ceramics, people do not realize its true value. Kaolin is pure clay mineral, having a fired chemistry of 1 part Al2O3 and 2 parts SiO2. But the raw clay crystals are hydrated, having 12% crystal-bound water. This is the secret to their plasticity. Al2O3 is essential to the chemistry of the vast majority of glazes and kaolin is ideal source material (because all glazes also need the SiO2 that it supplies and it readily decomposes in the melt). The other principle affordable and readily meltable supplier of Al2O3 are feldspars, however they also supply lots of KNaO (and in many cases oversupply it to get the needed Al2O3). --------Raw kaolin also supplies suspension to the glaze slurry------- and it hardens the dry glaze layer. However once raw kaolin percentages pass 20% in a recipe shrinkages can be to high (causing crawling). In these cases substituting part of the raw kaolin for calcined material solves the problem, maintaining the chemistry of the glaze but reducing the shrinkage and cracking. In other words, by substituting some of the raw kaolin for calcined the physical properties of the glaze slurry can be controlled without impacting the chemistry of the fired melt. Of course, mixing the raw and calcined materials must take into account the LOI of the raw material (12% less calcined is needed)."
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ohthatspretty
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Post by ohthatspretty on Mar 17, 2018 7:16:23 GMT -5
Great info here James. I appreciate your time!
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jamesp
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Post by jamesp on Mar 17, 2018 7:19:52 GMT -5
Great info here James. I appreciate your time! Copy and paste, nothing to
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pizzano
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Post by pizzano on Mar 17, 2018 11:27:56 GMT -5
So James......for what purpose and application would you recommend the use of AO Grits, say for tumbling purposes other than the "polish" stages on stone materials......? I realize you are heavy into glass/ceramic products but how would rotary/vibe tumbling be better served for agates, jaspers, quartz, ect. using AO rather than Sic......And are there benefits for cab/lap applications as well.....?.........Thanks..!
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