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Post by toiv0 on Feb 7, 2021 10:12:04 GMT -5
I read a couple threads where they talk about the amount of time it takes aluminum oxide break down. I can neither remember the content or find the threads. I put a load in the vibratory to take the crust off some turquoise green stone and take a few light scratches off a few cabs. Because I just wanted the rind and scratches out I used 500 grit so not to be too agressive and ruin the green stone. So I think I read 500 breaks down to a thousand in a couple days. Is this correct? Did I go agressive enoug
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victor1941
fully equipped rock polisher
Member since November 2011
Posts: 1,979
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Post by victor1941 on Feb 7, 2021 15:08:47 GMT -5
ToviO, I agree that it has been suggested that grit breaks down by half every 24 hours but have not seen (or looked for) scientific data presented in RTH or elsewhere. I also wonder if the type of vibe or rotary would affect the rate of breakdown with a like media or material. When I was in college, many years ago, I did an experiment breaking down raw clay(mined) to a powder and vibrating through calibrated sieves for the control. I then added the clay, water, and ceramic balls to a ball mill and measured particle size at specific time periods. The experiment was to determine how long it would take to get a specific particle size for product use.
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 766
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Post by lordsorril on Feb 7, 2021 21:38:26 GMT -5
If someone has access to a decent microscope: It should be easy to measure a sample of grit at different time points from a vibe tumbler to get a general idea.
Just like all things rock tumbling though: I think there are a lot of factors in play with how fast the grit breaks down.
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Post by hummingbirdstones on Feb 8, 2021 9:45:41 GMT -5
I read a couple threads where they talk about the amount of time it takes aluminum oxide break down. I can neither remember the content or find the threads. I put a load in the vibratory to take the crust off some turquoise green stone and take a few light scratches off a few cabs. Because I just wanted the rind and scratches out I used 500 grit so not to be too agressive and ruin the green stone. So I think I read 500 breaks down to a thousand in a couple days. Is this correct? Did I go agressive enoug I want to say that jamesp did one of those posts about how it breaks down. Maybe he'll refresh our memory (or lack thereof).
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
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Post by jamesp on Feb 9, 2021 4:17:13 GMT -5
I read a couple threads where they talk about the amount of time it takes aluminum oxide break down. I can neither remember the content or find the threads. I put a load in the vibratory to take the crust off some turquoise green stone and take a few light scratches off a few cabs. Because I just wanted the rind and scratches out I used 500 grit so not to be too agressive and ruin the green stone. So I think I read 500 breaks down to a thousand in a couple days. Is this correct? Did I go agressive enoug I want to say that jamesp did one of those posts about how it breaks down. Maybe he'll refresh our memory (or lack thereof). After 2 days AO 500 should be down to 1000 when running Mohs 7 rocks for sure Billy. But it may not break down very fast if running say Mohs 4 fluorite unless you add ceramic media or some other hard media. Say you are running 100% soft fluorite in SiC 60, the SiC 60 may take weeks to break down and your fluorite may grind to almost nothing with the aggressive SiC 60 staying 60 grit. But that is an extreme case. AO 500 is so much less aggressive than SiC 60 so it would probably never wear the flourite to almost nothing. The green stone sounds like it may be on the soft side. If you just doing a surface touch up the 500 should do fine.
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thebeef
having dreams about rocks
Member since September 2020
Posts: 62
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Post by thebeef on Feb 10, 2021 3:13:34 GMT -5
After 2 days AO 500 should be down to 1000 when running Mohs 7 rocks for sure Billy. But it may not break down very fast if running say Mohs 4 fluorite unless you add ceramic media or some other hard media. Say you are running 100% soft fluorite in SiC 60, the SiC 60 may take weeks to break down and your fluorite may grind to almost nothing with the aggressive SiC 60 staying 60 grit. But that is an extreme case. AO 500 is so much less aggressive than SiC 60 so it would probably never wear the flourite to almost nothing. The green stone sounds like it may be on the soft side. If you just doing a surface touch up the 500 should do fine. Considering how AO breaks down, I've been trying to discern the advantage to multiple steps of AO rather than just continuing with the original 500 as it breaks down.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
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Post by jamesp on Feb 10, 2021 4:46:04 GMT -5
In most cases it is quicker to use steps of abrasives in a tumbler to remove surface imperfections thebeef. Deep imperfections are removed fastest with coarse abrasives at the start. As the imperfections get shallower it is best to move to finer abrasives until the imperfections reach zero depth(polish). However coarse aluminum oxide can round off until it removes imperfections if left running long enough. AO 500 can deliver an excellent polish when used in a vibe. Using a powerful vibe these rocks were polished in 3 weeks using only AO 22. Or AO 220 for 3 days - AO 500 for 3 days - AO 14,000 for 1-2 days would have taken only 1 week. www.flickr.com/photos/67205364@N06/sets/72157681139306525
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thebeef
having dreams about rocks
Member since September 2020
Posts: 62
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Post by thebeef on Feb 10, 2021 18:22:12 GMT -5
In most cases it is quicker to use steps of abrasives in a tumbler to remove surface imperfections thebeef . Deep imperfections are removed fastest with coarse abrasives at the start. As the imperfections get shallower it is best to move to finer abrasives until the imperfections reach zero depth(polish). However coarse aluminum oxide can round off until it removes imperfections if left running long enough. AO 500 can deliver an excellent polish when used in a vibe. Using a powerful vibe these rocks were polished in 3 weeks using only AO 22. Or AO 220 for 3 days - AO 500 for 3 days - AO 14,000 for 1-2 days would have taken only 1 week. www.flickr.com/photos/67205364@N06/sets/72157681139306525I get that, generally. In my case, I do rough in rotaries and then move to a Lot-O for the later stages. Typically, it goes rotary rough SiC 60-90, Lot-O SiC 120-220, Lot-O AO 500, Lot-O AO 1000, occasionally an even finer AO/CO. So, what I'm trying to figure out is whether I'm redundant once I reach the AO stages - why not just let the AO keep working?
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
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Post by jamesp on Feb 11, 2021 6:45:57 GMT -5
In most cases it is quicker to use steps of abrasives in a tumbler to remove surface imperfections thebeef . Deep imperfections are removed fastest with coarse abrasives at the start. As the imperfections get shallower it is best to move to finer abrasives until the imperfections reach zero depth(polish). However coarse aluminum oxide can round off until it removes imperfections if left running long enough. AO 500 can deliver an excellent polish when used in a vibe. Using a powerful vibe these rocks were polished in 3 weeks using only AO 22. Or AO 220 for 3 days - AO 500 for 3 days - AO 14,000 for 1-2 days would have taken only 1 week. www.flickr.com/photos/67205364@N06/sets/72157681139306525I get that, generally. In my case, I do rough in rotaries and then move to a Lot-O for the later stages. Typically, it goes rotary rough SiC 60-90, Lot-O SiC 120-220, Lot-O AO 500, Lot-O AO 1000, occasionally an even finer AO/CO. So, what I'm trying to figure out is whether I'm redundant once I reach the AO stages - why not just let the AO keep working? Rotary then to vibe is a great way to tumble. The Lot-O does lay a fine polish down with AO 500. On Mohs 7 I often do a mix of real coarse SiC 4-8-16 in rotary, then SiC 500 in the vibe to remove coarse grit scratches, then AO 220, then AO 500 for final vibe polish.(SiC 500 is much more abrasive than AO 220). Because the vibe is faster than the rotary I only use the rotary for 1 step in most cases. AO 500 is capable of delivering a fine polish on Mohs 7 stones in many if not all vibes. It is often my next to last step and if doing a polish step it is very quick (like 8 hours) when doing glass. Where there can be a problem is when tumbling glass, obsidian and other soft materials because they do not break down Mohs 9 aluminum oxide near as effectively as Mohs 7 stones. Extreme example - if tumbling Mohs 2 soapstone, the soapstone would take a long time if ever to break down Mohs 9 AO. A softer abrasive is best used for soft materials if doing the break down thing.
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Post by greig on Feb 11, 2021 15:48:28 GMT -5
I just put some small pieces of turquoise rough (that were surface collected by a friend in Nevada) into a rotary tumbler without grit. Water only. These pieces were too small for me to cab.
I had read an article (but forget where) to start turquoise with 500 grit. The difficulty is the turquoise breakdown quickly (especially when collected shallow - it gets softer) and to be wary that it sometimes release little bits of quartz which will chew your other rocks. I was surprised that my slurry was thick after a few hours. I cleaned things up and started a tumble again with just water to see what happens. I currently only expect to use AO 1200 polish and will let the rocks tell me when done.
The idea of looking at grit under a microscope to see how it wears down is something I intend to try. Could be a video. ;-)
Greig
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