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Post by grumpybill on Aug 18, 2017 8:52:24 GMT -5
Well...I can verify the article's findings that finer grits remove more material than you'd expect...at least in small barrels with fairly small stones (none much over an inch).
I just did a cleanup after stage 2 (120-220 SiC) of a run that had blue quartz in it and was surprised by how blue the slurry was and how much smaller the pea-sized filler had become.
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,546
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Post by tkvancil on Aug 18, 2017 9:47:07 GMT -5
I think that their experiment is flawed. All ceramic wouldn't provide as much rolling force as a mixed sized batch of rock. Also it said one pound of water which is almost 3 cups worth, far too much for a small barrel. I use 2 cups of water in a 12# barrel with excellent results. IMHO water is the wild card in most tumbles.
Having said that more goes into the mix than water. Barrel size and configuration as well as barrel speed make a difference. Back when I had four 3# and two 6# barrels running, both set ups would use up 60/90 grit completely in one week from a cleanout and start fresh. However when I switched to 46/70 the 3# barrels would always have some coarse left at the end of a week but the 6# used it all up. Smooth vs. hex?
These days I run three 12# barrels and charge with 30 grit, clean out and start fresh each week. Two of them run at about 55rpm. After 3 days of tumbling I have to open them and top off with a little more rock. Volume is down enough that continued tumbling causes impact damage. At that 3 day point there are no noticeable coarse grit particles left. I then let them roll for the rest of the week. The ends of the barrels do suck in so more grinding does occur with the much finer broken down grit.
The third 12# barrel runs at about 28rpm. I did have trouble getting this one to use up the 30 grit. At the end of a week starting fresh I still had coarse grit left, about 60 mesh I'd estimate, and a fair amount of it. Initially I'd just let it go another week. Used up grit but lost time. Running low on grit one week I put in some 80 grit I had left from a ways back, 4tbs. 80 and 16tbs. 30 grit. Low and behold all grit used up in a week. Could all the smaller particles have suspended the larger ones? This last cleanout I pulled all rocks out by hand and let the slurry settle while I inspected the rocks. Dipped out all but about a half inch of the slurry and re-loaded with my standard formula. Barrel has collapsed indicating a good grind.
Looks like, in my case at least, barrel speed is as much a factor as slurry thickness.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Aug 18, 2017 9:51:24 GMT -5
Sic 30/46/60 can always be replaced with SiC 220 and a normal coarse grind run could be made with virgin rock. That should give an idea of how much material is removed by 220.
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