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Post by Bob on Oct 6, 2022 16:02:08 GMT -5
...It's either add less grit or increase the stage run time for that batch. For later stages, I usually cut down to 1/2 Tbsp per pound. The goal is not to have any significant grinding, all of that should have been done in the 1st stage. 220 and 600 are all just touching up the grinding marks done in the 1st stage so it should take half of coarse. Same with 500 AO, just do not need as much. The good thing about my method is that I use less of the more expensive grit.... I really like that and agree! Never thought about how could probably use less of 220 and finer for the reason you explain so well. May start trying that immediately. I'm already on the program! Last night, had a 20lb barrel finish 80 and ready for 220. I used only 1 cup of 220 instead of 2. And I had a 12lb barrel finish 60, and ready for 80, so I used 1/2 cup instead of 1 cup. Will be interesting to see what kind of slurry I have in a week. The part you wrote about touching up grinding marks was the crux for me of the matter. Though it's not 100% true for me. For example, coming out of a week in 80 I might leave a pit that is 1/2mm or less deep and let it go into 220 instead of back in 80 for another week. That's because I know 220 is just enough to usually take that out in one batch (1 week run). Using your method, I might have to not do that anymore and let that rock go back into 80 another week, but that would not matter for the big picture of savings. Like you say 600 and 1,000 grit aren't cheap.
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Post by Bob on Oct 13, 2022 11:03:28 GMT -5
Well, I processed that 20lb barrel last night. I noticed immediately that the slurry was thin. In a typical 20lb barrel in 220 stage, I might have 1, maybe 2 rocks get damaged and often none. But there were 10-15 damaged. I suspect it's because using only 1 instead of 2 cups of grit while using the same amount of water as usual. The grit itself I think is a cushion in the beginning, and as rock dust gets in the water the slurry becomes a cushion as it gets thicker during the week as the grit disappears. I need apparently to decrease the water I put in to adjust and will next time. This barrel now has rough rocks in 60 grit so won't be testing using less grit in it for a while.
But, as to the condition of the rocks that weren't damaged, they look fine to me and ready as far as I can tell for 600.
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hypodactylus
spending too much on rocks
Member since July 2021
Posts: 467
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Post by hypodactylus on Oct 13, 2022 12:09:57 GMT -5
Just a thought, but how would adding less water help solve your cushioning/damage problem? I understand that the resulting slurry would be thicker, but there would also be less of it. Air is less cushioning than water. All other variables kept the same, I am not sure adding less water would be helpful on its own. Maybe less water, combined with more media or small rocks?
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lapidarycentral
starting to spend too much on rocks
(Brian Rhode) LapidaryCentral.com - Fueling your Lapidary Addiction.
Member since August 2021
Posts: 218
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Post by lapidarycentral on Oct 13, 2022 12:14:20 GMT -5
I recently, 10 days ago, bought a Lortone QT12. Looking through the instructions I was amazed the instructions called for 20 tablespoons of grit for a load. I bought it to tumble larger rocks and/or tumble some rocks a little quicker than the smaller barrels do. I see other instructive videos say a Tbls per pound of rock. I'm a little confused. 20 Tbls coarse is just over a pound per tumble. For now I'm following Lortones instructions but is that much really needed? signed, I'm such a nube So far we've been using about 14 tablespoons for a qt12, and it seems to be working fine with most materials we've done. But, we do grind out any imperfections afterwards, so if your looking to skip that step, more would probably save a couple days of tumbling.
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Post by Bob on Oct 13, 2022 15:59:36 GMT -5
Just a thought, but how would adding less water help solve your cushioning/damage problem? I understand that the resulting slurry would be thicker, but there would also be less of it. Air is less cushioning than water. All other variables kept the same, I am not sure adding less water would be helpful on its own. Maybe less water, combined with more media or small rocks? I hear you and think your points are totally valid. In a 220 batch, about half the time I use plastic beads, and about half not. I have learned from experience that don't need them if there are plenty of smalls and mixed sizes. That was the case this time, no need for beads. A few years back, before I had enough experience, I would end up with thin slurries at the end of a week and I found them to be associated with greater rock damage, regardless of whether there are plastic beads or not. So I experimented by trial and error lowering the amount of water added and it solved the problem. Sometimes, when I am tumbling a load of touchy material that is softer such as amazonite, sodalite, obsidian, etc. I will overfill with water because I've also learned doing that can make a more gentle tumble with less damage at the end. So it looks like these two strategies conflict with each other and therefore make no sense and you have just caused me to think hard about that! Only now do I realize that when I overfill with water to lessen damage I also overfill the barrel to decrease the internal cascade face, generally filling the material to 80-85% full. And I realize only now I have never tried doing that with conventional hard stuff like agates and jaspers, etc. I guess this complexity of all this has caused me to realize for the first time that we are playing with the water level compared to rock level, water level in the barrel overall, rock level in the barrel overall, and any starting material that might act as cushioning (new grit, plastic beads, small ceramic pieces, etc.), the ending slurry thickness due to rock dust in the water--all that before even introducing the variable of speeds and materials and whether the barrel sides flex outward upon impact (rubber barrels) vs. don't (rubber lined barrels or poly barrels). And, what the water added is. I used very dirty water that was poured off and in which the rock dust has barely settled.
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hypodactylus
spending too much on rocks
Member since July 2021
Posts: 467
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Post by hypodactylus on Oct 13, 2022 17:04:36 GMT -5
Yeah, there are a lot of variables. I am personally trying to adjust my process with my larger tumbler to avoid damage to the rocks, so your post got me thinking.
I may have to play around with some of the things you have mentioned!
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Post by Bob on Oct 13, 2022 20:29:06 GMT -5
Yeah, there are a lot of variables. I am personally trying to adjust my process with my larger tumbler to avoid damage to the rocks, so your post got me thinking. I may have to play around with some of the things you have mentioned! Is your barrel 20lb or larger? What really helped me was slowing down the RPM on my large barrels.
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hypodactylus
spending too much on rocks
Member since July 2021
Posts: 467
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Post by hypodactylus on Oct 13, 2022 23:50:14 GMT -5
Is your barrel 20lb or larger? What really helped me was slowing down the RPM on my large barrels. No, just a 12lb barrel.
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Post by Bob on Oct 14, 2022 12:17:13 GMT -5
Well, last night I had a 12lb barrel with 1,000 grit for which I had used 1/2 cup rather than the usual 1 cup. When I saw how thin the slurry was, I knew immediately I had problems. Normally, I would have no damage at all at this stage in processing. I had 5-6 damaged pieces, even though there was also plastic pellets for cushioning (about 15% of so of rock material by volume).
It was a mistake I think for me to go all in on this so soon. I'm going to back off and take it a step at a time going forward. For instance, I just started this in another 1,000 batch and used 3/4 cups and also lowered the water.
Again, the rocks that successfully came out seem to be normal and ready for polish next.
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