mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 166
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Post by mgroothuis on Sept 2, 2023 19:08:03 GMT -5
I have a huge stockpile of rocks I’ve collected over the past 10 months of getting into this hobby. Some of my early-collected rocks are very nice unakite but they have more black flecks (mica?). After learning how a Lot-o undercuts this stuff, I’ve set them aside. Does rotary tumbling undercut the same or less?
I have only tumbled one large 3-4lb rock from beginning to end in the rotary. It turned out great, but it had minimal black. I’m wondering if it’s worth the effort and a month of tumbling some of my earlier finds.
Ah…. The learning process. Thanks.
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mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 166
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Post by mgroothuis on Sept 11, 2023 16:43:24 GMT -5
(crickets) ---tumbleweed rolls by---
Haha, I guess I'll just tumble and find out next month!
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Post by knave on Sept 11, 2023 17:07:21 GMT -5
mgroothuisHello, it’s unfortunate we didn’t reply yet. The rotary tends to make round shapes or at least rounded shapes. The vibes are great for finishing and polishing once the large flaws are gone and the desired shapes are achieved. Undercutting is gonna happen if the rock has a variable hardness. It may be slightly less in a rotary, I don’t know.
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dillonf
fully equipped rock polisher
Hounding and tumbling
Member since February 2022
Posts: 1,622
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Post by dillonf on Sept 11, 2023 17:08:55 GMT -5
mgroothuis I don't have a definitive answer for you, but I am starting to think that the Lot-O I have is more prone to undercutting than the rotary. I've polished unakite twice - the first time 100% in the rotary and it came out great. The second time I did coarse in the rotary and 220-polish in the lot-o and it came out even better. That is likely due to the quality of the rough not differences in what we each did. I got my rough from the rock shed. All that said if I was in your shoes and getting undercutting in the vib I would try 100% rotary. I'd keep it at ~75% full. When it gets to polish I'd make sure there are lots of smalls and run the polish for 2 weeks straight with no clean out after the first week. Hope that info is useful.
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Post by chris1956 on Sept 11, 2023 21:03:24 GMT -5
I have done some unakite in tumblers. I always start in rotary and finish (220 and polish) in vibratory. I haven't had too many issues with undercutting but haven't had a lot of black in the rocks I have done.
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ashley
Cave Dweller
Member since February 2023
Posts: 927
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Post by ashley on Sept 11, 2023 21:10:19 GMT -5
I would imagine that it would be the same but I don’t know for sure. Interested to see your experiment.
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mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 166
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Post by mgroothuis on Sept 12, 2023 14:42:02 GMT -5
I have done some unakite in tumblers. I always start in rotary and finish (220 and polish) in vibratory. I haven't had too many issues with undercutting but haven't had a lot of black in the rocks I have done. Same. Lots done in the Lot-o, but now I specifically pick rocks without any black.
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mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 166
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Post by mgroothuis on Sept 12, 2023 14:43:08 GMT -5
Thanks for the replies. I guess I'll just have to complete a run to see the true difference. I've been collecting bigger rocks that won't fit in the Lot-o. I have a QT12, QT66, and a 33B that aren't being used since I built my main tumbler cabinet. Those might be a good option for the rotary polish batches since my main tumbler is for rough stage.
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Post by Bob on Sept 28, 2023 10:41:49 GMT -5
Unakite is weird for me. I have never tumbled a barrel of 100% unakite to find out what happens--maybe it gets better. I mix it up with other stuff. Some batches are better than others. Some individual pieces undercut even when others that look like them come out good. If that happens, I try them again with another batch (meaning put back in 600 or 1,000 grit or even down to 220 if really messed up) and often they come out fine. I suspect there is some unknown ideal mix of sizes of other rocks that helps, but it would be very difficult to research that.
Even of my keepers of unakite that polished nicely, almost none I would call perfect w/o any flaws at all. Sometimes the faces look great but there is one edge that is a bit rough.
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Post by stardiamond on Sept 28, 2023 15:32:05 GMT -5
I don't tumble. My first cabbing set up was purchased used equipment. Worn 80 and 220 grit diamond wheels, a lapidary belt sander with worn 400 grit sandpaper and a leather polishing wheel with tin oxide. Some material came out great and some undercut. My solution was to go all diamond with a Genie. No undercutting but there are a zillion ways to polish and different material responds better to a different polish. There is no one way fits all.
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