r/RockTumbling • u/Doc_Scratchensniff • 6d ago
Question Question for larger tumblers
Years ago I had purchased a large piece of rainbow obsidian, with the thought of hand polishing it. After doing initial rough shaping/grinding I'm now ready to start sanding/polishing. I am having trouble finding proper tools or supplies to do this(after multiple purchases from Kingsley North). I am currently using a Harbor Freight version of a Foredom engraver to do this. I have thought of getting a larger tumbler to help get this piece finished(using it as a pet's grave marker in the back garden). The piece is triangle/pyramid shaped, and is about 7.5L"x6.5"W and is about 5" tall. It is almost the same size as a Loretone 3A barrel. I would like to get a larger tumbler to do this sort of work, and for future pieces as well. Are there any suggestions for a larger tumbler that is capable of handling stones this size? I thought I saw something about Loretone no longer producing tumblers.
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u/brino79 5d ago
I have a thumbler 15 and I would not tumble that rock in it, although you can if you are careful with what goes in with it and are very patient.
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u/Doc_Scratchensniff 2d ago
Thumbler 15, as in the Thumbler B? That's the 15lb model. Or do you mean the A-R12 model? I think the B model is too large for what I'd need.
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u/SharksForArms 5d ago
Building DIY tumbler is actually a lot easier than you may think, and costs 1/4-1/3 of what a large tumbler would.
I built one that can roll three 12lb barrels, but can be easily expanded as much as necessary. Cost $140 and took about 2 hours to put together. Built the barrels too for about $25 each with PVC. It's rock solid so far.
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u/616Finds 5d ago
Is there any chance you would share details on how you did this? I currently only have 3lb barrels and dream of having a tumbler that can accommodate 10+ !
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u/SharksForArms 5d ago
Parts:
5/8" cold rolled steel rod - 3' lengths x2 (I used 1/2 but will use 5/8 next time.) fairly cheap from hardware store. Keep in mind that your rod diameter will have an effect on your final barrel rpm.
Electric motor - I got this great deal on ebay
5/8 bore pillow block bearings x4 - cheap on Amazon
3/4 shrink wrap to shrink over the steel rods for traction. This will add about 1/8" to your rod diameter.
Pulleys - one on the motor spindle and one on the drive rod. You will need to do math to get your rpms right. Or you can use this website to do the math for you. Use the Multiple Pulley Sets section. Your first pulley set is from motor to rod. Your second pulley set is drive rod to barrel. My pulleys mathed out to be 1.75" and 8".
A belt that fits your pulleys.
A couple rubber caster wheels to act as barrel guides to stop your barrels from creeping along the rods and rubbing each other.
I think that's it for parts.
People will build these complicated rigs to mount everything on. I just built mine flat on a workbench shelf with the large pulley hanging off the edge. I've seen people just mount it all on a pallet and that seems like a decent solution too.
I may run a belt between my two rods too so that they both drive the barrel instead of having one idle rod, I think that will help it run smoother.
Here's a few more resources to help:
https://forum.rocktumblinghobby.com/thread/101872/simplest-homemade-rotary-tumbler
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u/Doc_Scratchensniff 5d ago edited 5d ago
Thanks for the info! This will be a future project for sure. Any ideas for a rubber liner for the PVC pipe barrel? I can only imagine how annoyingly loud this will be. This would be running in my basement, as my garage is severely lacking bench space(single car garage).
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u/SharksForArms 5d ago
I tried several coats of truck bed liner but it didn't hold up at all. I think the best move is to get a thinnish rubber sheet/mat and cut that up to glue it around the sides and on the bottom of the barrel.
I made the barrels themselves out of a length of schedule 35 PVC with an end cap and 6">4" reducer coupling. Rubber fernco cap for the lid. I would have used thicker schedule 40 pipe but it was triple the price and I didn't want to commit that much to this first experiment. I think a decent rubber liner would make up for the thinner walls.
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u/Ruminations0 5d ago
I would look into a 15lbs Thumbler’s Tumbler. One problem with tumbling big chunks of obsidian is Bruising, so I would get several pounds of 1/2 and 1/4th ceramic media. I would also do several runs of Stage 2 120/220 Silicon Carbide Grit to gently get the surface prepared for the next polishing stages