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Leeway for error in the rpm of a ball mill?


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Posted (edited)

So my 6lb harbor freight rock tumbler (two 3lb jars) arrived yesterday.😀 The first thing I did was make sure it works properly, then start to adjust the rpm according to the instructions on sky lighter. On sky lighter it said out of the box it should be going about 60rpm, but mine consistently runs at 51rpm. The ID of the jar is about 4.1in and the OD is 4.5in. My optimal speed to run it at is 90-91rpm, so I would need an outside diameter of about 7/8in. Lowe's doesn't have a lot of kinds of tubes that have an OD of 7/8in. But I found 3 that would work together. The first tube is 5/16 ID, 7/16 OD the next one is 3/8 ID, 5/8 OD, the next one is 5/8 ID, 7/8 OD. When I slide the tubes onto each other it actually turns out to be about 3in in circumference of the last tube because it was forced into the other, so it expanded a bit, so it would give me a speed of about 97.45 rpm. I don't know how far the rpm can be from the optimal rpm without making too much of a difference in the efficiency of my mill. Would it be better to go with a 3/4 OD tube and have about 80rpm or stick with the 7/8 OD tube that would give me about 97 rpm? How much would this decrease my efficiency?

 

Would I be able to sand the vinyl tubes down a bit to decrease the rpm?

 

I'm also using 200 (jar half full) of 1/2in by 1/2in stainless steel cylinders(cylpebs, slugs, or whatever you want to call them.) I don't know if that makes any difference.

Edited by PyroNinjaah
Posted

A few rpm either way wont make much difference. As long as you tested the rpm with the media and not just empty jars you`ll be fine ;)

Posted
Ok, I found out that on one of the "reinforced" vinyl tubes with the string between the layers that I could cut the taxpayer off and leave the bottom layer, so now it's most perfect and I'm getting 92 rpm.
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