Post by Admin on Nov 13, 2021 12:01:43 GMT -7
Nov 9, 2021 21:14:02 GMT -7 @ingawh said:
Who has the secret to tumbling Howlite? 
I haven't tumbled it before, but when I pulled them out, I must admit I was disappointed. I didn't even use just my old two-step, I added an extra step, but couldn't get a real shine - or is that just how howlite rolls?
I found a rough stone had broken and was probably buggering things up a bit, but even so, I had hoped for more.... I can go back a step and do a bit of re-smoothing, then I want to take another run at getting a clearer shine. What polishes has anyone tried that might coax a little more out this stone? Any other tricks-of-the-trade you have to share would be greatly appreciated.
Thanks, Team!
Nov 11, 2021 2:25:07 GMT -7 @jamesp said:
Good to see you tackling the tough challenges again @ingawh. The secret to tumbling soft stones from start to finish may just be the vibe.
Add also abrasive hardness relative to the soft stones(and media used) and slurry thickness.
Abrasives:
Relative abrasive hardness has to be an influence.
Take it to the extreme, Mohs 9 alum ox being used on a 100% batch of Mohs 2 soapstone will never break down to finer AO.
Add say 50% Mohs 7 pea gravel or ceramic media to soft stones and it's a different game, the media will assist breaking down the AO.
So 50 to 70 percent hard media is probably the way to go with AO on soft stones unless using softer abrasives like glass powders, diatomaceous earth, iron oxide powders, etc.
Vibe:
As far as the vibe is concerned I know that the oversea folks use variable amplitude/frequency vibes to tumble/polish soft stones. So the motor is variable speed and the counter-weights are adjustable.
Take it to the extreme - the Lot-O's intended vibration rate(frequency) is 50 vibes/sec or 3000 vibes/minute due to a 3000 rpm off-balanced motor. If the frequency stays the same but you double the amplitude or from 1mm to 2mm of each vibe cycle travel the acceleration rates increase exponentially. Increase the acceleration and the impact forces also rise exponentially. If the vibration travel could be increased from 1mm to say 6mm and maintain 3000 vibes per minute the vibe would likely damage hardened ball bearings, shatter ceramic media, and about destroy any material put in the hopper.
Most industrial vibes have a readout displaying real time frequency and amplitude. Very simple. If tumbling/polishing aluminum you go with soft media and low amplitude. To shot peen or harden steel surfaces you go with both elevated amplitude and frequency since you want to beat the crap out of the surface of the steel lol.
So a fixed amplitude/frequency vibe is just what it is. There is not much of an adjustment on the Lot-O to alter these parameters. Take a Vibrasonic lapidary vibe, it is a constant frequency vibe (3450/min) but the counter weights can be adjusted from a very low amplitude to a high amplitude . Because of the built in springs the optimum amplitude for an 8 pound hopper can be matched to the optimum amplitude for a 50 pound hopper by simply varying the counterweights. I know this, on a scale of 1 to 5 off-balance I set the sonic to 5 with a 14 pound hopper full of glass and it shattered it. It was like filling a 1 gallon paint can with tumbles and placing it into a paint shaker machine with about a 100mm amplitude and fairly high frequency.
Granted the paint shaker is a gross example but the same damaging forces occur within our little vibes.
Don't be surprised if even the gentle Lot-O is too violent for Mohs 3-4-5 stones. Many attempts have been made to get a high polish on softies on this forum.
So that is my opinion and you know what folks say about opinions lol.
I wish you luck !