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Post by pauls on Feb 25, 2014 20:33:36 GMT -5
I have a couple of batches in the polish at the moment, Its largely made up of saw offcuts so lots of slabby bits, but a good mix of sizes and shapes as well as roundish ones. I noticed that in the coarse grind stages the slabs get thinner very quickly but don't grind much on their edges, Looking in the barrel you can see why, the slabs tend to skate down rather than roll. In the polish these same slabby bits are taking a fantastic polish around the edges but are still quite dull on the flat edges, they are still skating so you would think the flats would be gleaming but they aren't. This is a vibrasonic tumbler with a bin shaped barrel and the stones roll much like a rotary, its not one of the donut shaped ones. I had plastic beads in but they seemed to absorb the vibrations and stop anything happening so I sieved them out and got the rolling action happening again but still nothing happening on the flats. I have previously polished flat pieces in a rotary and they come up fine, this is really my first go at the vibe. Any ideas whats happening?
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Post by pauls on Feb 25, 2014 22:57:44 GMT -5
This is going to be one of the shortest threads ever. I grabbed a handful of stones out of the tumbler, washed and dried them and had a look at them through a magnifier out in the sun. Lots of sun here. (rubbing salt into wounds) LOL. The first thing that struck me is how much they looked like newby cabs that get rushed through the sanding stages. First off to prove my theory I tried polishing the dull spots with the tin oxide buff, they took a reasonable polish but still had that newby look. Then I tried 600# and then polishing, much better but still micro pitted and far from a great polish. So back to 240# then 600# then polish, perfect. So the answer is they got rushed through the finer grits. Still new at Vibe tumbling, so a bit of experimenting with times etc. required. They are all back in 240# for a few days and will not be going further until they are good and ready.
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on Feb 25, 2014 23:55:52 GMT -5
To polish flats you need to have at most 1/4 filled with flats and 3/4 small pebbles of the same hardness. Even then you have to run each stage longer than usual.
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daisyd681
starting to spend too much on rocks
Member since January 2011
Posts: 104
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Post by daisyd681 on Feb 26, 2014 9:00:43 GMT -5
Everything I've read on here suggests that ceramic pellets are used in a vibe rather than plastic. I've got about a 50-50 mix of flats and pellets in the polish now. I can't speak to the shine as of yet, but the movement is definitely good with that mix. I had a bunch of smaller beach stones in there as well at first and the action wasn't so good. I tried taking some of the pellets out and it got worse. When I took all the beach stones out and left the flats and pellets I got the best action. I'm nowhere near an expert by any stretch of the imagination, this is just what I've found.
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Post by 150FromFundy on Feb 26, 2014 16:39:13 GMT -5
As Steve said, mix the load up. Too many flats simply get stuck together and slide against one another.
As daisyd681 said, use ceramic pellets in a vide. Plastic pellets are a little too light and tend to float on top. Ceramic pellets roll and rumble like rocks.
A vibe does little to alter the shape of the stones. Most of the grinding action will be in the 120/220 stage. If you want rounded edges, you need to get them rounded in the 120/220 stage. Once you move on to 500F, 1000F and polish, you are basically just removing scratches and having virtually no effect on shaping the stone.
Good luck.
Darryl.
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