petrifried
starting to spend too much on rocks
Member since August 2015
Posts: 100
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Post by petrifried on Oct 27, 2015 0:50:54 GMT -5
About 6 days in and just got a slurry going yesterday. Since things thickened up the rocks seem to be grinding much faster. (3 days@26rpms and 3 days@39 rpms not on purpose) Added about a cup sugar after a few days without a slurry. It didn't thicken up so I added a few small handfuls of sawdust and I had a nice looking slurry the next day. I took out 3 agates that I didn't want the exterior design to grind off. Dumped off some liquid tell it was below top of the rocks. A Handful of rocks that are in the course grind I pulled this one out in hopes of keeping the design. Any suggestions or criticism?
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Post by captbob on Oct 27, 2015 1:25:51 GMT -5
Rocks are shaping nicely. Hard to tell from pictures looking down in a barrel, but there seems to be quite a bit of empty space in there. How full is your barrel?
You didn't take a before picture did you? Some of those rocks look like they have been tumbling for much longer than 6 days unless they started out already well rounded.
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petrifried
starting to spend too much on rocks
Member since August 2015
Posts: 100
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Post by petrifried on Oct 27, 2015 2:12:06 GMT -5
It started out at 3/4 of a barrel, but is getting lower for sure, I think 2/3 , definitely well over 1/2 full. Some of those were tumbling for eight days in coarse grit before I moved and got set back up, sorry forgot to mention that. The rocks in this batch were all pretty well rounded by the Ocean or River before I found em. Should I add more rocks to get the barrel full again? But then I might be low on liquid.. Before photo that rock
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Oct 27, 2015 5:55:46 GMT -5
I would add a little water. Add fresh grit with out doing a clean out to maintain same slurry. At 39 RPM and 3-4 days the grit will be about worn out with barrel 2/3 full. Looks like you have mostly agate. They will do fine in 5/8-2/3 barrel and I would not add rocks but maintain a milkshake slurry(no thicker) throughout coarse grind.
You have a perfect mix of sizes and a fast coarse tumble going on there. Sugar is a great additive for thickening and lubricating. It causes gas in some cases, maybe the water or the rock composition. Never had gas w/sugar with my slightly acidic 6.7 PH water. I converted to clay because my sugar slurry was attracting ants.
On your last coarse grit addition I would add some smallish smooth pebbles to fill the barrel back to 3/4 for more gentle action. Better to have a 3/4 full barrel for 220-500-1000-polish cycles. Or transfer to vibe for 220-500-1000-polish cycles.
What coarse grit are you using ? I prefer SiC 30 or 45/70.
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petrifried
starting to spend too much on rocks
Member since August 2015
Posts: 100
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Post by petrifried on Oct 27, 2015 23:03:31 GMT -5
I am using 60/90 grit. I'm going to go to Ed's House of Gems tommorrow in Portland to get some more course grit and probably buy a 12lb lortone barrel and maybe a 6lb barrel also. I would like to have a dedicated barrel for polish.
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petrifried
starting to spend too much on rocks
Member since August 2015
Posts: 100
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Post by petrifried on Oct 30, 2015 13:44:18 GMT -5
I checked all the rocks and they are ready for the fine grind! I did a complete clean out and then tumbled them overnight with dawn dish soap, did another cleaning of everything and have the rocks in the barrel 3/4 full awaiting water and grit. I weighed the rocks and i was surprised to find that I have 14lbs of Rock making the barrel 3/4 full! What is the best way to measure the proper amount of grit? My Gem Tumbling and Baroque Jewelry Making book says 1lb of grit for 8 lbs of rock and the Pro-Am book says 1 1/2 ounces of grit for 1lb of Rock...
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Oct 30, 2015 14:50:12 GMT -5
I use one measuring cup of coarse grit for 14 pounds. One cup of SiC 220 for 14 pounds of rock. That was a fast coarse grind. I don't clean very much when going to 220, the coarse grit is usually ground to nothing after a week anyway. To each his own.
If you run barrels on the same set of shafts make sure they rub against each other well. Especially if they are different diameters.
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