jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 7:17:01 GMT -5
I have tumbled many small slabs and sawn chunks in the past with well balanced mix of rocks. Well, the wear on the center of the flat face varies with the size of the rocks in the rotary. Rolling lots of smalls in 'well balanced' rotary the center of the slab or flat face lacks grinding. More wear on the edges of the sawn face. Rolling all 1.5 -2.5 inch rocks w/out smalls does the opposite. They grind a slight concave into all sawn faces. It is a slight concave, but none the less concave and can be seen easily in the stone's reflected glare. No big deal, not a negative thing. Just an observation. See optical distortion in reflection. Every flat sawn face did this. Hard to see without the glare trick.
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Post by 1dave on Nov 29, 2016 7:22:15 GMT -5
Now that is interesting! A new control method.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 7:48:22 GMT -5
Might as well check out the rock It is Texas pet wood. 7 ounces. Sawn from one 4" X 3" X 2" cobble 8 ways. Half and then quarters. Outside skin of cobble, about how it looked when collected, a no brainer. Middle, lap sawn(in lumber terms) as is above view End sawn(cross cut) Overall
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 7:56:35 GMT -5
Yet another observation. Above rock has impact damage. Mild but damaged in one quadrant. Impact damages only on one face, lower right quadrant. This rock was run with a 14 ounce moss agate. I heard it banging and knew the barrel was not full enough and slurry to thin. Moss agates rarely get these impact damages. More durable. Many others don't either. This wood is easy to fracture with a hammer, so the reason I sawed it. Damage no surprise. All it takes is a few hours at too thin a slurry or not enough rocks in the barrel. Takes a long time to grind off if redoing. Folly of tumbling bigger rocks. Impact damage done in rotary, small half moon fractures at lower right side of rock
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 8:01:12 GMT -5
Now that is interesting! A new control method. Need a job ? If you were 50 years younger and wore a skirt.... Thanks for highlighting Dave. Why not, me always trying new stuff. That's what I do. Whether a screw up or not, highlight away; it is the torture of rocks that makes life bearable.
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Post by Peruano on Nov 29, 2016 8:07:12 GMT -5
I believe concavities in the center are easy to produce in vibes when you have too many slabs and not enough of the smalls to keep the slabs from clinging together (grit becomes trapped between slabs like the crème in an oreo and grinds and grinds and grinds). Bigger slabs are most likely to cling to each others, but that's hard to envision in a rotary. Is it possible your concavity from a similar phenomenon?
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 8:28:41 GMT -5
Yummy yellow/orange moss biscuit. Biscuit whole, bleach white coating ground off with diamond wheel. Shape preserved, classic moss biscuit a bit concave on one side and convex on the other. 1" X 3" X 4". 9 ounces. El primo size for finest moss. Big enough to be cross sawn for cabs. Collected buckets of these on the Rio. Every color and pattern and mix of colors imaginable.
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Post by captbob on Nov 29, 2016 8:36:55 GMT -5
still ready...
Will check the concave/convex thing next cleanout. Gotta see it for myself.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 8:41:28 GMT -5
I believe concavities in the center are easy to produce in vibes when you have too many slabs and not enough of the smalls to keep the slabs from clinging together (grit becomes trapped between slabs like the crème in an oreo and grinds and grinds and grinds). Bigger slabs are most likely to cling to each others, but that's hard to envision in a rotary. Is it possible your concavity from a similar phenomenon? Tom, if I had not sawn over a 100 pounds of Rio 'pebble slabs' cast in concrete back in the day and tumbled them I would keep my mouth shut. Back then I did conventional tumbles with a good mix of rocks. And had no vibe. These small slabs were hard to polish or grind in the center. Now tumbling bigger rounder rocks with no smalls and all the flat faces are coming out concave from the rotary. My short vibe runs would probably not remove that much material anyway. I believe the bigger rounder rocks has changed the point of grinding contact. Attacking flat faces. small slabs done back when
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Nov 29, 2016 8:45:02 GMT -5
still ready... Will check the concave/convex thing next cleanout. Gotta see it for myself. I remember the last load of Rio's you were rolling. Looked very similar to my 'bigger rocks' tumble. I should think your sawn faces will come out concave. No big deal, just an observation. May be best seen with rocks wet.
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