dottyt
spending too much on rocks
Member since July 2016
Posts: 305
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Post by dottyt on Aug 29, 2016 16:31:50 GMT -5
I just have a little 33B tumbler by Lortone with twin 3 lb. barrels. The barrels are 4.5 x 4.75 inches. What do you think the largest rock I could successfully tumble in it is? It would be one or two "big" rocks and a bunch of smaller ones. Thanks!
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Post by Jugglerguy on Aug 29, 2016 16:37:33 GMT -5
I think the directions that come with it say up to one inch. I routinely tumble rocks up to about two inches in mine. They will tumble slower, but they'll eventually get done. As you said, if you're going to put in larger rocks, balance it out with more small rocks. I wouldn't add any more than two big rocks, and one would be better. The good news is, you're not going to hurt anything by trying it out.
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Post by greig on Aug 29, 2016 21:04:11 GMT -5
The manual says large rocks should be no larger than 3/4 - 1 inch, with about 25% of the volume being smaller rocks (down to 1/4 inch). But hey, who reads the manual these days, except when something strange goes wrong? I also don't see a problem with a larger rock in there and have done it myself and everything worked out fine.
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Post by pauls on Aug 29, 2016 21:42:31 GMT -5
A big rock rumbling around can smash and chip other rocks so make sure everything you put in there is tough.
Mostly tumbling big rocks in a rotary is usually not a problem, don't do it in a vibe though as they can sit in the one spot and chew through the barrel.
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Post by Jugglerguy on Aug 29, 2016 21:58:45 GMT -5
A big rock rumbling around can smash and chip other rocks so make sure everything you put in there is tough. . I think smashing around would be a bigger problem in a bigger tumbler. In a three pound barrel, the rocks can't fall very far.
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dottyt
spending too much on rocks
Member since July 2016
Posts: 305
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Post by dottyt on Aug 29, 2016 23:40:00 GMT -5
Thanks everyone! I have done rocks that are about 2.5 inches. At least that is how big they are when they start, when they are done they are often only ~1 inch. Too many pointy points. I guess I need a bigger rotary tumbler. I also need a Lot-O. And more and better rocks. ;-)
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scottyh
starting to spend too much on rocks
Member since November 2007
Posts: 181
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Post by scottyh on Aug 30, 2016 2:15:09 GMT -5
In my experience if you want to tumble big rocks in a tumbler be prepared to use smaller rocks as cannon fodder. I would find a bunch of really flawed material to use as fodder if you want to tumble a big rock. Mind you what do yo call a big rock?
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
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Post by jamesp on Aug 30, 2016 3:34:01 GMT -5
Good quality hard agates and petrified wood makes it a lot easier. One big soft rock like obsidian is usually a disaster. I tumble a very hard petrified coral from the SE US coastal plain. I measure in ounces. In a 16 pound barrel with a 6 inch diameter I can tumble 60-70% 4-6 ounce rocks with 30-40% smalls using high quality hard materials. NOT obsidian. It will bruise the heck out of each other. Brazilian agate, most pet woods, pet palm, moss agates, cherts, and any other waxy agates can take a lot of abuse. You may be successful in coarse grind. But finishing big rocks to a polish is another concern. Again, the coral I tumble is able to withstand a lot of rough treatment. If finishing in a rotary I thicken the slurry with sugar for protection. Like 3-4 cups of sugar per 16 pounds of rock in AO 500 and polish stages. And if finishing in a vibe, 60-70% media or smalls(less than 1/2 inch) for 30-40% big rocks 5-9 ounces. For a 14 pound capacity vibe. 9 ounces w/wet shine This was a load that turned out with a fine polish. Large rocks 4-12 ounces. Smalls below. Snakeskin agates all run together, hard high quality agate. 16 pound rotary barrel with 6 pounds of large snakeskin's and 10 pounds average tumbles for coarse. 14 pound vibe with 8 pounds of 1/2 smalls and 6 pounds of snakeskin's Done with 2 grits, SiC 30 in the rotary, AO 500 in the vibe.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,562
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Post by jamesp on Aug 30, 2016 3:49:52 GMT -5
Some 4-5 ounce Rio tumbles. Pre-shaped and coarse ground for three weeks in rotary. Rio agates mostly a great target for tumbling big. Apparently if they made the trip to south Texas they can handle lots of abuse in the tumbler. Buy you some Rios. SiC 30 in the rotary, AO 500 in the vibe. Done with two grits. This tumble had a lot of large rocks, mostly Rios and coral www.flickr.com/photos/67205364@N06/sets/72157648700305650
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,711
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Post by Fossilman on Aug 30, 2016 9:21:12 GMT -5
I have a 3# too,have tumbled big rocks in it also... A said just a few,with many smaller ones for packing.....Never any problems!
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dottyt
spending too much on rocks
Member since July 2016
Posts: 305
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Post by dottyt on Aug 30, 2016 11:46:56 GMT -5
Thanks for all the good advice and the nice pics! I was mostly concerned that if a rock took up a certain percentage of the barrel space, not only would it not tumble, but it would stop the smaller rocks from tumbling. I would like to do a 3" rock, but that might be pushing it. Since my rough is generally very rough about 1/2 can get ground away before the rock is smooth enough to go to stage 2. I do not have any saws, grinders, etc. for pre-shaping. I think rounder rocks must tumble much better than jagged rocks.
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Post by greig on Aug 30, 2016 14:33:24 GMT -5
JamesP - Awesome pictures!
DottyT - You asked such a good question, that I did some more research on the mechanics of a tumble and will share what I learned:
Rotary tumblers work by "turning" the rocks. Ideally, rocks (1) roll along the bottom of the tumbler in the direction of the barrel rotation and (2) up the far side to above the half way point, then (3) across the top of the other rocks to the far side and down again to (1). Your tumbler has a smooth wall inside and small rocks will "turn" fine. Larger tumblers have shaped walls that help the rocks to "turn" and can do this with larger rocks than a smooth barrel tumbler. Bottom line - a barrel that is too full or has rocks which are too large will impede this cascading action or "turning" and you will have a loss of effectiveness in the abrasive effect on the various stones in the tumbler. As such, a larger rock should not hurt your machine or might not pound the other rocks, but it will affect the "turning" action necessary to effectively shape and polish your stones.
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Post by rocklicker on Aug 30, 2016 17:21:56 GMT -5
As scotty said, little rocks can be used as filler. Infact you can probably go with a big chunk and the rest filler, or 1/4 inch size rocks. You might stress out the motor if its too big doing that. Also it will probably take longer. I've tumbled some fist size rocks in a 12 pounder with a regular load and they tend to thump around in the barrel.
Steve
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