ChicagoDave
has rocks in the head
Member since June 2016
Posts: 720
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Post by ChicagoDave on Sept 23, 2016 13:28:17 GMT -5
OK, getting ready to order 25 pounds of rough grit from The Rock Shed. I've been thru 5lbs of 60/90 and a very small bag of 46/70. Not really enough to make a determination if it helped in any way. I have the QT-66 dual barrel 6lb tumbler. Just curious if anyone has some thoughts on the difference between these 2 grit sizes? I'll be running all other stages thru the Lot-O (120/220SiC, 500AO, 1000AO, AO Polish). Thanks in advance.
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Post by Garage Rocker on Sept 23, 2016 13:53:39 GMT -5
I like 46/70 in a barrel that size. I get a smooth, silky slurry after about 3-4 days. I stick with 60/90 in my 3 pound barrels, because it doesn't seem to break down the course grit that well. Not enough tumbling action, I guess. I'm a couple runs into a 50 pound bag of Sic 30 and I'm not sure I like it as much as the 46/70. I guess I'll have to learn to like it though.
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Post by captbob on Sept 23, 2016 13:58:39 GMT -5
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richardh
spending too much on rocks
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Post by richardh on Sept 23, 2016 16:33:29 GMT -5
I am definitely limited on my experience but I have gone through 5lbs of 60-90, 5lbs of 46-70 and 10lbs of 30. I am using a 3lb drum (rotary tumbler) and am definitely getting best results from the 60-90.
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Sept 23, 2016 16:36:25 GMT -5
I like 46/70 in a barrel that size. I get a smooth, silky slurry after about 3-4 days. I stick with 60/90 in my 3 pound barrels, because it doesn't seem to break down the course grit that well. Not enough tumbling action, I guess. I'm a couple runs into a 50 pound bag of Sic 30 and I'm not sure I like it as much as the 46/70. I guess I'll have to learn to like it though. Ha! Glad to read your post so I don't feel so dumb. I also am into a 50lb bag of 30 that I am not thrilled with. Just going to have to learn to love it for a while.
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jamesp
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Post by jamesp on Sept 23, 2016 18:00:14 GMT -5
I'll buy the 30 if you ever want to sell it.
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ChicagoDave
has rocks in the head
Member since June 2016
Posts: 720
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Post by ChicagoDave on Sept 23, 2016 20:49:48 GMT -5
Thanks for the info. Might have to seriously consider that 50lb bag. That seems like a major league level of commitment!
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Sept 23, 2016 21:24:57 GMT -5
I'll buy the 30 if you ever want to sell it. I probably would but I made so much fuss when I was asking for it that I would never hear the end of it if I ended up not using it all. I also think my future requests wouldn't be taken so seriously. The 30 isn't so bad but it does tear through the rocks in an impressive way. It really seems to rough up the softer rocks like I never imagined it would.
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jamesp
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Post by jamesp on Sept 24, 2016 4:42:19 GMT -5
If you have soft stones that are grinding unusually fast they likely will not take a polish. For doing hard rocks such as agate jasper and petrified wood I believe you will be satisfied with the SiC 30 in the QT-66 barrels. You may need to add a half cup of clay based kitty litter to get a slurry going at the start.
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Sept 24, 2016 8:45:40 GMT -5
If you have soft stones that are grinding unusually fast they likely will not take a polish. For doing hard rocks such as agate jasper and petrified wood I believe you will be satisfied with the SiC 30 in the QT-66 barrels. You may need to add a half cup of clay based kitty litter to get a slurry going at the start. I don't know what I'm doing wrong with the SiC 30 but it is tearing everything up including agate and Jasper. The pet wood seems to be doing ok though. I am using two three pound HF tumblers. When I used the 60-90 the grinding took a lot longer but there wasn't the roughing of the surface and uneven wear that I get with the 30.
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Sept 24, 2016 8:46:41 GMT -5
Maybe kitty litter is the key, I haven't tried that yet. So far I have always kept my slurry thin.
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jamesp
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Post by jamesp on Sept 24, 2016 9:10:16 GMT -5
Maybe kitty litter is the key, I haven't tried that yet. So far I have always kept my slurry thin. If you have rocks that are wearing way fast in any of the coarse grits mentioned in your thread here say over a two week period and 2-3 grit adds they probably are too soft. Hard rocks slow to rough shape, easy to polish. Most soft rocks exact opposite. The reason for the cat litter is simply to lift the heavy SiC 30 particles and get them circulating. To each his own, but me not a fan of clean slurry water when using 30-46-60 grits.
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Sept 24, 2016 10:38:52 GMT -5
Maybe kitty litter is the key, I haven't tried that yet. So far I have always kept my slurry thin. If you have rocks that are wearing way fast in any of the coarse grits mentioned in your thread here say over a two week period and 2-3 grit adds they probably are too soft. Hard rocks slow to rough shape, easy to polish. Most soft rocks exact opposite. The reason for the cat litter is simply to lift the heavy SiC 30 particles and get them circulating. To each his own, but me not a fan of clean slurry water when using 30-46-60 grits. The softest rocks I have had in the 30 grit have been jaspers. The other stuff is agate (Brazilian, Montana and Lake Superior) and pet wood that I picked up from the San Jacinto River. What I see is that there is what appears to be undercutting along the bands in the agate and there is a general roughing of the rocks. Instead of coming out smooth to the touch they feel rough like coarse sandpaper but without the really sharp edges of sandpaper. The good news for me is that they seem to smooth out fairly quickly in the 120-220 grit tumbles but the undercutting "grooves" take a while to smooth out. The pet wood is the only thing that doesn't really seem to be negatively impacted by the 30 grit. That material seems to be crazy tough. I saw a little of this effect when I was using 46-70 grit and none at all with the 60-90 grit. It could very well be something I am doing wrong but there are so many variables I'm not really sure where to start. As I said I am using a 3lb barrel on a rotary tumbler. The barrel has no ceramic media in it. It is filled about 80% of the way full with rocks then filled with water until the water level is about 1" from the top of the rocks. I then put in a tablespoon of grit in and roll it for a week. At the end of the week I wash everything out completely. Take any rocks out that appear to have a desirable shape and replace them with new rough. Then I start the entire process again. I find that the 30 grit is well broken down at the end of the week (no large particles that I can decant slurry away from). Earlier on I did some more or less controlled experiments earlier on where I did a set similar of rocks in each of my two barrels. I tried to keep everything constant except in one barrel I did a complete clean out every four days and in the other I just added another tablespoon of grit every four days. After 16 days the barrel with the total clean outs had lost close to 20% more mass than the barrel with the slurry buildup. Now the barrel with the slurry buildup only got a total of six tablespoons over the time period and the barrel with the full clean out got nine tablespoons of grit. I did start a second set of batches where in one I repeated the total clean out as described above and in the other I added two tablespoons of grit every four days. However after 9 days the whole barrel set up and I wasn't getting any tumbling action so I abandoned the experiment. This was all loosely based on a thread I saw here where someone did some similar experiments. My tests seemed to agree with the previously reported results so I just took that as confirmation of his conclusions. If only I had a dozen tumblers I could run simultaneously I could try a bunch of variables and tube up the process really well. It is a little difficult to stay disciplined and run these experiments when I keep looking at this forum and see so many beautiful photos of so many beautiful rocks. When I see them I get all excited and want to try different materials or rush my coarse grind... The conclusion I came to with my limited experiment was that if I didn't care about efficiency of grit consumption I could get through the coarse grind faster by doing a complete clean out each week. In other words I can buy a 20% faster grind by using 50% more grit if I didn't let the slurry build up. My supposition is that the thicker slurry reduces amount of force that the grit particles can put on the rock surface slowing the grind. The experiments were done using 46-70 grit so I think the effect of the greater force the grit had to scratch the surface of the rock wasn't so obvious. By moving to 30 grit the effect became more pronounced and started becoming an issue. I suspect that using a thicker slurry will help prevent this deep scoring of the rock surfaces that I am currently observing and will allow me to use up the rest of my 30 grit SiC without frustration.
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jamesp
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Post by jamesp on Sept 24, 2016 11:22:16 GMT -5
"My supposition is that the thicker slurry reduces amount of force that the grit particles can put on the rock surface slowing the grind."
I had thought this to be so but changed my thoughts. Muddy water(slurry) circulates grit and provides lubrication. Like a person floating in salt water, because it is heavier(denser). Up to a point, if the slurry gets to thick then cutting slows. I try to maintain milk shake consistency. To thin, pour some slurry out and add water.
I would not worry about surface scratches, either the next finer grit will remove them or in time the existing grit will break down to finer grit and remove the scratches.
But there are many ways to skin a cat. Many paths to tumble rocks. Have fun.
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richardh
spending too much on rocks
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Post by richardh on Sept 24, 2016 13:36:49 GMT -5
"My supposition is that the thicker slurry reduces amount of force that the grit particles can put on the rock surface slowing the grind." I had thought this to be so but changed my thoughts. Muddy water(slurry) circulates grit and provides lubrication. Like a person floating in salt water, because it is heavier(denser). Up to a point, if the slurry gets to thick then cutting slows. I try to maintain milk shake consistency. To thin, pour some slurry out and add water. I would not worry about surface scratches, either the next finer grit will remove them or in time the existing grit will break down to finer grit and remove the scratches. But there are many ways to skin a cat. Many paths to tumble rocks. Have fun. My experience is definitely limited compared to yours. I tend to like to experiment and collect data to try to learn if my thinking is correct or not. So far I am seeing that for fastest grinding little to no slurry is faster than thick slurry. At least in my tumbler under those given conditions. I readily admit that my method is not perfect and my data so far is very limited. Having said that my experience so far does seem to indicate that you are probably correct. Thicker slurry might not give the fastest results but it does appear to give better results and also consumes less grit. Next time I make it to the store I plan to pick up some kitty litter. Thanks for your help.
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Post by Garage Rocker on Sept 24, 2016 14:25:43 GMT -5
Your results will vary depending on barrel size. I run a totally different process in my 3 lb. barrels than I do my 12 pound barrel. 60/90 with 7-8 day total clean out vs. 30 (or preferably 46/70) and 3-4 day total clean out. ETA: jamesp, I suspect your hard pvc barrels help speed the coarse 30 grit breakdown compared to our rubber barrels. I'm having to run longer with the 30 than the 46/70 to get total breakdown, and don't notice any better (quicker) grinding action when I clean out. Maybe it is, but I'm not running a control so I wouldn't know. Anyway, I think I prefer the quicker run and more cycles in the same time frame.
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jamesp
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Post by jamesp on Sept 25, 2016 0:12:46 GMT -5
Your results will vary depending on barrel size. I run a totally different process in my 3 lb. barrels than I do my 12 pound barrel. 60/90 with 7-8 day total clean out vs. 30 (or preferably 46/70) and 3-4 day total clean out. ETA: jamesp, I suspect your hard pvc barrels help speed the coarse 30 grit breakdown compared to our rubber barrels. I'm having to run longer with the 30 than the 46/70 to get total breakdown, and don't notice any better (quicker) grinding action when I clean out. Maybe it is, but I'm not running a control so I wouldn't know. Anyway, I think I prefer the quicker run and more cycles in the same time frame. Tumbling, a many splendored thing. Interesting to hear the variations. Hard barrels and Georgia red clay may sure have impacts too. I'm a 30 man. If you have any SiC 30 you want to sell I will take it off your hands. Special case-Since running these big rocks I have to add grit every day. That one big rock acts as a ball mill. Did separation tests on the slurry, 16 hours and it's gone. Could be sooner. Very fast slurry build up. I have noticed tumbling larger rocks causes coarse grit to last way shorter, especially with out smalls. I would be wasting my time with finer grit.
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