88pathoffroad
spending too much on rocks
Oregon ROCKS!
Member since August 2008
Posts: 305
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Post by 88pathoffroad on Aug 31, 2008 17:05:20 GMT -5
I bought some 30-60 SD grit at a rock show (5 lbs, $5 - Hey!) and boy, is it rough stuff! Tears the crap out of my Thumler's Model B lid gasket. I found that inner tubes are the same exact thickness and seem to be the same composition of the old lid gasket, so I just cut up an old swim tube and used that for a replacement. I could make a rubber glove out of the old gasket! Heh.
Anyone else have experience using really rough grit for rough grind? Pluses or minuses?
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Post by Condor on Aug 31, 2008 17:54:08 GMT -5
Never used it, but I often wonder how well it works as a first stage rough. Will it really round out the rocks if left for a few weeks, do a good job on pitting? Those kinds of questions. To leave well enough alone, I'll stick to my 60/90.
Condor
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ejs
spending too much on rocks
Member since July 2008
Posts: 478
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Post by ejs on Aug 31, 2008 17:56:58 GMT -5
Will 30/60 grind down to 60/90 in a few days? So you may be able to run longer rough tumbles (essentially a few days in 30/60 and then a week in 60/90).
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Post by deb193redux on Aug 31, 2008 18:06:02 GMT -5
It seems to break down faster. I guess it does not break into two but more likeinto 10th's. So you do not get as much work out of it.
I used to use a lot fo 46/70 because the club had it for free. But it would be gone in 4 days instead of a week.
If it is cheap, use it. Otherwise do not go looking for it.
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lsmike
spending too much on rocks
Maxwell's demon lowers tumbling entropy
Member since January 2007
Posts: 468
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Post by lsmike on Sept 1, 2008 19:56:18 GMT -5
I tried it in a 12 pound rotary not as good as 60/90.I've been told it will work in BIG tumblers,say 40# or more.Mike.
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181lizard
Cave Dweller 
Still lurking :)
Member since December 2005
Posts: 2,171
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Post by 181lizard on Sept 1, 2008 21:46:54 GMT -5
I would be leary because of the aforementioned wear & tear of the equipment!!
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88pathoffroad
spending too much on rocks
Oregon ROCKS!
Member since August 2008
Posts: 305
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Post by 88pathoffroad on Sept 29, 2008 11:29:03 GMT -5
After running a 12 pound load for three weeks on the 30-60, I see what y'all mean. The 60-90 does a MUCH better job of rounding off corners and producing a nicely rounded batch of rock, at least in my tumbler. I got more rounding action out of my one-week 120-220 grit run than the last two weeks on the 30-60!
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Post by Hard Rock Cafe on Sept 29, 2008 11:52:25 GMT -5
I'm curious about the mechanics of this. Does anyone have an idea why a more coarse grit would not do as good a job rounding or why it would break down faster? It's counter-intuitive to me...
Thanks!
Chuck
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lparker
fully equipped rock polisher
Still doing too much for being retired!
Member since March 2008
Posts: 1,202
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Post by lparker on Sept 29, 2008 14:23:29 GMT -5
perhaps it's big enough to tumble itself? ummm, it's big enough to get caught directly between a rock and a hard place (probably another rock) and it shatters?? I'm running through a 25 lb batch of 46-60 and can't see any faster tumble either in my 15 lb rotaries. When I re-order, I'll be getting 60-90 again.
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Post by connrock on Sept 29, 2008 16:45:47 GMT -5
I used to use #30 grit then went to 30/60 and am now using 46/70.
I run a Model B at twice the normal speed and about 1/4 or less the amount of water normally used.
I have pretty good results and it works fast.
I have some chevron amethyst in the photo section that I did in a 6lb and 4lb Lortone running the normal speed and completed it in (I think) 23-24 days.
If I'm not mistaken I roughed it for something like 18 days with a 6 day grit change.
I finished it in my Lot-O-Tumbler with 220-500,1000 or Tripoli (can't remember that either) and Rapid Polish #61.
We've discussed this topic for several years now and some of us have good results and others don't.
I do know that I bought #30 SC grit from the Graves Co years ago and it was full of some kind of filler and wore down in a coupe days.
I had trouble with other vendors with the #30 and a filler as well so I just stay away from it now.
I use Mile's Supply now and their grit seems to be OK.
connrock
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Post by Hard Rock Cafe on Sept 29, 2008 21:27:29 GMT -5
I would say your results are somewhat better than "pretty good"! :-)
I've been using 36/90 because of an ordering mistake. It seems to work fine, but is shot after about 5 days. I can't say whether my rocks were more "round" with 60/90. If I still have some, I'll have to compare.
All things being equal (that is, no filler), I would expect the 36/90 to pass through 60/90 on it's way to sludge...
Chuck
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Post by snowdog on Sept 29, 2008 21:56:12 GMT -5
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Post by catmandewe on Sept 29, 2008 23:01:58 GMT -5
Yeah Dave that makes sense, its kind of like too aggressive of a hand saw makes it really hard to cut a board, but switch to a finer tooth saw and it cuts like butter.
Tony
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Post by docone31 on Sept 29, 2008 23:54:10 GMT -5
I wonder,
It sounds like the grit is sandblasting grit. The speed of wearing down without the results.
The designation 36-60, is the grit I used to use to sandblast steel, and aluminum.
I am thinking it is not corundum.
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flatlander
starting to shine!
Member since May 2007
Posts: 27
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Post by flatlander on Sept 30, 2008 16:19:57 GMT -5
I bought 50 lbs of 36 grit, and have had it in my tumbler for a couple of months now. I have replaced the liner of my model b as mentioned above, but I went to our local belting/rubber supply store and bought some 1/4" scraps for $5.00, they still seal as well, but I don't expect them to wear out anytime soon. Really poor results with the 36, I think the best answer of the above solutions is that the grit makes too big of a cut, without enough inertia to follow it through, it just skates across. Running the tumbler at double speed would resolve that problem. I bought the heavier grit, because it was available to me here, and hoped to speed up the rounding process. It has only slowed the rough grind process. Back to 60/90 for me.
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--- the bigger grit would cover more surface area so would try to cut a bigger scratch (chip,etc.) but unless it's a pretty soft stone it can't do it --- in the same surface area with 90grit /smaller you have several grit pieces making little scratches , one after another so it wears faster 
