sgemmett
off to a rocking start
Member since February 2009
Posts: 24
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Post by sgemmett on Apr 7, 2009 14:55:47 GMT -5
OK, I'm making up words now.  Last recharge I did I wondered for a second if I had just doubled the amount of grit, would I have been able to go 2 weeks before cracking open the barrel to check? So instead of the regular amount grit breaking down in 1 week and recharging how would adding more to start with work? |
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10thumbs
spending too much on rocks
I want to be reincarnated as a dog.
Member since March 2009
Posts: 480
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Post by 10thumbs on Apr 7, 2009 16:54:03 GMT -5
More grit than it takes to form an even coat over the rocks is probably a waste. I think you're up against the law of diminishing returns. I believe that it will take a lot longer for all the grit to break down but it will also take a lot longer for you to achieve the expected results.
I think you'll achieve significant more grinding action from 14 days of tumbling with a fresh recharge in the middle than you would from 14 days of straight tumbling with double the grit and no recharge. I'll bet that your slurry would become so thick with grit dust and rock goop after a week that the grinding action would basically halt anyway.
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sgemmett
off to a rocking start
Member since February 2009
Posts: 24
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Post by sgemmett on Apr 7, 2009 20:40:55 GMT -5
Got it, looking for the most grinding action I can get.
Thanks-
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Post by LCARS on Apr 7, 2009 23:48:36 GMT -5
Don't forget that grit doesn't just grind against the rocks, it also grinds against itself. This likely contributes more to the grit breaking down than the rock grinding action itself does. :nono: I have determined through experience that it is better to add less grit more often for optimal grinding action.  |
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pporky
fully equipped rock polisher
Member since May 2007
Posts: 1,932
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Post by pporky on Apr 8, 2009 4:02:30 GMT -5
I think I may have been guilty of overgritting and not recharging after a week, I was too busy and hadn't measured my grit I just poured some in, anyway when I opened my tumbler All of the stones were stuck together in like a sticky hard clay. They are a pig to clean up.I will be more careful in the future I hope this helps Bill
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Post by johnjsgems on Apr 8, 2009 9:58:17 GMT -5
I think LCARS is doing what I do. I usually use about 2/3 the grit called for but check every three to four days and add a little more if slurry is too thin. I don't know if I use less grit over all but adding fresh grit every 3-4 days probably grinds the first stage faster since there is more grit not broken down. If you run 60/90 7-10days a lot will have broken down completely not rough riding much by then. Just my theory.
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ejs
spending too much on rocks
Member since July 2008
Posts: 478
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Post by ejs on Apr 10, 2009 8:58:44 GMT -5
I have also found that less grit recharged more often results in faster grinding action (as measured by the % decrease in the weight of the rock). However, if I am going to be away for a while and cannot recharge, I might add some extra grit/water.
I have the stuck clay mess happen to me as well. When it did, I just added a bunch of water and let it tumble for a few hours. That cleaned up the mess. Then I rinsed and started over.
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rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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Post by rollingstone on Apr 11, 2009 2:59:34 GMT -5
Another voice in support of under-gritting (hah, another new word!) in the coarse grind stage. Lortone recommends 10 Tb of 60/90 grit in my 6 lb barrels, but I did a bunch of testing and found that it would entirely break down to finer than the next stage (120/220) within 2.5 to 5 days... usually in about 4 days.
So now I spread it out -- I add 4 Tb to start, 3 more Tb two days later, and the final 3 Tb two days after that. Then I leave it 4 more days to tumble and break down all the grit. So instead of recharging with 10 Tb grit every 4 or 5 days, I'm getting 8 days out of the same amount of grit, and I believe the amount of wear is at least as good, if not better, than adding more grit all at once. About half the grit, and at least as good or better grinding.
The exceptions I make to this are 1) when I don't have the time to tinker with things so closely so I just add the grit all at once and leave it for 4-7 days, and 2) when I'm tumbling something that is prone to fracturing so that I add plastic pellets in coarse grind -- then I'll add all 10 Tb grit at once because the pellets slow down the action in the barrel and make the grit last longer.
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MikeS
fully equipped rock polisher
Member since January 2009
Posts: 1,081
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Post by MikeS on Apr 11, 2009 19:42:48 GMT -5
one nice thing about a rotory tumbler is its forgiving nature when it comes to grit/rock/water ratios...if you think you have too much grit, just add more water so it doesn't clay up as bad and tumble it a bit longer...that kind of echoes the above advice...  |
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Post by MyNewHobby on Apr 11, 2009 21:16:40 GMT -5
To over or under ....
Again .... I am learning still ...
Is it not the general rule that says 60/90 breaks down completely within 5-7 days?
That is why we "recharge" at those intervals.
Once again .... need to know .... need to learn ...
As always ...
Julie
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MikeS
fully equipped rock polisher
Member since January 2009
Posts: 1,081
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Post by MikeS on Apr 11, 2009 21:37:08 GMT -5
depends a lot on the material being tumbled and if any filler like plastic pellets are used. Hard material breaks down the grit faster, plastic pellets slow the action of the grit, and soft material doesn't break down the grit as quickly...
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