kokosnood
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Post by kokosnood on Jan 3, 2024 22:34:27 GMT -5
Hi,
I've read through a few articles on grit size for the rough tumble in rotary tumblers. For small (3 lb) barrels I use 60/90.
I'm wondering what you all recommend for 6 or 12 pound barrels?
I'm getting ready to buy more grit and thought I'd ask. I just finished a large bag of 36 grit from the rock shed and I think it worked well on the early tumbles (I use a vibe for all the later stages.)
Thanks!
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rydersrocks
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Post by rydersrocks on Jan 4, 2024 8:07:10 GMT -5
Hey man! Sorry no one has responded to you. The best coarse grit it 36/70, 46/70, 35, or just a mixture of sizes. It does not matter which one you choose. Each option will do the same thing. you cam buy those silicon carbide grits from places like the rock shed and Kingsley north. 60/90 is usually recommended for 3 pound barrels but I just use 36/70 in them. It speeds up the rough stage a little bit. Use 1 tablespoon for every pound the barrel is rated for. For 6 pound barrel you can use 6 or maybe 7 tablespoons and for the 12 pound barrel you can use 12-14 tablespoons. More grit doesn't necessarily mean faster grinding with the 3 pound barrels I would only recommend 3 tablespoons and no more than 3 tablespoons. Happy tumbling!
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jimmie
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Post by jimmie on Jan 4, 2024 9:27:01 GMT -5
I use 36 grit in my 6lb tumblers. Seems to work fine for me. I purchase it from United abrasives , free shipping!
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dillonf
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Post by dillonf on Jan 4, 2024 12:03:38 GMT -5
For me it depends on how often you want to do cleanouts.
Cleanouts every week 80 grit in the 12 pounder 60/90
Cleanouts every 2 weeks 60/90 12 pounder 46/70
Cleanouts >every 2 weeks 46/70 or 36 grit.
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hypodactylus
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Post by hypodactylus on Jan 4, 2024 13:21:03 GMT -5
I use 36 grit in my 6lb tumblers. Seems to work fine for me. I purchase it from United abrasives , free shipping! Hadn't considered them before; what is the website? |
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hypodactylus
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Post by hypodactylus on Jan 4, 2024 13:24:52 GMT -5
I've been using 35/70 Silicon Carbide (SiC) in my QT12 barrels; it seems to work well. I couldn't tell you if it works any faster than 60/90 SiC, however. Probably going to try graded 46 SiC soon.
I have thought of trying the graded 30 SiC from Highland Park, but it always seems to be out of stock (in bulk).
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hplcman
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Post by hplcman on Jan 4, 2024 13:31:35 GMT -5
I just got a QT 66 and have been using the 60/90 SiC. I have been adding it in stages, according to a post I read on here a while ago. I'll add 1/4 cup grit and about 1/2 cup water and let that tumble for 2 days. On day 2 I add another 1/4 cup grit and another 1/2 cup water and tumble for 2 more days. On day 4 I do the same, though maybe a splash more water if the slurry is looking thick. I'll let that tumble for another 4-6 days before washing out. It's a bit labor intensive but I think I get better slurry development and MAYBE better grinding overall? I don't know.
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jimmie
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Post by jimmie on Jan 4, 2024 14:36:34 GMT -5
I use 36 grit in my 6lb tumblers. Seems to work fine for me. I purchase it from United abrasives , free shipping! Hadn't considered them before; what is the website? I get it on eBay |
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Post by chris1956 on Jan 4, 2024 16:05:31 GMT -5
I have been using 35/70 recently in QT12 barrel. It might be a little bit more agressive than 80 but not a lot.
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Post by pebblesky on Jan 4, 2024 17:10:09 GMT -5
I just got a QT 66 and have been using the 60/90 SiC. I have been adding it in stages, according to a post I read on here a while ago. I'll add 1/4 cup grit and about 1/2 cup water and let that tumble for 2 days. On day 2 I add another 1/4 cup grit and another 1/2 cup water and tumble for 2 more days. On day 4 I do the same, though maybe a splash more water if the slurry is looking thick. I'll let that tumble for another 4-6 days before washing out. It's a bit labor intensive but I think I get better slurry development and MAYBE better grinding overall? I don't know. Seems to be quite some work to me, since every time I open the lid I need to clean it up really carefully to avoid leakage. Do you have a fast process on dealing with the clean up work? |
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Post by HankRocks on Jan 4, 2024 17:30:15 GMT -5
For a normal Agate/Jasper load in my Model B's I am currently using 10 Tbsp of 35/70 SiC plus about a 1 1/2 cups of saved and dried slurry. Usually run for 8 to 9 days. Usually add a one or two larger rocks. Have not done any measurements, but the 35/70 seems faster grinding than 80. Might get some 30 SiC to start using. In theory I get better grit suspension right from the start and some increased cushioning.
If I am doing Arkansas Quartz or Apache Tears I will start with 80 SiC as the easier to grind material breaks grit down a bit slower. Sometimes reduce the amount of grit for those type batches.
Henry
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hplcman
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Post by hplcman on Jan 4, 2024 17:35:16 GMT -5
I just got a QT 66 and have been using the 60/90 SiC. I have been adding it in stages, according to a post I read on here a while ago. I'll add 1/4 cup grit and about 1/2 cup water and let that tumble for 2 days. On day 2 I add another 1/4 cup grit and another 1/2 cup water and tumble for 2 more days. On day 4 I do the same, though maybe a splash more water if the slurry is looking thick. I'll let that tumble for another 4-6 days before washing out. It's a bit labor intensive but I think I get better slurry development and MAYBE better grinding overall? I don't know. Seems to be quite some work to me, since every time I open the lid I need to clean it up really carefully to avoid leakage. Do you have a fast process on dealing with the clean up work? It IS a lot of work! But it's a labor of love.  I use a spray bottle with water to clean the seal on the barrel where the lid sits. I'll spray that off and then use a paper towel to clean it. It's a pretty quick job. I believe the theory behind adding the 60/90 in stages like this is to reduce the amount of grit lost by it grinding against itself. I guess it makes sense, though how much is really lost by just adding all of the grit at the beginning may not be much. |
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Post by HankRocks on Jan 4, 2024 21:57:59 GMT -5
Seems to be quite some work to me, since every time I open the lid I need to clean it up really carefully to avoid leakage. Do you have a fast process on dealing with the clean up work? It IS a lot of work! But it's a labor of love. I use a spray bottle with water to clean the seal on the barrel where the lid sits. I'll spray that off and then use a paper towel to clean it. It's a pretty quick job. I believe the theory behind adding the 60/90 in stages like this is to reduce the amount of grit lost by it grinding against itself. I guess it makes sense, though how much is really lost by just adding all of the grit at the beginning may not be much. The amount of grit lost by grinding against itself is in my mind reduced when the grit is suspended in the slurry and not as concentrated at the bottom and up the rotating upward side of the barrel. It's my thought on adding dried slurry at the start which should get the grit suspended earlier. Anyway, it's my theory/opinion and I just stick with it. I used to add grit at intervals and decided it was a bit time-consuming so I abandoned it. I may try that again on a run or two. And if I go that route I may use the opportunity to check for suspended grit. I do like to load the batch and let it run!! It keeps it simple and more time for cutting on my saws and switching the stages on my Vib-Lap which except for the polish stage is a daily activity. Henry |
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hypodactylus
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Post by hypodactylus on Jan 4, 2024 22:09:11 GMT -5
I've been using 2.5 cups of 35/70 Silicon Carbide (SiC) grit in my QT12 barrels for 2 week (14 days) runs.
I have wondered how much grit might be lost by grinding on itself (I don't feel like it is much), but the grit is broken down and the rocks feel smooth after the 2 week period.
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hplcman
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Post by hplcman on Jan 5, 2024 11:48:18 GMT -5
It IS a lot of work! But it's a labor of love. I use a spray bottle with water to clean the seal on the barrel where the lid sits. I'll spray that off and then use a paper towel to clean it. It's a pretty quick job. I believe the theory behind adding the 60/90 in stages like this is to reduce the amount of grit lost by it grinding against itself. I guess it makes sense, though how much is really lost by just adding all of the grit at the beginning may not be much. The amount of grit lost by grinding against itself is in my mind reduced when the grit is suspended in the slurry and not as concentrated at the bottom and up the rotating upward side of the barrel. It's my thought on adding dried slurry at the start which should get the grit suspended earlier. Anyway, it's my theory/opinion and I just stick with it. I used to add grit at intervals and decided it was a bit time-consuming so I abandoned it. I may try that again on a run or two. And if I go that route I may use the opportunity to check for suspended grit. I do like to load the batch and let it run!! It keeps it simple and more time for cutting on my saws and switching the stages on my Vib-Lap which except for the polish stage is a daily activity. Henry I can't imagine that adding the grit in stages is saving a significant amount of grit lost to self-abrasion, honestly. I think the only benefit of this process is a faster development of a thicker slurry since you're initially adding less water. Your process of adding dried slurry to thicken a new batch is probably doing the same thing in a more efficient way! This latest batch will probably be the last time I stage the addition of 60/90, and I'll probably go back to dumping it all in at the beginning and letting it run! Justin |
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hplcman
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Post by hplcman on Jan 5, 2024 11:53:13 GMT -5
I've been using 2.5 cups of 35/70 Silicon Carbide (SiC) grit in my QT12 barrels for 2 week (14 days) runs. I have wondered how much grit might be lost by grinding on itself (I don't feel like it is much), but the grit is broken down and the rocks feel smooth after the 2 week period. Do you ever check the slurry after 1 week? Is there still unspent grit in that slurry? Now that I have larger barrels (QT 66) I'm wondering if I should move on from the 60/90 that I typically use in my 3-pound barrels? When I use that grit in my QT 66 the grit is absolutely spent after 7 days or so... |
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Post by Starguy on Jan 5, 2024 12:39:35 GMT -5
I use 46/70 in the 12 pounders. It seems to take 6-7 days to wear out in the rotary. 60/90 works well too but it seems to be broken down in 4-5 days. Same with 80 graded.
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hypodactylus
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Post by hypodactylus on Jan 5, 2024 13:14:09 GMT -5
I've been using 2.5 cups of 35/70 Silicon Carbide (SiC) grit in my QT12 barrels...... Do you ever check the slurry after 1 week? Is there still unspent grit in that slurry? Now that I have larger barrels (QT 66) I'm wondering if I should move on from the 60/90 that I typically use in my 3-pound barrels? When I use that grit in my QT 66 the grit is absolutely spent after 7 days or so...
I can do 2 cups of 35/70 and generally have it broken down by the end of a 1 week run (1.5 might be a surer bet). However, if I do 3 cups for a 2 week run, I often end up having a little unspent grit and/or rougher feeling rocks.
It is kind of interesting; even though the time is doubled, I can only use 1.5 times the grit.
2.5 cups for a 1 week cycle would probably have unspent grit and/or rougher feeling rocks at the end.
I moved to generally doing 2 week rough grind cycles to save me a bit of time on the weekends (every other weekend, at least).
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hplcman
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Post by hplcman on Jan 5, 2024 13:43:05 GMT -5
Do you ever check the slurry after 1 week? Is there still unspent grit in that slurry? Now that I have larger barrels (QT 66) I'm wondering if I should move on from the 60/90 that I typically use in my 3-pound barrels? When I use that grit in my QT 66 the grit is absolutely spent after 7 days or so...
I can do 2 cups of 35/70 and generally have it broken down by the end of a 1 week run (1.5 might be a surer bet). However, if I do 3 cups for a 2 week run, I often end up having a little unspent grit and/or rougher feeling rocks.
It is kind of interesting; even though the time is doubled, I can only use 1.5 times the grit.
2.5 cups for a 1 week cycle would probably have unspent grit and/or rougher feeling rocks at the end.
I moved to generally doing 2 week rough grind cycles to save me a bit of time on the weekends (every other weekend, at least).
Thanks for that! As I'm learning I'm realizing that everyone has developed a technique that's a balance between good results and the time commitment to obtain those! I'm reluctant to get a vibratory tumbler because I can't babysit it during the day because I still work in an office (even though I love the shine these tumblers put on rocks!!!). |
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wseaton
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Post by wseaton on Jan 5, 2024 16:35:08 GMT -5
Done a lot of experimenting with this in my 17 rebel. What I found is too much silicon carbide at first converts to too much grey pudding (clay / betonite via techical terms?) and if the pudding gets too thick it acts as a lubricant and slows down grinding. Michigan Rocks guy did a test on this I think and his conclusions appear to be the same. Too much initial grit slows things down, and I'll die on a hill this is the reason why. I tend to doubt silicon carbide grit particles grind via contact with each other because they are pretty tough in terms of tensile strength. Just my intuition.
My current reference is 1/4 cup of silicon carbide 60-500 SC grit with 5lbs large ceramic breaks down entirely in 12 hours max in my 17. Yeah, it's that fast. No girt left - just pudding. I'm sure I could use a lot more and not impair grinding, but that's my main coefficient and I like reference points.
Now, if I were to pull half that ceramic out and replace with 1.5"rocks the breakdown of grit would significantly slow because of the significant decrease in surface area. Tested this as well. So, I tend to use fewer, larger rocks at a time and more grinding media (1" river rock works just as well as ceramic and is cheap) and gets done the fastest by far. But, there's a flip side to this. Having a larger volume of grinding media like ceramic or just filler rocks wastes grit because the grit just works against the media.
This is why beginners have such wildly different results. In a 3lb barrel how it's packed is hugely critical. Beginners tend to over load them. I optimized this in my dual harbor freight and got my 120-500 grit times down to 3 days max per phase *if* the barrels are loaded optimally. Optimally means rocks are allowed to freely tumble, but loaded with smaller media to allow more fluid rolling and max serface are for contact. Seems like a bit much science, but it's really common sense. My friends have 3lb hobby tumblers, and when they switched to this method they reported the same results. What took weeks now takes days. They just can do fewer rocks at a time. Its their choice of trade off.
Rough grinding is very subjective and not the same animal as #120 and onwards. It's based more on actual mass you need to remove and will vary according to rock. I've tumbled beach rocks already pretty smooth going directly to 120-220 and as shiny as cue balls in a week. They didn't need coarse grinding.
I've been experimenting with blasting grit and swear #46 aluminum oxide rough grinds faster than 60/90 SC, but I need to really get a scale and the same grade SC for an objective test. The advantage with AO is it's much cleaner and breaks down slower. For now though it's just subjective observation. Need tp try really coarse SC.
For polishing I use my smaller barrels. I found a tennis ball size rock polishes just as fast in my 3lb harbor freight as my 17 as long as I use 1/4 cderamic media. Obviously as some point the physics slant more towards having more surface area vs needing a lot of mass which rough grinding obviously requires. This is a cool discussion in any respect. Happy to report my experiences and see if it helps. When I see people taking weeks in 120-220 I just laugh.
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