lancemountain
starting to spend too much on rocks
Member since March 2017
Posts: 214
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Post by lancemountain on Nov 26, 2019 9:26:28 GMT -5
I’ve fallen in love with my QT-66- the 36 grit really does a great job. I have a pair of 33B’s in the basement. Can I get tougher than 60/90?
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Post by greig on Nov 26, 2019 10:22:07 GMT -5
IMHO: The rocks won't care about the size of the tumbler and grit in stage 1. Hopefully, you are tumbling very hard rock. Keep a good eye on the tumble, as 36 grit will be agressive and the rocks in a small tumbler tend to be smaller to start with. It will be fun to play with a nice pair of 33B's.
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Post by Drummond Island Rocks on Nov 26, 2019 10:53:51 GMT -5
It will be interesting to hear others take on this one. I have always been told the ideal stage one grits are 60/90 or straight 80 in 3 pound, 46/70 in 6-12 pound, and then 46/70 or 36 grit for 15 pound and up. 3 pound tumblers do not have enough rise and fall to break down the coarser grit.
Chuck
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Post by RocksInNJ on Nov 26, 2019 15:07:40 GMT -5
IMHO: It will be fun to play with a nice pair of 33B's. I remember those days lol.
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Post by aliengreensoul on Nov 26, 2019 18:53:13 GMT -5
It will be interesting to hear others take on this one. I have always been told the ideal stage one grits are 60/90 or straight 80 in 3 pound, 46/70 in 6-12 pound, and then 46/70 or 36 grit for 15 pound and up. 3 pound tumblers do not have enough rise and fall to break down the coarser grit. Chuck Sounds totally logical (Rise and fall height)
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julieooly
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Member since October 2018
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Post by julieooly on Nov 26, 2019 18:57:04 GMT -5
Agreed with Chuck. 60/90 is about as course as you probably want to go in a 3.
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Post by aDave on Nov 26, 2019 23:48:54 GMT -5
I also agree with Chuck's answer. However, I'll also throw a 4 lb barrel (45C) in the mix for 46/70. Before I got my QT66, 46/70 could be broken down adequately and shape rocks without a problem. Of course I'm speaking to rolling Mohs 7+ material.
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jamesp
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Post by jamesp on Nov 27, 2019 6:18:17 GMT -5
lancemountain - Try this with agates and other hard Mohs 7 rocks: Start with a single larger rock say 2" but chunky or roundish in shape(just bigger than a golf ball but smaller than a racquetball) and fill the rest of the barrel to about 70% with a bunch of smaller +/-1 inch rocks. The big rock will not only assist breaking down the SiC 36 but it will shape the small rocks quicker than you may think. I tinkered with coarse grinding a single big rock with smaller rocks in small diameter barrels running at both low and high speeds. The grind rate and the grit breakdown was darn fast at either speed. It would help if you add slurry thickener like kitty litter. 33 is just over 4 inches inside, my big rock barrels were just 5.5 inches inside. This was a typical big rock load weighing 7 pounds total with smalls for 5.5 inch inside barrel. This big rock is just over 3 inches. This single big rock trick can make a small barrel mean and aggressive. Some of the fastest grind times I ever had was running a small barrel at high speeds with the single big rock running with small rocks. Be sure not to overfill barrel with small rocks.
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agatepicker
off to a rocking start
Member since March 2017
Posts: 9
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Post by agatepicker on Nov 28, 2019 9:08:55 GMT -5
One pound of extra coarse grit (46/70) and supercoarse grit (20 mesh) can be less effective at material removal than one pound of 60/90. I found this surprising. The most likely reason for that is one pound of 60/90 grit contains a lot more particles than one pound of extra coarse grit. And those many particles of 60/90 have a much higher number of points and edges to do abrasion. What we call medium grit (150/220) is less effective at material removal than 60/90. And, finer grits are even less effective. This is what most people expect - but it is hard to explain after seeing the above. I would guess that these tiny grit particles can not gouge the material as deeply or as effectively. The graph below shows the results of six abrasion loss tests. In each test we started with four pounds of brand new large ceramic media (3/8" x 5/8"), one half pound of grit, and enough water to cover the material in a six-pound capacity tumbler barrel. The barrel of material was allowed to run for two weeks. Then the media was washed, dried, and weighed. In the graph below, the percentage of weight loss is is plotted on the vertical axis and the size of the grit is plotted on the horizontal axis. You can see from this graph that the person who decided that 60/90 should be used for the first material removal step in rock tumbling was a genius.
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Post by HankRocks on Nov 28, 2019 9:27:47 GMT -5
One pound of extra coarse grit (46/70) and supercoarse grit (20 mesh) can be less effective at material removal than one pound of 60/90. I found this surprising. The most likely reason for that is one pound of 60/90 grit contains a lot more particles than one pound of extra coarse grit. And those many particles of 60/90 have a much higher number of points and edges to do abrasion. What we call medium grit (150/220) is less effective at material removal than 60/90. And, finer grits are even less effective. This is what most people expect - but it is hard to explain after seeing the above. I would guess that these tiny grit particles can not gouge the material as deeply or as effectively. The graph below shows the results of six abrasion loss tests. In each test we started with four pounds of brand new large ceramic media (3/8" x 5/8"), one half pound of grit, and enough water to cover the material in a six-pound capacity tumbler barrel. The barrel of material was allowed to run for two weeks. Then the media was washed, dried, and weighed. In the graph below, the percentage of weight loss is is plotted on the vertical axis and the size of the grit is plotted on the horizontal axis. You can see from this graph that the person who decided that 60/90 should be used for the first material removal step in rock tumbling was a genius. So by your graph I should be using 500 instead of 46/70 in the 1st stage. For myself I will stick with the 46/70.
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agatepicker
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Posts: 9
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Post by agatepicker on Nov 28, 2019 9:33:39 GMT -5
I use 60/90 because it removes the most material.
It is possible that coarser grits will be better if you run longer than two weeks. Why, because the 60/90 will break down into less effective sizes - and the coarser grits will break down into more effective sizes.
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jamesp
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Member since October 2012
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Post by jamesp on Nov 28, 2019 9:49:39 GMT -5
One pound of extra coarse grit (46/70) and supercoarse grit (20 mesh) can be less effective at material removal than one pound of 60/90. I found this surprising. The most likely reason for that is one pound of 60/90 grit contains a lot more particles than one pound of extra coarse grit. And those many particles of 60/90 have a much higher number of points and edges to do abrasion. What we call medium grit (150/220) is less effective at material removal than 60/90. And, finer grits are even less effective. This is what most people expect - but it is hard to explain after seeing the above. I would guess that these tiny grit particles can not gouge the material as deeply or as effectively. The graph below shows the results of six abrasion loss tests. In each test we started with four pounds of brand new large ceramic media (3/8" x 5/8"), one half pound of grit, and enough water to cover the material in a six-pound capacity tumbler barrel. The barrel of material was allowed to run for two weeks. Then the media was washed, dried, and weighed. In the graph below, the percentage of weight loss is is plotted on the vertical axis and the size of the grit is plotted on the horizontal axis. You can see from this graph that the person who decided that 60/90 should be used for the first material removal step in rock tumbling was a genius. Wow, nice experiment agatepicker. You findings seem logical. If you consider the light grinding pressure in a rotary, each sharp particle can only scratch a very shallow scratch. It is likely that the more shallow scratches = the most material removed which sure seems related to the number of particles scratching. An issue to consider is the life of the 20 particles when rocks larger than ceramic media is used. In most cases 30 particles are broken down to 500 to 1000 particles in a normal week run to clean out. In my case running slurry at high speeds 30 particles are broken down to 500 to 1000 in 2 days. It seems logical to start with 30 or coarser for a longer scratching period over the 3 to 7 day interval. Virgin silicon carbide 30 on right, after 9 hours on left at high speed and slurry. Even in 2 days it is pretty much broken down to 500/1000. Same SiC after 9 hours carefully scavenged from the rotary after being vibrated to layers:
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agatepicker
off to a rocking start
Member since March 2017
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Post by agatepicker on Nov 28, 2019 9:59:56 GMT -5
Those are revealing photos jamesp. Thank you for sharing them.
Your points that larger rocks and different speeds will likely produce different results are excellent.
It would be fun to run tests on all of these, along with specific gravity and hardness differences in the rough.
Life is so short.
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agatepicker
off to a rocking start
Member since March 2017
Posts: 9
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Post by agatepicker on Nov 28, 2019 10:13:35 GMT -5
lancemountain - Try this with agates and other hard Mohs 7 rocks: Start with a single larger rock say 2" but chunky or roundish in shape(just bigger than a golf ball but smaller than a racquetball) and fill the rest of the barrel to about 70% with a bunch of smaller +/-1 inch rocks. The big rock will not only assist breaking down the SiC 36 but it will shape the small rocks quicker than you may think. This single big rock trick can make a small barrel mean and aggressive. Some of the fastest grind times I ever had was running a small barrel at high speeds with the single big rock running with small rocks. Be sure not to overfill barrel with small rocks. Thank you, jamesp for sharing the photo and your thoughts. I've tumbled big rocks with small rocks but never noticed that the small rocks rounded more effectively. Perhaps the big rock breaks the points and edges off of the small rocks?
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jamesp
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Member since October 2012
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Post by jamesp on Nov 28, 2019 11:17:40 GMT -5
The big rock is simply a pressure increasing device I believe agatepicker. I think the big rock brings more point pressure to grind harder inside the barrel. There is a lot of focus on larger barrel diameter barrels increasing grind rate but larger rocks bring their own contribution. But some of the fastest grind rates I ever encountered was rolling small diameter barrels at high speeds with a single big rock in the barrel. I do run milk shake consistency slurry to prevent banging and bruising within and to help stick the rocks to the walls of the barrel to keep a roll going. Geometry and speed was 5.5 inch I.D. barrel at 80 rpm and 1.5 pound big rock. An 8 inch barrel at that speed would probably beat the rocks to pieces and/or stick them to the barrel wall.
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victor1941
fully equipped rock polisher
Member since November 2011
Posts: 1,979
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Post by victor1941 on Nov 28, 2019 12:43:07 GMT -5
I like the discussion about abrasive size and grinding difference for a rotary but wonder if anyone has done an experiment with a vibratory tumbler like the Thumbler UV-18. I would like to see a comparison on how long the polyethylene bowl lasts when a 60/90 grit vs a 180/220 grit is used in this vibratory tumbler. I use my machine only for finishing preformed cabs off a 60 grit flat lap and was told the 60/90 was too aggressive on the bowl. The replacements bowls cost approximately $100 so any help from others would be appreciated.
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agatepicker
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Post by agatepicker on Nov 28, 2019 13:00:35 GMT -5
In a Thumler's vibratory tumbler, you can see how hard what you have tumbled has been on the bowl by rinsing your rough over a bucket, then checking to see how many black bowl particles are floating on the water. I don't use 60/90 in a Thumler's bowl based upon what I have seen. But, even during the polishing step you will find a few black bowl particles floating on the water.
Two things that are really hard on a Thumler's bowl are: 1) tumbling sharp angular rocks (they gouge the walls of the bowl - so run them a week first in rotary), and 2) running rocks in a bowl that is only partly filled (the rocks vibrate excessively, hammer the wall of the bowl, and spall off small pieces). Large stones without a lot of small filler can also cause excesive wear.
If you don't tumble angular rocks, keep the bowl filled to capacity, and use medium grits or smaller, a Thumler's bowl can last through a couple to a few years of regular use.
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Post by aDave on Nov 28, 2019 13:25:23 GMT -5
So by your graph I should be using 500 instead of 46/70 in the 1st stage. For myself I will stick with the 46/70. Great point, Henry. I noticed the same thing. I'm wondering if the "poorer" results with the 46/70 is due to less mass with each piece of ceramic as compared to what size rocks are normally rolled in larger barrels. The larger rocks (being heavier individually) are more effective in breaking down the larger grit. It was mentioned that larger grit may be more suitable for tumbling periods of two weeks, but I don't find any evidence of larger grit after 6-7 days in my QT-66 barrels. There's probably a correlation to material size/weight, barrel size, and speed , and what the end results are. I'm just too dumb to be able to figure out what it is. All I know is my what I've seen when moving from 60/90 to 46/70 when tumbling like materials. Like you, I'll be sticking with 46/70.
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Post by HankRocks on Nov 28, 2019 13:26:42 GMT -5
I keep all SiC runs in a Rotary, that includes 600 SiC. Usually run final polish in Vibratiory. The Pre-polish run(80 AO or 500 AO) is usually in the Rotary. Then Polish in the Vibratory. On a couple occasions I have made the Polish run in the Rotary. I always include a soap run after the last SiC run and the first AO run. The UV-18 has the hard plastic drum so I can see where it would wear more with the SiC. The Mini-Sonic 4 pound barrels are heavy duty HDPE so they are much more resistant to wear than the UV-18. Even so I do not run SiC in the Mini-Sonic, mostly to keep SiC out of any AO barrels. All this works for me because variety of Tumblers; 3 Model B Thumlers, a UV-18 and a 3 - 4 pound barrel Mini-Sonic. The 15 pound barrel can breakdown the larger SiC grit. I run 46/70 but have considered going to 30 SiC. As jamesp has pointed out, SiC cut's and AO smooths. I figure that barrels are affected accordingly. Those thick HDPE type barrels should last a long time.
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Post by parfive on Nov 28, 2019 22:37:00 GMT -5
agatepicker The ceramic media in your experiment, is it the same type of stuff people use for tumbling filler? I’m curious because I’ve never seen anyone mention such drastic material loss (of the filler) when tumbling. Always seemed like, “Yeah, it wears out eventually, but . . . “ Any idea what the mohs hardness is for the ceramics you used? I used to measure weight loss for the hell of it years ago (mohs 7 rocks, 3 lb barrels, 60/90, 500, anywhere from 1 to 5 weeks) and never saw ten percent or more. (I got 17% one time when I had Noreena and Picasso mixed in.)
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