astrofan
off to a rocking start
Member since October 2009
Posts: 5
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Post by astrofan on Nov 22, 2009 10:46:17 GMT -5
My family and I went rockhounding outside of Jerome AZ for agate. After bringing home our haul I thought it would be interesting to do some tumbling. Got the dual 3lb rotary tumbler from Thumler. It seems like a nice machine and much quieter than those kiddie tumblers of old.
We ran the coarse grit that Thumler sells. I had a good mix of stone sizes, but confess some were probably too big at 3" inches. We ran them twice--one week at a time with a recharge on the second run. We used plastic beads as recommended on this site.
Well almost all the stones now have pits with grit pretty much stuck in them. I can get some of the grit out with a pocket knife and I'm considering getting a wire brush, but then won't the next level of grit just get restuck in them?
What did I do wrong? Is this load fixable?
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Post by superioragates on Nov 22, 2009 10:50:16 GMT -5
With my agates I ground out the pits b-4 I start tumbling them, or I have the same problem. I use a dremel with a diamond bit. Others may have different suggestions for you tho.
Marie
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astrofan
off to a rocking start
Member since October 2009
Posts: 5
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Post by astrofan on Nov 22, 2009 11:50:23 GMT -5
Thanks for the tip. Also very nice, and inspiring, website.
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Post by Toad on Nov 22, 2009 12:03:32 GMT -5
Pre-grinding out pits helps a bunch, but not everyone can do that and is not necessary if you are willing to run in coarse grind until the pits are gone. Use multiple size rocks. A few 3 inchers and then some of smaller sizes - down to the size of small peas. Plastic beads aren't necessary on the coarse grind and may be slowing the tumbling action.
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Post by deb193redux on Nov 22, 2009 13:05:46 GMT -5
Not exactly sure what you mean by twice. If you mean you ran two charges of course grit, you need to do about 8 to 14 more. Shaping can take upto 16 weekly charges. Depends on the initial shape of the stones and how much material needs to be removed to get a smooth surface. With deep pits, this can be upto 1/4 inch, which will take a very very long time.
Some AZ material takes longer than other agate. Some AZ material tends to be more bubbly/frothy, or uneven on the outside.
If the stone has internal pits/voids, and more are exposed as the outer surface wears down, then the stone will never work out.
Other factors like the range of stone sizes, the amount of stone, the amount of water, and the amount of grit will add or subtract a week or two either way, but the amount of material that needs to be removed is the main thing.
In a 3lb barrel, there is no way you can do a 3" stone, let alone multiple ones. The stone has to be able to slide across the other stones as the barrel turns. A 3" stone that can only slide for 1" will need 10 or 20 times longer than a 1/2 inch stone.
In course grind, when lots of material needs to be removed, the plastic pellets offer no help and actually hurt. Introduce them in the 3rd or 4th stage.
If you have some very deep pits and crevices that are a lot worse than the majority, there is an advantage to breaking the stone in two, cutting the stone on the crevice or across the pit or grinding out the deepest pits. You do not need to do every pit, that is what the rough grind is for.
I would take out the biggest stones, or break them up. Then take out the stones that would need more than 1/4 inch of material removed. Make sure you still have a full batch, and then run it for 5 to 8 weekly charges.
Report back then.
IF you have questions about what pits might need pre-treatment, post a pic and folks will offer opinions.
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MikeS
fully equipped rock polisher
Member since January 2009
Posts: 1,081
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Post by MikeS on Nov 22, 2009 14:52:18 GMT -5
I use an electric toothbrush and hot soapy water to clean out pits and cracks between grits, it works very well. Make sure you don't let the grit and slurry dry in the pits...keep the rocks wet at all times while doing this....
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Post by Toad on Nov 22, 2009 15:18:06 GMT -5
Mikes method works for him, but is too labor intensive for me. I keep all my stones in 60/90 grit until all pits/cracks are gone. That way I don't have to worry about them on subsequesnt steps.
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Post by frane on Nov 22, 2009 20:03:42 GMT -5
I tend to run my harder stones like most jaspers and all agates in at the very least 8 weeks of rough grit. It is the only way to get some good results. They never tell you that at the beginning but we will!
Fran
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Post by connrock on Nov 23, 2009 6:16:04 GMT -5
Something you MUST learn is that there is no way to speed up the tumbling process.
You can pre-grind which may help but even that is VERY laborious at best.
I agree that those 3" rocks just won't tumble well in your size tumbler.
If you try to keep in mind that the only way (I know of) to get not only the best results but the fastest possible for any given material is to have as much "surface contact" between all of the tumbling rocks as possible.
The easiest way to think about surface contact in tumbling is to do a simple comparison.
Take 2 3" rocks and roll them around in you hands.
Now take a cup full of pea size rocks and roll them the same way.
The 2 big rocks hardly touch each other as you roll them but the small rocks are all touching each other.
In you mind add a little grit and water to each hand full of rocks and this is exactly what happens in you tumbler barrel.
You can have a full cup of grit in with those 2 big rocks but the grit will hardly do anything to them,,,,,unless you throw in some of those smaller rocks!!!!!!!!!
All of those small rocks are the work horses of tumbling.
MANY of us don't want to take up the room in our barrels with tiny no good for nothin rocks but without them we are just wasting time and money to get bad results.
If you can just remember "surface contact" in you tumbling future it WILL help a lot to get the maximum quality and speed possible.
connrock
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astrofan
off to a rocking start
Member since October 2009
Posts: 5
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Post by astrofan on Nov 23, 2009 12:30:36 GMT -5
It's said that this is a great site with extremely helpful members. It's obviously true. I can be patient, and think it's a good learning lesson for my 11 year old. It sounds like I should tumble until the pits are out. (Though on this first batch I may just Dremel some of the grit out.)
Do you need to recharge once a week using if tumbling for weeks? Do you agree the correct amount is 4 tablespoons per charge?
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Post by Toad on Nov 23, 2009 12:37:28 GMT -5
I'm not sure about how much grit as I haven't used that size tumbler before. Yes, a week is generally a good recharge schedule. Going longer won't hurt, but will be slower.
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Post by deb193redux on Nov 23, 2009 16:34:37 GMT -5
The week is an approximate figure for the grit to break down. Too much longer and you spend time running course rock with fine (broken) grit. Too much less and the mud never forms. The best action is when the grit is suspended in a light slurry instead of just water. This keeps more grit up in between the rocks.
If you trap the grit in a bucket, and flush all the mud out, then pour off the water and let the grit dry, you can visually compare the grit to fresh grit. (This works OK for course, but it much harder to compare finer grits.)
IF your week old grit is not much different form the fresh, you are not getting slurry and need to run longer than a week and/or change water/mix/fill. On the other hand if your week old grit looks very fine, consider a day less.
I like to see a few flecks of almost unused grit, buried in a big pile of worn down but still slightly rough grit. This tells me that I was getting abrasive action when I opened the barrel.
With a little practice, you can jumpstart the mud by carrying over a pinch or two of the old mud. This gets the action going ASAP. You can then do 5 day recharges, and at the expense of higher grit usage, you can keep the grit in the barrel closer to full strength.
But a week is a good rule of thumb, and life may be too short to worry about perfectly tuning each barrel. Sometimes good enough is more than perfect.
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Post by roswelljero on Nov 23, 2009 19:35:07 GMT -5
"Do you agree the correct amount is 4 tablespoons per charge?" That's what I use... Be sure the water is just under the top of the stones.  I've also found that soaking the rocks in very warm, almost hot water until the stone is warm expands the pits and allows the grit to fall out... Like others said, you really need to get rid of the pits... They will also trap polish. Later, jeri |
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Nov 24, 2009 0:09:33 GMT -5
Before you spend that much time, and that many dollars worth of grit, think about what it will look like when it's done. Heh, I have some really brilliantly polished plain brown jasper. Seemed like a good idea at the time. Maybe try a very small cold chisel and hammer (safety glasses) to remove material around the pits? You might also try starting out with 30/60 grit.
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