rxscram
spending too much on rocks
Member since August 2011
Posts: 484
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Post by rxscram on Jul 14, 2012 2:37:40 GMT -5
Hi All,
What are your opinions on the "best" rough grit? In all the batches I've done so far, I've been using mixed 60/90 silicon carbide, but I've had to learn a lot of patience to use it. I've had some rocks in the first stage for several months, and I'm still not satisfied. (The rocks themselves are worthy of continuing on though, otherwise I'd just pull them out.)
On average, I will leave a batch of rocks in stage one for a month or more, refreshing the grit every week or so. Even then, I have to send some rocks back repeatedly. I would say that every 2 batches of stage one yields a batch ready for stage 2.
Anyway, my 5 pound bucket of 60/90 mixed is just about empty, so I wanted to solicit opinions on what to replace it with. My choices as I see them are:
1. Buy a bucket of 46/70 mixed, for heavy duty grinding, and another bucket of 60/90. These are both from Lortone, which I have had good luck with.
2. Just buy another bucket of 60/90 from Lortone.
3. Branch out to eBay and buy graded grit (36 and 50 seem pretty cheap). And then buy 60/90 also.
Okay, aside from the initial coarse grit, I would like to get opinions on whether or not I should add an additional stage between "fine grit" and pre-polish. Since I'm using Lortone's 4-step kit, the "fine" grit is 120/220 mixed, followed by Aluminum Oxide pre-polish. This is working great for most of my stones, but I still have some that are not as shiny as I would like them. Would adding either a 320/400 mixed stage or a 500 graded stage help with this, do you think?
Thank you so much! Jeff
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rxscram
spending too much on rocks
Member since August 2011
Posts: 484
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Post by rxscram on Jul 14, 2012 2:42:48 GMT -5
Oh, I have another question too... does anybody think that going to a polish other than that from Lortone would make a difference? (In other words, is their polish any good? What grade is their aluminum oxide prepolish and polish?)
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herchenx
Cave Dweller
Member since January 2012
Posts: 3,360
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Post by herchenx on Jul 14, 2012 2:59:46 GMT -5
well, that is a lot to answer, but my experience says that some rocks, depending on what you are tumbling, can take months.
What are you tumbling, in what size batches?
I notice that small barrels - 3# and less - take longer than 6# or 12# barrels. On the flip side, my 65# barrel takes forever (and every). Tougher, harder material (agates) takes longer than quartz. Really odd shaped or deeply pitted/cracked takes longer.
I use 60/90 SiC from the rock shed for stage 1. I used some 46/70 and didn't think it was worth doing instead of 60/90.
All my grit and polish comes from the rockshed, I think they are cheaper than Lortone.
I do my prepolish using 500 AO in a vibe, then AO polish to finish - also in the vibe. I think my polish stands up to just about anyone's.
I bought from Lortone when I first bought my first tumbler, and from the rockshed and several other less expensive suppliers since then.
Your grit doesn't need to be "Nike" grit.
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Post by NatureNut on Jul 14, 2012 7:38:47 GMT -5
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jason12x12
freely admits to licking rocks
Member since October 2011
Posts: 798
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Post by jason12x12 on Jul 14, 2012 7:46:28 GMT -5
ive heard of people breaking up grinding wheels to put with rough grind,, sounds effective.
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cardiobill
freely admits to licking rocks
Member since March 2012
Posts: 879
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Post by cardiobill on Jul 14, 2012 8:05:23 GMT -5
I echo herchenx and jo- rockshed.
I have tried an extra step 400 and then 600 vs prepackaged "prepolish" or 500 grit (aluminum oxide) and I could not tell a bit of difference but it took an extra week.
As far as shiny rocks- some polish better than others. Some take longer than others. Make sure you burnish before you polish- that made a huge difference for me
I have no vested intrest in the rockshed (I live in ohio) but I have to give them a shout out. Everything comes quick. They try and keep shipping as low as possible. Their prices on everything seem to be as low as I can find things anywhere on the net. They are awesome
Bill
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rxscram
spending too much on rocks
Member since August 2011
Posts: 484
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Post by rxscram on Jul 14, 2012 12:25:36 GMT -5
Thanks for the input everybody. I placed an order with the rockshed.
I found the answer to my question about what Lortone's grit size was for their polish and pre-polish. The prepolish is 5 micron (just under 5000 grit), and the polish is 1 micron (14000).
Given this, I am going to try adding an extra stage, maybe 2 depending on the rock. Since the "medium/fine" grit is 120/220, I am going to add a 500 step for all my stones, and a 1000 for my particularly difficult ones. My rocks already stay in the pre-polish stage for close to a month, so it's not likely that this will add significant extra time.
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Post by paulshiroma on Jul 14, 2012 12:39:43 GMT -5
Hi Jeff - I use 46/70 as my first stage. I sort of follow your pattern but "recharge" the barrels about three times or so spaced about three to four days apart. In other words, if I start a fresh load on Sunday, I'll add two ounces of 46/70 on Wednesday, Saturday, and Wednesday. Or something like that. . The initial charge has only about six ounces of water or so to make sure the slurry is more like my Mom's Turkey Gravy that she serves up at Thanksgiving - on the thick side . I may add a bit of water to it if it starts turning to the consistency of Hawaiian Poi (think paste). I want the slurry to cling to the rocks not run off. About every week, I include additional rock to make up for the loss in volume. Then I just leave it in the barrels for several weeks until I'm ready to move them to the next stage. I usually have a few that stay for further rough stages; typically the ones that were added after the start of the run. Like everyone else, I buy through The Rock Shed. Thanks Paul
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rxscram
spending too much on rocks
Member since August 2011
Posts: 484
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Post by rxscram on Jul 18, 2012 10:41:57 GMT -5
Hi Paul,
Thank you. You have a tutorial up in another part of the website, correct? I've been using that for guidance in my rough stage.
Thanks, Jeff
P.S. Costa Mesa, eh? I work in Irvine- right around the corner!
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rxscram
spending too much on rocks
Member since August 2011
Posts: 484
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Post by rxscram on Jul 18, 2012 10:44:09 GMT -5
Another question for everybody... has anybody used .3 micron or smaller polish in a tumbler? (50,000 grit)?
I guess it's used in laps more than tumblers, but was curious if it would work in a tumbler.
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Post by johnjsgems on Jul 18, 2012 12:16:38 GMT -5
I have customers that buy my .3 aluminum for their rotaries because it works great. Even though I suggest to them that pretty much any stone that will polish in a rotary will polish well with my 3-4 micron polish for half the price. The .3 works considerably better in a vibe tumbler and on buffs will polish a far wider range of rocks. If you are tumbling softer stones in a rotary you probably should try a .3 aluminum.
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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 Jul 18, 2012 15:09:15 GMT -5
I apologize for the long-winded explanation, but here goes: For Rotary Tumblers
1. 47/60 is for giant tumblers, start with 60/90.
2. Buy all your grit and polish from the same (recommended) vendor to save on shipping.
3. Graded SiC is for laps, not tumblers.
4. There are three different types of alumina (AO) used in rock tumbling. From the finest to coarsest they are:
a) Sub-micron aluminum oxide is mono-crystalline or polycrystalline calcined alumina. The crystals are flat. It is created/sorted differently than levigated AO (below), and it is purer than "fused AO (further below) Sub-micron AO is fine polish. For example, .3 microns (about 100,000 grit).
b) Levigated AO is air or water sorted calcined alumina that is 3-5 microns in size (4,000 to 8,000 grit). The crystals are not as uniformly shaped as sub-micron and they are coarser, but levigated AO is still pretty pure. Left in the polish stage long enough it is (theoretically at least) possible that levigated alumina will break down into a sub-micron size, eliminating the need for sub-micron AO.
c) Fused Alumina is made by a different process and is less pure than calcined alumina. It is composed of larger, blockier crystals in sizes from 5 to 70 microns (3,000 to 300 grit). The most important difference between calcined and fused alumina though is the impurities. It is not all the same however, some is purer than others. Fused alumina might break down to sub-micron sized particles, but if it has a lot of impurities, it still might not produce a nice polish
5. SiC "pre-polish" (500 to 1,500 grit or finer) has completely different kinds of crystals (therefore action) than AO.
So... Maybe try 500 grit SiC for rocks that aren't getting good results with 500 grit AO.
Quality matters. If you are using low quality fused alumina for pre-polish, it might be too impure, or have the wrong kind of impurities to yield satisfactory results with all types of rock.
You'll likely get mixed pre-polish results if you haven't gotten the most out of your 120/220 stage. Don't move to the pre-polish stage before the rocks are ready for it.
I have seen AO graded 500 grit (so it was levigated alumina - pre-polish). I have seen sub-micron AO, so it was polycrystalline "finishing" polish. Most AO I've see though is only labeled "pre-polish" or "polish", so it could be just about any type, purity or particle size AO, or any mixture of those, so... that brings us back to recommended vendors and the quality of their products:
What they said.
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