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Post by scared0o0rabbit on Nov 25, 2009 20:29:56 GMT -5
So I drove all over town today seeing what I could find locally as far as grit to use in tumbling since I know the play sand I'd been messing with isn't really cutting it (pun fully intended =P ). I found at our local Harbor Freight Tools that they have big packages of 70 Grit Aluminum Oxide. Is aluminum oxide suitable for the earlier steps too? I see that a lot of people use silicon carbide for this step instead, but I'm just not seeing any real sources for this in the area.
Also, they had containers of 220 grit aluminum oxide, I assume if the 70 grit aluminum oxide is good for the course step, the 220 would be good for the next step? I didn't really see anything finer than that in my searching, so I figure I'm probably going to have to look around online for my pre-polish and polish, but if I can get things locally at a competitive price, that should save me some change on shipping. So will the 70 & 220 grits work for me, or would I just be wasting my money?
If the aluminum oxide will work for me, am I going to need to change the time between recharges from what I'm reading about people using silicon carbide, or will I end up with a similar amount of time between recharges?
Thanks for answering my noobish questions.
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Post by tkrueger3 on Nov 25, 2009 22:01:10 GMT -5
Here's a hint from my $.02 worth: therockshed.com/grit.htmlYou can order everything you need from this URL, or any of a number of others in the lapidary supplies trade. I get all my grit from The Rock Shed, and have found Shawn Kuhnel (the proprietor) to be totally honest and reliable, and with good prices. Just my :2cents: ... Tom
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Post by Hard Rock Cafe on Nov 25, 2009 22:04:20 GMT -5
From what I've been told, AlOx doesn't cut as well because it's not as sharp-edged as SiC. However, it does work well as a pre-polish and polish. The Rock Shed, Kingsley North, and Miles Supply are all popular grit suppliers.
Chuck
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Post by scared0o0rabbit on Nov 25, 2009 23:56:16 GMT -5
I actually just placed an order there earlier today, I can't do any more tumbling until it arrives, and if it comes through like I expect then I'll probably order some more grit there, I'd just like to be able to obtain supplies locally when I want to (the Chico, CA area).
As far as which course grit to get, I see three different grits, 60-90, 40-70, and 80. What do you recommend? I imagine it would depend on what I'm tumbling, but as far as being the most useful over the widest range of rocks, which should I get?
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Post by johnjsgems on Nov 25, 2009 23:59:26 GMT -5
60/90.
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rollingstone
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Post by rollingstone on Nov 27, 2009 18:11:49 GMT -5
40/70 grit is mainly intended for large tumblers. 80 grit has been graded so while it would work well for coarse grind it is going to cost you a lot more than 60/90 (which has grit that ranges in size from 60 mesh to 90 mesh). That said, some people swear by the uniform grit size, though I don't really see how it can make a difference as it begins to break down as soon as you turn the tumbler on. 60/90 is good for any size barrels (rotary barrels, not vibes) as the coarse grind grit.
As someone mentioned earlier, aluminum oxide isn't as sharp as silicon carbide so would take a lot longer to grind things. Silicon carbide is very brittle so when it breaks down it exposes more jagged cutting edges. Aluminum oxide is almost as hard as silicon carbide, but AlO tends to become rounded as it wears, so it's kind of like having tiny ball-bearings in the barrel. Super-fine AlO makes a great polish though!
One other thing... you can save and re-use AlO polish... I've never done it but some folks here do it as a matter of course.
-Don
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Saskrock
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Post by Saskrock on Nov 28, 2009 15:03:51 GMT -5
I tried AO grit once. Didn't do much of anything. Its hard but just doesn't cut.
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Post by goatgrinder on Aug 7, 2018 20:33:13 GMT -5
I visited Harbor Freight this a.m., after seeing a notice here that a 50lbs bag of #70 AO was $44.49 so I made a purchase. Then they gave me a better deal, @39.99, then a discount on that to $31.99, and with tax added the final bill was $34.55. Go now the deal is only good this month.
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Post by oregon on Aug 7, 2018 22:37:42 GMT -5
I visited Harbor Freight this a.m., after seeing a notice here that a 50lbs bag of #70 AO was $44.49 so I made a purchase. Then they gave me a better deal, @39.99, then a discount on that to $31.99, and with tax added the final bill was $34.55. Go now the deal is only good this month. I'm guessing the 8$ off is a 20% off coupon, do you know how they gave you the first discount? for that price I might have to give it a whirl...
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Wooferhound
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Post by Wooferhound on Aug 8, 2018 3:39:03 GMT -5
If you are looking to buy grit in bulk locally, look for Sand Blasting Media. Also check out the Abrasive Armory ebay store.
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goatgrinder
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Post by goatgrinder on Aug 8, 2018 18:54:18 GMT -5
I visited Harbor Freight this a.m., after seeing a notice here that a 50lbs bag of #70 AO was $44.49 so I made a purchase. Then they gave me a better deal, @39.99, then a discount on that to $31.99, and with tax added the final bill was $34.55. Go now the deal is only good this month. I'm guessing the 8$ off is a 20% off coupon, do you know how they gave you the first discount? for that price I might have to give it a whirl... Well at my HF they keep a copy of the coupons at the check out counter and laser those. I didn't have a coupon and don't know how the first discount came about. Now you wanna buy, huh?
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Post by TheRock on Aug 8, 2018 22:47:07 GMT -5
“The Bitterness of Poor Quality Remains Long After the Sweetness of Low Price is Forgotten” There is the right way to do something and AO aint it for shaping and rounding rocks. AO is for Polishing 500, 1000, 14,0000 and up. Who ever bought the 50 lbs of AO Grit is a good thing cause it will take that much to round a load of stones!
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Post by HankRocks on Aug 9, 2018 7:51:27 GMT -5
scared0o0rabbit As noted in several responses to the question in your original post, you will need Silicon Carbide for the initial smoothing of your rocks. It is a cutting agent and removes rock much faster that Aluminum Oxide. That said, don't despair over the AO you bought. I use 80 AO for my 2nd of 3 stages in my tumbling process. First stage is 46/70 SiC in 15 and 12 pound rotaries. If you have a 3 pound or 6 pound rotary you probably want to use 80 SiC as it breaks down better(faster) in the smaller barrels. I also sort rocks after 1st stage to see if they are smooth enough for my taste and ready to move on to the 2nd stage with the 80AO. If not smooth enough they go back in the 1st stage. I usually run about 10 days in the 2nd stage and most of the rocks come out with a nice dull sheen, ready for the polish stage. The 80 AO has broken down considerably and must be somewhere near a 1000 AO, a prepolish if you will. I do run a soap run between 1st and 2nd stages to remove any SiC from the rocks before advancing to the 2nd stage. This system works well for me and I am very pleased with the results. Remember Patience is your best tool in rock tumbling. Good luck.
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goatgrinder
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Post by goatgrinder on Aug 9, 2018 18:55:34 GMT -5
Oh yeah I use SiC in my QT12's for harder rocks. I purchased the AO for softer rocks and mostly smoothed out stones. I will also use it for the middle grit ranges as well. It doesn't break up, but wears down into smaller grit ranges much more slowly than SiC. More grind time. Thanks.
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NRG
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Post by NRG on Aug 11, 2018 18:05:45 GMT -5
Here's a hint from my $.02 worth: therockshed.com/grit.htmlYou can order everything you need from this URL, or any of a number of others in the lapidary supplies trade. I get all my grit from The Rock Shed, and have found Shawn Kuhnel (the proprietor) to be totally honest and reliable, and with good prices. Just my ![](http://www.rocktumblinghobby.com/smile/2cent.gif) ... Tom Not to mention the Tootsie rolls make him a fun vendor too!
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Post by fantastic5 on Aug 17, 2018 22:39:32 GMT -5
We have some if the HF AO 70 here at the house for my husband's sand blasting project. So I thought I would give it a whirl. I used 6tsp AO, 1/4 tsp flaked soap and 1tsp borax in my Lot-O batch with great results. I started with material that had been rotary shaping most of the summer. First picture is a general selection of what the material looked like going into the vibe. Next picture is after 6 days in the Lot-O with nothing but a squirt it two of water each day. Softer material is a mat finish, but the harder (mostly agate and corral) it showing a nice shine. Moved the whole load to the polish barrel this evening. ETA- I think jamesp has posted similar experiments in the past in his Viking vibe. ![](https://uploads.tapatalk-cdn.com/20180818/644d5f5e1e086cd4bcee545a3c3bdd46.jpg) ![](https://uploads.tapatalk-cdn.com/20180818/249e193081ca7567862cbd9918d3d924.jpg) ![](https://uploads.tapatalk-cdn.com/20180818/56609ae5c079f00a52bfd9dc46f7c640.jpg) ![](https://uploads.tapatalk-cdn.com/20180818/e82dbdc2c320a18d5aaedeefaf2e9f03.jpg) ![](https://uploads.tapatalk-cdn.com/20180818/79a5dd0c7f005ba3739646d49b221771.jpg)
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goatgrinder
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Post by goatgrinder on Aug 18, 2018 10:56:31 GMT -5
Oh yeah baby, that is what I'm talking about. Thanks for posting and good job polishing.
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