welshtumbler
off to a rocking start
Member since November 2017
Posts: 2
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Post by welshtumbler on Nov 1, 2017 14:40:51 GMT -5
Hi, i'm from the UK and fairly new to tumbling. The instructions that came with the 6lb rotary tumbler i bought last year recommend silicone carbide grit F80 for the first stage. After even only 24 hours the grit is quite a bit finer, so i tend to add fresh grit most days. Is there no grit that doesn't get broken up nearly so quickly, and therefore cheaper. Carborundum?? Is it best to use F80 grit until the pebbles are rounded and pit-free, before going onto a F400 grit? Most of the pebbles i tumble are large, mostly jasper. Thanks for any advice!
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Luminin
spending too much on rocks
Member since August 2017
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Post by Luminin on Nov 1, 2017 15:55:42 GMT -5
There are several different grits you can use.
Silicone Carbide is the most common for the first 2-3 stages as its shape (pyramid and breaks down into smaller pyramids) removes material quicker than most and I think is also cheaper to manufacture.
You can also use Aluminum Oxide, which due to its shape (round and it breaks down round) removes less material, but if you leave it running it can go from coarse to pre-polish-like finish, just takes a while. Aluminum Oxide is also typically used before pre-polish to aid in polishing softer material, it "cuts" less due to its shape.
There are several others, but the prices can be pretty steep.
I may be wrong about the "shapes", but that's how it was explained to me.
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jamesp
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Post by jamesp on Nov 1, 2017 18:22:41 GMT -5
For agates and other Mohs 7 rocks yes. Best economically. Unless you have access to sharp synthetic diamonds.
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Post by Jugglerguy on Nov 1, 2017 18:31:12 GMT -5
Carborundum and silicon carbide are the same thing.
James has tried just about every possible abrasive available. If he doesn't have any other ideas, no one does.
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jamesp
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Post by jamesp on Nov 1, 2017 18:51:15 GMT -5
Carborundum and silicon carbide are the same thing. James has tried just about every possible abrasive available. If he doesn't have any other ideas, no one does. Been saving my toe nail clippings Rob. What do you think ?
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Luminin
spending too much on rocks
Member since August 2017
Posts: 400
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Post by Luminin on Nov 1, 2017 19:27:17 GMT -5
ROFL! I'll read and even look at the pictures, I'll just be thankful they aren't scratch and sniff! jamesp
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Post by Jugglerguy on Nov 1, 2017 19:56:06 GMT -5
Carborundum and silicon carbide are the same thing. James has tried just about every possible abrasive available. If he doesn't have any other ideas, no one does. Been saving my toe nail clippings Rob. What do you think ? How many things did Edison try for light bulb filaments? The obvious stuff must not have worked. I’d say go for it!
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jamesp
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Post by jamesp on Nov 2, 2017 4:45:40 GMT -5
Nothing like the smell of inspiration in the morning !! thank you thank you Luminin Jugglerguy
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welshtumbler
off to a rocking start
Member since November 2017
Posts: 2
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Post by welshtumbler on Nov 2, 2017 13:44:17 GMT -5
Sorry, got confused over carborundum and corundum. I wonder how good tiny angular diamonds would be. Obviously it is the hardest naturally occurring mineral, but i wonder if it's brittle.
The instructions also say that the next finest grit (F220) is good for getting rid of minor pits "without making the stones too small". I can't see why this would be better than using F80 to round the stones and get rid of all the pits, before moving onto F400 grit.
Someone told me I should also fill about 10% of the barrel with pea-sized quartz grit (eg flint or chert). Does that speed the initial stage up?
Thanks again.
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Post by pauls on Nov 2, 2017 15:36:39 GMT -5
Hi Welsh tumbler, from an Aussie rock nut.
I have the same trouble with grit breaking down to nothing in a very short time, maybe all Silicon Carbides aren't the same. I know for sure that the Al Oxide I use is different to what the US tumblers describe, my Al Oxide stays sharp and continues cutting for ages and never breaks down enough to actually polish the rocks, from 500 grit to pre polish takes about two weeks theirs takes two days. I am experimenting at the moment with a batch to see how long the Al Oxide takes to get to a polish, two weeks so far and its starting to show a dull prepolish. I know that if I cleaned it out now and used tin oxide they would get a brilliant polish really quickly which is why I have never persisted with the AlOx.
Anyway, I do the same as you, just keep adding a bit each day, If you are doing the lot as a batch when the rocks are starting to look like they are getting there stop the additions and let it roll with the smashed grit for a few days to take out the pits left by the coarse grit, some people just leave it roll for longer and then go straight to polish.
If you roll with a good mixture of sizes you dont really need to waste grit on grinding filler.
The only way to speed the process is to individually grind and saw each rock to remove divots and cracks and edges. I mostly tumble Agates and throw most in to clean them up a bit before doing the grinding thing, some special ones get the full treatment first but generally I grab a handfull out of the tumbler and touch them up when I have a bit of spare time, I put aside any that are ready to move on, grind pits and saw along cracks on ones that need attention and toss basket cases. Top up to replace the ones removed.
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jamesp
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Member since October 2012
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Post by jamesp on Nov 2, 2017 17:37:51 GMT -5
Hi Welsh tumbler, from an Aussie rock nut. I have the same trouble with grit breaking down to nothing in a very short time, maybe all Silicon Carbides aren't the same. I know for sure that the Al Oxide I use is different to what the US tumblers describe, my Al Oxide stays sharp and continues cutting for ages and never breaks down enough to actually polish the rocks, from 500 grit to pre polish takes about two weeks theirs takes two days. I am experimenting at the moment with a batch to see how long the Al Oxide takes to get to a polish, two weeks so far and its starting to show a dull prepolish. I know that if I cleaned it out now and used tin oxide they would get a brilliant polish really quickly which is why I have never persisted with the AlOx. Anyway, I do the same as you, just keep adding a bit each day, If you are doing the lot as a batch when the rocks are starting to look like they are getting there stop the additions and let it roll with the smashed grit for a few days to take out the pits left by the coarse grit, some people just leave it roll for longer and then go straight to polish. If you roll with a good mixture of sizes you dont really need to waste grit on grinding filler. The only way to speed the process is to individually grind and saw each rock to remove divots and cracks and edges. I mostly tumble Agates and throw most in to clean them up a bit before doing the grinding thing, some special ones get the full treatment first but generally I grab a handfull out of the tumbler and touch them up when I have a bit of spare time, I put aside any that are ready to move on, grind pits and saw along cracks on ones that need attention and toss basket cases. Top up to replace the ones removed. pauls, are you using a rotary or a vibe ? Note on alum ox in a rotary verses vibe: I have tried getting a polish or even a near polish using Alum Ox 80 in rotary. Maybe a sheen at 3 weeks with perfect conditions. Rotaries are just slower to break down abrasive. On a very different note, my powerful vibe tears AO 80 up and takes rocks from coarse grit finish to darn near wet polish in two days. Here is some theory. Rocks are moving against each other 3000 times per minute in many factory vibes. Equivalent to a mild vibratory hammer. The more gentle Lot-O tumbler is a vibe and is much slower to break AO 80 down. Believe it is simply gentler. The height of the rocks is over 6 inches deep in my vibe. All that weight assists breaking abrasive. You can plunge your hand down to the bottom into the rocks when it is running. You can feel with your finger tips the pressure from the weight of 6 inches of rock bearing down on your fingers and feel the vibratory forces at the bottom. There is lot of high speed forces at work in a vibe. Especially in the belly of the hopper. My Vibrasonic has a large 1/3 HP motor spinning a substantial counterweight. It's just mean. Problematic for soft stones. It beats them up. But it does reduce AO quickly and does nicely on Mohs 7 rocks.
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Post by pauls on Nov 2, 2017 18:18:45 GMT -5
jamesp
So we don't take welshtumblers thread off the rails can you open an old thread about AlOx that we can reuse and discuss?
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jamesp
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Post by jamesp on Nov 2, 2017 18:41:12 GMT -5
jamesp So we don't take welshtumblers thread off the rails can you open an old thread about AlOx that we can reuse and discuss? Guessing that welshtumbler will find out that the rotary and coarse SiC will do the best job for the money for rounding his stones. I have tried other coarse abrasives in the rotary, so far nothing can touch efficiency of silicon carbide for shaping. I did want to shed light on the vibe for finishing operations. There are other ceramic abrasives beside silicon carbide and aluminum oxide in the high hardness range that may not have ever been tried in a rock tumbler. There are even several kinds of silicon carbide. I know of a commercial tumbler pays more for green SiC. I am curious about boron carbide. No idea what Elbore is. Looks like boron carbide is about $20 per pound. that's a problem. sandblastingabrasives.com/boron-carbide-abrasive-powders-order-page-grits-60-through-1500-5lbs-or-more-783.html
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jamesp
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Post by jamesp on Nov 2, 2017 18:59:04 GMT -5
Sorry, image transferred so large.
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Post by gmitch067 on Nov 2, 2017 21:53:24 GMT -5
jamesp So we don't take welshtumblers thread off the rails can you open an old thread about AlOx that we can reuse and discuss? Guessing that welshtumbler will find out that the rotary and coarse SiC will do the best job for the money for rounding his stones. I have tried other coarse abrasives in the rotary, so far nothing can touch efficiency of silicon carbide for shaping. I did want to shed light on the vibe for finishing operations. There are other ceramic abrasives beside silicon carbide and aluminum oxide in the high hardness range that may not have ever been tried in a rock tumbler. There are even several kinds of silicon carbide. I know of a commercial tumbler pays more for green SiC. I am curious about boron carbide. No idea what Elbore is. Looks like boron carbide is about $20 per pound. that's a problem. sandblastingabrasives.com/boron-carbide-abrasive-powders-order-page-grits-60-through-1500-5lbs-or-more-783.htmlThank you jamesp for this info! When I started tumbling 11 months ago I purchased from Amazon a few pounds of Sapphire and Ruby corundum... only to discover that Silicon Carbide didn't work so well. I have since been using the smaller pebbles as grit for the 1st stage in the tumblers (they DO hold up well after many months of tumbling!). At one time I was considering the purchase of Boron Carbide to attack the Corundum and get my shiny jooooles... BUT at $20 per pound (!!!) it is not worth it. Oh Well....
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Post by pauls on Nov 3, 2017 0:48:52 GMT -5
I bought a 25 Kg bag of 500 grit white AlOx so I am quite keen to figure out the best way of using it.
I have tried using it in the vibe but I was surprised by how much it chewed into the plastic barrel and those things aren't cheap to replace.
Presently I am running about 10Kg of Agate in the rotary with half a cup of AlOx, at the start I tried putting in about 1Kg of Garnets as smalls but pulled them out and started again when they began breaking up. 2nd week and the grit doesn't feel sharp any more the rocks are beginning to have a nice prepolish but no sign of polish yet.
James, the results I am getting from the expensive AlOxide grit is very similar to my earlier experiments with Kaolin as polish.
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jamesp
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Post by jamesp on Nov 3, 2017 2:05:34 GMT -5
Interesting link for B4C and cBN gmitch067Looks like those boron based abrasives are never going to be affordable for hobby folks. Should you run into a 5 gallon bucket of it in say a junkyard it may behoove you selling it to add to retirement fund. www.advancedabrasives.com/index.cfm?page=ca-boron-carbideInteresting link for the various forms and phases of aluminum oxide paulsThe coarse forms of alum ox that I have purchased to do the 2 day polish in the Vibrasonic were both fused. Fused AO 80 and AO 22. Could tell no difference in the 80 or the 22, both did the job in 2 days. The only difference was that the aO 80 was completely disintegrated, and the aO 22 was still intact but rounded after 2 days. I had used 2 other AO 80's, one was brown and one was purplish. No idea what form/phase it was. But they did the exact same job as the fused AO 80. www.azom.com/article.aspx?ArticleID=1389pauls - I did buy a bag of graded and screened white kaolin. ***It is free of silica. I believe it was mined in Britain. My raw field kaolin is full of tiny quartz pebbles and sand which is bothersome for polishing. It says it is 3 to 5 microns. Anxious to give it a go for final polish. As far as those different forms/phases of alum ox; they are complicated and above my domain of knowledge. Wish I knew a ceramics engineer. That technology is his bailiwick.
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,546
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Post by tkvancil on Nov 3, 2017 9:15:50 GMT -5
welshtumbler If it's available to you there in the UK try a coarser grit. 60/90 or 46/70 would be my suggestion for a 6 pound tumbler. I used F80 for a long time because that's what my instructions said as well. These coarser grits may hold up to your liking. I'm sure they grind faster than the 80.
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notjustone
spending too much on rocks
Member since January 2017
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Post by notjustone on Nov 3, 2017 10:10:04 GMT -5
I alaways wondered about using the abrasive ceramic media
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Post by pauls on Nov 3, 2017 15:29:41 GMT -5
I alaways wondered about using the abrasive ceramic media I don't know about the abrasive media but I have smashed up old grinding wheels, my experience was that Lapidary wheels are OK, they are usually quite soft and designed to keep exposing new grit, so actually break down and add to the grit slurry, harder engineering type grinding wheels eventually rounded to pebbles, the grains of grit flatten and become useless for grinding.
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