rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on May 10, 2014 19:54:14 GMT -5
Hi, all - I'm in the process of cutting some Parral Agate and am finding it VERY slow going. This material, along with Polka Dot Agate, is the hardest agate I've ever cut. My saw gets to a fairly thick spot and then the feed stops. It's the slip clutch in the motor. Actually, the gear in the motor just slips when it encounters a lot of resistance. I've run the feed rate down to below 4in/hr and it still won't cut.
Anyhow, the rock starts to ride up on the blade and this is what eventually stops the feed. I've run into trouble like this, before, with the blade I use. It's a 14" Covington "Black" sintered, continuous rim blade. It's a pretty stout blade and is fairly thick. And it's fairly new, as well. Might have like 20-30 slabs on it. It strikes me that the blade is just plain dull. It cuts other rocks, like Graveyard Point Agate, just fine.
I have a grinding wheel a friend sent me and have heard here that cutting one can "sharpen" a blade by exposing new/more diamonds. I don't know what the wheel is made of, however, and don't want to make the same mistake I made with my last blade (cut a very coarse diamond wheel dressing stick) and cut the wrong material. This wheel appears to be around 100 grit and is grey in color. I've seen different colors of grinding wheels - brown, green, and grey/black - and I think the color can determine what the wheel's composition is. Can anyone tell me the right wheel to use and if this light grey one is correct to use? And how much, if any, damage cutting one of these wheels might do to a diamond blade? Thanks, Rick
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Thunder69
Cave Dweller
Thunder 2000-2015
Member since January 2009
Posts: 3,102
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Post by Thunder69 on May 10, 2014 21:09:31 GMT -5
Some folks have a fire brick to sharpen the blade.. I use a piece of obsidian and make a few cuts on it to sharpen mine....John
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Post by Rockoonz on May 10, 2014 22:34:48 GMT -5
You want to use Aluminum Oxide, not Silicone carbide. Color is not necessarily an indicator on what it is though. If I had it in my hands I could tell the difference. Fire brick, especially the type that looks pourus is a good sharpener. Obsidian does a fine job of removing glazing or residue to expose diamonds, but it will not remove the small amount of steel needed to truly sharpen a blade
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rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on May 11, 2014 1:10:30 GMT -5
I agree about the obsidian. I completely slabbed a fair sized chunk and it didn't make the slightest difference. I found a few small Norton wheels - 2 of them about 2.5" and brown, and the other is dark gray and very coarse. Says it's a 6" but I measure 4.25. There are part numbers on them. I;ll google and see if I can find out what they are. Thanks, Rick
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rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on May 11, 2014 2:07:45 GMT -5
Well, from what little I can find out, (the numbers on the wheels are, apparently, obsolete) these 3 wheels are aluminum oxide. Apparently there is a numbering convention for grinding wheels and these are "A180" and "A60" which should mean that the two small, brown ones are 180 grit AlO2 and the bigger one is 60 grit. The big fat grey one I can't tell because all of the labeling/markings are gone. I'm going to try to force this slab through to the end by rotating it to cut thinner/shorter sections of the rock and then make a cut or two in one of these wheels. Sure hope it helps/works! C-ya, Rick
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Post by roy on May 11, 2014 9:31:51 GMT -5
in my ten " saw i use 303c blade when i had a 12" saws they all had the same 303c never once have i had a problem with them cutting and i cut everything and alot of it ! in my 16" hp i have a 303s and the same go's i cut pokadot,brazilion ,ect but in my 18" saw i had a 301 style blade in it and i have had all kinds of problems with it lost the feed geers then the feed clamp and now the feed rod so do go cheap on the blade get your self a good blade and cutting will improve for you
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Post by Rockoonz on May 11, 2014 10:43:01 GMT -5
Thanks for the report, Roy. I was considering a 301 in 12" for my 14" HP as soon as the old stock continuous rim blade wears out. I guess I'll stick with a 303c.
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Post by mohs on May 11, 2014 12:10:06 GMT -5
I bought a wheel yesterday from a shop. Told the owner that I wanted a S/C wheel. He pulled off the shelf a black/grey Norton 6” wheel. Well I know some S/C wheels color can be black. I’ve never used one. Always just used the green wheels.
When the owner said he sale it for $15.00. I didn’t hesitate. That was a bargain. The owner is a fairly knowledgeable rocker So I didn’t look at the label besides seeing that it was a Norton. Good stuff in grinding.
I mounted it on my cabbing machine and it wouldn’t touch rock! Inspecting the label. It’s a Norton Alundum 37100. I assume that to be aluminum oxide.
So again I get a less than perfect product off the shelf Geeeezz. I’ll bring it back and trade for some rocks
O and as a side note. That agate geometric heart aligned! I got it grind.
Hope you get your saw situation sweetened Ed
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rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on May 12, 2014 4:18:06 GMT -5
I think "alundum" is some combination of aluminum oxide and corundum. Just a guess. I went ahead and cut a slice of my 4-5" aluminum oxide wheel with my black Covington blade. While it was cutting, I worked on straightening out an old - not much used - gold Covington blade I had. Got it so straight that I just removed the black one, made a quick cut through the wheel with the gold blade and just used that one. Cut the Parral just fine!
A couple of months ago I'd had a problem with the same black blade not cutting Polka Dot agate. I switched to the gold one and it cut it just fine. Left some nasty saw marks, so I just took it back off and went with the black blade until my recent problems cutting Parral Agate with it. The gold blade is one of those notched jobs and cuts a thinner kerf than the black, sintered one. Now that it's fairly straight, I probably won't use the black one until I'm cutting something softer.
This is my second black Covington 14". The last one wouldn't cut Polka Dot worth carp and I ruined it "sharpening" it by cutting a silicon carbide "diamond wheel dresser" stick. I, also, scrubbed every last diamond off of my 10" push through saw's blade with the same stick. The black Covington blade *seemed* to make a smoother cut but the darn things are just plain dull right out of the box! I want to get a 16" segmented 303 or 301 MK(?) blade like everyone here recommends but my Ebay rock selling has dropped off a lot in the last 3 weeks and my Paypal balance is precariously low. Since I'm out of work long term, I only let myself buy supplies with whatever I make selling slabs on Ebay. Sure wish I could get the prices some of the "big boys" there do! If anybody wants to help me get a decent blade, just look for "rykksROX" in the Lapidary Materials pages and make some crazy high bids - LOL The slabs I'm selling were almost all bought from the 4 or 5 "big" sellers there and I'm lucky to even get $9.99 for them. C-ya, Rick
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Post by mohs on May 12, 2014 10:27:39 GMT -5
Hi Rick
I think your right about the alumdum being a variation of corundum.
Grinding wheel specs get complicated fast. It seems like the aluminum oxide wheel should be hard enough to grind rocks. Corundum being a 9 on the mohs scale. But the wheels just can’t make the grind grade. Although aluminum oxide or it variations make a good polishing substance.
Wish I could help on the e-bay thing. My ability to earn money as hit rock bottom, also. This is why I need to go back to the rock shop and return this alumdum grinding wheel. Fifteen dollars for something that doesn’t grind-- puts my finances in tough bind.
Best
Ed
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Post by johnjsgems on May 12, 2014 11:07:48 GMT -5
One year at Madras BD was demonstrating their new 10" saw and tried to cut polka dot. It stalled the saw. They dressed it repeatedly with no luck. They broke down and put a 301 blade on and it sailed right through. Must be some hard stuff.
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rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on May 12, 2014 19:34:42 GMT -5
Yep - EXTREMELY hard. And Parral Agate is every bit as hard as PDA. They both shine up like nobody's business - as good as Morrisonite. I was really jazzed about slabbing the Parral because it polishes so well and is so rare. The first two slabs are kinda butchered as far as being flat, though I did do a pretty good job of realigning the chunk with every rotation of it, so not overly bad. I cut 3 more slabs with the gold blade last night with no problems and they turned out pretty good.
I'm running the feed motor at around 3.0 to 3.5 inches per hour. Pretty slow. I could probably bump it up to around 5 but I've reined in my impatience. The present setting is working great, so why fix what ain't broken? Besides, I don't want to get all impetuous and dish the blade I just hammered straight and re-tensioned. I'll wait until I'm cutting something that's not so obstinate. Never did find out if the AlO2 "fixed" the black, sintered blade but I suspect, even if it was improved, that it would still have had trouble with the Parral. It's a good bit thicker than the notched, gold blade. C-ya, Rick
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Post by mohs on May 12, 2014 20:01:38 GMT -5
Hey Rick where'ya learn hammering & re-tensioning a saw blade? I've done enough of it, to know, I don't know what I'm doing. mostly
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rykk
spending too much on rocks
Member since September 2011
Posts: 428
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Post by rykk on May 12, 2014 20:39:35 GMT -5
I'm just like you. If I beat on it long enough, I can get one straight. The gold Covington blade was super messed up. a couple fair edge dings from rocks jumping the vise - or chunks breaking off, mid cut - twisted, and dished. Here's a link to where I learned the most from: www.carbideprocessors.com/pages/saw-blades/hammering-saw-blades.htmlTook a good bit of pounding to get it decent. Actually, it's better than when it was brand new. Three out of three gold Covington blades I've had were warped/dinged right out of the box brand new. I set it on a 13" round sheet of plywood and pound a block of pressure treated 2x4 with a 4lb hand sledge to get the dings and dishing out. This one was so bad that I had to pound the edge to straighten out discontinuities. The 2x4 prevented any damage to the diamonds. After it was straight, I balanced it in my hand and tossed it up and caught it and held it by the edge and wiggled it. Made a sound/feeling like pushing a dent in and out of a tin can. Found the culprit areas and those I hammered without the wood block and that restored the tension. At least it acts that way now that I'm using the blade. I had tried once before with this blade and got it straight but I reckon not re-tensioned. I actually heard it pop/chime in the saw on about the 3rd slab afterward. Sure enough, the saw marks were back and it had dished again. This time I did the extra, bare hammer pounding until the "tin can" action stopped and it *seems* to be holding up now. C-ya, Rick C-ya, Rick
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Post by Rockoonz on May 12, 2014 21:13:55 GMT -5
Hi Rick I think your right about the alumdum being a variation of corundum. Grinding wheel specs get complicated fast. It seems like the aluminum oxide wheel should be hard enough to grind rocks. Corundum being a 9 on the mohs scale. But the wheels just can’t make the grind grade. Although aluminum oxide or it variations make a good polishing substance. Wish I could help on the e-bay thing. My ability to earn money as hit rock bottom, also. This is why I need to go back to the rock shop and return this alumdum grinding wheel. Fifteen dollars for something that doesn’t grind-- puts my finances in tough bind. Best Ed Yep Corundum=Aluminum Oxide Carborundum=Silicone Carbide
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Post by mohs on May 12, 2014 21:42:49 GMT -5
Yep Corundum=Aluminum Oxide Carborundum=Silicone Carbide Thanks Lee those two distinction are easy to confuse as are these 2 Silicon = Rock Silicone = are those real ? mostly
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Post by Rockoonz on May 12, 2014 23:02:33 GMT -5
I make that spelling error regularly, Funny since I work for a place that makes things out of silicone (no, not those) as well as other polymers and elastomerics.
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