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Post by phil on May 25, 2013 14:48:04 GMT -5
Hi All.... I've got a bunch of round nodules that I want to slab completely. Not interested in polishing half rounds, I like slabs I can cab, turn into wind chimes, etc. Other than having to clamp very carefully or epoxy to a 2 x 2, and then start the cut - again very carefully till the blade is in 1/8th inch or so, are there any secrets to keeping the blade from straying on a rounded surface? Or any secrets to clamping the nodule in the vice other than epoxying to a board?
Thanks! Phil
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Post by beefjello on May 25, 2013 15:09:36 GMT -5
Hi Phil! Some folks will set their rounds in a milk carton or other container and fill with plaster. Once hardened stick the block in your vise. I know Jamesp does something similar with cement. Good luck and if you try it please take pics of the process and post them
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Post by tntmom on May 25, 2013 17:00:17 GMT -5
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Post by phil on May 25, 2013 19:18:08 GMT -5
Thanks. the slab grabbers I have don't work very well on a complete nodule... they keep slipping off once in the saw.
Tried the plaster of paris, cement thing years ago. It trashed my oil beyond filtering, so I don't think I want do do that again to 10 gallons of oil....
thanks! Any other suggestions? Phil
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Post by parfive on May 25, 2013 19:51:53 GMT -5
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Post by Bluesky78987 on May 25, 2013 19:52:24 GMT -5
Maybe hand start a groove first, then vice it up?
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Post by Rockoonz on May 25, 2013 20:06:23 GMT -5
Sounds to me like you're more concerned with the blade not deflecting on the curved edge of the geodes. My approach with agate geodes is keep the blade sharp and keep the cutting speed low with the highest blade RPM recomended. My feeds on my saws are all slower than 1" every 5 minutes, the 24 inch is more like 1"/8min. I also make sure the rock will not even slightly move in the vice. Shifting rocks, dull blades or loose wobbly vice carriages are responsible for most bent blades, not the shape of the rock
Lee
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Post by phil on May 25, 2013 22:10:34 GMT -5
Thanks folks...
Parfive, it's the kind where you tighten down several screws against the rock. Usually works very well, but not with round, smooth nodules. Kinda like trying to hold on to a whole peeled hard boiled egg with oily hands then squeezing.
Bluesky, thanks... kinda doing that but...
Lee, You've got it right. I've got the nodules from you plus some local river rolled smooth agates plus some obsidian, all of which are round with no edges to grab onto. If I clamp them in the vice, I can only cut a real small portion sticking out.... and the blade wants to bend to follow the curvature of the stones. Only way I've ever figured out to do them is to epoxy a 2x2 or 2x4, etc to the outer surface, then carefully and ever so slowly introduce the blade till I get a cut started that's at least 1/8th to 1/4 inch deep into the rock so it doesn't deflect. A royal pain in the butt, and very labor intensive. I was hoping some genius out there had figured out a better way. The way above, I can slab the whole thing, with only a real thin slice of waste at the very end.
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Post by deb193redux on May 25, 2013 22:14:57 GMT -5
you need to cut the nodule in half, then use slab grabber on each half
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Post by phil on May 26, 2013 0:22:01 GMT -5
you need to cut the nodule in half, then use slab grabber on each half Thanks. Can't grab that far off center to get even close to a center cut. Visualize a rock shaped like a worn tennis ball, smooth and about 6 inches in diameter. Kinda like trying to clamp down on a ground and semi polished rock sphere. In order to get the vice to hold it at all, I'd have to tighten down like crazy on the middle to keep the rock stable and avoid trashing the blade. Usually even have to use wooden shims too. Even then, the exposure I get to cut is maybe 20% of the nodule. Then I still have the deflection problem. Sounds like the old epoxy and labor intensive hand dressing is still the only way. Thanks!
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Post by Rockoonz on May 26, 2013 1:36:34 GMT -5
What kind of saw? I'm guessing maybe a vice that clamps a bar across the top of the rock like a lortone? Those are tough, the board and glue or plaster block is about the only way to make those work. Maybe one of these would help. www.eloxite.com/store/product.php?id_product=2146
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Post by deb193redux on May 26, 2013 7:41:57 GMT -5
unless it is very smooth, you can clamp it, and cut one slab off each far end. then turn it 90 deg and clamp on the new cut faces to permit cutting in half, then grab each half.
I do this with 5" coconut agate nodules on my LS12 now and then.
if it is really smooth, I hand frrd on my 10" trim to cut in half.
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on May 26, 2013 8:49:36 GMT -5
I've done the milk carton filled with plaster of paris and small nodules several times and never had an issue with my oil. Maybe it depends on what kind of oil is used. I use mineral oil. The one problem I do have with this method: after each cut you need to check to make sure that any exposed stone is solidly in place. I once had a piece of stone come loose out of the plaster and jam the saw -- learned to do a through inspection after each cut.
I recently bought a special clamp for cutting small nodules in half. It was sold as a thunderegg clamp. A local machinist/lapidarist makes them. It's spring loaded jaws with a slot down the middle for the blade. You have to carefully set the length of the cut to not cut the clamp in half. This clamp lets me cut small thundereggs right through the middle -- no more offset cuts.
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Post by Peruano on May 26, 2013 9:57:18 GMT -5
Steve, Is it fair to ask for a photo? It sounds like a useful device. "Tom
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Dr DG
fully equipped rock polisher
Gone Fishing
Member since April 2005
Posts: 1,848
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Post by Dr DG on May 26, 2013 12:18:55 GMT -5
Phil cut off one end, as long you get a flat, glue it to a 2X4 , you can use white wood glue, or water glass. I cut round rocks that all the time.
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Post by phil on May 26, 2013 12:29:10 GMT -5
Thanks all. I have 2 14 inch saws. one is a covington with autofeed and the other a lortone drop saw. The covington is too much trouble to cut a round, so that leaves me the Drop saw. Guess I'll just keep filing and epoxying one end then hand feeding the starts so once clamped in, I can just adjust the blade for slice after slice till all gone. That gator clamp looks interesting. I may have to get one. I really appreciate all the help. Thanks! Phil
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Post by parfive on May 26, 2013 14:50:26 GMT -5
Lortone drop saw here too. Gimme a polished sphere, dip it in greased lightning, and I’ll slab that sucker no problem. Let’s say it’s a 4” sphere. Or one of your round nodules. Cut the two grooves for the grabber about 1/2” below the equator. Use a saw blade, edge of a hard wheel on the cabber, whatever. Clamp it in the grabber, there’s about 2 1/2” exposed to cut. Clamp the grabber in the saw. I like 0.200” slabs. Kerf on my 14” blade is 0.050”. That’s a ¼” every cut. Cut 9 slabs off the 4” sphere without ever shutting off the saw. After each cut, just lift the arm up with the saw still running, crank it in 4 turns for ~0.200” and then ease the blade back down into the next cut. Repeat till you run out of rock and/or hit the clamp. ;D If you want to keep slabbing the chunk that’s left in the clamp, the other style of grabber with the flathead screws is handy. Or just reverse it in the factory version. See the first pic. .
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on May 26, 2013 19:33:06 GMT -5
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Post by parfive on May 26, 2013 21:15:50 GMT -5
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