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Post by Starguy on Jun 15, 2014 22:08:45 GMT -5
I have pounds of medium sized Lake Superior agates that I want to slab. I also have about 40 lbs of bruneau jasper nodules which are primarily round. My plan is to purchase a 16" Covington slab/trim saw. Has anyone ever made concrete blocks with agates or jasper in the blocks then slabbed the concrete block. I think the medium sized agates and round bruneau nodules will be hard to clamp in the saw's vice. A square or rectangular concrete block would be easy to clamp.
I would leave part of the block without any agate/jasper to reduce the amount of waste. The bruneau is pretty valuable and I don't want to waste any of it as end cuts.
I read somewhere that you shouldn't use sand in the concrete because it can come loose and spin on the edge of the saw blade. If anybody has tried this, I would be interested in hearing about your experience.
thanks
Brent
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Post by jakesrocks on Jun 15, 2014 22:28:29 GMT -5
This is an old trick that has been around for ages. But use mortar mix instead of concrete. The 1/2 gallon heavy waxed paper milk containers make ideal forms to cast in. After the mortar mix has hardened, just peel the waxed paper off.
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Sabre52
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Post by Sabre52 on Jun 15, 2014 22:29:10 GMT -5
Yeah, I've done it a lot with Woodward Rch plume agate. And yep, mortar mix. Waxed cardboard milk or OJ cartons used to make great molds. Works well but you have to remember three things 1. As you've said, put in enough concrete before or after you add nodules to provide the section of agate free block that will go in the vice. If you start with agates at the bottom of the milk carton, they will obviously be in the vice and unslabable ( I did not think of this first time I tried it. *L*) 2. This technique does not allow you to choose where the saw cuts through the pattern. With plume at least, this meant some good patterns were lost when the blade didn't transect the plume in a good spot. You will essentially be cutting blind but with something like Lakers it should not be that important. Could be with Bruneau though. Also with the expensive Bruneau, the 16 inch blade will have a much wider kerf than if you cut them individually on maybe a ten inch saw which results in more valuable stone being lost to the blade. I was using a 20 inch saw and I figured I lost almost one slab for every two or three cuts due to the blade thickness . 3. Don't crowd your agates too much in the concrete. You want them held tight in place as having the block crack open or having stone fragments break out and jamb you blade while cutting can be catastrophic....Mel
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QuailRiver
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Post by QuailRiver on Jun 15, 2014 23:44:48 GMT -5
Another option I use sometimes on KY Agate nodules is for the nodules that are shaped where they can be gripped in the vise securely enough to make one cut near the center. I cut the nodule in half the way you would a thunderegg and then mount each half in a slab grabber vise, or glue the flat face to a piece of wood and then slab each of the two halves individually. But there are some nodules which are shaped where it's just too risky (or impossible) and those need to be set in mortar. Larry C.
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Post by Starguy on Jun 16, 2014 20:38:27 GMT -5
Thanks everybody for some great advice. I hadn't thought about using milk / OJ cartons for forms. I was thinking of making some forms from pine boards. I still may make two or three sizes of wood forms with hinges so they can be re-used. Also thought about sheathing the inside of the forms with metal flashing for easy release and re-use. I've been grinding flat faces on some of the rocks I want to orient in a particular direction. I figure I can put these in the bottom of the forms so they kind of maintain their alignment. The Slab grabbers are really cool. I might be able to make some of them too. I have taps and dies to thread the holes in the steel.
First thing is I need to purchase a slab saw. I've been looking at 16" Covington slab saws. I have $1290 saved up so far but need around $2100. I probably have 2 tons of rocks that need to be slabbed. They are mostly agates and Jaspers. Is this a good choice of saws or would I be better off saving more money and getting something bigger? Most of the rocks are in the 4"-6" range. I have a few larger 12+inch Jasper's and plume agates. I was thinking I could break the largest pieces into manageable sizes somehow. I know that's not the ideal solution but it's hard to justify the extra money for a really large saw. I would probably need a 24" saw to do right by all of the rocks I have. I would also like to get an 8" cabbing machine in the next few years as well. They aren't cheap either.
I was thinking of planting some money trees. No luck finding seeds. Planting dollar bills doesn't work. All my extra $20 s go in my saw fund.
thanks again for the advice.
later
Brent
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Post by jakesrocks on Jun 16, 2014 21:29:13 GMT -5
Brent, you'll hear both sides of the line on the Covington saw. Some love them. Some hate them. Personally, I own a 16" Covington with power feed. I love it. I've only had 2 problems with it. One was with the power feed in below freezing weather. I contacted Covington about the problem, and told them how to fix it. The other problem was the Covington blade. It's junk. If they'll give you the option, go with a BD 301 or 303 blade. I now have a 16" Covington blade hanging on the garage wall collecting dust, And a 303S blade on the saw. The Covington blade will be used for cutting obsidian and softer materials.
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Post by parfive on Jun 16, 2014 21:57:42 GMT -5
Sixteen-inch saw is gonna take oil. If you wanna gunk up that oil as fast as possible, go the mortar route.
Any other method – vise, grabbers, even glued to a stick – beats that by a mile.
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Post by Rockoonz on Jun 17, 2014 0:15:48 GMT -5
Agree with Rich, makes good mud. Also with a grabber or glue you know exactly where you're cutting.
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gemfeller
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Post by gemfeller on Jun 17, 2014 1:01:37 GMT -5
Sixteen-inch saw is gonna take oil. If you wanna gunk up that oil as fast as possible, go the mortar route. Agree on the mud but there's a faster way to gunk it up -- use Plaster of Paris. I did once -- Ooops! Even so it did a pretty good job on Agate Creek nodules from Oz and small Mexican nodules - Coyamito, etc. I wouldn't use the method on Bruneau or any valuable stone that benefits from careful orientation to preserve pattern.
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Deleted
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Post by Deleted on Jun 17, 2014 6:50:28 GMT -5
There is an old school rock guru that showed me a slick trick.i have about 200 lbs of marfa plume nodules and this has worked like a champ.grind a flat spot on nodule,epoxy a 1" nut to flat spot,"let it cure 72hrs.the longer the better son"sorry thats how the old man told me.lol.now put a little thread sealer on a 2 or 3" piece of all thread and thread it into the nut,now you should have what looks like a rock Popsicle.it is important to epoxy nut on proper side or saw could loosen nut during cut.this is time consuming,but will yield the most.tried the mortar thing.to much gunk Dave
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jamesp
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Post by jamesp on Jun 17, 2014 7:55:42 GMT -5
I use tile grout for joints less than 1/8". It has no sand, but uses polymers that actually lubricate the cut. Home depot brand called Mafa I think. This cut was made with sanded grout and scrubs a lot(grout for tile joints bigger than 1/8"). Cast in a nursery container. 18 inch saw. 8 inch container. Sand trails visible. another: end result:
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Post by jakesrocks on Jun 17, 2014 9:35:00 GMT -5
Hey Brent, One more thing about the 16" Covington saw. Unless you like chasing pulleys, as soon as you've mounted the motor on the saw, (It comes separate from the saw), remove the set screws from both pulleys. Put a little non hardening LockTite on both set screws. Reinstall the screws, check pulley alignment with a long straight edge, and tighten the set screws.
On a couple of occasions before I figured out what was happening, I had to chase a pulley down the driveway.
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Post by Starguy on Jun 20, 2014 19:05:59 GMT -5
James
I think your agate stacks are exactly shat I want to do with my small to medium lakers. I haven't started slabbing yet but I will get a saw soon. I have a 10" Lortone slab/trim saw but it's useless for slabbing the stones I want to cut.
I can't wait to get a slab saw. I know I'll want to use it the day I get it so I'm trying to prepare in advance. Thanks for the advice.
later
Brent
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Post by johnjsgems on Jun 20, 2014 19:46:10 GMT -5
Covington 16" comes with an MK301 blade now. Seems to be a popular model. You can keep price down by buying the table top model and putting it on a sturdy table. Don't forget to budget freight as it isn't light (130 lbs. plus 16 lbs. motor). Ship by FedEx Ground now I think. Many discount dealers out there too.
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jamesp
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Post by jamesp on Jun 20, 2014 20:13:48 GMT -5
James I think your agate stacks are exactly shat I want to do with my small to medium lakers. I haven't started slabbing yet but I will get a saw soon. I have a 10" Lortone slab/trim saw but it's useless for slabbing the stones I want to cut. I can't wait to get a slab saw. I know I'll want to use it the day I get it so I'm trying to prepare in advance. Thanks for the advice. later Brent The portland does make your saw oil dirty. I found it to settle to the bottom though. The polymer grout ran much cleaner than the grout w/sand particles. I sawed about 100 pounds of those small round pebbles from the Rio Grande. But I built a wood form that was 10" X 7" tall and 12" long. That 'block' was a full mouth full for the 18 inch blade, making each cut efficient. And the length of 12 inches provides a bunch of slabs. Mix the grout well so that the heels will not release from their bond. make sure the pebbles are clean and dry so the grout will hold them w/good bond. Here is a tumbled slab of straight porttland cement. plain old driveway mix w/sand. Bond is excellent. this is 'sand less grout' that cut so smooth. You see no sand in the joints. some Texas concrete that was found in rubble. great bond strength Some Georgia concrete also from rubble
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jamesp
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Post by jamesp on Jun 20, 2014 20:28:39 GMT -5
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Post by victor1941 on Jun 20, 2014 22:03:46 GMT -5
I would like to add other methods that works for me on plume and other valuable material that you don't want to place in containers with a cement binder or grippers. one method is to use Loctite premium PL construction adhesive and bond the rock to a 2x2 or 2x4 inch by 6 inch section of wood with the proper rock orientation. I smear the adhesive on both parts and fill the gaps as necessary for a good bond and cured at a warm temperature for several days before cutting. when finished with the last cut the end piece can be removed by placing in water for a week. if useable, this section can be glued to a flat wood piece with sodium silicate for another cut. my saw blade does not like to cut this Loctite adhesive so I suggest keeping the blade out of this adhesive. the other method that I use with plume is to try and figure the plume orientation and use my flat lap with a 60 grit to make a flat surface or use my trim saw to cut a flat surface and then use sodium silicate to glue to a wooden block. I fill any gaps with a paint brush and let harden for several days. Make sure you clean the oil from the rock surface before glueing. I soak this in water with dish washing soap for removal in several days. If speed is needed for removal of sodium silicate I saw an article on RTH indicating boiling to speed the process. I have not tried this so I don't know how well this works.
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quartz
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Post by quartz on Jun 20, 2014 23:23:26 GMT -5
A couple years ago I cut a bunch of obsidian for a knapper and used sodium silicate [waterglass] on 2x4's for the second side. Detached 20+ pieces easily in an afternoon using hot water.
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jamesp
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Post by jamesp on Jun 21, 2014 9:30:43 GMT -5
Nothing like the rush you get from sawing those small pebbles. They get picked over and are often of very high quality. The wide variety of the Rio Grande gravels are perfect, never know what the heck you will get.
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jamesp
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Post by jamesp on Jun 21, 2014 9:36:23 GMT -5
Marbles sawn in sanded white grout. A good test for adhesion of mix.
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