meviva
Cave Dweller
Member since July 2013
Posts: 1,474
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Post by meviva on Nov 2, 2014 12:46:22 GMT -5
When cutting into a good sized rock do you cut in half or just start slabbing from the end?
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Post by captbob on Nov 2, 2014 12:51:54 GMT -5
Unless you are cutting to make it fit a smaller saw / fit better in that saw, or to create a faced specimen (like a septarian nodule), I see no reason for the first cut to be in the middle. Even if cutting thick to produce thick slabs to turn into tumbling material I would start at one end and work my way towards the other.
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Post by Jugglerguy on Nov 2, 2014 16:00:09 GMT -5
I don't have a lot of cutting experience, but I start at the end and slab until I get to the vice. Then I clean the rock well and glue the flat face to a board. Then i can put the board in the vice and start at the other end. The last slab, in the middle of the rock, is never perfect. One side of the slab is always thicker and thee other side is thinner. It might still be usable, but will need to be evened out. If I started cutting in the middle, I think I'd have to glue both sides of the rock and have two bad slabs.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,635
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Post by QuailRiver on Nov 2, 2014 21:58:19 GMT -5
I usually start at the end and work inward with the exception of some of the more rounded nodules of agates like Brazilians and Ky Agates where the rounded shape makes them difficult to securely clamp in the saw. Those I will try to saw the first cut near the center and then use a slab grabber to hold them in the vise or glue the flat sawed faces to a wooden block to hold them securely while then slicing each half from the end towards the middle cut. Larry C.
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,688
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Post by Fossilman on Nov 3, 2014 0:26:05 GMT -5
If it fits my vice and saw,I start from the end and slab away.....
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jerrys
spending too much on rocks
Member since February 2014
Posts: 263
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Post by jerrys on Nov 4, 2014 12:06:50 GMT -5
The answer depends on why you are cutting the rock. When cutting sphere preforms, I start by cutting off the side that would be the hardest to clamp in the vice. When cutting agate or wood for specimens, I clamp for the most quality slabs with out re-clamping. When cutting for cabs, I cut for best quality. This may require several face cuts and re-orienting. Thundereggs would be cut for the largest face or orienting with the flow bands.
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panamark
fully equipped rock polisher
Member since September 2012
Posts: 1,343
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Post by panamark on Nov 4, 2014 17:29:34 GMT -5
To answer your question specifically, no, it usually isn't best to cut right thru the middle first, unless it is a thunder egg
Sometimes you can clamp a rock and just slab away left to right until the vice gets in the way. Some rocks are pretty easy to read which orientation to cut because they have strong flow of the colors. Probably most of my rocks I have found that the best cuts are about 10 degrees off parallel to the flow patterns in the rock. Most petwood though I cut perpendicular or nearly perpendiculur, i.e. straight across the grain like you would cut firewood.
But similar to Jerry, sometimes you get a rock that you can't tell what will be the best orientation. For those I start with one simple thin face cut. Then with the window to the rock open I will hold it towards the sun and try to figure out the best orientation for cuts. Sometimes I still can't figure it out so I will rotate the rock 90 degrees and make another face cut. Usually 2 cuts will cinch it, but today I had a fascinating/difficult agate that I ended up cutting a face in all 3 dimensions so the x, y, and z dimensions were all shown.
I guess everybody has his own technique, but experience will teach you your style.
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Post by jakesrocks on Nov 4, 2014 19:21:04 GMT -5
A lot also depends on the value of the material to be cut. On more expensive material I grind and semi polish small windows all around the piece. From these windows I can choose the best direction to cut.
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meviva
Cave Dweller
Member since July 2013
Posts: 1,474
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Post by meviva on Nov 4, 2014 20:19:19 GMT -5
Thanks everyone. It give me something to think about. I have a 10" tile saw so I don't have a vise just my hands. Andrea
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Post by Jugglerguy on Nov 4, 2014 20:25:48 GMT -5
If I'm holding the rocks by hand, where I start doesn't matter as much to me. Every cut is difficult to get exactly parallel to the last. My saw has a little fence-like guide that I can move up to the blade. That helps keep the cuts more parallel.
If you're careful, you can roll the rocks through and cut larger rocks. Just make sure you get a good start on the cut before you start rolling the rock or you can make a mess of the cut.
Once again, I speak from not much experience, so others may be able to give you better advice about hand cutting.
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meviva
Cave Dweller
Member since July 2013
Posts: 1,474
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Post by meviva on Nov 4, 2014 22:23:25 GMT -5
After reading the responses it seems that where you start is not as important as which direction to cut to get the best looking slabs. I think I'm going to try to cut a small slice from two sides then cut the direction of the one I like best. Getting the slices even is hard to do.
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Post by phil on Nov 5, 2014 13:12:06 GMT -5
Getting slices even.... yeah hard to do by hand, but... here are a few tricks, I'll see if I can explain them well enough...
For a smaller saw, say 10 inch or less where you are cutting using the saw's flat table: Cut a piece of 2x2, 2x4, etc, and cut it 1 inch longer than the distance between the blade and the edge of the table opposite the side where you cut. Then, starting from the end, measure and cut thin kerf's that match the thickness of the tables apron every 1/4 inch. Once you get the first cut done, make sure to include the kerf width in your following measurements, so that every "notch" is exactly 1/4 inch (or 5/16, whatever the thickness of slab you prefer) apart. Then it's easy to position the wood "spacer" to get consistant and parallel slabs by placing the block at the 1/4 or 1/2 or whatever thickness you desire and clamping it in place. CAUTION!!! DO NOT POSITION THE SPACER DIRECTLY IN LINE WITH THE BLADE! YOU COULD JAM UP THE SAW! PLACE THE SPACER IN FRONT OF THE BLADE SO THAT AS YOU SLIDE PAST THE SPACER, YOU END UP WITH THE SLAB NOT BEING BETWEEN THE BLADE AND SPACER. Hope that makes sense, it's very important.
On to the larger saws where you say you aren't getting uniform flat "last" cuts when glued to a block, or whatever. Check to make sure your vise is parallel to the blade. Then make another different "spacer". Lets say the closest cut you can get to your vise is 1/2 inch. Make a spacer that's 3/4 inch thick that slips over the wood "handle" that you glued to the rock. Fairly close fit. Take your time and be tight tolerances in your work. Then simply fit the spacer (should look like a c shaped bracket) over the wood handle, and tighten your vice while holding the whole shebang in place. Remove the spacer and your lat slab will be flat and true. Now all you have to do is adjust your thickness's a little bit when you get down to a thickness that will yield about 3 slabs, averaging the thickness across all 3 slabs so you end up with even thickness's, give or take. Voila! Not more overly thick or thin last slices. Hope this helped! Phil
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Nov 5, 2014 13:46:16 GMT -5
I take a big hunk and start slabbing. I am making a cube, so when I get to where I wanna be, I then turn the stone 90 degrees and slab some more. I turn 90 degrees again and keep at it until I need to turn 90 degrees again and again and again until the cube within the stone is revealed.
I call it slab to cube.
Most folks look at a rough rock and see the patterns their cabs or tumbles will show. I try to visualize the cube, and then from that what I can expect to see in the sphere. I've been at it for four years.
I'll let you know when I get good at it.
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Post by Jugglerguy on Nov 5, 2014 14:19:53 GMT -5
Phil, I have a little fence on my saw that does the same thing you describe in your first paragraph. It works pretty well. Here's a picture: It's on the right side of the blade and is pulled back out of the way in this picture. I read your second paragraph a couple times and I don't really understand how your C-shaped thing works. I just eyeball the rock when I clamp it in so that the cut side is lined up with the blade. Then I crank it back from the blade and start cutting. Sometimes it works, sometimes it doesn't. I'd love to see a picture of your gizmo.
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Post by captbob on Nov 5, 2014 15:04:45 GMT -5
Gotta be careful who you ask to see a picture of his gizmo!
just sayin'...
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Post by Jugglerguy on Nov 5, 2014 17:04:49 GMT -5
Oh.
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Post by phil on Nov 5, 2014 17:56:12 GMT -5
I read your second paragraph a couple times and I don't really understand how your C-shaped thing works. I just eyeball the rock when I clamp it in so that the cut side is lined up with the blade. Then I crank it back from the blade and start cutting. Sometimes it works, sometimes it doesn't. I'd love to see a picture of your gizmo. Take your left hand and grab your right wrist. Your left hand is in a c-shape. That's how it slides over the "handle" so you don't clamp it in the vise crooked.
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zarguy
fully equipped rock polisher
Cedar City, Utah - rockhound heaven!
Member since December 2005
Posts: 1,791
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Post by zarguy on Nov 10, 2014 1:57:44 GMT -5
After reading the responses it seems that where you start is not as important as which direction to cut to get the best looking slabs. I think I'm going to try to cut a small slice from two sides then cut the direction of the one I like best. Getting the slices even is hard to do. Meviva, You hit it right on the nose. Many times you have to chase the pattern in the stone. Not all stones have a repeated pattern that you can just cookie-cut slabs & cabs out of. The pattern may be unique & perhaps only a fraction of the stone. Of course this is expensive unless you can use or sell what's left after you've cut that killer slab or cab. Since you're asking about slabbing, you should see this old thread on the subject of gluing rocks to boards for slabbing end pieces & odd shapes, etc. Click this link & scroll down about 1/3 of the page to the pictures I posted of my notched vise jaw boards. forum.rocktumblinghobby.com/thread/65165/best-glue-end-cuts?page=3This ensures that the last slab of the chunk or nub has parallel sides of a known thickness every time (except when I mess up on counting turns of the crank)
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