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Post by Bluesky78987 on Jun 18, 2012 16:14:12 GMT -5
I would like to cut thin strips from slabs for an intarsia-like project I am contemplating.
I have access to 8, 10 and 12" saws. The 12 has the sharpest blade right now. Assume materials would be a wide variety, from hard to soft.
When I tried some practice strips, however, the cutting would go fine 90% of the way across, and then the piece would always break off, ruining the last corner. Is there a way to get it to not do that? Or do I just make more than I need, and use the ones where it breaks using extra material, and grind the lip off later?
I'm probably doing it wrong, since I'm a newb.
What's the right technique for this?
Thanks!
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Post by johnjsgems on Jun 18, 2012 17:49:57 GMT -5
Did you not get the MK145 yet? That saw with the 303C blade will cut any straight line you want.
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Post by Bluesky78987 on Jun 18, 2012 18:12:21 GMT -5
Yeah, I got it. Haven't set it up yet, will have to use it for any Howelite I cut! I just assume it's going to behave the same as the ones at the shop, where the rock tends to break in that last quarter inch.
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Post by rockpickerforever on Jun 18, 2012 20:14:15 GMT -5
Okay, just a thought... What if you take a slab and make a bunch of cuts, across the short direction, parallel to each other, but not going all the way across. So you'd have a slab with long notches, resembling a comb. Now, turn it 90 degrees, and cut the tines loose. Or would that be too wasteful? Jean
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Post by Bluesky78987 on Jun 18, 2012 20:15:30 GMT -5
That would work, but as I cut across each one, would it not tend to break? I'm not sure, maybe the comb method would be better.
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Post by Rockoonz on Jun 18, 2012 20:46:13 GMT -5
If you can slow down the feed on your saw it will help. If you're using a weight feed put a bucket of water under the weight so it will be about half submerged at the end of the cuts.
Lee
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Post by Bluesky78987 on Jun 18, 2012 20:48:11 GMT -5
I'm hand sawing (whatever the proper term is). So go as slow as humanly possible, ok. I'm trying to be really careful to guide the rock straight and not create any sideways forces on it, but they still seem to break most times.
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Post by deb193redux on Jun 18, 2012 21:02:08 GMT -5
If I understand you have a slab of normal thickness, and you want to slice "thin" strips that are 1/4" high by "thin". Is thin 1/8" or 1/16"?
The physics of this is very difficult. It would be easier to cut a "thin slab" and then to cut 1/4" wide strips.
But, why not just work with lengths at least 1/2" longer then you need, so no problem if it breaks at the last 1/4"?
You might also consider silicone adhesive to put the slab on top of 1" fire brick. Then there would be more support for the "thin" strip.
Otherwise maybe a picture of a cut in progress just before it breaks, or just after - so we can see exactly what you are trying to do.
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Post by Bluesky78987 on Jun 18, 2012 21:09:00 GMT -5
I'm trying to cut strips like 1/4" wide on a 1/4" slab. I can get a nice little strip, but a crappy corner at the end of it. I guess the problem is not that it's a strip - it's that little bit at the end of the cut, I need it not to break. Interesting idea on the fire brick (runs to google!).
Basically, when I cut out a shape, imagine I'm cutting out a square. I start by cutting down the right side. Great. When the saw gets to the end of the slab, it breaks off, leaving a little screwup. But that's ok, becuase then I turn the slab and cut across the bottom, cutting off the screwup. Same result. Turn again, cut up the left side, same result. The problem is the last cut - when I'm coming to the end of the top side, and I need it to cut cleanly all the way to the end without breaking off (because I can't cut off any more). I guess the problem isn't unique to strips, particularly, it's just annoying because they are in more need of being perfect.
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Post by johnjsgems on Jun 18, 2012 21:15:24 GMT -5
Try the new saw. The .020" 303C turning 5500 rpm will out cut any of the thick, clunky old club saws.
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Post by Bluesky78987 on Jun 18, 2012 21:35:20 GMT -5
Ok, will try that. Thanks. Love the Ameritool by the way - thanks!
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Post by 3rdrockfromthefun on Jun 18, 2012 22:15:30 GMT -5
There is, in fact, a way to do what you're talking about. I don't know all of the details regarding recipes for plaster/cement etc, but basically you take something to use as a form (cut the top off a plastic gallon milk jug, for example - I've seen this done) and you fill it with plaster or a plaster+cement mix and embed your rock in it. When it dries you clamp the entire thing, carton and all if you like, to the table and saw in thin strips. The person I read who was doing this (lap/gemstone forum) put several rocks into the same form and reported back, with pictures, good results. After cutting I'm told the plaster comes off pretty easily - but during the cut it provides stability and something large, solid and uniform for the clamp to bite down on.
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Post by deb193redux on Jun 19, 2012 7:41:10 GMT -5
Ok, 1/4 x 1/4 is not that thin. This should be possible, and the "nubs" will be improved by a thinner blade spinning faster.
But, saws are for rough cuts. You should cut about 1/16 to 1/8" larger than your shape all around and then grind down to the line. I do not think you can final cut small rectangles and squares for intarsia without finishing the edges on a medium grit (e.g., 220) grinding wheel.
You can also try a band saw or ring saw if you need more than straight cuts. These saws will have less breakage, but are slow, and there is some small wobble to the cut that may also need to be smoothed on a grinder. If you cut curves then you may need a small grinding drum like on a glass grinder.
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gerard
starting to spend too much on rocks
Member since April 2011
Posts: 218
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Post by gerard on Jun 19, 2012 10:06:18 GMT -5
I cut thin slices by cutting a 1/4" slab in half into two 1/8" slabs then grind them thinner on a flat lap. Some materials are just too soft for this but hard fracture free jade or agate work fine.
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Post by Bluesky78987 on Jun 19, 2012 12:17:14 GMT -5
Thanks all -- I think the problem might be expectations - Daniel hit the nail on the head I guess, I'm expecting perfect cuts from a rough cut tool. Possible that the faster spinning tile saw with lapidary blade might do better, but I'll plan to leave extra space and grind down from now on.
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dshalldms
starting to spend too much on rocks
Member since January 2008
Posts: 113
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Post by dshalldms on Jun 30, 2012 5:33:02 GMT -5
Try bonding a backing strip to your material.
Make the backing strip slightly larger than the material that you are working.
Any break out will be on the backing strip and not the piece that you are working.
Good luck,
Derek
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Post by 3rdrockfromthefun on Jun 30, 2012 10:56:08 GMT -5
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