# Cutting Lava Rock



## Tihsho (Sep 21, 2009)

Anyone have experience with cutting, not shattering, lava rock? I'm looking to split some rock that I have in half so that I can mount them to my background with the flat side facing the glass. 

In the past, I've used a chisel and a hammer to split up large rocks, but in this case I'm trying to get a clean flat cut so that a single rock would provide two useful pieces that are flat for a lava rock mosaic look. Based on the shape of the stones, I'm not sure a tile saw would work, I'm thinking I might have to rent a water fed diamond chopsaw for a clean cut.


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## Reptihab (Sep 23, 2020)

A diamond wet saw is what I use but only because I have one for work. If you have a skill saw a masonry blade for it will work.


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## Tihsho (Sep 21, 2009)

Yeah, thought so... Just need to see what the rental costs are on this and just order and do a ton of splits at once.

As for the skill saw/circular saw option... Since lava rocks are not flat like tile or boards that skill saws can simply cut like a hot knife through butter, how to you hold the rock in place while trying to make a straight cut... I'd be interested to know more as the picture I have in my mind to do this is looking extremely precarious.


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## jgragg (Nov 23, 2009)

A smaller, very effective tool would be a handheld 4" or 4.5" angle grinder (or "cut-off wheel") with concrete (diamond-coated) blade. These are such versatile tools it's best to just own one (you can also mount metal-cutting, and different, metal-grinding blades on them - all are super handy). Besides your main cut you can also do a lot of touching-up with careful glancing passes with the concrete blade. I use my angle grinder ALL THE TIME. Seriously - just go buy one. They kick ass. These are the best thing ever for making paver patios.

This little tool can make cuts maybe 5/4" deep.

A much bigger tool would be a gas-powered concrete saw. Think chainsaw powerhead, with a diamond-coated blade instead of a bar and chain. You rent the powerhead and typically buy the blade (about $50 for the 14" version).

This big mutha tool can make cuts maybe 5" deep, maybe a little more. They easily get through a 4" sidewalk or patio, I'll tell ya that. You definitely want to use the garden-hose hookup thing, and keep the water running (a weak dribble will do).

Obviously you need to *take good care*. These tools will fuck you up in a New York minute. But used with care, hey buddy, whoa daddy. A bench-mounted vise, a fabricated armature of sorts from lumber, tying it down to stakes with rope or twine, gluing down the discard side to a piece of scrap 2x4 you can stand or kneel on, or hell, even just half-burying the stone in the ground (clay would be best, gravel would suck) could all be made to work. You gotta _get creative to get creative_, if that makes sense.

Good luck!


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## Tihsho (Sep 21, 2009)

The angle grinder with a death wheel isn't a bad idea. I have a few down in my shop for automotive metal work I do. Thing with an angle grinder is just to be smart about it. 

Have you used an angle grinder on lava rock before? Does it cut clean or are there a lot of chunks being thrown with the high RPM of the wheels? Might just have to buy another face shield so I don't mess up my good one with sharp chunks of lava rock flying around.


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## jhupp (Feb 27, 2004)

I've cut lava rock with an angle grinder. Pretty much a hot knife through butter. The porosity of the lava rack makes it real easy to cut.

I used a 6" diamond coated blade. One of the cheap Menard's brand ones. I cut it wet to keep the dust down; which resulted in a grit shower while cutting. But no dust.


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## Tihsho (Sep 21, 2009)

Figured it would be easy, but was more so concerned about the porosity causing chunks flying off. I've never used an angle grider with water... this might be interesting...


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