Hey folks, I have a few cuts I need to make in 1/2” cement board. I’ve been having a real tough time with score + snap actually working - I suspect maybe because it’s thicker board?

I know there are specific blades for cutting cement board, but they’re super expensive given the small number of cuts I need to make. I’m wondering if I can just use an old 24T circular saw framing blade (and then throw it away since it’s old anyhow) for those 3-4 cuts or if there is any reason other than more dust (I have a respirator) not to do this?

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DoubleDongle-F t1_je8b5sg wrote on March 30, 2023 at 3:23 AM

It should work. Score and snap is fine for Durock and other similar gray mesh-backed cement boards, but doesn't work that great with Hardie Backer and its clones. You'll trash your blade, but it should cut. Might be bad for the saw itself, but a few cuts shouldn't kill it.

I use an angle grinder with a diamond wheel for this kind of thing if I'm being serious about it. You can also use a jab saw, like for sheet rock, on Durock, but not Hardie Backer.

Motamonster89 t1_jea5czw wrote on March 30, 2023 at 3:08 PM

I was going to suggest a grinder with diamond blade too just wear a decent mask, that dust is terrible for you.

NotWorthTheTimeX t1_je84kcy wrote on March 30, 2023 at 2:28 AM

You can do exactly what you’re asking. It will throw a few sparks so try not to work over flammable materials.

Chrontius t1_je85zgl wrote on March 30, 2023 at 2:39 AM

I mean, you can do it, but boy is that miserable. At some point, the blade just got so dull it wouldn't cut, and just friction-heated the board and blade.

I was pretty fucking shocked to see just how quickly your shitty blade became completely useless, though.

RamBone22 t1_je7rl9z wrote on March 30, 2023 at 12:49 AM

Keep making cuts along a straight edge over and over. You’ll burn a blade per 4’ cut. And the blade is screaming hot afterwards. Let it cool before putting in the trash can. Then the snap should be easier.

Edit: also it’s more about a high quantity of cuts with less pressure vs. forcing the blade into the board

cbryancu t1_je8252w wrote on March 30, 2023 at 2:09 AM

No special blade for cement boards needed, just run the blade a bunch of times.

You can use the saw, but it may make a rough cut if it's dull and may vibrate which may not give you straight cut. The saw could get damaged as well, it is not designed to shed the cement dust which can get drawn into motor. Just a few cuts probably won't do any real damage.

I'd just score it a bunch of times with knife.

DeVonSwi t1_je8ufvf wrote on March 30, 2023 at 6:57 AM

Use this blade in your circular saw: https://www.homedepot.com/p/DEWALT-7-in-x-1-8-in-Masonry-Abrasive-Saw-Blade-Bulk-DW3521/202579871

homelessdreamer t1_je8wstc wrote on March 30, 2023 at 7:30 AM

I have always just used my crap blades and toss them when finished the most important detail to lengthen the life of your saw is once you are done open the saw and clean the brushes on your motor. In general that is good practice to do regularly regardless but especially with cement dust. If your tool is visibly sparking most the time is just dirty brushes.

2muchyarn t1_je9557q wrote on March 30, 2023 at 9:34 AM

I used a jigsaw. I wet down the cut to help reduce the dust and wore a mask. I had to buy a better jigsaw than the one I had, but the accuracy of the cuts and speed made it well worth it.

sccoootttt t1_je9ds6p wrote on March 30, 2023 at 11:23 AM

My technique was to score with one or two passes (was also generally using a shitty blade), and then set the scored sheet over a thin scrap of wood or another piece of cement board or something and the to just use body weight and apply force with my feet by standing over/on it and it will cleanly snap across the scored line that is aligned on the thin wood beneath. Seemed like the lazy way out, but it worked for what I was doing!

bassboat1 t1_je9nggt wrote on March 30, 2023 at 12:54 PM

The old carbide blade will work. The 4 T ones for cement board last monger, but are just as miserable to run. I switched over to Hardiboard, and bought a set of drill-powered snips for the last couple of jobs: gamechanger!

skydiver1958 t1_jec0d30 wrote on March 30, 2023 at 10:22 PM

What most people don't know about score and snap with cement board is there is one side only for the score. Still hard on knife blades but if you score on I believe the backside you get a better result.

Yes you could use a saw but of course a disposable blade and use a cheap saw you aren't attached to. The dust may fuck it up