I cut 3/4” plywood with a circular saw on a big special knockdown table because I lack the room for a panel saw. I was using a 6.5” Black & Decker Woodhawk that I have had for 10 or so years. It was clearly underpowered but would labor through the 3/4” plywood eventually. I bought a Porter-Cable 7.5” 325MAG saw, installed a brand-new Dewalt plywood blade, and proceeded to try to cut some 3/4” plywood (some sanded plywood from Lowe’s) with it. From the first few inches, the saw blade smoked and the wood smoked and burned. The saw labored through the cut ( 48”) but left the wood burned on both sides of the cut and the sawblade black. I then switched to another brand-new Dewalt plywood blade and tried the next cut. After about 12”, I gave up because the wood and sawblade were still burning. I took out the old Woodhawk with an old plywood blade and finished my work, slowly but surely without burning either the wood or the sawblade. The plywood was adequately supported for the cutting. The brand repair center said nothing was wrong with the saw itself, but the second blade had warped due to overheating.
Is this result typical of what I can expect from a 7.5” saw cutting plywood? If so, what size circular saw do I need to cut plywood safely without burning? I have a table saw but I can’t safely cut a 4’ x 8’ sheet on that by myself, which is my usual mode of operation.
Don’t know without seeing the saw but it sounds like the arbor is/was misaligned with the shoe. That is, assuming you were using a straight edge to guide the saw. Can’t blame the plywood if your smaller saw worked fine.
Ed
-- Come on in, the beer is cold and the wood is dry. www.crookedlittletree.com
I know you said you had a new plywood cutting blade on it, but what brand was it? You may want to use a multipurpose blade and see if that makes a difference. I know that the plywood cutting blade should work without smoking and burning. Any good circular saw should cut the plywood without what you have experienced. If you continue using you saw with this abuse, I’m affraid that you risk getting hurt or at the least, burning up your saw motor.
Take it back and try another of the same model. May be something in the saw not working correctly. I’d also guess that the blade is on backwards… If not, I’d look at the tool.
We use a Skil worm drive with Freud blades. I can’t remember the number of the blade but it never bogs down even in 1 1/2 ” Alder or Oak. I think the problem is your blades. The saw should cut the ply like butter. I had ply blade cut a crooked line in a sheet of plywood one time. When I took it out it looked like a potato chip. I’ve never used a plywood blade since. If you are worried about tear out use masking tape and for sure use a straight edge.
Sounds like you may also have problems with torquing the blade, so you’re getting plywood in contact with the side of the blade rather than just the teeth.
It’s not a function of saw power, it’s a function of the blade generating heat, and how it’s dissipating heat. So either the blade isn’t big enough and you’re not radiating enough energy (which is possible, but I doubt it if you’re having that problem in a foot of cutting), or there’s something in your technique with the blade that’s causing the side of the blade to rub on the wood, heating far more than the teeth of the blade would.
I had similar problems with a low-end saw whenever I tried to cut along a straight-edge. I now have a Festool TS55 circular saw that runs on a rail, and have had no problems with blade alignment relative to the guide, and can rip two-by wet fir with no problems.
The blade was a Dewalt plywood blade. It was installed properly, even the repair shop said that. I’m going to try a conventional blade and see how that works. Switching to a plywood blade helped wen I was using the small saw, but maybe a conventional blade will work better on the larger saw. If that doesn’t work, I’m going to buy one of the Festtool saws. I received the saw as a gift and I didn’t save the box, which I need to return the saw, so I’m stuck with it.
Thanks for all of your insights into this problem.
For what it’s worth, I had the same problem with a 18v battery saw with a plywood blade from DeWalt. The saw just smoked and literally burned the wood before killing the battery. I took the darn things apart and discovered the blade had been incorrectly stamped at the factory. Look at the teeth and rotation of the saw motor with out a blade attached. Try flipping the blade. I got a 325 MAG and had ZERO trouble with it, just sorry imported blades from China.
This is probably self evident but I wanted to post it anyway. When you cut any wood the saw blade should barely extend past the wood being cut. I like 1/8 to 1/4 so that more teeth are in contact with the wood at any given time during the cut.
I use a Skil trim saw for all plywood cutting. Uusually, with a 4” carbide- tipped blade. I always use a locking guide bar, eiither 24” or 50”, and run the saw base alongside the guide bar. I support the cut off piece and, while cutting, stop the cut 8” in and apply a clamp across the kerf to help keep the sheet flat before resuming the cut. . With some wood stock I apply masking tape over both the face and rear cutting line and only allow 1/8” of the blade to show beneath the board.. I’ve never had a problem with this simple set up. It sounds, as some commentors have said, that there was an alignment problem.
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