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Breaking down plywood is an issue for most hobbyist woodworkers. I’ve done it on my table saw, but it’s a 2 person job and even then it’s a pain. The best way I’ve found is to use a circular saw and some sort of straight-edge. So, I’m showing you how to build one yourself, as I build mine. I’ll also explain the other options out there and their problems.
There are straight-edges available that clamp, and they work great, but you have to account for not only the measurement of the piece you’re cutting, but also the distance on your saw from the blade to the edge of the base. I’ve used one quite a bit, but you introduce an extra measurement and that’s another opportunity for error.
There are retro-fit products available that turn your circular saw into a track saw. They also work pretty well, but they don’t fit perfectly and have some slop (move side to side enough to change the cut a bit) in them. Over time the edge becomes uneven and it’s hard to line the track up.
Things to Think About
There are a couple of considerations to think through before you build this jig.
(1) The saw motor and any other parts should clear the fence at your desired depth. Lower the saw until it touches the saw and then raise it up just a bit to give plenty of clearance. That’s your lowest depth. Now, place some stock under the fence and confirm the blade will cut all the way through.
(2) It is possible to make the fence extremely straight without a straight edge. You could purchase your plywood at the home center and then have them cut it down on their panel saw. The other option, and what I do in the video above, is to utilize the factory edge on the plywood. Examine each edge and pick the one that is the straightest.
(3) The cutting side of the jig should start out wider than the saw base. This is to give enough room to make a nice zero clearance cut as the last step.
(4) The other side of the jig should be wide enough to accommodate clamps since you won’t be able to clamp on the fence or cutting side. I measured 6” from the fence to the right side of the jig.
Building the Jig
From the best factory edge measure 3” in and make a free-hand cut.
With the saw in place flip the fence over with the factory edge facing right and, up against the saw and then strike a line on each side to mark its basic location. Measure 6” from the right side of the fence to the right side of the jig and make a mark at each end.
Use your saw to cutout the jig, free-hand, at those marks. Glue the fence down and either drive screws, brad nails, or use clamps to keep it tight against the jig until the glue dries. It’s not really important that the fence is parallel to the edge as long as there is room for the saw to make a cut.
Run your saw along the fence and make a zero clearance cut keeping even and consistent pressure against the fence.
Make a Test Cut
Now that your jig is built it’s time to make a test cut. Measure and mark the piece to be cut and set the jig right at the marks. Clamp the jig down and run the saw along the saw guide again keeping even and consistent pressure against the fence.
You likely won’t need to build an 8ft guide like the one in this video, but a 4ft guide is much more useful. It allows you to make crosscuts and shorter rip cuts.
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