The goal, here, is to fit the shelves as closely to the space as is possible given my skill level and the materials and techniques available to me. The problem is compounded by the fact that the wall (which I built from the studs out, so cannot blame anyone else for) is not straight nor plumb nor square. This is not an unusual circumstance, I’m told, but I suspect my out-of-whackness is probably excessive. In any case, I must proceed carefully, double- and triple-checking my measurements and my assumptions as to the shape of the space I am filling with … well, more space, but space delimited by boards.
Here you see the standards, each of which has been cut to the exact size of the space it must occupy. Well, that’s the plan anyway. There are gaps in the joints, which I will have to fill with shims and hide with trim. But we’re doing pretty well all things considered.
When I started out on this phase of the project, I hit a bit of a snag. After a few cuts (long rips — 5, 6, or 8 feet), the blade would start wandering in the wood. It would scorch and the wood would as well.
I had seen parts of this before, so was not entirely panicked. But, after allowing the blade to (I thought) cool down enough, it would still do it. I didn’t think it all the way through, (not at all unusual for me), and panicked.
You said that.
Did I? So I did no I didn’t. Spankings for Dolly!
But I degrease.
I e-mailed Og for advice. He shot back that it was probably the plywood (made in China). The resin was probably heating up more easily, flowing more freely, and causing major problems. While I was afraid I’d done permanent damage to my saw, he suggested there probably wasn’t any.
Old carpentry hands are, of course, snickering behind their hands. You lot can stop that. Go ahead and laugh out loud. I am.
You see, I’d forgotten what little I once knew about cutting plywood.
Most cuts made with circular saws are either crosscuts of dimensional lumber — i.e., your typical softwood 2×4 — or, if rips, also in dimensional lumber, and not in sheet goods. Short. Easy. Keep the blade cool.
Plywood, unlike plain boards, is made up of layers of wood veneer stacked in alternating grain directions and glued together under heat and pressure. The dual directionality of the grain is one of the factors that contributes to its extraordinary strength. (The WWII light attack bomber, the Mosquito, was made of plywood, as was the legendary Spruce Goose.) But it also makes cutting it harder. Ordinarily, not a problem except for when you’re doing lots of long rips all at once. Then the blade heats up. And the glue softens, and becomes a resinous colloid that sticks to the blade and scorches at relatively low temperatures. (You can touch a hot saw blade and only get a first degree burn. Not that I recommend it. But you’ll get scorched resin.)
Back in the day, when I worked in a wood shop, we used to rip lots of plywood. We made waterbeds. Part of the waterbed — back then — was the plywood deck… the part of the riser that supports the mattress. Nowadays, if they still make the things, they’ll be made of OSB — oriented strand board. But back then, plywood. We used 5/8″ (that’s the thickness) CDX plywood. CDX is the grade. The CD part means that one side has a C quality — the best is A, then B, and so-forth — and the other D, which is as bad as it gets. The grades are based on the number, size, and eggregiousness of knots, inclusions, and voids. The X part meant it was exterior grade — also known as sheathing, the stuff they use to clad the outside of a house under the siding and the shingles on the roof. Nowadays, they mostly use OSB, but… well, you no doubt know that song by now.
Because the veneers that make up a sheet of CDX plywood are a bit on the rough side, the glues they use have to be slathered on good and thick and have to be of a rather aggressive nature. Which means, yes, you guessed it, it’s some of the nastiest shit you could wish on a saw blade.
When we cut this stuff, we did it on a radial arm saw, which ran a 10-inch blade. For plywood, we used a blade that had about thirty teeth that had very small bits of carbide on the tips and big gussets between the teeth. This made the teeth into excellent radiators, meaning it took a lot to heat it up. Not only that, but it was my job to clean the blade. To do that, I’d take a solvent and an old toothbrush that you wouldn’t wish on your worst enemy and scrub the resin and pitch and sawdust off the blade. Once in a while, we’d have a nice little old man sharpen our blades, and they got a more thorough cleaning while he was at it.
All of which should tell you I should have known what was happening when my dinky little 7 1/4″ blade, hollow-ground, with teensy teeth and no gussets or vents or anything started heating up and walking all over the place. But I didn’t. Or, rather, it took me a while to make the connection.
Over the last weekend, I acquired a Freud teflon-coated blade, a 40-tooth, red monster with hefty carbide tips on the teeth. I’ve been spraying it with WD40 for every cut. And, after about a dozen cuts, I can detect no buildup of pitch on the blade, and the cuts are smooth as satin.
Next I need to work on my marking precision. Cut a couple of boards today. Was utterly anal about everything. They’re not square to each other. Bummer. I think it will work, but if not, there’s always the edge trimmer on the router.