Sunday, February 13, 2011

Cutting table, chapter one: the racetrack

So, since Saturdays are designated as "My day" shop project days, I took yesterday to get going on phase one of the cutting table build. This will take a few Saturdays to get through, but will be beneficial in the long-term.

The general idea came from this post by a guy named Steve Jones over on the Festool User's Group website. He came up with a more efficient way to process plywood, that I really think makes sense. In short, the concept is that a Festool track saw is a lot lighter and easier to handle than a full sheet of plywood. Since the two need to be moved past each other in a directed fashion, why not move the lighter of the two? It makes a lot of sense to me... especially since full sized sheets are heavy and awkward, and I'm more likely to bungle the process or damage the parts in the process of dealing with them as a result.

In the case of this particular project, the top and bottom of the torsion box that I'm building for the table have full-sheet dimensions: 48"x96". Since the parts coming out of the process are basically the same size as they were when they went in, and we only have one cart for full sheets of plywood, I didn't have any other place to put each sheet after it was processed. So, I did the only thing I could: I dropped the blade on Chris' Oliver table saw, cleared everything off, and started race-tracking the parts around our huge outfeed tables. I have a pair of long trestles that are designed for supporting plywood when it's being fed into or out of a saw, so I used them to help slide panels to other surfaces, too... like the contractor saw, which is on the left in the above picture. And at the far end, near the double doors, is the plywood cart, holding incoming sheets. It was an interesting day.

For this phase of the project, the chief frustration was my dado stack. When I originally got set up, I bought a Freud Dial-a-dado. The short story is that there's a large aluminum adjusting knob that adjusts a threaded spacer between the outer plate, and then next inner one, to make minute adjustments to the width of the dado that's being cut. In theory, it's great, because it means no fussing with shims. In practice, it has proven to be a royal pain in the ass. As the steel arbor nut is tightened down against the aluminum adjusting knob to hold the stack securely in place, it grinds in, turns the knob, and throws the adjustment way off. So, the nice, precise adjustment mechanism becomes instantly imprecise, and it took me roughly an hour to get the proper width dialed in and secured. I was not happy.

The big eureka moment of the day was figuring out how to make sure that the dados had consistent depth. Since the outfeed table isn't as level as I'd like, and plywood can warp, it's hard to keep the sheet from lifting up away from the cutter. The solution was to take the insert out of the saw, round down the front edge, and adjust the leveling screws to get the front edge re-aligned with the table surface. Why does this work? The depth of cut is gauged against the top surface of the insert, and the problem comes when the plywood isn't in contact with that surface. Rounding the front end of the insert and re-aligning it had the end result of lifting the center of the insert up. So, it was always supporting the plywood, and the depth of cut was maintained.

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