I didn’t really spent much time thinking about how the desk top would be built. I planed and jointed the walnut along with the maple and cherry.
I proceeded to glue up the panels using a biscuit jointer. With a top this large (39×72) I used 4 – 10” wide boards and glued them in pairs then glued the pairs together.
I also clamped the ends and middle to keep the board from cupping from the clamping pressure.
From there I glued up the final 4 board panel. After sanding the top with 150 grit on my belt sander to even out the glue joints I came to the realization that this behemoth was too big to run across the table saw to clean up the ends. That brought things to a halt in a hurry.
First, I tried to use the hand held circulating saw and the aluminum straight edge that I go to on plywood. For some reason the blade was on backwards. After burning the blade and scorching the wood, and nearly burning out the windings on the saw I realize the error of my ways. I bought a new blade and crosscut the end.
Better, but still not good enough. Time for one of my least favorite methods of making a clean, straight edge, using a router and a straight bit. I don’t like this method because I’m not a fan of a ½” bit sticking inch out of a 1 HP router, spinning at 6,000 rpm or whatever it is, combined with the tendancy for the router to want to twist when you turn it on, before starting the cut, while you hold it with one hand and turn it on or off. It is a recipe for something bad to happen. Still, necessity is the mother of invention so I set out to make the cut as square, straight, and most importanly, safe as possible.
Laying out a perpendicular line to the edge can also be a chore, and since I needed it to be true, layout took a while, with lots of cross checks and starting over. Ultimately, I threw away one of my big squares that wasn’t really square any more and a straight edge that had bowed. That took a while but it was worth the effort. It took a couple of passes get through the 4/4 board without bogging the bit down in the end grain.
End result a 39” x 68” top that passed the corner- to-corner diagonal test with less than 1/16” difference and no light showing along either edge of long square when I checked the corners. Success!!!
Lesson learned: I need to think about how to handle big pieces before starting any preliminary work on them like gluing up a 40×80 piece of walnut because I got impatient to start on the dek top. I should have cut the boards a lot closer to the finished length and I also should have squared up the individual boards before gluing them together.
Next problem that I hadn’t really worked out: How do I make the tenons for the breadboard ends? I needed a 2” wide tenon, ½” thick, cut into the ends of the top. By now, I had spent a lot more time thinking about a safe, stable approach to the tenons and came back to the router.
After scribing the line for the shoulder of the tenon, I measured the distance from the straight edge of the plunge router base to the ½” bit I was using and set up straight edge off the cut line by that distance (2-3/4”). I also made 3 – ½” wide strips to use as filler strips along the straight edge to get the router bit over to the edge. I didn’t want to move the straight edge once it was set. I set the depth step on the plunge router up so that the 1st step was 1/8” and then dialed the second step was 3/32” for a total of 7/32”. The digital calipers confirmed everything was accurate.
After each pass was routered to the final depth I removed a strip which indexed the router by ½”, with the last pass run along the straight edge.
Once the various setting were locked in on the router and squares, it was fairly short, though dusty, work to router both sides of one end, flip the board, and do the same thing to the other end.
I cut the sides back an inch and now I have most of a desk top. I just need to make the breadboard ends.
-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"