I couldn’t help but think that canoe joint bits could be used for more than just making cedar-strip canoes. If they enabled wood parts to form delicate curved shapes like that, shouldn’t they be just as useful for making curved tops for boxes or even curved door fronts? So, with a variety of Rockler’s new one-piece bits and a two-piece set from Freud, I thought I’d see how easy it is to create a curved surface.
Both work the same way: One profile cuts a rounded or bullnose profile on one side of a strip ½” or wider; then the mating profile cuts a concave profile on the other edge. To make curves, match the profiles together so that the rounded profile pivots within the concave to allow a slight curve. Well, that’s the theory.
To make this joint work, I first needed to control both cuts in the thin strips. (Canoes would normally use pieces only ¼” thick, but I felt more comfortable experimenting on ½”-thick strips.) That meant outfitting the router table with hold-downs (shown in photo 1) and feather boards. You’ll also need a push stick to keep fingers safely away from the action. I cut the rounded edge first so that this surface, instead of two thin slivers left by the other profile, would ride firmly against the feather boards while making the mating cut.
I didn’t exactly use the best lumber with the straightest grain for this experiment. (It was more an excuse to rid the shop of oak shorts.) But that’s what you’ll want if you try making one of these for real. You’ll also want all the pieces planed to the same thickness. After pulling together enough scraps to assemble the round waste bin that would be my “project,” I soon discovered that wild cathedral grain (these were scraps for a reason) gave me the most splintering and tear-out problems when making concave cuts, as you can see in photo 2. With a stack of parts cut to length and routed (photo 3), I used a tablesaw to make kerfs on the inside faces about 1″ from the bottom to accept a round disk.
Determining the disk diameter was process of trial and error using the taped-together slats for the approximate disk diameter and then sanding the disk edges until it fit snugly in the saw kerfs.
The real trick was the glue-up. This is definitely an operation where you’ll want to do a couple of dry-assembly practice sessions. That’s because you may be gluing and assembling 20 or more pieces to make a waste bin large enough to hold more than one wadded-up tissue. To hold the whole thing together, I used a combination of 3M Stretchy Tape, a bungee cord, and a band clamp (photo 4). Even then, I couldn’t get each joint to meet at exactly the same angle. One solution might have been to insert a partially inflated toy ball to apply even pressure from the inside as the clamps pull the pieces together on the outside. That’ll have to be for Waste Bin ver. 2.0.
Fortunately, the joints sanded down smooth with no glue-line problems affecting the stain (photo 5). If you decided to try this project and discover ways to do it better and easier, please post a reply.