Once the glue had cured over-night the pattern was traced onto the Walnut. I used the bandsaw to get that roughed out. That was interesting, although I have a pretty large table on the bandsaw maneuvering a 6' long piece of 8/4 Walnut around and sawing to the line was challenging. This is where the stackable torsion boxes came into play. By stacking them together they match the hight of the bandsaw table. Then, with Diane supporting the cut off piece the shape was cut out.
Routing, ah yes, let's see now; eye protection -- check; ear protection -- check; dust protection -- check. Okay, I'm ready to do this now:
|Ready for Pattern Routing|
The plan is to shape the inside edge first, somewhat of a trial to see how the OSB (oriented strand board) would work as a pattern for the router. Once the inside pattern matched the template I would re-attach it, line it up exactly to the routed curve, and then proceed to cut the outside curve on the bandsaw.
|Two Passes on the Template|
Here you can see how pattern routing works. There is a bit in the router that has a bearing mounted above the cutter. This bearing follows the template to trim the piece below it and make it a copy. Only problem here is that the Walnut is about 1 3/4" thick and then add the 1/2" thickness of the OSB template you'll need a really long bit to cut the entire part. Don't have one of those and figure why make that investment, a spokeshave will cut cleaner and give a much better finish.
Along the way I learned why not to use OSB for a template. It is full of voids which I didn't realize on the back of the shelf but became evident on the front. Because of the voids the bearing would go into the template a bit which gave me some discrepancies as I routed. Soon as I saw that I knew it was time to stop and repair the edge.
I used some putty to build up and reinforce the voided areas. Once it was dry the areas were sanded smooth to give the bearing a better surface to ride on. The material I prefer to make patterns from is MDF (medium density fiberboard) which cuts, files, and sands easily. Another advantage is that it's very smooth so the router can glide over it easily, OSB has a rough surface that the router base would catch on. Basically, MDF is a higher grade of particle board that has no grain direction and, most important of all, no voids. When you do this operation, and your bit isn't long enough to cut the entire thickness, it's done in small passes. Because the spinning bit can tear the wood out as the grain direction changes it's best to take very light cuts. Once you're down a quarter of an or so it's best to remove the template and use the area previously cut as your guide.
Now that all of the noisy machine work is complete it's time to refine the edge with spokeshaves and a block plane. That's on tap for tomorrow.