With the routing from the previous step complete, all the major pieces excepting the back and seat boards are done. Those boards will wait until assembly time to be cut and fit to whatever the final dimensions turn out to be. I don’t anticipate they will be different from the plan by much, but I would hate to be wrong and there’s no reason for me to cut them until I have to.
But, they are integral to the chair and the positioning of the parts. So, I mocked up a back board from cardboard (we have a surprising amount of this stuff floating around) and some scraps. and put it all together on the table saw. Side view:
And, front view:
There is one last step in the process before we get to the dreaded pins. That is boring holes the holes for the pins. The upper and lower back stretchers, the front seat and leg stretchers all get one on each side. That’s eight per chair, so 16 total. These holes will be 3/4″ x 2-1/2″ and they need to be positioned pretty carefully. The leg stretcher is big (2-1/2″ square), so that one’s not a worry. The other components are just 1-1/4″ thick, so getting the hole in the center is critical to the structural integrity of the chair.
Also, in order for the chair to be able to be assembled, they have to be pretty close to perfectly parallel to the long axis of the board. Otherwise you will never get a board to go over both the requisite pins simultaneously.
These holes are to be drilled into end grain; a notoriously challenging prospect. It also really limits your choices of bits. Any kind of spiral bit is going to clog up almost instantly. A forstner bit is the way to go, if you have one long enough.
As it happens, I have one that I kept from some auction junk box lot. It wasn’t especially sharp, but a few minutes with file helped (some). This was made for some machine, not a standard homeowner drill press. Fortunately, I don’t have a standard, homeowner drill press. I have a honking big one.that had no problem with the larger bit.
A feature of this drill press is that the can tilt vertically. Which nicely solves the problem of securing the work-piece. Combining that with some careful positioning of the fence I was able to get the stock centered and parallel to the bit. The fence stop made a handy mount point. So, here’s what that looked like:
Drilling the 16 holes took a fair bit of time. I was going slow being super careful to accurately position the holes. I also needed to let the bit cool. End grain is brutal and the chips don’t clear out the way they should because of the vertical grain. So while I could fully employ the power of the 2HP motor to this endeavor and plow straight on down to full depth, when I got there, I wouldn’t be able to extract the bit from the packed chips above it in the hole.That is, until the fire started by the super hot bit burned far enough to consume most of the chips holding it in place.
So let’s not do that. Low speed, clear the chips regularly and let the bit cool between holes.
Next up, the pins.
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