Glastonbury Chairs – Part III: Vaporizing Wood

The next step on this journey is the back and seat side rails. Much more complex than the front/back/top rails. These have exposed ends which need treatment, need to pass through the seat pins and have a stopped dado to receive the back and seat boards.

We start by locating and drilling the holes for the pins. These need to be precise if you want the chair to be able to be assembled more than once and not require a hammer. It’s best to do that while they are still rectangles. Then we can clip the corners and chamfer the edges before moving on to the dados.

The width of the dados isn’t super important. They have to be less than or equal to the thickness of the back/seat boards and they only need to be 1/2″ or maybe 3/4″ deep depending on the type and size of wood, etc. They should not run out the end of the rails, that’s unsightly. The longest they can be is to the pin holes, though you could stop them short. Their sole purpose is supporting the back/seat boards.

There are ways to cut stopped dados on the router table, but they don’t fill me with joy. I like to see the cuts as they happen because, with power tools, things can go to hell in a heartbeat. If I am watching, I might be able to stop things before the piece has fully embraced it’s firewood fate.

So, out comes the bench mounted twin screw vise (a.k.a Moxon vise). These parts are short enough that they fit in it. Otherwise I have a similar but much larger and less attractive vise that has a 36″ capacity. It’s a simple matter of setting up the plunge router to have it’s fence ride on the back jaw and have the bit centered on the board.

If you are super anal about centering the groove, you could use an undersized bit offset to one side of the groove (e.g., a 1/2″ bit cutting a 3/4″ dado). Run that once against one side of the planned dado, then, rotate the board w/o changing anything else and run it again. This will finish the dado and will guarantee the groove is centered.

That said, for this application, they don’t need to be centered. For these chairs, they are centered. However, on the oak ones I made with Reynard, we offset them so the portion of the rail “above” the dado was thinner than below. That gives the seat support more strength and has less of the rail intruding into the seat proper.

However, if the groove is not centered, the back rails and the seat rails will have a left and right. That is to say they need to be mirror images of each other. Or you will be sad.

Back to cutting dados. You are removing a lot of wood, that’s going to really strain the motor and heat up the bit which will in turn cause all sorts of problems. So, run dados these in a couple of passes going progressively deeper until you hit the full depth. I used three passes. Four or five would probably have been better, but my attention span only extended to 3 passes.

I hate using a hand held router indoors. It’s a total mess and you can’t avoid the fine dust. Yes, I know they make little shrouds for the router, but it’s hard enough to see and control as it is and those aren’t all that great either.

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