Chair Joinery: Tapered Tenons & Tapered Mortises
Because chairs take abuse like a rented mule, the simple mortise-and-tenon joint is sometimes not enough.
In traditional Windsor chair construction, the legs and spindles are attached to the plank seat using tenons that are cone-shaped along their lengths. So the mortises have to be the same shape. These tapered joints are clever. The more you sit in the chair, the tighter the seat-to-leg joints become.
Making these joints requires some cleverness. For years I used a tapered reamer from England that never worked well. I had borrowed a reamer made by Fred Emhoff and it worked well, but was no fun to sharpen. I’ve also used wooden reamers with a bit of steel embedded in it, which scrapes the sides of the mortise.
All those solutions worked, but none as well as the Veritas Pro Tapered Reamer. For less than $43, it is a great value. I’ve paid more for reamers that didn’t work as well. The blade is removable and easy to sharpen. And – best of all – you can adjust the depth of cut. This is worth more than the price of rubies. With softer woods – pine, poplar and mahogany – you need a deeper cut. This reamer delivers.
I’ve not used the Lee Valley Standard Reamers. They are less expensive, but you cannot adjust your depth of cut and they are more difficult to sharpen like a traditional steel reamer.
On the tenon side of things, I used to turn my tapered tenons on a lathe. That works fine, but it is slower than using a dedicated spoke cutter (unless you are a production turner, of course. I’m not).
The Veritas Tapered Tenon Cutter is, quite simply, the best one I have used (and I’ve used many). I use the 1/2” model – the size is the resulting diameter of the tip of the tenon. The blade is easy to sharpen, like a spokeshave blade. But the best thing about the tool is that it offers registration marks on the body of the tool so you can set the blade to exactly the correct skew. I know that the perfect skew for mahogany, for example, is to set the blade so it’s on the second mark at the opening of the tool and on the third mark at the top.
The body of the tool is heavy, which helps keep it in the cut. The only modification I have been pondering is making a long wooden handle for the tool so it will work more like an old-fashioned auger. After 32 mortises this week, my wrist is a little sore.
These tools aren’t new. I’ve been using them for a couple years. But as I was making a pair of Roorkhee chairs for an upcoming article, I was reminded of just how good they are. If you make traditional chairs, these are highly recommended.
— Christopher Schwarz