Mitered Mortise & Tenon – June 2018
A mitered mortise and tenon joint brings an English charm to a New England-style chest.
by Peter Follansbee
For me, the timing of writing for a magazine is hard to wrap my head around. The season that I write in is never the season my stuff gets read. As I write this column, it is late November in New England, and the column is for the April issue of the magazine. So we’re just heading into the other side of the winter as you read this.
As I worked in the shop today, I was thinking about how fall and winter are some of the best times for this work. Spring and summer have many distractions, and the heat and humidity of full summer are often overpowering for this getting-older green woodworker. I’d rather split big oak logs in cooler weather. They stay green longer then, too – no need to hurry. And the shop is an inviting place on dreary fall days.
Today, I’m working on a joined chest for a client. This one is not a copy of any particular chest, but just a generic example. I decided to add an English flair to it (as opposed to New England, my usual vantage point) by using a mitered shoulder on the tenons that overlap a beveled edge on the mortised parts. The full effect of this format is to create a beveled frame around each carved panel. Not at all unusual in old England, this technique stands out like a sore thumb when we find it on New England chests. I know of one very large group of chests, referred to as “Hadley” chests, that always feature this joint on the chest front.
The framing on the sides and back have 90º tenon shoulders meeting square-edged mortised members. There’s perhaps 200 or more of these chests, and I’ve never seen one of them without the mitered front joints. Other than the Hadley chests, I know of exactly one other New England chest that uses this joint. Not one other group of chests, just one chest. All the others use square-edge framing and 90º shoulders. Sometimes these have stopped bevels around the panel openings, sometimes moulded edges fading in and out around the panel openings. But always 90º at the joint.
Full tilt. The sawn angle of the front angle is tricky – a chiseled trench guides the saw. Get close to the correct angle, but tune up the fit by planing the rail to fit.
I haven’t cut this joint in maybe 10 years, so I practiced a couple to get the hang of it. It’s frustrating, because I’m so used to my joints going together right off the saw and chisel, with nary a test-fit. This joint has me almost back to square one.
First I lay out the front shoulder across the muntin. Then I use a mortise gauge to strike the thickness and “setback” of the tenon, in this case the tenon is 5⁄16″ thick, set back from the rail’s face 3⁄8″. Now I use a miter gauge, or an adjustable bevel set at 45º to strike from the front shoulder to the front of the tenon. Then I use a square to carry this point back to create the rear shoulder.
Undercutting that front shoulder is the kicker. It’s really about tilting the saw over a good bit – more than I think. I score across the shoulder with a knife, then pare behind this line with a chisel to make a slight trench for the saw to lean in while I’m cutting this shoulder. Then the rear shoulder is back to normal. I always cut these just behind the line, so they don’t hit the mortised part. Then I split the cheeks and pare across the tenon faces to bring the tenon to its final thickness. I lay out the planed bevel with a marking gauge. I usually set it so the bevel almost but not quite reaches the panel groove. You have to tilt the plane over more than you think, same as sawing the shoulder. I keep checking my progress with the miter gauge or an adjustable bevel.
I chop the mortise with a 5⁄16″ mortise chisel and a mallet. There’s a slew of methods to chopping mortises; I stay out of any debate about one method versus another. It’s like the joiners’ version of pins versus tails.
After chopping the mortise, I plow the panel groove and then plane the bevel. When I’m planing this bevel, I keep checking the progress by inserting the tenon and seeing how the beveled shoulder is meeting the bevel on the mortise. Check often, make small adjustments.
It takes me some fiddling around as I test-fit this joint to get it the way I want it. Ideally, the tenon’s long sloping shoulder slips right over the bevel on the mortised member. The test joints helped me get warmed up to this joint again. By the time I was cutting the chest front (eight joints) I was getting back up to speed. Now the sensible thing to do would be to make them on my next chest too. Nah, that’s not me. PWM
Purchase the June 2018 issue of Popular Woodworking here.