I received an email a couple days ago from a student at the University of Michigan that goes like this:
Hi Mark,
I just discovered your blog – very nice.
I was impressed by your parametric Mission Table. Especially how you handled the parametric mortise and tenon joints. I’ve been able to make parametric tenons no problem – but I don’t know how to make the mortises auto-update when the tenon changes. Does your model do that? If so – any way you can share it – or a part of it – so I can see how you accomplished that?
Again, thanks for your blog.
Sincerely,
Mark Meier

The short answer was no.
Generally mortise and tenon joints are sized to the available tooling, and are based on the particulars of the design at hand. In my case, I use a Powermatic 719A Mortiser (shown to the right) and have ¼”, ⅜”, ½”, ⅝” and ¾” hollow chisels. While designing a piece, I pick one of the chisel sizes based on the strength (or other factors) needed for the furniture item in question. A ¾” thick stretcher on an end table usually gets a ¼” tenon, and the leg gets a ¼” mortise to match.
But in the case of work being sent to a CNC router (or template routing by hand), there is a bit more flexibility as to joint size. You may want to tweak a tenon size up a bit when switching from white oak to pine for instance.






