Sorry for the crummy phone-cam pic. I’ll have good photos soon.
Making a tenon (the male part) is no big deal if you have a good table saw and a tenoning jig, which we do. Making a blind mortise (the female part) is no big deal if you have a dedicated mortiser, which we do. This machine is a drill press with a special bit inside a hollow four cornered chisel. In short, it’s a drill press that drills square holes. Drill a bunch of square holes in a line and you have a mortise. Don’t drill all the way through, or you’ll have an unintentional through mortise, AKA firewood. This machine is pretty accurate, but the edges and bottom of this slot are not perfectly even and clean. This is OK if you are covering this mess up with your tenoned piece, in this case a shelf between the legs of a table. Smear some glue on it, hammer it together, clamp it, and nobody will ever see the raggedy slot.
A through mortise however must have a tight fit to the tenon and clean crisp edges. No chips, no tearout, and straight lines on both sides. It’s all visible, baby. You’ve got to make the mortise undersized, then carefully chisel and file up to your layout lines. Test fit, then file some more, repeat until satisfactory. Patience and time are required.
This table is our first non-commissioned piece and will be for sale soon. Stay tuned.
*this is actually my second through-tenon mortise. the first one is in the ‘to burn’ bin.