Thread: Oblique drawbored mortice and tenon joints

I searched the forum for information on how to cut oblique mortice and tennon joints for a timber rack I am building. Having failed to find such information, I hope to contribute to the common knowledge base by showing how I made these joints. Comments and suggestions are welcome.

Generally speaking, there are two ways of constructing oblique M&T joints. Either make a square tenon and an oblique mortice, or the other way around. I could not think of a way of consistently making oblique mortices, without resorting to enslaved demons, and, therefore cut oblique mortices. (Conjurers may try tilting the table of the drill press for boring oblique mortices.)

I started by cutting the tenon end at 85 degrees.


I, then, used this new edge as a reference for marking the tenon. To help cutting, the edges of the tenon should be deep enough to allow for the saw kerf.




And here is the marked tenon ready for cutting the edges.


And the cut tenon.


Then, I marked the cheeks


And cut them.


Then I used the tenon to mark the mortice. The pencil line marks the top of the arm, and the mortise is cut relative to that position.


I used the techniques described by Bob Smalser for cutting the mortice and making the drawbore.

And here is the final result:


Oh, before loading my timber on my new rack I tested the strength of the joints by pulling down on the arms. The joint is, apparently, very strong, and held well. The arm, however, remained in my hand. Apparently I will have to use the Gumby approach for storing timber.