Domino Joiner and Obtuse Angles

[WoodenGoblet]

I want to join to pieces of 1 1/4" x 3 1/4" lumber that are cut at 50 degrees using my domino joiner. Do I set the angle of the joiner at 40 degrees or 50 degrees to join the two pieces?

 

[ChuckS]

Could you show the pieces/angle in a sketch? It can be neither depending on how they are joined.

 

[Birdhunter]

I am assuming both boards are 1 1/4" thick and 3 1/4" wide.

The way I am picturing this, I would lay the boards flat and set the fence at 90 degrees and cut one mortise parallel to the 3 1/4" side on both boards. Since the boards are over 1" thick, you could use a fairly thick tenon. You would have to be careful that the mortise does not blow out the back of the board and is centered in the middle of the boards.