Angled Mortices and Tenons: A Brief Study of Making Them on Table Saw or Horizontal Router

Since my shop is currently buried under about 1600 loose parts of a classic (read that as 45 years old)  motorcycle  that I am restoring, I do not have a fresh project to post as my first article here.  Instead, I dredged up a quick study I did on compound angled mortise and tenon making from a chair project I did last year.  Since I am sure there are a lot of you that already know what follows, please forgive my naïve pedantics.  Hope this is interesting to those remaining curious folks.

Recently I have been tackling the more complex assemblies involved in chairs that have back legs angled outward towards the sides (back leg is rotated a few degrees), and flared back rests that come out of plane in two directions.  That means there is a lot of compound angle joinery.  Traditionally, careful marking of the tenon cheeks and shoulders combined with hand sawing and chisel work is the method of choice.  It is precise, wonderful when executed with skill, a point I am still a bit shaky on, and consequently time consuming.  I wanted a 'better' way.  Additionally, I was having trouble visualizing just what the best alternative would be.  Should I go for 1) straight tenons with angled mortices, 2) angled tenons and straight mortices, or 3) just throw in the towel and go with floating tenons and make angled mortises as appropriate.  To get my head straight I drew up the three alternatives (see below) and listed out in order the cutting steps along with the pros and cons of using that method of joinery.  Other than hand saws, my go to machines are the table saw and a horizontal router jig that I built on a CNC bed.  So I went through the exercise for each method of joinery for each of the two machines.

By the way, if you do want to use hand saws, I really like the Japanese pull saws, which I do use often for some other work.  They seem to cut all by themselves and I am just along for the ride.  Its magic.

Here in plan view are the three alternative methods with the pros and cons I could envision.

1) First alternative - Straight tenons and angled mortices

2) Second Alternative - Angled tenons and straight mortices

3)Third Alternative - Floating tenons and doubly angled mortices

You've probably seen it right away.  The second alternative machined on the horizontal router was an easy choice.  The results were more than satisfactory.  After a few false starts, on scrap wood of course, I learned how to set up for the cut so that the base of the tenon was in the desired position on the rail.  Mortices were easily cut on a morticing machine (I use the Jet table top version).  Since the horizontal router is capable of holding single digit thousands of an inch accuracy, I quickly learned to cut the tenons about 5 to 8 thousands thinner to get a nice friction fit without binding.

Comments welcome.  Better ideas more than welcome.