Jig-made round tenons

I have never seen that before, neat jig.
Herb

It's sure a different way to go about it. keeping the bearing against the inside of the hole will be necessary or you will get a divot in the side of your round tenon. A floating tenon (think dowel) of a slightly smaller diameter with a drill hole to match might yield better and more consistent results. That's the beauty of woodworking. There are usually several ways to do everything, so you can choose whichever will work with the tools that you have or which will solve the problem the best and easiest way for you. This sure is a novel approach.

Charley

Looks fairly simple, but it is more complicated than it looks. The hole has to be the right size for the bit and the fence positioned exactly right so the rung is centered in the circle. If the tenons are not straight with the rung as many chairs with legs on an angle,then the rung has to be clamped on the right angle.
Herb