Old thread of course. Apologies.

I use a Wirth Machine for making tenons. Changing setups is a hassle unless you don't care about the tenon slopping around in the long dimension. In cabinet doors this probably doesn't matter, but I'm making chairs and I want it exact. The Wirth Machine spindle (unlike the Matchmaker and Multi-router) moves in an arc and so centering a tenon exactly is trickier since the centerline moves when the offset of the tenon from the reference face (or tenon thickness) changes.

I'll probably see about making a centering bit of some sort. One could mark out the dead center of the desired tenon and set the stops from there I think to align the template center precisely to the tenon center.