The components for the Kitchenaid PTO adapter complete and laid out.
The turned and filed 12mm Aluminum Bar, turned down to 8mm (Bearing race inner diameter and inner diameter of the flexible coupling) and drilled to take a wire pin. The pin is to stop the bearing from moving down the shaft during use.
Note the piece of copper wire to use as the bearing retaining pin and the Skate bearing.
The purpose of the bearing is to keep the PTO shaft roughly aligned with the center of the housing even when the alignment is displaced. I guess it stops things catching and rubbing.