The original was just a steel disc with lots of non-adjustable backlash determined by how (not very) close to it the outer sleeve was pinned to the shaft during manufacture. The new one carries a ball bearing and spacer so the backlash is determined by the precision of the ball/race fit. If I were doing it again, I'd make this block thicker and mount two ball bearings with a spacer between and some bearing preload. It's amazing how much play there is in a single ball bearing. I never thought of this until later but couldn't have done it originally anyway because I was fitting it to the original leadscrew and was limited to the thickness of the original thrust plate.