All 3 axis are the same, 3 endplates with the bronze things, and 3 of the others. As you say, maybe the design changed and was possibly documented in any instructions that were originally supplied. I did think a collar and grub screw was a bad idea, especially on a threaded rod. All 3 axis do move very smoothly (took some doing), but I'll take your advice and reassemble using pairs of locking nuts rather than the collars. I was concerned that I was missing something with the nuts at the other end but seems Im not.
Do I need to be concerned about play between the bearing and the threaded rod ath the bronze unsupported end? there isnt a lot, probably < .5mm movement between the rod and the bearing. Im assuming that if anything then the threaded rod will eventually wear rather than the bearing, but other than act as a guide/support this end doesnt do anything so it wont affect the movement?
Thanks
Calv