Just in case it helps anybody I found that a 1.27mm allen key is a very good fit into the grub screw that holds the encoder disc hub. That's 50 thousand's of an inch in Imperial measurement. Just a caution regarding use of Torx drivers. I found that a T5x50 (the micro type) would undo the grub screw but was not a good enough fit to tighten it back up. I recommended getting hold of the correct sized key (1.27mm).?
