Peter

Further to my last comment, I also found that the bottom locking collar came loose after tightening the bottom bolts from Step 9. I reckon the grub screw had been sitting on the apex of a thread and it was popped-off into the next groove. In the end I gave up with using the end plate to compress the mechanism and just made sure the collars were pressed hard apart before tightening the grub screws. I'm just a beginner at this, and I need to respect the years of experience that's gone into this machine, but this process of eliminating slack seems awkward. Could the leadscrew be tensioned rather than compressed? Is there an alternative to the locking collars, locknuts perhaps?

On completion of this step the leadscrew had notable tight spots, and one full turn of the bottom bolts from Step 9 had seemed to be a lot of compression on the lead screw that transfers right through to the stepper motor. I played around with the tightening sequence for half an hour and mostly got rid of the tight spots by leaving a 1mm gap between the ends of the shafts inside the coupler. However I can see that this means that upwards force on the spindle during operation will now be taken by the top flanged radial bearing rather than the stepper motor bearings - but that's good isn't it?

Found the Drag-Chain-Mount in the bag labelled 'X&Y-Limit-Switch-Mounts', let's hope the two little bits of plastic in the 'Drag-Chain-Mount' bag turn out to be the limit switch mounts !