Robin,
That could be one of the problems I'm having if the adjusting bolts a moving then I could be jamming up the bed. Maybe I could mark the bolts and see if they move. Maybe I should start on the screws! You are right they are really sloppy. I have a feeling I'll have to get the inside of the bed machined away to get some space for the nut. What size ball screw did you use?

Thanks,
Ant