Originally Posted by
fatal-exception
Good advise LeeWay! I back your previous comments 100%.
None of the rolled ball screws I've ever had felt tight on the screw. They are almost always loose. I would not replace the balls unless you were sure that they are worn. Precision ground screws fit perfectly with no slop in any direction and must be setup with a higher degree of precision. You can be out 'a bit' with rolled screws and still have a very low friction drive, this helps at the ends of the screw.
Something else not mentioned yet is that if the bearing journals at the ends of the screw are not concentric to the ball nut rotation, you will see binding action in a cyclic pattern near the pillow blocks. If your steppers cant overcome this, it could stall at varying locations. One of my mini mills is plagued with this problem at the top of the z axis. Thankfully I don't use that extent very often.
Paul