I bought a ball screw on ebay along with my water cooled spindle and decided the end supports were really good value. So all goes well (re-assembling a ball-nut not withstanding after a little mishap when unpacking) and something didn't seem right with the fixed end.

On closer inspection the fixed end bearing had a lot of play, even when pre-loaded which took me by surprize given how snugly the bearings fit.

So I took off the spacer and seal to reveal the bearings and could feel the back lash in the bearings moving axially in the block. Taking a vernier caliper to the problem revealed 0.46mm backlash measured off the outer race of one of the bearings by moving the bearings by hand.

Have I missed something in assembling these? Do I need to insert some sort of washer/spacer inside of these bearings? Do I need to open the unit at the bearing plate?

Any help would be gladly appreciated. I will post some pictures when I am back home.