I've just fitted the Y axis ballscrew (from Chai) to my Warco WM16 mill and have noticed that there is 0.2mm of end float in the BK12 bearing block. I've tried tightening the locking nut as tight as I can do it with a 19mm spanner and I'm still getting 0.2mm float through the bearing. The bearing block is solid to the machine but the shaft is floating...I assume it's actually the bearings that are moving as the shaft is locked to them via the collars. There is plenty of thread on the ballscrew, so the locknut hasn't bottomed out. Is this normal???

Any suggestions?