Question About Bearing Preloads for A CNC Machine

How about following the manufacturers instructions, always a good place to start. Or when all else fails follow the manufacturers instructions

Failing this, get in contact with the manufacturer whom I feel would only be too pleased to furnish the required information.

I can't tell you in inch/pounds, for that you would have to contact the bearing copany or talk to an engineer at a compny such as Hardinge in Elmira Ny. They really are the experts at this.

I worked at a company that built retrofit mills, and we always did it by feel. As long as you can still turn the ball screw by hand (grabbing the actual screw with your hand not a wrench) it is not too tight. After the machine is operational, measure the backlash. It should be less than .0002 or something is not quite right. That something may or may not be the bearing.