Rotating Ballnut - design ideas

[Jonathan]

Is the 50% figure for static or dynamic loading?

Yes that's static, forgot to mention that! I can't find a rating for dynamic, just interesting explanations about how the bearing responds to axial load.

... less resistance, and are more tolerant should dirt get into them.

Fair enough, those are both clearly important for this application.

According to the SKF site the axial internal clearence for a 40mm bore double row angular contact bearing is 11um. So that's like having 11um end float on the screw if I used the design with the single bearing. I'm not sure how bad that amount is - it doesn't sound like much. C2 clearance bearings only have 2um clearance.