Quote Originally Posted by routercnc View Post
I have had them come loose occasionally over the years. I've always managed to tighten the nut and carefully tighten the grub screw but yes there is the fear of stripping the thread or more likely rounding out the allen key hole.

Other options to think about:
As you say, longer screws and double lock or jam nuts
Maybe blue loctite on the nut but don't get it near the bearing, or maybe PTFE tape??
Dropping a short length / disc of brass rod in the grub screw hole first, then the grub screw will mold it onto the thread
Making a brand new nut from steel (and then heat treating it) with a larger grub screw?

Anything from anyone else?

The other thing to think about is how to hold the ball screw when tightening the nut (once it is all installed with coupler on etc.). I fold up plenty of shop towels into a narrow strip about 30 mm wide then wrap it around the ball screw. Then apply as much pressure as you dare using a mole grips . . . . . pause while I find the US name for such as tool . . . . vice grips, to hold the ballscrew and tighten the nut using a spanner/wrench.
Thank you for all the suggestions, I will give them a try for sure.