How to get the balls back in a ballnut?

[Jonathan]

I've done this a couple of times...
Ideally you want a tube which is the pitch diameter of the ballnut minus the diameter of one ball, so if you imagine the nut fully populated it would just slide inside. You can then hopefully gradually slide the tube in, position the balls in the tracks with tweesers and grease to make them stick. With all the balls inside and the retaining tube, it will be the same as having a new nut, so you just push the tube up against the end of the screw and carefully twist the nut back onto the screw ensuring that the tube doesn't loose contact, else the balls may drop out. You can also try putting the balls in with the nut on the end of the screw and turning it as you go, that's worked for me once.

If you've got a strong magnet then stick it to the side of the ballnut, so when you put the balls in they will just stick to the nut. Ideally, I think you should demagnetise the nut afterwards. Obviously with any of these methods ensure everything is very clean before you start since swarf or just about anything except grease/oil in the nut will damage it over time, and it's sensible to do it in a tray as the balls are bound to fall out again!

On the plus side, it's a good opportunity to clean the ballnut! I've known ones I've got from chai to have small bits of metal floating around in them, which really doesn't help, especially when trying to get zero backlash by preloading...