Question:
While disassembling one of our machines we accidentally wound the ball nut off the ball screw about two or three turns. We managed to get it back on but when we run it the thing locked up. We have tried to free it off but the ball nut just gets tighter. The ballscrew was OK before this happened so it doesn't need to be rebuilt, it just needs freeing off. How can we do this?

Answer:
The chances are that your actions have destroyed a perfectly good ball screw. Whether it is salvageable depends on how aggressive you were trying to free it off and where on the screw it locked up. If the damage is confined to the end of the screw, it may be made serviceable by being reconditioned but usually the damage is so substantial that a replacement is needed.
When a ball nut is partially wound off the screw, never try to work it back on. Remove the nut completely, then reassemble it correctly. If it gets jammed while you are removing it, it is advisable to stop what you are doing and call a professional. It may not be cheap but will be far less costly than a new ball screw.