Question:
We did some work on the table slide of an older boring mill but two weeks later the ballscrew locked up. One wiper was pushed out and pieces of ball could be seen in the end of the nut. A week after we installed a new ball screw the same thing happened. What is the problem?

Answer:
Each ball screw is design to operate up to a predetermined load. When the load on the unit is excessive the ballscrew fails, your case is a prime example of this.
The chances are that either the slide is too tight, the ball screw is incorrectly installed, or both. This type of problem is quite common when machine tools undergo major rebuilding because slide-ways are reground and turkite replaced changing the relative position between slide and way.