Xavierdemoura is right in how he checks it. Which should be done as a final check in installing a ball screw always. It checks that there is no float in the screw when moving back and forth. The way I usually set it is basically hit the nut till it sounds solid. As long as the nut goes on very free to begin with you will notice a huge sound difference as you tap the nut tight. You will notice the captured end gets tight very quickly and when you hit the other end to stretch the screw you can here it little by little become more solid. Once you have stretched the screw and taken up all the backlash the sound when tapping on the nut should be solid. It may be hard to here it in a loud shop sometimes but as you do them double check with an indicator as Xavier.. suggests. Make sure you move back and forth quickly to put the most load on the ball screw and check for float.
Programming is like ***: one mistake and you have to support it for the rest of your life