Nut Install Tool
Ball nuts will come with a small plastic or card board tube through the center of the nut to keep the balls from falling out. This tube should be up to the end of the screw as you thread the nut on. I made a steel pin that will slide inside the tube. The pin has a strong magnet inserted into one end so it is flush with the end of the pin.
The pin is held to the end of the screw by the magnet, and the tube is slid over the pin. The pin holds the tube concentric with the screw and makes it easier to thread the nut onto the screw and off the tube.