Anti-backlash nut test

Tap both holes with a 1/4-20 tap, and put a spring between the square piece and the square pocket it goes in. This allows you to use 1/4-20 all-thread rod as a leadscrew with (hopefully) very small backlash. This is designed to be inserted into a hole, then use a screw to hold a cap on (for my specific application, rebuilding a desktop MAXNC 15 CNC mill)