Well this is cheaper than buying them by a long shot. Backlash nuts are important in CNC and robotics to as its the movement a nut may have on a threaded rod. Think of slippage or unwanted movement. Seems like alot of work thought, and I am not too fond of melting plastic inside.
http://www.instructables.com/id/DIY-Anti-Backlash-Nuts-Super-Cheap-and-Simple/?ALLSTEPS