When items require a screw to go into plastic threads, it's not uncommon for the threads to be stripped. This can occur over time as pressure is put on the screw while it moves, thereby causing the plastic threads to become worn. This problem can be fixed by re-tapping the threads with a tap. Taps can be purchased from a hardware store or most home improvement stores. They come in a variety of sizes so one can be purchased to repair any size threads.
Things You'll Need
Tap to fit the current threads
Remove the screw from the threads. If the threads are stripped, this should be fairly easy.
Insert the tap into the threaded area. Make sure the tap is inserted straight to avoid cross threading.
Tighten an adjustable wrench around the end of the tap.
Twist the tap using the adjustable wrench. Screw the tap evenly into the threaded area, as far in as the length of the screw.
Remove the tap and reinsert the screw.