Cross threading a nut, bolt or a pipe fitting is a pain because it can end up ruining one set of threads or both. It’s an especially easy error to make when working with plastic threads. When working with a combination of plastic and metal threads, the mistake can be even easier to make. To avoid this, there is a simple procedure to follow.
Instead of screwing the connection or fastener in the direction necessary to engage the threads (usually clockwise), lightly place the threaded pieces together and rotate counterclockwise by hand until you hear and feel a “click” which indicates that the starting threads on both pieces are lined up. Then turn in a clockwise direction by hand to engage the threads properly.
If you encounter resistance when tightening by hand, back it off and repeat the process. It also helps to make certain that both pieces are centered on one another to get a legitimate “click” and engage the threads properly. For example, with a threaded stud sticking straight up, you can check alignment from the sides to make certain the nut and bolt are straight up and down. You can also look to see that the top of the nut is level.
When in doubt about whether you’ve heard and felt the “click,” simply keep rotating the piece counterclockwise until you hear and feel it again, and then begin tightening by hand. With practice, you’ll begin to recognize the sound and feel of the “click” that indicates threads are properly aligned for tightening.
Follow this simple approach, and you’ll avoid cross-threading nuts, bolts and pipe connections, and save yourself time, aggravation and money.