Cross-Threading

Cross-threading is a type of thread damage that happens when a screw, bolt, or nut is started at an angle or with misaligned threads, causing the threads to cut, deform, or ride over each other instead of engaging cleanly. It often feels like the fastener is binding early, turns roughly, or will not seat properly. Cross-threading can occur even when the diameter and pitch are correct, especially if the fastener is forced, started with a power tool, or assembled in a tight or hard-to-see location.

Cross-threading matters because it weakens the joint and can permanently damage the fastener, nut, or tapped hole. It can lead to stripped threads, poor clamp load, loosening, or fastener failure, and it often requires re-tapping, installing a thread insert, or replacing parts to fix. To prevent cross-threading, start fasteners by hand for several turns, keep the parts aligned, verify the correct thread size and pitch, and stop immediately if resistance is higher than expected.