Along with the pitch, or number of threads per unit length, thread friction contributes to the self-locking, or “non-overhauling” property of most screw threads. Self-locking threads easily ...

The two halves of the washer have interlocking wedges, the angle of which exceeds the pitch of the bolt threads. As the bolt is tightened, the higher pitch of the washers pulls the bolt back ...

To restore bolt threads, follow these steps: Start by finding the thread count (SAE) or pitch (metric). Hold the thread file against the bolt threads until you find the size that matches.