Two nuts having different helical paths, moving along the same bolt shaft, is the key to the PLB and its ability to resist loosening even under severe vibration-shock.
The primary coarse ( nut A ) and secondary fine ( nut B ) travel along two distinct, separate, helix angles causing them to move at different speeds relative to the bolt shaft. The primary coarse nut travels faster than the secondary fine nut and when subject to vibrational forces the slower traveling fine pitch nut prevents the coarse pitch nut from loosening as with traditional bolt, nut and washer fastener.

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