Definition
A thin, stamped sheet-metal locking nut used as a secondary fastener. It is run down on top of a standard nut to prevent the standard nut from backing off under vibration. The Pal nut deforms slightly as it tightens, gripping the threads to resist loosening.
Plain English
A thin metal nut that is added on top of a regular nut to keep the regular nut from working its way loose due to vibration.
Context Anchor
Seen in aircraft maintenance, parts lists, and hardware inspections where small fasteners need a simple locking device.
Derivation
Named after the Pal Nut Company, which patented and manufactured this style of stamped locking nut in the early 20th century. The name is a brand that became the common term, similar to how 'Crescent wrench' is used generically.
Why Pilots Care
Vibration in flight can loosen ordinary nuts; Pal Nuts provide a reliable, lightweight way to keep critical fasteners tight and prevent loss of control or component failure.
Analogy
Think of it like a spring clip shaped into a nut. It is not just sitting on the threads; its springy metal edges press into them to resist loosening.
Intuition Check
Do not assume a Pal Nut is just a normal nut. The key idea is locking action: its thin spring metal is designed to grip the threads and resist vibration.
Example Sentence 1
The mechanic torqued the castle nut, then ran a Pal nut down on top to lock it in place.
Example Sentence 2
During the annual inspection, several Pal Nuts on the wing attach bolts were checked for proper seating.