Definition
A hardened steel pin that connects a piston to the small end of a connecting rod inside a reciprocating engine, allowing the rod to pivot as the piston moves up and down in the cylinder. Also called a piston pin or gudgeon pin.
Plain English
The short metal pin that links the piston to the rod that drives the crankshaft. It lets the rod swing back and forth while the piston travels straight up and down.
Context Anchor
Seen in piston-engine construction, engine maintenance, overhaul records, and discussions of internal engine wear.
Derivation
Called a 'wrist pin' because the joint it forms acts like a human wrist — a small pivot point that allows the connecting rod to angle from side to side as the piston moves in a straight line.
Why Pilots Care
A worn or broken wrist pin can cause severe engine damage or failure in flight.
Analogy
A wrist pin works somewhat like the pin in a door hinge: it holds two parts together, but still lets one part pivot around the pin.
Intuition Check
This is not a part on the pilot’s wrist. In an engine, “wrist” points to a small pivoting joint inside the piston assembly.
Example Sentence 1
During the overhaul, the mechanic measured each wrist pin for wear before reinstalling the pistons.
Example Sentence 2
Proper lubrication of the wrist pin prevents seizure during extended high-power climbs.