Definition
A mechanical fit in which the inside diameter of the outer part is slightly smaller than the outside diameter of the inner part, so the two pieces must be forced together using pressure, heat, or cooling. Once assembled, the parts grip each other tightly through the squeeze between the surfaces, with no clearance between them.
Plain English
The hole is slightly smaller than the part going into it, so the two pieces have to be pressed or shrunk together. Once joined, they hold tightly without bolts or pins because they are squeezing each other.
Context Anchor
Seen in aircraft engine and component maintenance, especially when parts such as bearings, bushings, shafts, or sleeves must be held firmly in place.
Derivation
‘Interference’ here means the two parts physically interfere with each other — they occupy overlapping space before assembly, so one has to give. It is not interference in the sense of getting in the way or disrupting something.
Why Pilots Care
Creates vibration-resistant joints in rotating engine parts that must remain secure under high loads and temperature changes.
Analogy
It is like pushing a slightly oversized plug into a hole. It does not drop in easily, but once it is seated, the tightness helps hold it there.
Intuition Check
Interference does not mean radio noise or something blocking a signal here. It means the parts are sized so they press tightly against each other when assembled.
Example Sentence 1
The valve guide is installed with an interference fit, so the cylinder head is heated before the guide is pressed into place.
Example Sentence 2
During overhaul the hub was installed with an interference fit so it would not loosen from engine vibration.