Definition
A method of assembling two parts in which the inside part is made slightly larger than the hole in the outside part, so that the two must be forced together under pressure. Once assembled, friction alone holds them in place without the need for fasteners, adhesives, or threads.
Plain English
Two parts squeezed together so tightly that they grip each other and stay put without bolts, glue, or pins.
Context Anchor
Seen in aircraft maintenance and parts installation, especially when reading about bearings, bushings, sleeves, pins, or similar parts that are installed tightly into a hole or housing.
Derivation
From 'press' (to push with force) and 'fit' (the way two parts come together). The term simply describes how the parts are joined: pressed into their fit.
Why Pilots Care
A press-fit part must be installed and removed correctly. Too much force, uneven force, or the wrong tool can damage the part or the surrounding structure, while a loose fit can let the part move when it should stay fixed.
Analogy
It is like pushing a cork tightly into a bottle. The cork stays in place because it is squeezed firmly by the opening around it.
Intuition Check
Do not read “press fit” as simply “a part that fits when pressed.” The key idea is that the part is intentionally slightly too tight, and that tightness is what holds it in place.
Example Sentence 1
The bushing is installed in the control arm using a press fit and does not require any retaining hardware.
Example Sentence 2
During the propeller overhaul, the technician checked the press fit of the hub components to ensure they would not loosen under rotation.