Definition
A class of mechanical fit between two mating parts in which the shaft is slightly larger than the hole, so the parts must be pressed or lightly hammered together. Once assembled, the parts are held firmly by friction and require force to separate. A tight-drive fit is looser than a force fit but tighter than a push fit.
Plain English
A way of joining two parts where one is just a touch bigger than the hole it goes into, so you have to drive it in with force. Once it's in, it stays put because of the squeeze between the two surfaces.
Context Anchor
Seen in aircraft maintenance instructions for installing parts such as bushings, sleeves, bearings, or pins.
Derivation
Drive' here means to force into place by striking or pressing, as in driving a nail. 'Tight' indicates the parts grip each other firmly. Together the term describes a fit that must be driven in and stays tight without fasteners.
Why Pilots Care
Ensures components remain securely positioned under vibration and load, preventing wear or failure in flight-critical systems.
Analogy
It is like pushing a cork into a bottle that is just slightly smaller than the cork. The tight contact is what keeps it from falling out.
Intuition Check
Tight-drive fit does not mean simply “tighten it hard.” It means the part’s size is intentionally close enough that it must be driven or pressed into place.
Example Sentence 1
The bushing is installed in the housing with a tight-drive fit, so it must be pressed in rather than slipped into place by hand.
Example Sentence 2
A tight-drive fit between the propeller hub and the crankshaft flange prevents any slippage during operation.