Definition
A solid metal fastening pin whose diameter decreases gradually from one end to the other, designed to be driven into a matching tapered hole to lock two parts together precisely and prevent relative movement. The taper allows the pin to wedge tightly as it is seated, producing a secure, vibration-resistant fit that can be removed and reinstalled without losing accuracy.
Plain English
A pin that is wider at one end and narrower at the other. It is hammered or pressed into a hole that has the same shape, so it wedges in firmly and holds two parts together exactly where they belong.
Context Anchor
Seen in aircraft maintenance, hardware, and inspection discussions where parts must be held firmly in the same position each time.
Derivation
From 'taper,' meaning to grow gradually narrower, used here to describe the pin's shape. The term tells you exactly what makes it different from a straight pin: the gradual change in diameter is what creates the locking action.
Why Pilots Care
Tapered pins are used in flight-critical assemblies such as control linkages and propeller components. A loose or improperly seated tapered pin can allow play in a control system, so understanding what they are matters during preflight inspections and when reviewing maintenance work.
Intuition Check
Do not think of a tapered pin as just a regular pin with a pointed end. The important feature is the gradual change in diameter that matches the hole and creates a tight fit.
Example Sentence 1
The mechanic drove a new tapered pin into the control horn to secure it to the shaft.
Example Sentence 2
During propeller installation the tapered pins ensured the hub remained correctly indexed to the crankshaft flange.