Definition
A hand tool used to tighten or loosen a round nut or collar that has holes or notches drilled around its outer edge. The tool has one or more pins that fit into those holes, allowing the technician to apply turning force where a normal wrench cannot grip.
Plain English
A special wrench with a small pin on the end. The pin slots into a hole on a round nut so you can turn it. Used where a regular wrench has nothing to grab onto.
Context Anchor
Seen in aircraft maintenance instructions when a round retaining nut, collar, or ring must be removed or tightened with the correct tool.
Derivation
‘Spanner’ is the British term for what Americans call a wrench, from an old German word meaning ‘to stretch or tighten.’ ‘Pin’ describes the small projection on the tool that engages the hole. So a pin spanner is literally a ‘pin wrench’ — a wrench that grips by pin rather than by jaw.
Why Pilots Care
Allows safe removal and installation of critical components without rounding or slipping.
Intuition Check
A pin spanner is not just any wrench. The important feature is the pins: they fit into holes or notches and turn the part from those points.
Example Sentence 1
The mechanic used a pin spanner to loosen the retaining nut on the propeller hub.
Example Sentence 2
Using the correct pin size on the spanner prevents damage to the holes in the retaining ring.