View source for Engineering:Linchpin

{{Short description|Pin to prevent a rotating part from sliding off an axle}}
[[File:A aesthetic linchpin.JPG|thumb|Wagon wheel, with forged linchpin]]
[[File:Lynch-pin.jpg|thumb|A modern linchpin with an integral spring retainer]]

A '''linchpin''', also spelled '''linch pin''', '''lynchpin''', or '''lynch pin''', is a [[Engineering:Fastener|fastener]] used to prevent a wheel or other part from sliding off the [[Engineering:Axle|axle]] upon which it is riding. The word is first attested in the late fourteenth century and derives from [[Social:Middle English|Middle English]] elements meaning "axletree pin".<ref>"linch-pin, n.". OED Online. June 2014. Oxford University Press. http://www.oed.com/view/Entry/108578 (accessed August 25, 2014; now behind [[Paywall|paywall]]).</ref><ref>"linchpin (n.)". Online Etymology Dictionary. https://www.etymonline.com/word/linchpin (accessed 1 June 2018).</ref>

Securing implements onto the [[Engineering:Three-point hitch|three-point hitch]] of a [[Engineering:Tractor|tractor]] is an example of application.  Linchpins may also be used in place of an [[Engineering:R-clip|R-clip]] for securing hitch pins.<ref>{{cite web |url=https://www.globalspec.com/learnmore/building_construction/building_supplies/fasteners/hitch_pins_linch_pins |url-status=dead |archive-url=https://web.archive.org/web/20100818233034/http://www.globalspec.com/LearnMore/Building_Construction/Building_Supplies/Fasteners/Hitch_Pins_Linch_Pins |archive-date=2010-08-18 |title=Hitch Pins and Linch Pins Information on GlobalSpec}}</ref>

==Metaphorical use==
The word "linchpin" is also used figuratively to mean "something [or someone] that holds the various elements of a complicated structure together".<ref>{{cite web |url=http://dictionary.reference.com/browse/linchpin |title=Linchpin |publisher=Dictionary.reference.com |date= |accessdate=2012-03-24}}</ref>

==See also==
* {{annotated link|Engineering:Circle cotter}}
* {{annotated link|Engineering:Circlip}}
* {{annotated link|Engineering:Cotter (pin)}}
* {{annotated link|Engineering:Hairpin clip}}
* {{annotated link|Engineering:Kingpin (automotive part)}}
* {{annotated link|Engineering:R-clip}}
* {{annotated link|Engineering:Split pin}}
* {{annotated link|Engineering:Spring pin}}

== References ==
{{reflist}}


[[Category:Fasteners]]


{{Sourceattribution|Linchpin}}