Editing Axle (section)

{{short description|Central shaft for a rotating wheel or gear}}
{{distinguish|Axl (disambiguation){{!}}Axl|Axel (disambiguation){{!}}Axel}}
{{more citations needed|date=August 2018}}
{{Use dmy dates|date=March 2022}}

[[File:Rollingstock axle.jpg|thumb|upright=1.1|Railroad car [[Train wheel|wheels]] affixed to a straight axle, limiting them to rotate in unison. This is called a [[Wheelset (rail transport)|wheelset]].]]
[[File:Denney Axle.jpg|thumb|upright=1.1|A [[Denney axle]]]]
An '''axle''' or '''axletree''' is a central shaft for a [[rotation|rotating]] [[wheel and axle|wheel]] or [[gear]]. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle.<ref>{{cite book|title=Mechanical Engineering design |date=2010 |publisher=McGraw Hill |isbn=978-0073529288 |pages=360 |edition=9th |url= https://www.bookdepository.com/Shigleys-Mechanical-Engineering-Design-Richard-G-Budynas/9780073529288}}</ref> In the former case, [[bearing (mechanical)|bearings]] or [[Bushing (bearing)|bushings]] are provided at the mounting points where the axle is supported.  In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle.  Sometimes, especially on bicycles, the latter type of axle is referred to as a ''[[spindle (tool)|spindle]]''.