Originally Posted by
steve sumner
...axles are stationary, spindles turn
Sheldon Brown mentions this in his glossary of terms under "Axle":
The shaft at the middle of a bearing. There is some controversy as to whether "axle" or "spindle" should be used in particular contexts. The distinction is based on whether the axle/spindle is stationary, as that in a hub, or rotates, as that in a bottom bracket. There have been bitter flame wars fought in magazine letters columns over this point.
That said, the part in question is also commonly referred to as the "crank axle", as indicated HERE.
"Crank Axle" does not appear in Sheldon's glossary, FWIW.