I bent a Dura-ace axle and a Maillard axle this past year.(a bend is as good as broke according to Herr Jobst) I know when the Dura-ace axle on my singlespeeder went: during a freewheel with bad pawls incident. Freewheel slipped just a little while standing and when it reengaged, whack! Probably would have bent most any axle.
Pete Geurds
Douglassville, PA