Report of blower impeller rubbing with housing and excessive axial/radial play.
Caused by failed 47-146-1 bearing (total time unknown).
Bearings replaced, blower assy inspected and returned to service.
Approx 150 hrs later, shaft sheared.
Most probable cause for shaft failure; stress fatigue.
Even though the shaft did not show any evidence of visual damage at inspection, it should have been replaced.
Material fatigue subsequent to overload or stress is generally not detectable by NDI methods.