[bestgenman]

Tom, I'm betting it is one of the muffins style fans. The bearings are covered by the propeller blades and I'm not sure how to gain access. You might try pulling the propeller off as it is pressed on to the shaft but it may ruin the whole fan! These fans are not expensive and Newark Electronics http://www.newark.com/ has a large selection, the trouble is selecting the CFM!!
Hope this helps.
Gordon