Squirrel Cage Fan Repair

I have dozens of squirrel cage fans that run 24-7. The motors get replaced fairly regularly, which is to be expected. The ID on the fans gets oversized and I have drilled some out and added and sleeve with a thru hole for the set screw. This is a pain in the rear to do. The question is there an easier way to repair a squirrel cage fan ID? Fan ID is 0.50" and there is room to go to a least 0.625". Thanks.

As you have found out a squirrel cage fan hanging off the end bearing of a motor does not last very long. Can you not modify them for a bearing to support the non-motor end?
The problem with what you are doing is that the fan and motor must be balanced both staticaly and dynamicaly to minimise the fan's vibration and hence its wearing its shaft mounting hole and I guess the motor bearing as well.
Where I worked, the fans were on 24/7, regreased once a year and lasted 10 years +. Interestingly the only fan failures were with squirrel cage fans fited to a shaft that was belt driven (bearing each end). The bearings got worn and the whole thing got excessively noisy. Another case of bad balancing during manufacture, I guess.
Frank