IMO, you should look for a skinny ball-bearing to replace the bushing altogether. Alternately, use a new bronze bushing, the self-lubricating kind.

BTW, I'd say that the fan shaft is not only shiny, but very skinny too at 1/8". Is the squirrel cage well balanced? If not, it may have caused the premature grinding of the original bushing.

My guess is that bearing is a sintered, porous bronze bearing. When new, it was saturated with oil. If it squeaks, it is dry. re-oil it with a good oxidation resistant oil such as oil used on oil clock-works. Also, if you can find a ball or roller bearing of proper size, you replace it with one of these. The outer diameter should be a light press fit in the housing. If it is only a close fit, some means must be provided to retrain it.

It is a cheap fan of course, so I doubt it is very well balanced. I'll try oiling the bushing... Looking into how to replace the oil in a sintered bronze bushing, I see some ideas that may work, as long as the oil has not cooked and turned into carbon in the pores. One idea I saw is that some hardware stores may actually sell a replacement bushing.

Alternatively, I've found a source for a bearing that may fit, but I would need to make a housing for it. So I'll try oiling the bushing, or replacing it first, then pick up a bearing. They are not that expensive. (40 years ago, my machinist dad had piles of bearings laying around in his shop. Sadly, none in my shop now.)

So soak it in oil? That should keep it going for a while while I pick up a bearing.

For a general source of parts of this type, try mscdirect.com. Or, if you live in an area where there is still industry, look for a bearing store. Some longtime hardware stores may also have representative bushings and bearings.

kas

The manufacturer oil impregnates porous bearings using vacuum. Put the bearings in a vacuum chamber and cover with oil plus a little to spare; pull a vacuum to suck air out of the bearings, hold, and then release the vacuum to drive oil into the bearings. Two to three cycles of this does a good job of filling the spaces with oil.

This is impractical for most homeowners, but you can help the bearing by applying oil to the space between the shaft and bearing. It will gradually creep in. periodically, apply more oil until it will not take any more. if the bearing quiets, the motor can be run between oil applications. This is a slow process, but it can extend the service life of the bearing and give you time to plan your repair.

Look at the housing holding the bearing. Sometimes, an oil hole is provided near the center of the bearing's length. This is a maintenance hole. It will accept only a drop or two of oil and the surface tension will keep it there to soak into the bearing. When the oil is depleted, add some more.

If the cost is low enough, replacing the fan may be the best solution. Re-oiling a sintered bearing can keep you going until a permanent fix is found.

Sintered sleeve bearing are made in standard sizes by makers such as Boston Gear:

Boston Gear Sleeve Bearings

Search on line for other sources and places where to buy.

I bought some flanged sintered bronze bushings from amazon.com of all places.

I did also look on Amazon, as I'm often surprised at how many things I can find there. They had a wide variety of flanged sintered bronze bushings, but I did not find any there that seemed a good fit.

My current long term plan is to go with a bearing, since I have a source that might fit.

Until then, I did a quick test. I took the old bushing, and drilled a moderately oversized hole in some aluminum stock that would fit the bushing. Fill the hole with a light machine oil that I had on hand. Then heat the aluminum from below with a heat gun. The bushing started to exude air bubbles, which I assume means the oil was replacing air in the interstices of the sintered bronze. When the bubbles stopped, I dried off the bushing, and replaced it in the fan assembly. Sadly, I don't have a vacuum chamber to put it in to do a better job.

The fan is now running quietly. I'll see how long this works. If it goes for a few months before the problem recurs, then I'll see if I can choose a better oil for the job. Anyway, I'm learning a bit about bronze bushings, so it is time well spent for me.