[exray]

In models that old I suspect there's some expansion going on due to impurities and or dissimilar alloys in the metal pieces. Kroil seems to be pretty good for freeing them up although some remain somewhat tight even after they break free. Its usually not the fault of dried grease - that would be easy!

I've disassembled some later era ones - particularly those with an aluminum shaft - and found them very corroded inside the bushing. IF you can get the shaft out of the bushing its an easy fix.