A833 disassembly - Hangup - Main shaft wear?

Even if you could get a file in there, I don't think it would touch that shaft.
I'm with Del's method, in post #6. I've done hundreds that way. You can fix it up later after the parts are off. I don't even bother with a wooden block; that shaft is harder than any steel table. Just grab the gears in one hand and the 3-4 section of the shaft with the other,hang on tight, and bam the tail on the table. Done!