Thanks for the article, it's very useful. Spent 8 hours yesterday taking my planer apart. Though the machine looked to be good shape, none of the gears came off without a resolute fight. It was so frustrating that the thought of hacking the machine to bits with a sledgehammer came to mind repeatedly. In the end, 2 simple methods saved the day:
-using thin strips of emery cloth to clean/smooth the shafts ahead of the gears, so they would slide off more easily.
-Using a heat gun on some of the more stubborn parts.