My little chipper spit the key on the chipper wheel shaft, and the pulley wandered back and forth on the shaft while spinning before I could get it shut down. Threw both belts and marred the shaft up a bit. Manufacturer sent me a new pulley, compression flange, key, belts, knife and the wheel/shaft assembly with bearings and all. In the meantime, I decided that the problem was that the original key was a tad undersized and was loose in the keyway. I bought a foot of key bar at the implement dealership a few blocks away. It is slightly larger in both dimensions, so I cut a piece to length and hand filed it for a snug fit. I could still push it out with light tapping on a punch, so it's still not holding it all in place on the shaft. So today I made two bushings out of PVC pipe (don't laugh, this was to see if my idea would work) one on the inside of the pulley to keep the key from coming out that way, and one on the outside of the pulley to keep it from coming out that way, and at the same time they keep the pulley where it is supposed to be.
The plan is to replace these with bronze bushings... I may have to manufacture them by cutting down a long one.
As you can see, this is working as expected. I chipped for two hours today and believe it or not, the PVC bushing never got hot or melted. I believe the bronze ones would definitely be the cure. I have no idea why they just didn't do this at the factory. In any case, I have an entire brand new moving parts replacement set for the machine when I finally wear these ones out. As you can see in the last pic, the bushings keep the belt aligned properly and keep the pulley from trying to wander on the shaft. I actually hate these type of pulleys, they're rather famous for doing this. They use them on some of the big chippers and other equipment, too. If they spit the key, the damage to the shaft means a new compression flange and key aren't likely to hold everything tight enough without replacing the shaft, too.
Well, at least it's back up and chipping with little downtime, and the manufacturer looked at the pics I emailed them and sent everything out right away. They said it looked like the pulley probably didn't get tightened down at the factory, which is certainly possible, but I'm still convinced the key was a little undersized.