I can not get the locking collar to budge. After getting all of those installed, the unit was still vibrating more than I wanted, so I looked a little more and discovered that the rotor bearing on on the drive side was mostly disintegrated. Unit was missing some blades and appeared to have all of the original duck feet, so I replaced all missing and old knives with some side slicers from FM. Just acquired a JD 25A of the 644700 series of serials for a couple hundred dollars.
