Originally Posted by
3alarmer
...sometimes it helps if you put in the non fixed cup first, and screw it in just a few turns (not all the way). This gives you a smaller hole for the spindle to exit on that side, which in turn helps to straighten and center the sealed unit with the fixed cup that is integral to it. Then youi do the backward turning until you feel a little click business, and you should be OK. Anyway, that's how I do them.
This is exactly what I do for two-piece cartridge bearings, where you have a cartridge assembly and then a non drive side "cup" as a retainer.
But I join @
CliffordK in asking if you know in absolute certainty that it's French-threaded. Swiss threads use the 35x1mm French threads, but the drive side is left hand thread (like English and others) rather than the French's right hand thread.