Too late...the task is accomplished and (probably) the damage is done. I noticed when I set it up: the piece you referred to (they call it the "Support Disc #5") would slide past the threads of the big bolt, but then butted up against a narrow lip that was the beginning of the thread-less shaft. That's why, in the second pic of my last post, you can see like 1 1/2" of shaft between the narrow support disc (black) and the thrust bearing (silver colored).
I cranked
the hell out of the thing (adding a piece of pipe into the mix---making my breaker bar 2' long or better. Leverage is a wonderful and dangerous thing, ain't it?
). It turned, but only with A LOT of effort. I kept stopping, removing the crescent wrench (the stopper, on the inside bolt head), looking for progress on bearing movement, oddly never really seeing any. I hadn't gotten far before I realized that it was the 1 1/2" gap that was compressing, the bearing itself not moving a whit. At that point I realized something was not right but figured I was more or less committed---any damage done to the support disc was done, and wasn't going to get any worse by my continued effort. AND, once that 1 1/2" gap disappeared altogether and the support disc contacted the thrust bearing, something else had to start moving, presumably the bearing. That proved to be true, and ultimately the bearing came out cleanly.
Now, however, I have the support disc semi-permanently wedged onto the bolt against the thrust bearing:
It IS tight. I might be able to carefully beat it out with a hammer (buffered with a block of wood), but may just leave it for now until it becomes apparent I even need to get it off. As far as I can tell, I may in fact not need to do that, may still be able to use the tool as is. But I definitely could be wrong about that...time will tell. (My peanut brain can't think that far ahead!)
In all honesty, I don't know what went wrong. The support disc was oriented right, because it had a thin lip that fit nicely into the next piece (the wide spacer sleeve). It just seemed like the hole in the center was not quite as big as it should have been.
Oh well, onto the next step...
Threaded Mode
