This is an inherent problem with the BX22 and 23. I don't know if they have solved it on the follow on products (BX24,25) or not.
If you always turn the seat in the same direction when swiveling it, the nut has a tendency to either tighten up so much the bolt will actually snap off, or, if you always turn it the other way, the nut can loosen up and fall off.
If you make a conscience effort to turn the seat one way when you put it in the backhoe position, and then turn it in the opposite direction when you turn it back around, the problem is avoided.
To answer your question of how it is fastened onto the tractor, yes, it is a single carriage bolt, with a flat washer and nut on the bottom. Just make sure the nut you use is one of those with the nylon insert so that you can leave it loose enough to be able to swivel the seat, but tight enough so the seat doesn't flop around.
As far as a detailed break down of the other parts such as the ball bearing detents and flexible plates in there, the best thing to do would be to get to your dealers parts department and have them show you the break down. Most dealers will even print you out the page you are interested in.
