Hi Ron,
I've just stripped my SB45 down a few days ago and the nut in question is a standard RH thread. The easiest way to remove it is with a rattle gun - if you have access to one. I would imagine it's a little tricky to hold the shaft still to crack the nut otherwise (but not impossible). Hopefully some of the other guys may be able to give you some better advice.
Cheers,
Michael