Interesting replies. My idea was some sort of split locking collar, which John mentioned. Using the taper has drawbacks in that the you cannot pass work through the spindle along with increasing the overhang of the chuck. The set screw idea seems like it would work without damaging the spindle. I would not be entirely against a small modification to the spindle if it made the lathe more versatile. I see some Atlas/Craftsman lathes have flats on the spindle shoulder that could be used with a locking collar. I don't think there is enough meat on a SB9 collar to do the same. It would be nice if it did as that would be a good place to put a thin wrench to remove a stuck chuck.
