It might be better to find another BB shell to cut the threaded ends off, and weld them to each side of yours, then extend the axle in the middle the same amount as you extended the BB shell, away from the hardened surfaces. Also, if you wanted, quite often a more modern square taper uses the same threads, you could do the upgrade if you felt like it...
I did that to this old lugged Australian BB shell that was originally cotter pin style:
Luke.
I did that to this old lugged Australian BB shell that was originally cotter pin style:
Luke.