Got the main body of the square taper BB out, but the ‘plain’ side was stuck fast.
Wd40, hammer and chisel, even made a tool. No good.
Very handy friend over the road makes hand made iron beds comes up with a super simple solution.
He welded an iron bar onto it, only about 8 inches long and it twisted right out. The threads all fine.
He’s got proper mans tools.

Tool in a vice, use the frame as a lever.

This is the reason I will never sell my MIG welder. A mate had a seized seatbelt mounting bolt on an old car. After he’d spent hours soaking it in plusgas, twatting big spanners with a lump hammer to shock it off he was nowhere.

Took me five minutes to weld a 3 foot long bar onto it, one twist and it moved :o) You can’t beat leverage.

another approach is to use a crank bolt and a large washer to keep the tool in the cup notches.

Only keep the tool screwed on for just long enough to get it moving, then you need to let of the crank bolt.

As above, sit BB tool in the vice and turn the frame.

Recommend not using a cheap vice either, cracked a Clarke 4″ in two whilst performing this operation once.

Trouble was after much chisel action, I’d left only two notches intact.