Yet another stuck BB. Help me save my frame! So I have two bikes and a year ago I went through the challenge of unscrewing a stuck BB. The solution was to put the tool in a vice and twist the frame around it.

Today I have an even more difficult challenge. My cheaper bike is now about 5 years old and has been through dust, mud and salty snow. The BB is rattling and needs to be changed. I tried. 

The BB is obviously cheap, both cups being plastic. I used the proper tool, put an elongation bar on the wrench, followed the correct direction for unscrewing ... and ruined both of my cups. The wrench just cut through the plastic teeth of the cup.

My BB is of the following type:



What can I do? I tried drying the cups apart with a soldering iron - which cut through the plastic somehow. Can I inject something inside, that will melt the cups? Can I pour spirits and set it alight, without damaging my aluminum frame and the paint around?
I thought about this a little more, and here is what I'd probably attempt:

The cup has a "shoulder" on the inside that retains the bearing cartridge.  Attack the shoulder somehow (break it, use your Dremel, et al) until it's possible to drive out the cartridge from the other end.  Then, with the cartridge out, is should be possible to pry the remainder of the cup out with minimal damage to the threads.