The last resort whenever one cylindrical object is threaded into another and won't come loose: Use a hacksaw to make two cuts through the bearing cup all the way down to the shell threads. The hacksaw can just graze the shell threads without harming them - it takes some judgement and cutting parallel to the wall of the shell, not at an angle. When you've made your two cuts, a small section of the cup can be removed, and the rest of the cup will unthread easily. Plumbers use this technique to get a stuck pipe out of a fitting. Unless you have a mini-sawzall, you'll need a stiff hacksaw blade with a handle on one end, and some patience.