[johnbuckley]

All of the above in that order 1) a good fitting screw driver, 2) heat . 3) An overnight soak with penetrating /easing oil. 4) Posssibly using an extractor 5) Finally coup-de-grace very very careful drilling with incremental sizes of drill through the brass and then un winding the brass shards remaining in the threads of the housing ( a left hand drill helps but is not essential) . I usually managed to shift them with with 1) or 2) rather than resorting to 4) and 5)