I have one of these
http://www.chainreactioncycles.com/M...px?ModelID=995

You never get them off with a chisel or drift, very much doubt it's italian thread but you never know.

big fuck-off pair of stilsons should do it.

they tighten the grip as you turn, I've not been beaten by these type before, at least then you can try it both ways and see which one feels likely to unscrew