<VV> frozen sheared bolts

[Kinzelman, Andy]

Harry,
This doesn't address your question, sorry.  However, this is the procedure I use when I work with steel bolts into aluminum.   If the breakaway torque feels excessive, I first slightly tighten the bolt, then alternately loosen & tighten it.  Each successive tighten/loosen act seems to allow more rotation; I continue until I've managed a full rotation, or so.  Then the bolt typically threads right out.  No guarantee that the threads aren't damaged, but I can usually get those stubborn bolts out without breaking them.
Good luck,
Andy K.