Originally Posted by
Peek the Geek
As suggested, I did try tapping various sides with a punch and could pop one side up at a time, but never enough for it to come out or even have enough to grab with a needlenose.
Also, I can't cut a slot across the bolt with a dremel, because the bolt is recessed in the stem too far.
Perhaps I'll give the heat expansion method a try.
P the G,
The 'heat' method is only effective on metals with different expansion rates: e.g. aluminum and steel. The broken allen wrench and the bolt are both steel.
If you have a dremel tool you should be able to take a pointed carbide cutter and work it gently around the hex cavity in the bolt head . . . tapering it [bell-mouthing it]. eventually you will have enlarged it enough to let the broken wrench piece fall out.
There should be enough of the original socket in the bolt to use a standard allen wrench in it and remove the bolt. Replace the bolt with a new one.