Originally Posted by 3alarmer

This comes up occasionally at the bike coop, so I finally
sent away for a pair of the #3 Jacobs Chuck wedges
that have shown up from time to time as the solution.

They worked well when most recently a guy brought in
his bike with the crank he'd stripped by accident in attempting
removal. My guess is they will work for you, too.

http://www.drillspot.com/products/94...68_3_wedge_set