Sorry to be late to the party and to sidetrack the conversation - but in 3alarmer's case, there appeared to be just enough adjuster screw there to tack weld a 5 or 6mm nut onto it with a MIG welder - and then pray a deep socket will give you enough leverage as it tries to bend and twist coming out.
Not an option if you don't have the welder, but an alternate thought. Might be a valid idea for a really stuck one.
-Kurt
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