Hi,

There is a novel technique that I don't recall being discussed on this forum. I've used it and it works, but there may be safety concerns that apply to your particular situation. I can't say.

It requires a stick welder and a helper. The preferred current is DC straight polarity, meaning electrode negative, but AC would probably work if that is all that is available.

Cut off the small end of an Allen key, and put the straight long end into the electrode holder. With the welder OFF, insert the free end of the key into your bolt and apply some pressure.

Signal your helper to turn the welder ON, and signal again a few seconds later to turn it OFF after the bolt turns red. Let it cool to touch, apply oil and tap the bolt head with a suitable punch to help it along. On rare cases multiple cycles may be required.

The amperage selected depends on the size of the key, but I use the high end of what I would use on a comparable welding rod. This also works with stuck bleeder valves. Of course, disconnect the battery and connect the ground directly to the part that houses the bolt.

Peter