A Spectacular Method of Removing Broken or Seized Bolts
I use a direct method to remove broken and seized bolts or studs in iron or steel; a cutting torch applied directly to the stub-end. Once the stub is glowing bright red, I hit the oxygen lever and a fountain of steel erupts from the hole. Be certain to wear protective clothing! Strangely, the female threads in the part are never damaged by this treatment. A clean up of the hole with a thread chasing tap restores the part to near-new condition without the risk of drilling off center or oversizing. This may be because there is always an air gap between even a seized bolt and whatever it is threaded in to. The air gap must insulate the female threads. This method works particularly well on blind holes with broken exhaust manifold studs in cylinder heads or manifolds, and broken motor mount bolts in blocks.

Jack DeRyke (via email)

September, 2013