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This Thread and specifically the posts by Subford. Another thread talks about getting or making a Bushing. 3/8" OD by a smaller size ID, say 1/8". Use the Bushing as a Guide to drill the broken bolt dead center. A number of replies have mentioned that a Left-Handed Drill Bit often backs the broken piece out, during the drilling process.
I'd guess that the suggestions involving welding would call for having somebody visit your coach to work on that bolt. I've heard that a REALLY good welder, can heat the center of the broken fastener with a fine cutting torch. Then when it glows, s/he hits the Oxygen and the piece vaporizes. The idea is that the casting doesn't get as hot as the bolt since it's so massive. VERY skilled hand with the torch...
