Ouch Dave!

I agree with the neck being too narrow to drill. Could that threaded stub be screwed into the drill body or is it part of the casting?

If so, maybe grind it flat an drill it out for a smaller diameter screw. Then you could possibly cut the threads from a bolt that match the original, drill it out and tap for the new, smaller screw, and then thread it onto the body. Or just make an extension from the same bolt but cut/thread a reduced tip that could then be threaded into a matching hole in the body?