I just broke a tap in an aluminium casting, LM25[T6]. it's a 3/8 unc roll tap in a blind hole, it's in the length of the thread[~21mm]. the hole was a few thou undersize, i have done almost 250 holes with it, all drilled the same size..
the casting is to valuble to waste so it has to come out.
I was going to heat teh broken bit with the tig to soften it, so I can bore it. I remeber someone saying about a home made discharge thing to remove taps, how did it work?
any other suggestions?
-- thanks richard