Screw extractors - as crap as they seem?

HSS taps have a useful property when broken in a non-blind hole. You can
gas axe them out quite successfully, leaving the thread untouched. I
discovered this when the print shop next door brought a roller into the
workshop and nothing else was going to remove it (spark erosion, yes,
but this was a Saturday afternoon). I told them I'd burn it out and
couldn't guarantee the end of the roller would be undamaged but they
said to go ahead anyway, it was worth a try.

I got the tap to start melting, turned off the acetylene and let the tap
burn away with just an oxygen feed. Bugger me; it vanished as clean as a
whistle and all that was needed was a quick touch on the threads with a
couple of taps and it was hunky dory.

 

We often gas axe broken taps, especially small ones, using the method
you've described. I use the MMA and high amps method on big taps when
I've been a bit hasty with pneumatic tapping heads and dropped myself
in the shit. I've beaten a 7.5" tap into submission like this and in
the end it fell into about 4 nice sized chunks.