Ron DeBlock wrote:
Do you have a welder or access to one? MIG, Fluxcore or stick will work.
Weld a nut to the the stub and turn it out with a wrench. I've done this
with broken bolts, but I've heard it works with taps.

I've tried this with broken 3 mm taps and a stick welder. I didn't have
any success. The weld always broke before the tap came out, and I had to
make a new part :-(.

Chris