That's a good tip for MIG or stick.

With the TIG welder skip the washer and just weld a little pile on top of the broken bolt, even if it's broken off below the surface. Once the pile is tall enough to grab with vice grips give it a try. Sometimes on stubborn ones it'll take a few attempts. Part of why this works so well is the concentrated heat on the bolt alone.

I've used this method on screws as small as 6-32 and up to 5/8" so far, from broken off flush or just proud to well below the surface. Admittedly small ones below surface get a little tricky.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-