John, just do a search on u-tube “broken tap removal using an EDM machine”, there are plenty of how to videos on how it works.
It I’d basically just an electrode that burns the tap/bolt out without doing any damage to the threads.
When set up right, it works really slick.

Don

Edit: Wow Kevin, I knew they have been around a long time, but not that long!

Last edited by 2-Ton; 04/05/2024 1:18 AM.
1967 GMC 9500 Fire Ladder Truck
"The Flag Pole"
In the Stovebolt Gallery
1946 2-Ton grain truck
1946 3/4-ton pickup,
1953 1-ton pickup
1957 1-ton flatbed dually,
1954 Pontiac Straight Eight
Of all the things I've lost in my life, I miss my mind the most!