I broke a tap in the aluminum block of the v8 you see in the heading. I was beside myself as to what to do about it. I found a web site suggesting burning it out with a home made edm. The electronics was simple consisting of a few items I had laying around and a variable power supply I already had. I think a battery charger could be used as a power source, or maybe a 12v car battery. Anyway, I made the tool from some brass and used my mill to guide it. Built a dam of clay around the blind hole to hold the liquid. I used motor oil for cutting oil. Had the tap burned out in 10 minutes. Had an amp meter in the circuit and downfed the stylest to keep the current at about half the max current. BTW, I tried a steel tool and couldn't make any progress. I tried water for a cutting fluid and couldn't make that work either. Its messy. The surprising parts was that the threads in the block were as good a if nothing had ever happened. A google search will bring up the site.