I had built one about 10 years back, real basic unit that I used to remove broken taps and such...
No longer have it, but I found a surplus power supply that was relatively high voltage [I think over 200v], and used manual feed with a current meter for monitoring, don't remember current draw anymore.
For a wash fluid I used plain diesel fuel, low pressure with relatively large volume to carry away the dust..not real safe, but was real handy and worked well enough..
I do remember that indicated current [and resulting arc size] would make quite a difference on the actual diameter of the cut, mine wasn't a wire style, just plain ground to shape carbon electrodes [arc-air rods]..
enjoy...