Engrave metals with Electrical Discharge Machining (sort of)

I am carrying out a series of experiments to give you an idea of how EDM works.

The classic EDM electronics works with voltages higher than 50V at high frequencies. I'd like to find ways to machine with spark erosion at voltages below 50V and with really simple electronics. First successful implementations make use of the so called "Wagner Hammer", a device composed of a lifting magnet and a breaker switch:

Next step was turning a DC motor into a Wagner Hammer and engrave some more steel discs:

The results are promising. This engraving is just 15x16mm with the timestamp engraved with a digit height of no more than 2.2mm:

More experiments will follow, soon...