The aim of this paper is to report on micro EDM milling of stainless steel with ultrathin and high aspect ratio microtools and explore possibilities for machining with small discharges using a ballast resistor. Machining of channels is demonstrated with a 9 µm tungsten microtool with 29 nJ/discharge without damaging the tool. Depending on the value of the ballast resistor Rb, the channel width is about 31-36 µm with aspect ratio of 1.4-1.8. The most significant result is that the relative tool wear ratio is below 0.01% when Rb is greater than 100 Ω. It allows machining at 50 V operating voltage with 1 nF working capacitance without using the stray capacitance of the machine.