linuxcnc poses edm tool to wkpc. hal cuts with it. Custom Mcodes set the depth and retract heights, another sets on & off time in uSecs (granularity of 100uS due to thread used for oscillator), another sets the sparkout time and the shorted time limits, another sets the Ipeak values. An Lm339 is used as a window comparator, telling Hal to add or subtract from present position... this maintains the gap and in turn the process. wish the sound wasnt lost in 3gp->ogv transcoding, it was steady. see the final surface finsih at http://imagebin.org/246027 i used the 'reduce offset' pyvcp btn to act like peck drilling, works well, and a head shot of me at end happy happy! i dont hear audio in ffox17.0.1 BUT if i save the .ogg file, its fine played back by Ubuntu's Totem. then you can hear how constant it is.