If youre referring to CNC routers, theyre not designed to cut steel. Its not a good application for one. But with the proper tooling and speeds and feeds .25mm material removal could be doable I would say. I dont know what the tolerances are though. plus/minus what?. It sounds to me like the best way to do this would be an EDM, burn an electrode and burn the part. mirror finishes and precise tolerance control.Fascinating print process. Can CNCs give the z-axis tolerances you need? Outside of an honest to God machine shop that is.