Mirror finish : Surface finish value?

CNC machining cannot give a mirror finish. The cutting tools used are similar to what is used for regular machining, which means that only a similar surface finish will result.
Medical devices like artificial joints and heart valves have to be dimensionally accurate and have working surfaces with a mirror finish. We routinely do CNC machining of the basic component followed by an elaborate post machining surface finishing operation. This consists of Wet cutdown by tumbling, dry finish tumbling, tumble shot peening to impart surface hardness and final manual buffing to a mirror finish.

The finished part has a surface finish of better than 0.1 micrometer Ra.