I am a very active fit 68 yr old that is a retired Machinist with Tool & Die certifications. Over half of my 45 years as a machinist was spent running CNC machines. Just like they say with other professions, once a machinist always as machinist. 0.0005 in is close work, anything else is a rough measurement. Drives my wife crazy when I tell her something is off the width of a hair. (0.003 in)