Confusingly, "Thou" (thousandth) and "mil" (mille, Latin for thousand) are the same thing: 0.001". Thou is definitely more common, but mil persists for film thickness, e.g. 4 mil trash bags are made from 0.004" plastic film.
In precision machining, you'll also hear "tenths" (one tenth of a thou or 0.0001").
No comments yet.