I have been asked to provide some of our technical docs in both metric and US units. For the most part, that is easy enough:
approx 1cm → approx 1/2"
500μm → 0.02"
But then I start getting stuck:
- 50μm → 0.002" or 2 thou or 2 mils? Is there a common symbol for thou/mills?
- 20nm → ???
I imagine that people who care about nanometers have mostly gone metric now anyway, but it would still be good to provide US measurements for everything. What units are commonly used for lengths smaller than 0.001" in the US, and what symbols are used for them?
If it varies across different fields, the relevant ones would be optics, precision machining and mechanical engineering.