But it doesn't use base 12. Take distance. Values smaller than 1/64" are measured using "thou", "tenths", and "millionths", which are decimal multiples of 1/1000', 1/10000", and 1/1000000" respectively.

Values between 1/64" and 1" are measured using dyadic rationals, i.e. base-2 fractions.

Above 1" it's mostly base 12,except for the yard.