CONVERTING METRIC & INFERIAL THREAD PITCHES

[mklotz]

Lots of folks seem confused about the process of converting from one system to another. This note provides an easy-to-remember rule that can be used for both conversions - inferial to metric or vice versa.

M = metric pitch measured in mm/th(read)
E = inferial pitch measured in tpi [th(read)/inch]

25.4 (mm/in) / M (mm/th) = (25.4 / M) (mm/in * th/mm) = 25.4 / M (th/in) = 25.4 / M tpi

25.4 (mm/in) / E (th/in) = (25.4 / E) (mm/in * in/th) = 25.4 / E (mm/th)

i.e., whatever you've got, E or M, divide it into 25.4 to get the other