American Drills and Taps

Thinking about Kadee couplings you get offered taps and screws and drills you get advertised by Kadee - these come with confusing notations like 2-56 and #50 - here is a decoder to those notations - concentrating on the small sizes relevant to Kadees

American Drill Sizes

#43 ....2.2mm
#48 ....1.9mm
#50 ....1.8mm
#53 ....1.5mm
#56 ....1.2mm
#62 ....1.0mm

American Screw sizes

Tend to be of form X-YY (e.g. 0-80) where X is the diameter and YY is the threads per inch

000 ~ 0.85mm
oo ~ 1.2mm
o ~ 1.5mm
1 ~ 1.85mm
2 ~ 2.2mm