Used to metric measures, I always struggle when find references to inches and so, having to resource to the calculator. But if we are speaking about #s of screws, drills, and so, I'm completely lost! What is a tap 56-2? How many millimeters are a drill #50??? :curse: It was a pity, because in the net there is a wealth of information written by fellow US & english modelers that work with imperial measures. :cry: Enter the internet wonders: The drill size table & converter!! http://www.csgnetwork.com/drillsizeconvert.html My «calculator days» are gone now, and I wanted to put this link here. Maybe another «metric guy» find it of use! :thumb: P.S. Oh, I forgot to mention: in this link there is a BUNCH of other calculators, converters & tables!