This week on Marc Spess' Live show we learned about Board member TetsuKawamura's Armature Calculator. I did a google translate of the page to understand it a little better and it appears it is metric.
This is a very useful starting reference, the only other place i've seen any of this figured out is in Tom Brierton's Stop-Motion Armature Machining manual (page 49, Bearing/Rod chart). I'm sure some of the numbers could be played with depending on the metal used. Tetsu even mentions at the bottom that some of the numbers the software generates are not those of standardized metric screw sizes so will have to be rounded to the nearest real world equivalent.
Looking at his site it looks like Tetsu made the prototypes of Animateclay's armbenders line? interesting.