I've just learned of the different screw size types and that one number 8 isn't the same as another number 8. You conversion chart [url=http://www.diydoctor.org.uk/projects/screwsize.htm]here[/url] shows that, for example, a 4 x 40mm is equal to 8 x 1Â½".
However, the gauge diameters in both imperial and metric measurements aren't measured in respective units (or are they)?
Your table implies that the metric gauge is a measurement in mm as 'mm' is shown in the column. Perhaps it should say 'metric gauge' instead.