> Classic DIP (dual in-line package) integrated circuits and headers have 100 mil spacing: ten pins per inch. IIRC, you drill a 25 mil hole for the pins. This i

> Classic DIP (dual in-line package) integrated circuits and headers have 100 mil spacing: ten pins per inch. IIRC, you drill a 25 mil hole for the pins. This is international. But that's just a historic accident. Related, the metric system was forced upon trade in Germany not before the early seventies. Only few units previously used survived, e.g. the 'Pfund' (pound, now redefined as 'half kg'). My father continued to use 'Zoll' (inch) and lamented American made machinery using threads on nuts which differed from those used in Germany (and everywhere else). Even I know the folding carpenter's ruler only as 'Zollstock' (no one says 'Gliedermaßstab'). And while I used to be very opinionated about the imperial- vs. metric system, after twenty years in California, I feel comfortable at 75°Fahrenheit and am exhausted, if I have to walk more than a few miles. I even caught myself recently referring to a width as 'about a yard'...