A couple of things I've noticed over the years:
19mm is really really close to 3/4". It's actually 0.748 inches but I'm not sure any equipment I work with has the bolt heads cut to better than two thousandths, at least not until I get down to the pocketwatches :-).The ratio of height to base for a equilateral (60 degree for all angles) triangle is really really close to 13:15. (Of course the real number is sqrt(3)/2 =~ 0.8660, but that's surprisingly close to 13:15 =~ 0.8666).
Is there any deep numerological signifigance to these, or just random luck?
It is nice to use a 3/4" socket and 19mm socket nearly interchangeably. I think the spark plug hex on my lawnmower is officially 3/4" but don't really know. Many (most?) auto lug nuts are
19mm or 3/4" but I don't know which ones are officially which or what.The 13:15 ratio for an equilateral triangle comes out really nice for laying out hexagonal grids in "nice" numbers.
Tim.