>
> I have a (non-crackpot) theory about hex bolts and wrenches. This is just off the top of my head, but wrenches are square and bolts are hex, so both measurements refer to different things.
>
> The wrench measurement is presumably the width of the opening on the end, and the bolt measurement is presumably the side length. That means the distance between parallel sides of the hex bolt (and therefore the size of wrench you want) is actually sqrt(3) or about 1.732 times as big as the hex side length.
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> (The trig makes sense if you divide the equilateral hexagon into 6 equilateral triangles. Split an equilateral triangle in half and you have two right triangles with side lengths of 1 : 1/2 : sqrt(3)/2. Or you can just trust me.)
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> Of course, if my theory is right some of your numbers appear to be wrong. But that's my theory.
>
> ^v^:)^v^
> F"mathie"B

Hex heads are measured across the center from one flat to the other. Therefore, an open-end wrench with a half inch opening will fit a half inch hex. Box ends and sockets fit the flat sides all the way around. Square head bolts are more or less obselete.
Howard