On Mon, 31 Dec 2007 09:47:53 -0800 (PST), Tim Shoppa
wrote:

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
pocke****ches :-).

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.

pi~=355/113 with an error of only 0.002% (22/7 is in error by 0.9%)

You can find a rational fraction approximation to any decimal number
by the process of continued fractions. This procedure is implemented
in the RFRAC program on my page.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.myvirtualnetwork.com/mklotz