rant

10 inches = 254 millimeters. Sounds like round numbers to me.

The US implemented JIC electrical standards in WW2. These provided a standard set of electrical schematic symbols and cross
referencing. Too bad it takes such all out crises to develop needed standardization.

A lot of CNC programs use the micron as the basic unit. My Fowler indicator switches from inch to metric with a couple of button
pushes. It displays to a resolution of .001 mm.



[Peter Reilley] I heard a story about the 2,54 conversion factor. At the beginning of WWII there were three different conversions in
use; the US used 2,54 plus a few millionths, the British used 2.54 minus a few millionths, and the Canadians used exactly 2.54.

Since this could cause a problem with making machinery compatible for the war effort they called a conference to settle the issue.
This level of difference did not matter to most industries since it was beyond where they worked or could even measure. It did
matter to the national labs and the few manufacturers making the most precise equipment.

At the conference they quickly agreed to 2.54, the Canadian standard. The US representative commented that the difficulty of
recalibrating the measurement equipment at all the large US corporations would be a huge effort and would take some time.

The representative from Moore Special Tool said that there was actually no problem! Moore Special Tool made all of the calibration
equipment used at all of the top calibration labs at the time. They had independently decided that the conversion standard should
be 2.54. All of the equipment that they sold and the calibration services that they provided reflected the 2.54 and not the official
US standard. Since no private calibration lab could measure to this level without using Moore instruments they, in effect, were
using the 2.54 conversion already.

ps: I don't know if this is true or if I have all the facts straight but it is a great story. I could not find any references on
line. It is touched on in "Foundations of
Mechanical Accuracy" by Wayne R. Moore, possibly the greatest coffee table book of all time (for machinists ;-}).

[ Stan] Anyone else think the inch could be adjusted a bit? I mean 25.4, what kind of a figure is that? Some sod in history must
have said '25.6? bugger that lets make it 25.4, that will really mess them up when they start messing around with binary'. Will
anyone notice if the inch grows a little bit? Its based on the average thumb after all, we could just say the average thumb has got
a bit bigger. Could have a go at the mm either. There's a bit of bar in Paris that says what a meter looks like, a quick rub with a
file on the end of it and life would be a whole lot simpler. Or how about calling it a metric inch? Blame the Japanese for it and
make a 16 inch metric foot so it looks convincing....anyone?....please?...pretty please?...





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