RonMacPherson said:
... Forget the French scientist's name who conceived of and formulated the metric system, but remember being instructed about him in high school physics; So unless California textbooks in the early 60's were in error, it was a frenchman's conception. ...
Not so much that the high school textbooks were in error as they tend to present oversimplified versions of events that have long and complex evolutions.
The Frenchman you read about was most likely Antoine Lavoisier. Lavoisier, a renowned scientist (and coincidently a French government official), was the man who spearheaded France’s “metric conversion.”
Lavoisier did not “create” the metric system. He worked with other scientists of his day to sort of “bring it together, iron it out and put it one place.”
That quintessentially metric unit of distance, the meter, was described by English scientist John Wilkins a century before Lavoisier’s time. Some historians believe it came to Lavoisier by way of his good buddy Ben Franklin.
Metric temperature measurements are found in either degrees Celsius or degrees Kelvin. They’re named for the scale’s inventor, Swedish astronomer Anders Celsius and the guy who came up with the idea of the absolute temperature scale, Irish physicist William Thomson, Lord Kelvin.
RonMacPherson said:
... remember when Japanese metrics in the early 70's weren't the same as most european metric, they would choose a different thread pitch for a lot of their fasteners...
Which brings up a very important point, the difference between a standard system of measurements (SI in this case) and a standard for a thingamajig (like a bolt).
A standard for a system of measurement simply describes the basic units of measure. The standard for the thingamajig describe the thing itself. The thing itself works the way it works regardless of what units you use to describe it (and some standards are written with both SI and US customary units).
The US and its allies use common ammunition among their military forces. The same ammo standards are also used in civilian firearms. It doesn’t matter whether you call them .223 and .308 or 5.56mm and 7.62mm. They’re the same bullets.
RonMacPherson said:
...I still think the Whitworth system is the best as far as providing the best strength of fit.
An excellent standard, not because it’s measured in inches, but because the thread geometric profiles and ratios produce a very strong fastener.
PC.