Andrew;

The Congress of the United States approved going metric in 1865. I was a Metrology Engineer for 15 years. Metrology is the Science of Measurement and we used the Metric and English systems of measurement for international complience of measurement. All manufacturers must have traceability to a National measurement Laboratory.

A great arguement about keeping the English standard presented by American Engineers has to do with screws - how many threads per inch, etc. The English system screws have a great deal of strength compared to the metric screws. Why not redesign metric screws to be stronger and go metric? The arguement is cost which I heard for many years.

Another country that has not gone metric is Yeman.

Tom