Hey PF keep the soapbox mate. I enjoy your very specific and rational thinking. I didnt know how lead shot was sized but it doesn't seem all that logical now I know.

The decimal/metric system is very easy to grasp and it is hard to change from what you were brought up on. I too have problems still with a persons height, I still think I am 5' 7" tall not about 170cm but I am OK with being 75 Kg. Isnt that strange.

I mainly think metric now but using different spanners (oh yeah americans call them wrenches lol) I am very versatile in that I can use metric, AF and BSW ones with some precision.

Copper pipe in Australia is measured OD not ID as in the US. The US idea is the most practical in this instance.

We have Australian Standards that have caused some confusion if you are not conversant with them,. 1/2" pipe is 15mm but if you converted it exactly the it would be 12.7mm so the 15mm is sometimes confused with 5/8" but now that is 18mm with 20mm for 3/4". OD of course.

If you work in the industry as I have it is no problem. I design and install medical gas reticulation systems for hospitals and other gaseous applications. I have had a long involvement with the AS2896 - Design and Installation of Medical Gas Systems for Human Use. I have actually had several of my submissions adopted into the standard, something of which I am quite proud.