I remembered that American manufacturers have clung, unwisely, to imperial measurements, rejecting the SI system.QUOTE]

oed: OK Sorry, but you've struck a nerve. YOU CAN'T SAY THAT!!!
YES, and here I have no complaint...
You are probably right later in your post about conversion factors, and how it may have happened, and I have seen this problem occur in engineers' calculations. And the Intonation problem on the Gibsons of late has been well identified by some master luthiers both sides of the Atlantic. No argument there.
HOWEVER, and yes I saw where you're posting from! As 1st a Brit, where incidentally the IMPERIAL measuring system was invented/standardised, and 2nd working in an industry where we use both ALL the time, and both work just as well for us. I have to defend the Imperial system.
We Brits built an Empire, and half the industry around it on Imperial. We also helped a lot of people around the World using it to standardise things like railways, when Europe was all over the place with theirs.
Actually in certain respects, measurements and particularly when using hyper accurate guages, Imperial is often far more accurate. Believe it or not but a lot of guages in engineering are twice the diameter and more accurate in Imperial than their metric equivalent.
All the CNC's that I have access to don't care, so if there is a incorrect factor it shouldn't be the machine, but the programmer.
If you doubt what I say, well. In my biz we go from 0-90mph and back again 25 times per second. Sometimes we do it faster. Yes we use metric, but Imperial still works fine for us.
Oh, if you didn't know. The US military did a study on turning completely metric. The costs would have run into 'Billions' so they didn't.
I like the Foot, Yard, Mile, Inch, they work fine for me! It was good enough for Isambard Kingdom Brunel!
Ditch the Pound and I'll be invoicing in US$!
The US may have broken off the chains of Imperialist oppression, but they knew a good thing when they saw it!
:soapbox: :usa2: :usa: What No Union Jack???