RE: Metric-Imperial / First angle and Third angle

>"...if everyone changed 100% to metric, all those old products would

(eventually) be impossible to fix..."

It will never be impossible with the talent on this list, but it maybe just
plain be expensive !!!

The above and many other negative arguments, like re-tooling costs where
used when Australia took the plunge into the "metric world"... before the UK
I might add... currency in the early 60's and measurement in the early
70's...

In the earlier days of transition the ugly thing that really irked me, was
the metric-thread bolts were cut/roller on old stock imperial blanks, giving
a bolt with metric thread and imperial head... a nightmare when working on
equipment!!!

This problem has passed and metric equipment with metric bolts use metric
spanners (wrenches)... Now the major thing is the term "preferred sizes" or
"non-preferred size" as the case may be... all imperial hardware now carries
a price premium... and with "non-preferred size" the price goes through the
roof (if you can get them)... commonly used imperial hardware is still
available, but the list of sizes/thread forms is shrinking fast... BSW & BSF
are all but gone, UNF is fading fast but UNC is holding in there... threads
like BSP & NPT along with SAE-"O"ring are still used extensively in the
hydraulic world, where metric hasn't taken off...

In my early school years I was taught the Imperial system... then in High
school we were told to forget that and learn the Metric system (no
converting allowed)... then when I joined the Navy and was working on
aircraft, I had to use Imperial again on all the British and American made
aircraft... the interesting thing here was, even the French/metric aircraft
had ribs spaced in inches with metric designations...
So now I am very "at home" with either system... I find if you can work with
decimal inches, metric is easy... everything is in multiples of 10, 100 or
1000...

And as for America holding on to the "inches & gallons"... I think it is
slipping from your grasp without notice... most of the hardware in the
"American made" automobiles is metric, even the fuel (gas) tanks hold
quantities to a whole liter amount (or a fractional gallon amount)...

Both systems have merit... although working things in fractional inches
instead of decimal inches does tend to be a PITA... and if someone wants to
say "why don't you just convert it?"... why not convert to metric???

From my stand point, the only thing that HAS to be avoided, is the mixing of
both "standards" on a project...
"Standard"??? boy, this is a word used loosely... American?, British?,
Metric?, ISO?, there are many flavors within each... look at your
Machinery's Handbook (ISO-Metric, ISO-British)... Metric (French, German,
Japanese)... The list is huge, but each has its purpose... "horses for
courses"...

It is worth looking at the definition of the word "standard" in a
dictionary... amongst others...
"...specimen or specification by which something may be tested or measured;
required degree of some quality..." Oxford, 1969.
"...usual, regular, or average; accepted as correct..." Collins, 1996.

That's my babble over with.

Happy use of YOUR preferred flavor,
Bryan