On Sun, 5 Apr 2015 09:30:11 -0700 (PDT),
wrote:

On Sunday, April 5, 2015 at 10:34:56 AM UTC-4, Lloyd E. Sponenburgh wrote:
Ignoramus10114 fired this volley in
:

strength not an issue


Then one sizes it according to what you want to mount.

I mentioned 2.5x.45 metric... some also use 3 x 0.5mm, but even
that's smaller than 6-32.

If you need to mount through screw insulators (like for mounting
a transistor or a floating-case regulator like an LM-317, you may
be hard-put to find any insulators that will fit even 6-32... metric
has more-or-less filled that market.

With a rapidly expanding international market where demand for metric outstrips demand for trade (in everyplace but the US), its not surprising.

That has little to do with it. Except for construction and
transportation equipment, it's mostly a matter of whether the industry
is heavily involved with science, in which case US fasteners are
metric fasteners, just as they are everywhere else, or if it has an
international supply chain.

It's useful to look at three markets: the market for off-road
equipment (mining, construction, etc.); the market for automobiles;
and the market for electronic devices.

In the first case, the issues are that the market is truly global and
that the equipment has to be repairable around the world. Thus,
Caterpillar was the first large US company to go 100% metric, beck in
the '70s.

In the case of automobiles, US-built cars have never had much of a
global market but they are now the end of a global *supply chain*. It
is cheaper, and more flexible, to use metric fasteners for US-built
cars, when they may be built from parts supplied by 20 different
countries.

Electronic devices are designed and built in an environment that is
close to the underlying science, where metrics have been the lingua
france in the US for most of a century. Metrics are followed in the
engineering and in the assembly; repair is a miniscule economic issue.
Also, the supply chain is not only multinational, but also ad hoc; you
may not know this week where your parts will be coming from next week.

The upshot is that, with 70% of our economy based on domestic
consumption, there is little or no economic advantage to making
sweeping changes to metrics in other industries. Thus, change is slow.
And it has little advantage for anyone other than those industries
described above.

--
Ed Huntress