From: Steve Malikoff (MIL-VEH account) (44gpw@phaedra.apana.org.au)
Date: Sat Apr 26 2003 - 05:03:29 PDT
G'day all,
Well I'm hope I'm wrong but I see this thread as just another along the
lines of "let's see how we can scorn the French, the UN, Europe and anyone
else who doesn't think the same as we do" threads that we've had recently.
I'm no fan of the french, but I can tell you as someone who uses metric,
imperial, Whitworth, BA, SAE and any other thread used in engineering and
model engineering you'd care to name, the metric system is the simplest
and most consistent of them all. They might be the "bad guys" for many
on this US-centric list, but they DID come up with an excellent measurement
system. SI Units are used by science and industry worldwide.
Out of the 197 countries in the world, there are 3, yes THREE that still
use imperial measurements (ref. US Metric Association website):
1) Liberia (convenient for registering large oil tankers)
2) Burma (not the pinnacle of democracy)
....and drum roll please...
3) The USA. (one of the first countries to introduce a DECIMAL currency!)
Drill tapping size in metric: diameter minus pitch. (Wow, difficult hey!)
Water temperature: zero = ice. 100 degrees ASL = boiling. (Complicated?)
Metric powers of ten: how many fingers do you have? Can you count them?
The beauty of metric is its consistency and its "impartiality". By that I
mean, if you saw an imperial measurement of 63/64" you would think why
didn't the designer just round it to an inch, right? That's the human sense
of "nice round numbers" influencing something that is cold, hard engineering.
63/64" in metric? Metric doesn't CARE if it is 25.0mm, or a round inch at
25.4mm. So what if a measurement is 3006mm (the exact length of my Weasel)
or 1.8mm (the hull thickness). It's just a number. Adding metric measurements?
You can do it in your head, or if you really need it, on any basic four-function
calculator. Adding 63/64" plus 11/16" plus 2 3/4"? I'll get back to you on
that one. Metric subsumes any imperial measurement without bias.
So stop bashing an excellent system and give it some credit. I grew up
here in Oz during the changeover in the early seventies, and am fluent in
both imperial and metric. My HMV's are imperial and that is fine for a quaint
piece of history. I'm building a track band mold for new Weasel tracks, and
dealing with metric in my (US-written) CAD program is dead-easy.
Why, even a NASA Mars-probe rocket scientist could understand it.. ..or perhaps
not :)
Steve Malikoff.
steven (at) phaedra.apana.org.au
On Fri, Apr 25, 2003 at 03:54:57PM -0400, Fred Martin wrote:
> SAE threads...tap drill size = Tap diameter minus 1/N... (N being number
> of threads per inch) and you can figure out the size tap drill on the
> way to the tool crib, in your head...example...3/4-10...ten into one
> goes .100", subtract that from .750 = .650...closest twist drill to that
> is .656 or 21/32". Can you tell me how to do it for metrics? Hmmmm! How
> about doing it in the lathe? Major diameter - 1.0825 over N = bore
> size...Hmmm again. Am I in left field? ...I've opened myself up
> here...let 'er rip...I have broad shoulders. Fred Martin
>
> Glen Bedel wrote:
> > Compromise for the "UN Coalition" Metric threads with inch heads.....
> >
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