If asked why I'm interested... I just can't see Boeing shifting to the SI
system when they lead the world in technology using ft, lbs, thrust, Mach
speed, known strengths of material in thousands of pounds per square inch,
BTU required for the thrust, drag, gravity, air pressure in the tires in
lbs/sq/in, and everything they have been designing since that first biplane
that flew the mail from San Fran to Alaska to keep up with the steamships
mail delivery, and later the famous Boeing School of Aeronautics in Oakland
where virtually every world-class aeronautical enterprise used to leverage
themselves into leadership roles.
Why would there be a reason for them to go through their whole history and
library of data from endless successes and failures in order to meet the
world myopic desire to metricate?
On Sun, 16 Sep 2007 13:03:23 -0700, the renowned Too_Many_Tools
Metric, which is fine with me, but also first-angle orthographic
projection (as opposed to North American 3rd angle projection), which
I really don't like.
They also will happily make stuff with Imperial fasteners, NPT
fittings etc. if export markets demand it and pay enough for it to be
This seems like a non-issue to me. Any modern 3D modelling system
works in internal units than can be switched to whichever system you
like (including dual units) without changing the underlying model. I
am designing some systems for aircraft, and we use a mix of mm and
inches, usually kg for mass, usually Imperial fasteners (because
they're cheaper and more available), but it's not really much of an
issue in this corner of the real world. Getting used to GD&T seems
like more of a hassle.
"it's the network..." "The Journey is the reward"
firstname.lastname@example.org Info for manufacturers: http://www.trexon.com
On Sat, 15 Sep 2007 19:19:06 GMT, "Wayne Lundberg"
Though 3rd angle projection is customary in the US and 1st angle is
more common in Europe and Asia; the choice of one or the other has
nothing to do with the units used. Title blocks include the truncated
cone symbol to eliminate any possibility of ambiguity.
Mach numbers are unitless.
A pragmatic recognition of the need to compete in the international
Ned, have you looked at the engineering manuals that fill wall to wall
libraries... all in the HP, Lbs, Inch doctrine? Why in the world would we
give it all up when we are the leaders in technology, innovation, invention?
The SI is an elitist figment of imagination with zero value in itself. All
SI units have been copied from other knowledge and add nothing of value to
It was one of the little things the commies did to undermine the US
economy. There was no reason for it.. the system works. Its just like
the present government has started a war that will only cost the average
american over half of his savings in real buying power.
Ironically, different divisions of Boeing have different drawing
standards for different reasons, and the standards evolve constantly, as one
would expect, given the different tools available for design. Facilities
uses Autocad, Commercial Aircraft uses CATIA (forgot the name of the system
the 787 uses, which is a bit different) and my tiny little lab uses
Solidworks. You'll find just about every system and standard that exists
all in use at this enormous company that isn't micromanaged so tightly that
someone cares about such things.
Aerospace equipment and standards, having been developed using the
traditional units, are still being made that way, and since they're
expensive due to regulatory issues. Imagine what the price of a rivet would
be now that it has to be redesigned using metric standards and then find
someone who wants to buy them... just so they can pay more? Airbus,
Embraer, and Bombardier all use inch fasteners. Would you as a passenger
think you need to pay more for the plane just because the drawings are done
using one standard over the other.
On the other hand, NASA has made the announcement that all future space
missions will be metric. Don't know how much of that design dictates metric
fasteners, but it'll be interesting. They'd like to avoid the unit
conversion that has resulted in a few embarrassing accidents. My lab will
ask for quotes in both metric and inch, sometimes a mix of both, depending
on the project, the materials, the customer, and the designer. I'm getting
used to working with mixed units, although I'm not to the point I prefer one
over the other.
That's an interesting story, Carl. I think a lot of pro-metrification folks
fail to separate the advantages metrics offer in scientific and some
engineering calculations from their complete *lack* of advantage in
measurement -- which is what we're talking about, in manufacturing. As soon
as someone starts talking about the conversion of odd, old units in the
traditional "Imperial" system, you realize they aren't talking about the
issue as it really exists. Where it matters, metrics are used in the US.
When it comes to measurement, the advantages of metrics are illusory.
I couldn't agree more. I've worked with both systems as a machinist in
the industry (it's been awhile back) and couldn't really see much
difference other than I was more comfortable with inches as that's what
I used the most. The one exception was really old prints that were
still in fractional inches but nobody serious has used that system since
what, the fifties?
When it comes to typical size parts who really cares if the unit of
measure divides evenly into miles or leagues or rods or whatever. I
suppose as an exercise in metrification one could dimension his parts in
kilometers just to show how cool powers of ten work...
It's a Linux world....well, it oughta be.
Sure. If you're doing a calculation involving, say, force, volume, and mass,
metrics usually (but not always) make your work easier. If you're measuring
the diameter of a crankshaft journal, metrics provide no advantage
Most manufactured metal parts can be measured in inches; we don't get
involved with feet, yards, etc., and the rest of the red herrings that the
pro-metrics folks toss into the discussion. It's mostly inches and decimal
So the units don't matter. Mathematically, we handle them the same, whether
they're inch or metric. And most of the occasions we have in manufacturing
to use inch (or Imperial) units versus metric ones are cases of linear
There is no benefit at all in using metric measure... other than the fact that
pretty well the entire rest of the world uses it. In modern manufacturing
outside the USA, Imperial measure is an historical curiosity and children
haven't been taught Imperial measure for two or three decades even in the UK.
If you want to sell to the rest of the world, think metric. If you want to buy
from the rest of the world, think metric.
I'll even have a dual inch/metric machine in the workshop when I finish
refurbishing it... it's a Hardinge HLV :-). everything else is Imperial, but I
do have metric micrometers up to 100mm for when they're needed.
SWMBO is currently baby sitting 3 grand daughters in the other London,
having one hell of a time trying to cook in metric. She has been
ignoring the metric system here in the dominion in the hope that it
will go away. She says they don't have measuring cups or spoons or
anything useful to work with there! Even the ovens are all wrong and
she burns things.
Until as recent as a few years back, the international measurment
standard was a platinum bar with 2 X's engraved on it, preserved in
Paris. The X's are 1000mm apart. This bar is the standard that all
measurements were defined from, with the Inch being defined as
25.4mm. Now the standard length is calculated from the distance light
travels in a vucuum. Tradition tells us that the inch was one twelth
of the length of Hercules foot.
It is interesting to note that while people may argue against
metrification, in reality the Imperial system is now derived from the
This year the BSPF and BSPT thread standards have now been given a new
"Metric" Designation ISO Rc Series (Taper) and ISO G Parallel
Series. They are still designated with fractions and TPI, but have
been incorporated into SI standards. This is a good example of
"Inchification". Hope this makes some of you Yankees feel a bit
Cheers from Down Under
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