Hi Pat,
Unfortunately, information shared on this forum regarding metric usage in the
automotive, aerospace, and electronics industries does not match my
experiences. I would love to see a more comprehensive write-up with sources
and examples to back up the claims made by metric advocates.
To summarize my experiences:
- Inches totally dominate for length, except for microscopic scales
- Superstar scientists and engineers think and work in metric. Work-horse
engineers think in inches. Somewhere between the superstars and work horses,
designs end up hard inch-pounds.
- Metric units are used frequently for mass, temperature, power, and volume
- Metric units are used exclusively for electrical properties (volts, amps,
ohms, etc.)
NASA / Aerospace: Inches are completely dominant in engineering design.
Almost all parts are designed and made hard-inches. NASA is more metric than
the defense department and private industry, and continues to use inch-pounds
in part because industrial partners have a hard time dealing with metric.
Hardware involving astronauts is almost 100% non-metric. The lab where I
work (JPL) is the most metric NASA lab. Probably less than 30% of all parts
are designed all metric (the rest are designed in inches) and even parts
designed in metric are often converted to inches for machining. Note that
JPL engineers are practically all bilingual, and everyone mixes units
depending on the context.
Electronic industry: Most lengths, designs, and wire sizes are in inches.
Everyone uses SI units for electricity: volts, amps, ohms, henries, farads,
etc. Temperature is specified in Celsius for some things and Fahrenheit for
others. The really high-tech stuff (integrated circuit chips and some
microwave engineering) are done metric. Everything else, however, is inches.
Electronic parts sizes are all specified in inches. Circuit boards are laid
out in inches. Wire sizes are specified in American Wire Gauge or inches.
Auto industry: I have a friend who a few years ago worked on air bags for the
American automotive industry. He says his work was 100% inches. Not metric.
I've seen claims that the auto industry is metric, but I haven't seen any
good references or documents to back up this claim. What fraction of
drawings at Ford or GM are in inches, and what fraction are metric? I would
also like to take a walk through an automotive machine shop and see how
things are made.
I've spent an awful lot of time working in a variety of science/electronics
oriented laboratories. Here are a few observations:
Fasteners (screws, etc.) inches completely dominate
Tools: Mostly inches
Almost all parts are measured in inches
Breadboards, optical benches, etc.: All inches
Volume: Usually measured in ml or liters
Mass: Usually metric
Force: Mostly pounds
Torque: Mostly ozf in, lbf in, or lbf ft
Pressure: PSI, atmospheres, or Torr (Never pascals or bars)
Temperature: Usually Kelvins or degrees Celsius
SUMMARY: Inches completely dominate American engineering. Almost everything
is designed hard-inches. Consumer products are NOT dumbed-down for the
public. However, except for length, other metric units are widely used.
On Sunday 05 October 2003 04:58, Pat Naughtin wrote:
> Dear John, Han, and All,
>
> Front end down-dumbing
>
> There are a number of areas where an entire industry is metric and � just
> before release to the public � there is a dumbing down by the
> marketing/media department for the public.
>
> I will call this 'Front end down-dumbing'.
>
> Let me give you some examples.
>
> The world motor industry
> In the 1970s the whole world motor vehicle industry changed to metric
> measures. They did this to achieve massive savings by adopting the 'world
> car concept' where component parts could be sourced from the best priced
> parts anywhere in the world. Since the mid 1970s all � I'll repeat that ALL
> � cars in the world have been made using only metric measures. There are
> about 10 000 parts in a car and each of these needs on average 10
> measurements � making 100 000 measurements in all. In the USA the car is
> then fitted with its down-dumbing equipment, a speedometer labelled 'mph',
> and odometer labelled 'ml', and a tyre labelled 14. These three labels are
> generally sufficient for the new car owner to believe that they are driving
> an 'English' designed, and 'English' built, and that all is right in this
> 'English' world. Note that this is three labels (not measurements) out of
> 100 000 or 99.997 %. Apparently 0,003 % is enough to convince the public of
> the 'truth'.
>
> NASA
> As I understand it, but please correct me where I'm wrong, NASA has two
> classes of programs: the heritage programs designed in metric (by Von Braun
> et al) and then converted and specified in feet and inches for the US
> engineers to build them, and the more modern programs designed in metric,
> specified in metric and built in metric. Once a program is under way the
> data is then given to the down-dumbing department (probably called
> something like NASA Public Relations) where all the data is converted to
> 'English' values for press releases, 'English' values for web-sites,
> 'English' values for political speeches and to generally give the allusion
> that NASA is completely 'English'.
>
> Computer industry
> The research done on my computer to design the chips was done using
> nanometres, the silicon masks were then designed using micrometres, the
> component parts were then designed and built in millimetres with a
> precision to the nearest tenth of a millimetre. Then this data was given to
> the down-dumbing department (in the USA) who then dumbed it down to
> 'English'. I believe that every part of every component in my computer was
> designed and built using metric units; it wasn't until the marketing/public
> relations people became involved that the down-dumbing took place.
>
> In these three examples, it's interesting to note that the down-dumbing
> only occurs at the interface between the company and the public. The
> companies involved would not consider going back to old measures at all �
> ever � the costs would be far too great. But they will tolerate the
> down-dumbing process. Maybe management of these enterprises does not
> believe that running whole down-dumbing departments is costing them
> anything.
>
> Cheers,
>
> Pat Naughtin LCAMS
> Geelong, Australia
