Units

[cdspk]

I'm used to seeing feet, inches and pounds usedin this forum but had kind of assumed it was a legacy thing, I was quite surprised to learn that (as one of the last three countries with Burma and Liberia) the US still has imperial units as its official measurement system.

From a professional point of view it would be useful to know whether US college engineering students are taughtat all inSI units aswe're starting to see a lot more US graduates here in the UK,

Cheers, Sean

[StephenW]

Yes, When I was in school here in the US (1996-2003, Texas Tech University) we used SI units in class more than imperial units. I was also working at the time for a company building construction equipment for Caterpillar who uses SI units also.
That being said, most US students (in my opinion) still don't have a feel for SI units. Day to day life is still thought of in feet, inches, lbs and then converted if necessary. I'm one of those...I have worked at companies that use SI units for 14 yrs and still basically convert everything in my head so I get a relative feel for the size or weight or whatever.

Steve

----------

[ptc-1932745]

I can comment that in my career (I'm now 50) we always used SI units, in
High School and College, (Ill Institute of Technology, Cleveland State
Univ., Univ. of Akron) Although I never used them in industry.



I personally would like to see us eliminate all use of imperial units
from 'professional' services such as Engineering and manufacturing,
leaving only Imperial units for some consumer goods such as food,
gasoline, building materials, etc... I think that this is happening. I
understand that in England a wooden wall stud is still called a 4x2,
even though it is not manufactured in inches. ( it's probably more
difficult to call it a 100x50, this doesn't quite roll off of the
tongue, maybe 10x5 (in cm) would be better).



My children are all being taught SI units (cm, mm, and km for length,
and kg and gm for weight) in their day to day studies in primary school.




One of the first uses I find for going to SI units is describing
mechanical components, with the concepts of fractional measurements
being the most troublesome.



For example to 'accurately' show a dimension of 3/16", the decimal value
is .1875". When modeling this in Pro-e you need all 4 decimal places,
the system does not use fractions directly. When showing the dimension
on a drawing, showing .1875 +/-.0300 is frowned upon (at my workplace)
because of all of the trailing zeros in the tolerance. I have the
option of showing the dimension as 3/16+/-1/32, but this is messy in
pro-E. I could just round up/down to 2 or three decimal places, but for
'design intent' I do really want the nominal dimension to be 3/16", not
.19".



One of our customers uses imperial units but shows all dimensions to 4
decimal places, trailing zeros be damned. They also comment that the
number of decimal places does not imply a tolerance, and explicitly show
all dimension tolerances that differ from the 'default' tolerance.



Happily this will all go by the wayside when digital product definition
becomes more mainstream.



Note that you do not have this duality of fractional vs. decimal
dimensioning in SI units. I find also that more people are willing to
use 'preferred numbers' when using decimal dimensions.



I anticipate that because a majority of machinists are taught in
imperial units, and most shops have most of their measuring tools
defined in imperial units, that they will be around for some time. Two
things can change this, CMM inspection to digital product definition
models, and the requirement to report inspection results in the native
units. (no measuring the features using imperial gages, and then
converting and reporting the result in SI units).





Christopher F. Gosnell



FPD Company

124 Hidden Valley Road

McMurray, PA 15317

[lylebeidler]

I graduated from Penn State with a B.S. in Mechanical Engineering in 2000.
In my studies there, we used SI units at least half the time. It varied by
textbook & instructor. Many professors insisted on using both (sometimes in
the same problem) as they knew we would face that scenario on graduation ( a
fact which has been borne out in my professional life)





--



Lyle Beidler
MGS Inc
178 Muddy Creek Church Rd
Denver PA 17517
717-336-7528
Fax 717-336-0514
<">mailto:-> -
<">http://www.mgsincorporated.com>

[ptc-593619]

Sean,

The imperial system is alive and well here in the USA. Most
professionals use it with aplomb, the SI system is as foreign as a five
legged cow. It does cause some confusion and I suspect most "American"
Engineers carry out a conversion in their heads when using the metric
system. For me, it is difficult to get used to "thous" again and I try
my best to convert any Engineers to microns though to date I have had
little success. It is all rather a moot point because if a guy/gal is of
any worth he/she will work in both systems while finding one more
comfortable.

I still can't get used to weighing too much in pounds instead of stones!

Cheers back at ya,

Richard

[JWayman]

I have had problems in the past when in conversation with the US office of
our UK company, I would talk about 'mils' (meaning millimetres) and they
would talk about 'mils' (meaning milli-inches - always referred to as
'thous' in England). Huge potential for embarrassment, but fortunately, it
was always sorted out before anything was manufactured!

Talking to machinists, the good old 'thou' is still used a lot, as it is
just such a convenient unit for turning and milling - much more useful than
0.0254mm.

In UK, we have been officially SI for longer than I can remember
(literally), but my children still glibly use Feet, Inches and Stones when
describing a person's height and weight. Incidentally, I don't suppose 12
Stone means any more to a US engineer than 76kg would, despite being a valid
Imperial unit! Equally, telling me a person weighs 168 pounds is no help at
all. It's what you are used to. When I was a teenager, we used to pick
Brussels Sprouts into a Bushel Box. You don't hear much about Bushels these
days. It's a handy volume measurement, though.

For modelling, calculations, drawings, etc. I would always choose SI, though
- it is much easier that way. Particularly, I find it useful, in engineering
calculations, to strip everything on both sides of the equation back to m,
kg and s, just to make sure that the units make sense. I find it much more
difficult to do that in Imperial units.

There remains the mystery that, in England, engineers talk in millimetres
and metres, but children are taught in centimetres and metres. I am sure
there is a good reason...
Then there are all the other obscure unit systems, like the one that refers
to parts of the anatomy of a gnat in relation to a small distance.

Interesting to hear that US schools teach SI, though. We will all get to
using the same system eventually.

Cheers,
John

[jnanesh.sajjan]

Well, a lot of discussion happened over this topic in other forums. And
it is a good topic to understand more about the pluses and minuses of
both the worlds of units of measurement.

[StephenW]

After sending this I realized I didn't put the most important part...I WOULD MUCH RATHER WORK IN SI UNITS. It's so much easier. This is coming from a guy who grew up using imperial units and yes I did learn a little about the metric system in grade school all the way through college. But when I actually became immersed in it in business, I realized how much easier it is to use. So many things take care of themselves in SI. AND, like someone else said, no pesky fractions to make life difficult.

Now I work in the oil industry in Houston. Wow, what a step back in the past. We still put fractions on drawings for welding.

[dgschaefer]

Back in grade school in the 70's, there was a push by politicians to
move to 'the metric system', but it seems that they pushed to hard and
fast. The older generations pushed back, I think there was some
silliness of metric not being American and whatnot, and so they backed
off and no one would touch it. Seems if we just started putting both
units on things for a while, it may take a generation, but we'll get
there.

Personally, I'm more comfortable with imperial units, but certainly
understand the benefits of metric.

Doug Schaefer

[rreifsnyder]

God, I hope we never use SI for general purpose. I'm fully conversant with SI and can and will use it when needed, but I hate the idea that they tried to force this on us beginning in the 70's as someone else pointed out. Even with all the pressure we simply won't use SI and the time has come for us to stop pushing it. I have no problem teaching it alongside the Imperial units (English units here) just as we should learn any other languages we can. We have wasted far too much effort and money trying to force this. If and when people decide that they are comfortable with it, it will change. I've always found it interesting that even the rest of the world has maintained certain things in inches, namely wheel sizes on cars. They are still in 14,15,16 inch and so on. In the early 80's Ford and Michelin tried coming out with 360mm and 395 mm wheels and tires for some of their cars. It couldn't catch on not just here but everywhere. I'm not for forcing anyone else to change to English units please don't try to force us to change ours. It's another language, that's all. We need to be conversant in both.

Rob Reifsnyder
Mechanical Design Engineer/ Pro/E Librarian
L
Mission Systems & Sensors (MS2)
497 Electronics Parkway
Liverpool, NY 13088
EP5-Quad2, Cube 281

[tcooper]

Didn't NASA try using both units on a Mars mission? I believe that didn't work so well. 😉

Tim P. Cooper
LMES, Houston
ITL Facility and Mockups Design
LM1 / Rm. 666

Physical Address: Correspondence:
2625 Bay Area Blvd LM1, Mail Code: A7A
Houston, TX 77058 P.O. Box 58487
(281) 283-4372 Houston, TX 77258-8784
(281) 283-4340 (F)

[MikeCavins]

My recollection is that there was an issue with the cost of converting
every single road sign (among other things) in the US from miles to
kilometers.

It's not a big deal for Rhode Island, but California had big huge
problem with it.


Mike


Mike Cavins
Design Engineer
CSC Worldwide
(614) 527-5767

>>> "Reifsnyder, Robert" <-> 9/21/2010 9:57 AM
>>>

God, I hope we never use SI for general purpose. I’m fully conversant
with SI and can and will use it when needed, but I hate the idea that
they tried to force this on us beginning in the 70’s as someone else
pointed out. Even with all the pressure we simply won’t use SI and the
time has come for us to stop pushing it. I have no problem teaching it
alongside the Imperial units (English units here) just as we should
learn any other languages we can. We have wasted far too much effort and
money trying to force this. If and when people decide that they are
comfortable with it, it will change. I’ve always found it interesting
that even the rest of the world has maintained certain things in inches,
namely wheel sizes on cars. They are still in 14,15,16 inch and so on.
In the early 80’s Ford and Michelin tried coming out with 360mm and 395
mm wheels and tires for some of their cars. It couldn’t catch on not
just here but everywhere. I’m not for forcing anyone else to change to
English units please don’t try to force us to change ours. It’s another
language, that’s all. We need to be conversant in both.


Rob Reifsnyder
Mechanical Design Engineer/ Pro/E Librarian
L
Mission Systems & Sensors (MS2)
497 Electronics Parkway
Liverpool, NY 13088
EP5-Quad2, Cube 281

[BobSchwerdlin]

Yes, I believe they had catastrophic results because some orbital calculations were done in Imperial units and some were done in SI, only to have mission failure. BUMMER !

Bob

[TimMcLellan]

I don't want to sway too far off the original question - Most students are
taught both and I use both every day.



Rob has a good analogy. Now the next big question, which one is more
efficient and effective for your business?



I find that a majority of my clients use SI (e.g. Consumer Electronics,
Automotive, Consumer products, etc) while some (e.g. Defense) primarily use
Imperial (English) units. I believe that this is due to business aspects
(Assembly and Manufacturing is primarily in the U.S.). Do what is right
and valuable for your business.



A quick search came up with this (Very pro SI - but interesting comments):

[ptc-157102]

All,



Way back in the 60's, most of my courses used metric measures (though you
were not so concerned with hardware types}. Some companies put inch inside
the box and metric on the outside (!?).



Most of the military is in SI. Many multinational companies with products
that are export require that the interface hardware be metric. Finding
American screws in most countries is harder than finding metric screws here.




One company was changing from inch/fractional to inch/decimal and sure
enough 10 inches= 1 foot! To mitigate the errors, we got into the habit of
designing with decimal fractions, .312 not .30 or .35.



Bill

[mheath]

If you look in the Machinery's Handbook it states " In 1866 the United States, by act of Congress, passed a law making legal the meter, the only measure of length that has been legalized by the United States Government." .

[pfariello]

Wow, I had to scroll way back in my inbox to see where this all started.

Thinking back, my engineering classes were taught in both units, graduated in 95.

Patrick Fariello

[dgschaefer]

Interesting info on the history of the metric system here:


the fundamental measurement standards of the United States. Our
non-metric units have been defined in terms of these metric standards
ever since."

So, it seems that officially, the inch in the US is defined as 0.0254
meters! 😄

Doug Schaefer
Senior Project Engineer, Mechanical
- <">mailto:->
www.design-central.com

[bbenitez]

I've been a Designer for almost 35 years

The BEST three years of my career were the three spent using JIS Metric
Units.



.34375, .6875, .90625 - how does one explain to an engineering student the
value of using these fractions?



Anthony R. Benitez

Senior Mechanical Designer

Drafting Supervisor

Applied Research Laboratories

The University of Texas at Austin

[kdemont]

I didn't realize that the government thought they could legislate thought that
far back in our history.

[joepaul88]

Well, knowledge on this exploder isn’t limited to Pro/E anymore I guess. Made me curious, found this site and lo and behold, it is listed at the end.

[ptc-169947]

Hi all,

Because we are still on 32 bit machines, many users have had to enable the 3 gig switch to get a little more out of their systems. This has resulted in display isseus for some of us, but usually a driver update takes care of it.
One user, when adding the path multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional with /3GB" /3GB to the boot.ini gets an error when booting up that reads
<windows root=">\system32\hal.dll cannot be found. Computer boots up fine when not enabling the switch.

Any ideas? In the meantime I told him to do a windows live update.

Thanks,
Stefan

[MikePhillips]

I have seen graphics card issues related to the 3GB switch before. You
might try adding an additional switch (/userva=2900) along with the 3GB
switch. You can read about this option (and others) using the link below.
This solved the issue we had at my previous employer.

[kimndave9]

I'm fine with the units - English, metric, whatever. I would like the
slug to make a winning run at overtaking the pound mass.

What irritates me is First angle projection.

OK - I'm just messing with the Europeans on this. It's just fun to try
to describe the difference to people who don't draft, but want to know
why there is so much complaining about the imported (into the country,
not into Pro/E) drawings.

I recall the following as true - removing some fasteners on an engine
had metric threads but imperial heads. I guess the taps were metric and
the serviceability was for the American market. Either that or they were
very out-of-spec bolt heads.

Dave S.

[jnanesh.sajjan]

I agree with Dave. It is somewhat troublesome when somebody looks at the
drawing (without looking at the angle of projection), he might draw some
conclusion about the part based on his "angle of projection" working
style. Of course, it is not advised to study the drawing w/o knowing
which AOP is used. However humans are prone to make mistakes!!



Jnanesha KS

[merrill.rosenow]

The transition in the US to metric is slow, but progressing. As far as I have been told, NASA, air ports and hospitals in the US all use metric exclusively.Thedeepest sticking point would be to get all the manufacturers to switch. Sadly we are deeply entrentched in the Imperial system. We have even bastardized it to get by, hence the decimal form of the inch.

[mbraaten]

Slightly off topic, but very interesting from Mental Floss (had to
share). Six Unit Conversion Disasters...

[dgallup]

Who says the US has not adopted the metric system? Do not use Wikipedia for anything more important than wrapping fish. I have been designing in SI units for over 25 years in good ole South Carolina USA. Vendors who insist in redrawing in imperial units get dumped. Here is a short summary of the US laws making SI units the preferred measurement system:

The Education Amendments of 1974 (Public Law 92-380) encouraged educational agencies and institutions to prepare students to use the metric system of measurement as part of the regular educational program.

The Metric Conversion Act of 1975 (Public Law 94-168) passed by Congress. The Metric Act established the U.S. Metric Board to coordinate and plan the increasing use and voluntary conversion to the metric system. However, the Metric Act was devoid of any target dates for metric conversion.

The Omnibus Trade and Competitiveness Act of 1988 (Public Law 100-418) amended and strengthened the Metric Conversion Act of 1975, designating the metric system as the preferred measurement system, and requiring each federal agency to be metric by the end of fiscal year 1992.

President George H. W. Bush signed Executive Order 12770, Metric Usage in Federal Government Programs directing all executive departments and federal agencies implement the use of the metric system. The Executive Order is also available as an appendix to: Interpretation of the SI for the United States and Federal Government Metric Conversion Policy

[pfariello]

I must say that it is hard to find any issues with the imperial pint when drinking beer.

Patrick Fariello

[JWayman]

But is that the 16 fluid oz. US Imperial pint, or the 20 fluid oz. UK
Imperial pint? 🐵