To metric or not to metric? Is that (still) the question?

Recently, in response to an article headline that included our good ol’ Fahrenheit temperature unit, a reader took us to task for not using the international Celsius standard.

That sparked a conversation about the U.S.’s continued use of the imperial system of measurement, both in the wider culture but especially in the design engineering world.

So what do you, our Engineering Exchange members, think? Is it worth it to revisit the subject of using only metric units, or do we continue to accommodate both metric and imperial units?

And what about the wider culture? Do we start with teaching our children only the metric system from a very early age and let them lead the way? Do we begin to calculate kilometers per liter instead of mpg?

Tell us what you think.

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Comment by Roger Davies on June 14, 2011 at 6:04pm


The point I was trying to make is that there is nothing wrong with ANSI/ASTM the way it was without the SI stuff. The first one I noticed, that burned my butt, was the switching, in a feature control frame, of the datum letter and the tolerance. Why change it? If the Europeans want to talk backwords, let 'em! The toilet plunger datum flag has already been mentioned.

Comment by Ken Smith on June 14, 2011 at 6:03pm

If the US gov passed a law declaring all businesses, including all branches of military, to switch to metric system it would create a nightmare for all CFO's and Procurement Mgrs.  Every number-cruncher would be chained to the front of the Receiving dock protesting (kind of funny to think about).  Seriously though, everyone in the supply chain from the manufacture to the end user would have to inventory twice the amount of hardware to support legacy equipment.  Customers who have identicality contracts with suppliers would have to take existing equipment out of service and incure labor costs to convert to metric.


Can it be done, sure, but at a cost most businesses can't sustain.  Right or wrong it all comes down to money.


I read somewhere that Thomas Jefferson proposed the idea of using a universal system, but congress shut it down.  It would be interesting to think what the impact would be. 

Comment by Donald Moloney on June 14, 2011 at 5:13pm

I agree with Ken Smith. USA is part of a proud coalition of countries still using Imperial units. It would be un-American to convert to that frog munchin' SI system. We saved their asses in WW2 from commies so they should convert to OUR system because they OWE us that! It's not like using a different measurement system is hurting our exports. Stand proud with the great nations of Burma and Liberia! 'merica! 

Comment by Andrew Dreasler on June 14, 2011 at 1:40pm

It may be infeasible to covert 'legacy' equipment over, but if we stick with SI for new equipment, the legacy equipment will fade away as it 'ages out.'


That's one reason it is a slow process, part of it is waiting for the newest machines with SAE bolts holding it together to become obsolete.

Comment by Forrest Higgs on June 14, 2011 at 1:28pm

LOL!  We could convert in a moment.  We get the vast majority of our tools and virtually all of our fasteners from China.  We'd just have to stop ordering UTS/SAE and go for SI instead.  :-D


Comment by Ken Smith on June 14, 2011 at 1:23pm

Cost of converting to metric makes it impossible to switch over.  Training, tools, measuring equipment, tooling; not to mention converting fasteners, fittings and adapters over to metric on every existing piece of machinery made in the good o'l USA.  Imagine all of the cars, busses, trains, ships and planes, as well as, manufacturing equipment and tooling that uses American fasteners. If we started today making everything using the metric system, it would take a minimum of 50 years to phase out all existing equipment which would still require support and maintenance.  Today we are repowering 50 year old ships and locomotives with new engines that still use ... American fasteners.  Customers who have fleet vehicles want everything to be the same to have interchangability when exchanging old for new and compatability with tools and other equipment.


It's less expensive to have 2 set's of manuals, a digital caliper and a coversion app on my desktop/phone.  That said, in a perfect world, having one system is the right answer.  MHO, after we saved France (and the rest of Europe) from communist rule, we should have made a stipulation for converting everyone to the American System.

Comment by Andrew Dreasler on June 14, 2011 at 12:15pm

Dana brings up a good point, part of the resistance is Nationalism, or to say it without the sugar coating, the traditional mutual dislike between America and France.


The "metric System' is part of the SI, the International System of Measurements, or to use the name that the initials are derived from, Système International d'unités.  The idea that France may be right about something outside of wine, fashion, and snobbishness tends to make many Americans uncomfortable.  The fact that they WERE right in calling the plans for the Second Gulf War foolish due to the lack of exit strategy just adds to the discomfort.  If Joe Red-Blooded American still dislikes the French for the things they did right, you can bet that he will not want to do anything that even LOOKS like following the French.


Perhaps what we need is a partial step to ease the public into metric. Possibly a new 'Imperial' unit that would lead to easy conversion later, something like the penta-inch, or 'p-inch' (pronounced 'pinch') This unit, exactly five inches long would be easy to work with, allow for simple decimalization ( as one Imperial inch is 0.2 p-inch ) and converting to millimeters is cake as one p-inch is exactly 127mm.  Extending the measure further (if you'll pardon the turn of phrase) we would have the 'Freedom Foot' which is exactly 10 inches, or 2 p-inches, or 254mm.  Using the Freedom Foot along with inches becomes highly intuitive, unit indicators become almost optional. Say something is 1 Freedom Foot and 1.2 p-inches long, you could write that as 1FF1.2p-in, 1FF6", or even leave out the Freedom Foot indicator entirely, 16".


Now I was born after the Second War to end all Wars, so I only know this second hand, but I've heard two theories why France officially dislikes the US;


1) The French claim that the only culture we have is what is in the yogurt.


2) We rescued France from enemy occupation twice, and they will not forgive us for that.


(Opinions i9n the above post are not necessarily my own.  I try to stay out of politics, in my opinion, France is no better or worse than any other European country.  We Americans may take an 'Independent' attitude since we '...have been kicked out of every decent country in the world...', to steal a movie line, but we're really no berrer or worse than them.  Every nation has its strengths and weaknesses.)

Comment by Dana Patelzick on June 14, 2011 at 11:38am
Roger Davies touches on one of the issues of why the US does not go to SI and that is a patriotic or pride issue.  SI is from somewhere else.  Unfortunately Imperial or in the US USCS came from somewhere else also.  In the case of USCS it is tweaked Imperial and except for a few things it is not a lot different.  Engineering is about solving problems.  Repeatedly screwing around with the inch-pound-second system in all its permutations just gets in the way and invites error.
Comment by Roger Davies on June 14, 2011 at 8:01am

Let's change the subject. I think we have beaten the dead-horse of newtons enough.


As a very patriotic American, it REALLY frosts me to see ANSI/ASTM put in so much SI stuff into Y14.5., metric stuff aside. That toilet plunger datum flag is one of my pet peeves! How stupid! I don't know who came up with that thing, but, it must have been a Frenchman. OOPS, is that PIC? Maybe it's just my age, 65.

Comment by Karl Zemlin on June 14, 2011 at 5:52am

Drop imperial.  There is no reason to hold on to it.  It has nothing to do with math for me.

My company designs and builds engineered industrial equipment.  The company is global.  Our biggest customers are global.  Availability of imperial tools and fasteners in the rest of the world is poor, compared to getting metric tools and fasteners here in the US.

We try to design products that can be manufactured to be the same and interchangeable whether they are made here in the US, in Japan, Germany, South America, or China.  The biggest hinderance is material stock sizes.  We are faced with a lot of machining to get stock to common sizes.  Metric material sizes are hard to get and expensive here in the US.  It increases our costs and makes it more difficult to compete.

Units is units - I can do the math either way.  Its simply the fact that 2" does NOT equal 50mm that makes things a PITA for us.


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