The Great Metric System Debate.

[Daniel]

Hey man - Metric is great - IF you grew up your whole life using it. Otherwise it is a royal pain in the.. whatever. I understand metric, but it is just too much bother to convert to a system that I have never had to use and in reallity offers no real benefits. One can measure just as accurately in either system. It is also easier to divide thins in half, as we do for all the franctions - 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 than it will ever be to divide things by 10. (Fold this paper into 10 equal parts...)

And we all know that the "standard meter" myth (that is is some portion of the distance from the north pole to the equator) was just an attempt by the French to try to justify a system that was really based on dividing the inch into 25.4 sections because they screwed up and failed to divide the inch in 25 segments. Then the Milimeter and the Meter would both have made sense.(25 millimeters to the inch and 40 inches to the meter) But because some Frenchman used some poorly made (Non-Starret, non-Mitutoyo) tools to measure out his NON-INCH millimeter those who use the millimeter have to put up with odd dimensions. And it is interresting that they try to this day to blame it all on the Americans when it was really just the result of some tizzy between the British and French going back who knows how far. The British have made a feeble attempt to placate the French (the british are europeans after all...) but what with stones and other silly units of measure they have still managed to stick it to the French. So the last bastion of sense and reason is the U. S. of A. who still have enough brass to uphold the noble, sensible and reasonable INCH, FOOT, and YARD as the only proper units of measure.

Wow! Is this the type of thinking that comes from the American educational system? But why am I not surprised? There was never an attempt by the French or anyone else to divide the meter in any parts other than multiples and sub-multiples of 10. The inch of 25.4 mm did not exist until 1960. Before that the inch kept changing in length every few years. Every country, state, province, city, town and village had their own size of inches. Which one was the right one? Was there ever a right one? The "pouce" was the name used for inch in France. At the time of the introduction of the metric system, the pouce used in Paris was equal to 27.07 mm, thus 1.67 mm longer then the American inch post 1960.

Can you ever trust a unit that can't stay constant?

 

[Daniel]

Anthony THAT is a PERFECT answer! :bow: :bow: :bow:

A size is a size. It doesn't matter if it is in tenths of a centimeter or thirty secondths of an inch.
Either way you will hit it or miss it.

You can't blame the measurement system for making it more difficult.


Rick

It matters to the person when a round number in metric doesn't come out as a round number in obsolete units. If I need a hole drilled that must be 50.00 mm +/-0.01 in diameter and the same dimension is 1.968 503 937 inches, are you going to tell me that such a number is acceptable in inch units? It isn't. People who insist on using obsolete units want the numbers to be round. But if you try to round a highly precise metric dimension in inches, it will no longer be precise in metric and the hole will end up being the wrong diameter and the part will be rejected.

 

[Daniel]

Marv, Until you've watched French, German, and Japanese engineers scrambling across 5 acres of land looking for the pieces from their inflator that failed because they misread the powers of 10 in their Pascal calculations, you don't know just how "good" the metric system is. Why is it that so many "metric countries" have changed from N-m to kGf-cm for torque? Have you ever tried to apply an M10 (X1.5) screw to a cast aluminum part?

These all indicate that the "mesh" of Newton-derived units is pretty poor. It can be truly funny to look at the rework budget for companies that have gone "all metric" as they fail to realize that there are still five different and incompatible standards for tolerance and allowance with respect to metric screwthreads. I have lived through three fairly major adjustments to basic units of the metric system -- it is still a work in progress at best.

Obviously Lew's story here is complete fiction by a person disgruntled because he has shown himself to be obsolete in a metric world. What I see is a world that increasingly buys German, Japanese, Italian, Chinese and products designed, engineered, manufactured and serviced in metric units and decreasingly buys American products made in obsolete units.

I use metric fasteners all of the time and never had a problem with them. I would also say that the American Automobile and heavy machine industries that still exist will disagree with you. They are fully metric and function perfectly well with it. The only times problems are encountered is when some has been tries to introduce obsolete units into the equation resulting in errors

Maybe it is time for Lew to come into the real world and depart from his fantasy world where USC is wonderful and metric is tragic. Maybe if USC was so wonderful, business after business would not be fleeing the US for the metric countries and instead the world's manufacturing would be moving to the US to take advantage of the wonderful world of USC. The fact that industry is leaving the US proves that USC and those that support it suck.

Germany didn't become the world's largest exporter by using inches.

 

[cidrontmg]

"BTW, if I multiply 3.6875 by 25.4 I get 99.6625. Where did you get 93.66233775?"

Hm. I don´t, but this IS a chinese calculator. 3.6875 x 25.4 seems in this technical marvel to be 93.6625...

 

[Maryak]

BTW, if I multiply 3.6875 by 25.4 I get 99.6625. Where did you get 93.66233775?

25.4 mm = 1 inch is a convenience number decreed by ISO in 1959 much like the US declared 39.34" = 1 metre. The various experiments to actually measure one against the other gave results varying from - 25.399978, 25. 399956, 25.400051 mm/inch. I chose the middle one to get the above. Who knows what the actual of one to the other is, and who cares. 25.4 works for me. This debate has kinda gone from the sublime to the ridiculous and I felt left out. :

Best Regards
Bob

 

[shred]

What's funny is most 'designs' care not one whit about the system they are measured in these days.

Take, say, an item probably everyone on here has within 4 feet of them. Tens of millions manufactured every year. The humble computer mouse.

Know how the cord length on a standard USB mouse was determined? A "designer" dragged a piece of cord across a couple raised floor tiles, picked it up and said "about that long". Saw it first-hand.

 

[Lew_Merrick_PE]

Obviously Lew's story here is complete fiction by a person disgruntled because he has shown himself to be obsolete in a metric world. What I see is a world that increasingly buys German, Japanese, Italian, Chinese and products designed, engineered, manufactured and serviced in metric units and decreasingly buys American products made in obsolete units.

Sorry Daniel, it's true. Less than two years ago I "solved" an assembly problem at a major marketer of consumer electronics by pointing out that their German supplied screws were being assembled into Chinese supplied nuts. If you dig through the complete set of ISO screwthread tolerances & allowances, you will find that there is a different set of tolerances & allowances -- Germany uses the DIN derived set and China uses the JIC derived set. In large-scale manufacture, you have a 43% chance that the two will not assemble correctly. The "fix" was relatively simple -- specify the controlling tolerance and allowance standard on the drawings!

I use all sorts of units of measure. As I noted at the beginning of this diatribe set, I lived in a metric world until just before my tenth birthday. I was frustrated trying to learn traditional American measure. As I lived in an area dependent on pulp & paper, we still used 1/128th's of in inch. Yeah, tell me about it. When I work in optics, we typically use 240 nm as the unit of measure (1/4 wave of standard IR emitters). When I work in nuclear operations, we typically use the "shake" (about 20 cm -- the distance light travels in 1 ns). When I am designing manufacturing lines, I like to use the "stone" because of its historical significance. Etc.

My "complaint" with the metric system is two-fold. The Newton, and units derived from it, have an extremely poor "mesh" that leads people -- even those who have never used anything but metric measure -- to make mistakes. The other is that the metric system of screwthreads is really poorly thought out and applied. Yes, it has been (just barely) more than a decade since "regional" threads were removed from the ISO standards. That does fix a lot, but until the allowances and tolerances are unified, it is still problematic. More importantly from my side of the street, the ability to tailor a screwthread to the material being used for the design is nowhere near as well considered as those offered by the UN thread series.

My "observation" is that the metric system itself is being "rejected" by countries and companies when it comes to the Newton. Most of the JIC-derived metric world uses the kgf-cm measure for torque. I first saw that applied when (as noted above) I ordered metric torque wrenches from France for a NASA project (though those were "calibrated" in kgf-m). If you want a mess on your hands, write up a torque specification in N-m on a drawing for something that will be assembled in China! They (most Chinese manufacturers) have less of a problem with lb-in or lb-ft.

I have done work for more than 350 companies and government agencies across five continents. If you have an airbag restraint system in your car, there is a 30% chance that it is one of the units I developed and qualified. That is where I am "coming from" here.

 

[Maryak]

OK,

We have just proven that the unsolvable is unsolvable. Going round in ever decreasing circles we end up you know where, doing you know what.

Before we reach that point I am locking this thread so we can all get back to making models to the measurement system of our choice.

Best Regards
Bob