Metric/imperial

I am going to use the system my machines are built for. I'm a home shop guy, so my machines are older US industrial machines like a Bridgeport mill. When the used machines are all metric, then we might see guys like us moving to metric.

GWE

Well, US used to have a huge manufacturing base which used imperial, so metric didn't catch on. Now this base is mostly gone, the Chinese use metric primarily, and employ imperial for US orders only. I have heard that often they have parallel production lines, one supplied with M6 bolts and another with 1/4-20 bolts.

Anyway, it should be easier to switch nowadays. I hang around NIST, so I'll try to remember to mention it, maybe they'll get back the enthusiasm and start doing something about it, again :)

p

IIRC, the USA was among the first nations to embrace the metric system. However, it did so in its own, peculiar way, by declaring the use of the metric system lawful for anyone who wished to use it. Apparently nobody did.

In most European countries, it was made illegal to use the old systems, they were no longer taught in school, and the benefits of the metric system was preached in all the churches (well, perhaps I exaggerate a bit, but you get my drift). A massive propaganda effort coupled with legal means made us accept the newfangled system.

The metric system was designed to be convenient to use along with the common decimal system for writing numbers. Thus it scales easily to lower or higher units in the system. A thousandth of a kilometer is a meter, a thousandth of a meter is a millimeter, a thousandth of that is a micrometer.

On the other hand, a thousandth of a mile is 5', 3.36´´. (This is an unfair example, of course, because how often do you really have to know how long is a thousandth of a mile, but it illustrates the principle.)

As long as you work only with inches and thous, you have exactly the same benefits as the metric system provides, and then the systems are equal. But when you have to set your machine to, say, 3/16", and the dials only show thous, you have to calculate that 3/16" is 187.5 thous. The European machinist does not as often have to calculate such things, because all measures are given as mm and decimal fractions of mm.

S.

Strange how all the science I did in the US in junior and senior high school in the mid 1970s to early 1980s was all taught in metric SI units. I would have had to go to university in the US to get taught poundals and slugs.

"Tom Gardner" wrote in news:PXs5i.9548$ snipped-for-privacy@newssvr11.news.prodigy.net:

Tom, I can't answer your questions, but I can tell you that after using the metric system pretty much exclusively for the last 15 years, I can't even think in imperial units anymore. Even for carpentry work at home, I use metric. My sense of distance is calibrated to millimeters, not inches. Imperial just seems so wacked at all the conversion you have to do to go from one unit to another. (37/64ths is how many thou?)

Some things have changed. Consider automobiles. They shifed over but when you consider all of the other manufacturing that went on why bother to change?

Why do Canadians use two dollar bills/coins where in the US they never cought on?

I supose it depends what industry you are working metal for.

Your last sentence is absolutely right. It wouldn't matter if 1m would be

1.53672 m in reality. Or if it would not be a meter (or metre) but a "fung" or "serr" or whatever name you like. The problem with the imperial system are the odd conversion factors and the fact that it has not just one unit. Inch, foot, yard, furlong, chain, mile. Maybe centuries ago, the imperial system was handy for cabinet-maker's work. Or for a blacksmith. But with industrialization and higher demands on accuracy it became more weird. 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/1000 (how does that 1/1000 fit?).

The metric system is based on *one* unit (m) and factors that are even spaced (admittedly, with some others mixed in for convenience). kilo, (deci, centi), milli, micro. That's why it was so easy for the metric system to adobt to higher precision over centuries. Maybe the mm was ridiculous 200 years ago. Now, the micrometer is the unit (err .. factored unit) for precision work.

The metric system has no conversion, just decimal factors. The imperial has strange-numbered conversions and has non-intuitive factors.

Nick

Intelligence, perhaps??

What was their other choice??

And we will never totally change over, the entire country is surveyed in acres, feet, and inches. Consider the absolute insanity of trying to convert all of that to metric form.

But I pose another question to you, considering any dimension can be stated in either system with equal accuracy, why change?? We made it to the top of the international food chain with the imperial system, so it can't be so bad. Perhaps it is the dumbing down of America (well under way, by the way) that makes the metric system so desirable to some??

George

The bill is gone, but the Toonie lives on. Now if you're looking for listening devices.....

/mark

Canada changed over in 1980. You still see measures in Imperial and Metric in grocery stores. When I work on prints I constantly see mtric dimensions that are obvious conversions from feet. Lengths of delivered steel are 6280 ( 20 feet) Imperial will be in the background for generations to come. In engineering I am sure there are disputes about whether to use Pascal or Kg. per square metre. Randy

Beware the pink ribbon coins:

Best regards, Spehro Pefhany

What is the metric system? Most bearings are metric. If you are working on machinery, the nuts and bolts are metric. The problem with metric nuts and bolts is the lack of standardization. Japanese metric is different from US metric is different from Italian metric is different from German metric. Forget about pipe threads. Ever compare the price of metric bolts to imperial? Just what is a metric 4x8 sheet of plywood anyway?

Actually, it was the quarters with the red poppy... /mark

What does this mean exactly? I've heard this many times, (usually from a US source), but have never come across a meaningful example. As far as I know, Metric thread forms and pitches are standardized, although hex head sizes may be different. I don't see how Imperial could possibly be seen as superior in this case anyway. (If you look at things globally)

You trying tell us that Standard is better?

Sure. In the US they're sometimes more expensive for a similar grade of bolt, but I bet the situation is reversed in Germany. :-)

Still 4X8. You can measure it in metric if you like. 122cm X 244cm :-)

Now. What are the standard dimensions of a 2X4?

Pete

AH! HA! I think You have something there. :-) ...lew...

Interesting question, I am in the middle of designing lab classes for a machine design class and have to deal with it. The lectures will be taught in SI units. Should I have the students build in SI or English units? This is precisely the point where students learn to "think" in the chosen set of units.

My dilemma: All the shaft materials are English, all bronze bearings are English, ball bearings mostly metric, manual lathes and mills are English, CNC lathes and mills are bimodal, all the calipers are English, tape measures are English, short rules are English, long rules are SI, drill bits are English (fractional,number,letter!!!), steel and alumminum stock is English, tube/pipe is English, and last but not least, the instructor (that's ME!!!) prefers English. (Because I THINK in English units!!)

I was planning to teach this in English units, just announce that on first day of class. May have to think on that a bit.

Tom Gardner wrote:

FUD! It is simply nonsense.

Nick

Absolute claptrap.

I guess you probably reckon the ISO and IEC are "European" standard organisations each with individual organisations in Japan, Italy and Germany defining their own individual standards depending on the direction of the wind and the strength of the coffee that morning. (by the way Japan is not even remotely in Europe)

Steve Austin?

That 6 million dollar rebuild you had a few years back obviously left out a few vital connections in your cranium :)

I use both systems in my work and the US would be better off adopting metric. Except when it comes to women's measurements.

36-24-36 just sounds a lot sexier than 91.44 - 60.96 - 91.44cm.

Ed (remembering when models weren't anorexic)