Metric vs Imperial or vice versa

[rake60]

It's not like some waring faction.

John your post made me remember the first time my wife went grocery
shopping here.

She is from Canada.
She went to the Deli in the store and asked for 1/2 kilo of sliced baked ham.
The kids working the Deli looked at each other as if they had been invaded
by aliens!
Sad part is there is a button on that scale that converts it to metric.
They didn't even know what it was for... :

She's domesticated now.
Last time we went to Canada she was giving my stepson he77 for driving 100MPH!
He calmly answers "Mom that's klicks not miles." LOL

Rick

 

[Rog02]

Bold statement. Can you explain what you mean?

The original concept of the metric system was to establish the length of measure that would be equivalent to 1/10,000,000 of the distance from the equator to the geographical north pole. From that standard, the rest of the metric system would be derived. The following is quoted from the SIZES website. For the complete text please go to http://www.sizes.com/units/meter.htm

Measuring the quadrant

Obviously it would be impossible to survey the distance between the North Pole and the equator, the whole 90°. No one had ever been to the North Pole. But if one could measure a significant piece of a meridian, the rest could be calculated. The two ends of the line to be measured had to be at sea level, and somewhere near the middle of the pole-to-equator quadrant. As it happens, there is only one such meridian on earth: from Dunkirk to Barcelona, which covers about a tenth of the distance from the pole to the equator. The distance lies almost entirely in France, which did not escape the French, nor indeed such impartial observers as Thomas Jefferson.

The survey was put in the hands of P. F. A. Méchain and J. B. J. Delambre. (See map; caution, 1.05 MB file.) In the summer of 1792, Delambre began working his way south from the coast near Dunkirk, while Méchain started north from the Mediterranean. They would meet at Rodez, 300 miles south of Paris. Méchain's share was shorter, but more difficult, for it crossed the Pyrenees Mountains that separate Spain and France. In September the Republic was declared.

The French revolution was soon in full swing. Within a few months France was at war with Great Britain, Austria, Prussia, Holland and Spain; Louis XVI had been executed, and Parisian mobs were massacring various groups. The Terror was not far off. In such a climate the surveyors were regularly arrested. The flags on their survey poles were white—the color of the royalists! They were from Paris. All they had going for them was that their story—we are measuring the distance from Dunkirk to Barcelona—was so unbelievable in the midst of war and revolution that no real spy would have used it.

Once when Delambre was seized his captors compelled him to make his explanations in the most republican way, to an audience of volunteers on their way to the war. The troops did not find the trigonometry lecture entertaining. Delambre was saved from the crowd by an official who took him into protective custody, and was eventually released only because the National Convention ordered it.

On August 8, 1793, the National Convention abolished the Academy of Sciences as unrepublican. The Committee of Public Safety, however, remained intent on doing away with the old feudal measures and needed the help of the Academicians to do it, so it persuaded the Convention to create a new, independent temporary commission (Commission temporaire des poids et mesures républicains) with the same members. In November Lavoisier was arrested; the commission asked for his release; the Committee of Public Safety responded by kicking five more members off the commission, including Delambre. Seeing which way the wind blew, the commission then devoted itself to preparing revolutionary denunciations of the old weights and measures. Delambre thought they should kill the whole meridian-measuring project and just accept the provisional meter.

But war requires maps. A military cartographer who was also a Jacobin was put in charge of map-making. Needing trained people, he brought Delambre and Méchain back to Paris. (Méchain had prudently withdrawn to Genoa, narrowly escaping pirates.)

On April 7, 1795 an order establishing the names now in use (meter, liter, gram) also reestablished the commission (except for Lavoisier, who had been guillotined the previous year) and ordered resumption of the survey.

Delambre finished his portion in the fall of 1797. But Méchain had yet to reach Rodez. Sick, with winter coming, he wrote to his colleague, “I will sacrifice everything, give up everything, rather than return without completing my part.” And so the survey stalled. But Méchain recovered and resumed work; in September 1798 he reached Rodez.

To this point, except for the sides of two triangles, only angles had been measured, the angles of contiguous triangles stretching all the way from Dunkirk to Barcelona. If any side of only one of these triangles were known, the dimensions of all the others could be calculated, and from them the distance along the meridian. While Mechain labored in the south, Delambre measured one of the baselines with a special ruler. It took him 33 days.

On November 28, 1798, the French convened an international meeting of experts from friendly powers and puppet states. One of the meeting's committees consisted of four persons, each of whom independently calculated the length of the meter from the measurements made by Delambre and Méchain (and from certain assumptions about the shape of the earth). Their calculations agreed. The meter was established at 0.144 lignes of the toise de Perou shorter than than the provisional meter.

Today the length of the earth's quadrant can be measured relatively easily by the use of satellites. Such measurements show that the meter is actually about 1/5 of a millimeter shorter than one ten-millionth of the earth's quadrant. The startling thing about this fact is not that the meter does not conform to its original conception, but that two 18th century surveyors should have come so close.

As a side note Marv, metric time is still common in the repair industry. A day is still 24 hours in length except the hour is divided into 100 units (referred to as time units). It makes calculating billable hours much easier. :big: Americans tend to do the same thing except the hour is divided in tenths.

 

[whatsit]

Been away from computers a bit and missed everyone.
So here's my .02

I remember back when Jimmy Carter was president and decided we were going to convert to metric I
must have been about 12.
The main issue I saw then was everyone was trying to convert imperial to metric or metric to imperial
which made it more confusing than just going metric. After I was out of the Army I went to work doing
construction. I worked for a company that wanted to see if building houses using metric would be any
faster or easier for the carpenters. They gave us all metric measuring tools and the plans and we went
to work. We did find it was quicker and easier to do the calculations in our heads. And for me that was
plus. I am quite capable of working with fractions but do convert them into decimal because it is easier.
As far as what Marv says about the average person and math or measuring below 1/4 inch is pretty close
to the mark. My kids wouldn't know how to measure much of anything if I didn't have them help out in the
shop once in a while. The shop classes they took in school were a joke they didn't even have micrometers
available in the metal shop. Sorry for dragging away from topic.

In summary: I have to use imperial for most of the things I do. But the experience I had using the metric
system in construction showed me how easy it is. I still have my tools from that job and have built many
things using them.

Speaking of math I have to thank MarvK and his different calculators or I'd be up a creek. One of my kids say
that's cheating because I made him learn the calculations on paper before I let him program them into his calc.
Needless to say my kids are better at math than me.

Have a good day
KevinF

 

[mklotz]

Roger,

I guessed that you would drag out this old chestnut of a misconception.

Yes, it's true that the French, being children of the Enlightment, tried to tie the length of the meter to a quadrant of the earth. Although they did a surprisingly good job of measuring it given their primitive instrumentation, they were off a bit. (In reality, it would be very difficult to make this measurement with high accuracy today.)

But, what you fail to understand is THAT NONE OF THIS MATTERS. The French could have chosen any old length for the meter because, once the length is established and everyone agrees to use it, it becomes the STANDARD, the length against which everything else is measured. The idea that there is some 'accuracy' associated with a primary standard is nonsense. Standards are the things that determine accuracy - that's what traceability is all about.

The only "flaw" was in French surveying. The system of measurement they established is perfectly valid.

As an aside, the only real requirement for a primary standard is that it can be reproduced accurately. We don't want to travel to Paris to calibrate a secondary meter standard so we define it in terms of a time and monochromatic light. That way, any well-equipped laboratory can generate a secondary standard without reference to the primary.

 

[shred]

As an aside, the only real requirement for a primary standard is that it can be reproduced accurately. We don't want to travel to Paris to calibrate a secondary meter standard so we define it in terms of a time and monochromatic light. That way, any well-equipped laboratory can generate a secondary standard without reference to the primary.

Have they redefined the kilogram yet, or do people that really really care still need to pop by Paris every so often with theirs to check?

The key to the metric system is the divide-by-ten and multiply-by-ten. It doesn't matter all that much what the actual standards physically are (though I believe some of them aren't particularly intuitive to human psychology, that's another issue entirely)

Interestingly, the binary base-two system drives digital logic. There were early experiments with base-10 electronics that just didn't work out, and now here we are, talking about decimal inches and base-ten systems on something that at the core of it could be thought of as a fractional device (just don't mention the associated ugliness of applying SI prefixes to powers of 1024) ???

 

[mklotz]

AFAIK, the kilogram standard is still a lump of metal in Paris. It will probably remain that way until we figure out a way to count individual atoms into a container.

People tend to confuse the metric system with its decimal properties. That's not correct. The real advantage is that there is only one primary standard for each dimension and all subdivisions are obtained in an orderly manner by using well-known prefixes. I said earlier that the Imperial system could be fixed (but it isn't worth doing). If we had a bunch of prefixes (e.g., half-, quarter-) and calibrated lengths in half-feet, quarter-feet, etc.. the system would be more rational, albeit computationally difficult for a populace who can't add fractions (a problem unanticipated by the people who construct measurement systems - nobody thought mankind would get dumber).

Roger claimed he was using metric time because the hour is divided into 100 parts.
That's decimalization, and has nothing to do with the metric system. It's a subtle distinction, but one worth understanding.

I guess my question is: If traditional measures of convenience are so wonderful, why did the English, who so love tradition, decimalize their money?

 

[Bogstandard]

This post has really got exciting, I am really glad I resurrected it.

I am sitting in the sidelines and soaking it all up, it is so nice having a post where everyone has their own little ideas about the things we do and how it affects us, without falling out over it. Wonderful.

I never realised that this would generate so many points of view, and bring to the fore how we all cope with the problem, and also how people would like it to all end up. If only politicians and people in the know could get together and sort something out.

Marv, to answer your point about going to a decimal monetary system rather than the coconut bartering system we had before.
I am sure it was the foresight of the money men in the country, when they saw that eventually, with the coming of better communications and money handling systems, we had to get onto the bandwagon, otherwise our antiquated monetary system just wouldn't be able to be handled by the worldwide community stock markets. Just try adding and subtracting our old pounds/shillings/pence on a pocket calculator. It is almost impossible without converting it to a decimal in the first place.

So why not miss out the middle bit?

This might also be a good reason why the metric system is better than the imperial one. It is just a matter of tens and bigger tens with lots of zeroes on the end. Exactly as imperial is when converted to decimal to work with, like the imperial users do on here.

So why not miss out the middle bit?

I am sure that if the fraction element of imperial was somehow phased out, and the thousandths (mils) system used, it would then be an easy step from imperial to metric, as people would already have an understanding of the 'tens' system.

Even though I mark my sketches on here for a fractional system (so it can be understood by all imperial users), if I was doing a drawing for the UK market, in imperial, it would be marked up in decimal, because nowadays in the UK that is the way it is understood. Imperial fractions are very rarely used any more.

John

 

[mklotz]

John,

"Coconut bartering" - I love it. And, for all I know, you had an ancient coin called the coconut - probably worth 27 shillings or some such just to keep things confused.

As I mentioned before, my experience with the old money was that the natives had as much problem with it as we visitors. Given the decline in education, I think the situation would be desperate today if you still used it.

I wonder too how much it harmed your not insignificant tourist industry. I know I had several Americans tell me that they didn't want to visit England because they thought the money system was designed to cheat them.

Decimalization can't save us from the products of of our self-esteem oriented education system. I recently bought something and the bill totaled $9.57. I gave the (18-20 year old) girl $10 and seven cents. She was dumbfounded and called her supervisor to help. It took about five minutes before the two of them presented me with $1.50. I laid the dollar on the counter and told them it was a tip. They were ecstatic.

And yes, I share your pleasure about the way this thread has gone. It's a divisive topic because it's not well understood and I've seen it turn to bitter ad hominem attacks on other fora. Everyone here has been very polite and gentlemanly.

 

[rake60]

The more I think about the Metric vs Imperial the less significant it seems to me.

Of course there are "Scale Dimensions" on every print.
If it's an Imperial dimensioned print that means + or - 1/64" or .015"
If it's Metric that means + or - .3MM or about .012"

Now take a look at a critical dimension such as a bearing fit.
If the bearing bore is 6-3/4" the dimension on the print will be 6.749" + 0.00" - .0005"
Should it be a Metric size, say 172MM the print dimension would be 171.97MM + 0.00MM - .001MM
The numbers may be different, but the sizes are not.

I work off of Metric prints that call for sizes of a nominal 38.1MM and 50.8MM
That looks like an odd size until you do the math. It's 1-1/2" and 2" just in a different format.

Is there a difference in those sizes?

Rick

 

[Bogstandard]

Marv,

It wasn't the monetary system that caused the cheating, it was the London attitude of being able to confuse people with the system, and take advantage of the poor tourist and so rip them off. I would doubt if that would happen in almost any other city in the country.
I stopped going to London after I was charged in a private car park £20 ($40) for three hours parking. The municipal car parks aren't much cheaper.

Rick,

You have hit the nail square on the head. Imperial and metric are compatible.

John

 

[Loose nut]

The part that makes changing over from Imp. to metric is that they rationalized it to far. As an example, pressure used to be measured in kilograms /sq centimeter now it's a pascal, force now uses Newtons (not the fig kind). When I learned the metric system in school (just because I hate it doesn't mean I can't use it) everything was spelled out for you, now you have to remember what the definition is of what you are measuring with, this just added another level of confusion to an already confusing problem. This rationalization was fought against by the scientific community but without any luck.

Doesn't any body know how shotgun bore are measured in Metric.

 

[zeusrekning]

I put more thought into it yesterday to see what my prejudice was. It was hard and still is for me to remember the prefixes. With my ignition I kept having to look up Milli and micro when calculating amperage's.

 

[shred]

...
Doesn't any body know how shotgun bore are measured in Metric.

Same old "gauge" (or "bore") as used everywhere I've been in Europe and S. America.. Maybe there's a metric standard somewhere, but nobody uses it.. Ammunition designations are one place you don't want to rely on the stated number being anything close to what reality is.. "7mm" really means .284", 9mm bullets aren't quite 9mm in diameter, 10mms are ~10.1mm, etc, etc.. You never have to convert between them, so it's not really a problem once everybody learns that, like 2x4"s or 2" water pipe, nothing actually measures the stated dimension, it's just a naming scheme.

 

[gilessim]

I mentioned before that ,here in Italy , that the plumbing fittings are still in whitworth ,inches or "pollice"meaning Thumbs, tubing and everything else, is metric!, odd isn't it?

BTW I have noticed that trains here run on the left like the UK, presumably because we invented them!!!

I'd be curious to know on what side the trains run in the States, can anyone enlighten me?

Giles

 

[gilessim]

I don't know much about diesels but I know that most spark plugs are Imperial because Champion set the standards. I grew up around cars and worked part time in a friends autoparts store when I was a kid but there were never many diesel motors around in the UK (diesel always cost about the same as gasoline but people never really caught on that you did more miles with a diesel engine!) I can only imagine that it was decided to use the same spark plug threads for the injectors to make things "simple"!.

Giles

P.S. hope I didn't open a can of worms here!

 

[Circlip]

Fractions are not used over here any longer John cos the kids don't understand them. But as far as the metric system is taught in schools over here, have you tried talking to them about millimetres?? They're taught in centimetres. Decimalisation created its own problems as well. It all started degenerating from that time, that's when the numbers on cash register keys changed to pictures of the items being bought. Ian.

 

[mklotz]

The original metric system had successive units separated by a single power of ten, e.g., 10 mm = 1 cm, 10 cm = 1 decimeter, 10 decimeter = 1 meter. With the introduction of SI, a bunch of pundits, somewhat detached from reality, decided to go to what is called 'engineering notation' where successive units are separated by a power of ten that is evenly divisible by three, e.g., 1000 mm = 1 m, 1000 m = 1 km. Units like the centimeter and decimeter don't fit into this 'enlightened' scheme so their use was frowned upon in the 'official' version of the metric system (although, obviously, they remain perfectly valid measures).

In my opinion this was a grave mistake. The man in the street can't comfortably work with numbers much larger than ten. It's arguably easier for him to visualize 2.5 cm than it is to visualize 25 mm. Perhaps that's why the medical profession here in the States continues to use centimeters.

Abandoning these perfectly legitimate intermediate units like the centimeter seems inconsistent with other SI attempts to make the metric system more usable. Nobody who works with forces wants to say kilogram-meter-per-second-squared over and over again so that's been named a Newton. The pascal is a tiny increment of pressure so the bar was defined as 100000 pascal. (By happy circumstance, 1 bar = 14.5 psi, or almost atmospheric pressure.) If we're going to have these more usable names for these compound units, why not retain the other intermediate fundamental units like the centimeter?

Finally, zeus was complaining about not being able to remember the accepted prefixes.
My UNIT program has a complete list of them available with a single key press. I've reproduced the list here for those interested.

YOTTA 1E+024
ZETTA 1E+021
EXA 1E+018
PETA 1E+015
TERA 1E+012
GIGA 1E+009
MEGA 1E+006
MYRIA 1E+004
KILO 1E+003
HECTO 1E+002
DECA 1E+001
==================
SEMI 5E-001
DEMI 5E-001
DECI 1E-001
CENTI 1E-002
MILLI 1E-003
MICRO 1E-006
NANO 1E-009
PICO 1E-012
FEMTO 1E-015
ATTO 1E-018
ZEPTO 1E-021
YOCTO 1E-024

 

[shred]

Marv's table reminded me of a vendor visit not long ago (I work in the high-tech industry). They had a demo showing off how they could detect tiny amounts of capacitance-- you could hold your hand open about a foot (sorry, 30cm.. IMO intuitive units should be comfortable to hold in one hand) above the detector and it could determine the distance, angle and tilt of your hand-- which is about an atto-farad's worth of capacitance changes. I'd not knowingly run into a measured atto-anything before or since (FWIW, in one atto-second a beam of light would go about the distance of 3 hydrogen atoms.. )

 

[Jadecy]

This is indeed an interesting thread.

Being from a EE backgrounda and currently employed as a business system programmer I always remember kilo, mega, giga and mili,micro,nano, pica. In programming kilo doesn't mean a true 1000 because of binary. It is in actuality 1024. I also do a lot of work on cars which is where the following comes from:

I don't really care what is used as long as it is consistant. Anyone that has ever worked on an "American" car (ie. pontiac, chevy, gmc, ford,...) knows exactly what I am talking about. I've worked on a lot of Honda and Toyota products and you can practically disassemble them with a handful of wrenches. All metric by the way not that it matters. By the time you take anything off of a pontiac or ford you have more than half of your tools out of the tool box and I'm talking about a large toolbox with deep well and shallow well sockets, boxed end, 12 points wrenches for thse special head bolts, open end, torx bits, allen wrenches,...and they are all mixed metric and what used to be called "standard". I think they try not to use the same type of bolt twice on the vehicle.

Sorry about the rant but that is what I've seen over and over again in "american" manufacturing.

Give me fractions, decimal, metric, inches, hooblongs, or whatsits I don't care but DO NOT mix them on a single drawing, a single device, or a manufactured item!

 

[shred]

Marv and others with a mixed toolbox will get a chuckle out of this...

So I'm at home this afternoon, out sick from work (thus I blame the cold medicine for the following) and as I'm in-process of repainting my old lathe, decide I feel well enough to strip it down a little more. Next thing to come off is the motor.. held on by 4 largeish bolts. So I go to the toolbox and grab a selection of wrenches that are handy and look about right... 14mm, 12mm.. the 13 isn't handy, but I take the two over to see.. 14's too big and 12's too small.. dangit.. well, no sign of the 13.. here's a 1/2".. might be cheating, but it's only 4 bolts, right?.. hey, this 1/2" fits pretty well, it won't booger up the heads too bad... About two minutes later I remember I'm unbolting the original motor from a 1930's-era US-made lathe.. :