# Metric vs Imperial or vice versa



## Bogstandard (Apr 5, 2008)

This is a follow on from a little heads on a few days ago over metric vs imperial.

I thought I would like to transfer it over here so people can have an easy say and express their own views on the subject.

I won't say things like, I use it because that is all I have ever used.

So lets have a good discussion on the subject, and if you can keep it from getting too technical, maybe some more people will get involved.

So I will start it off.

I used imperial almost exclusively for nearly thirty years. I was taught imperial in school and all my technical training, my first major encounter with metric was when I had to work on 'foreign' aircraft, and only then did I realise what a simple and accurate system it was.

It was a rather difficult time, one side of the hangar was in imperial (old Bell and Sikorsky helicopters (American design)), and the other side was in metric (new French 'Aerospaciale' helicopters), and I was expected to swap between the two at a moments notice. So after a time it became a natural progression that I could work just as easily in both, but keeping both totally separate.
It wasn't until later, when I went to work for a UK based American company that I had to relate to both at the same time, as we were making metric products for worldwide distribution based on an American imperial system. So I had to become pretty slick at quick conversions in my head to keep up with the design engineers (both English and American, one using metric, one imperial).

So basically I was lucky and it was forced onto me, and I had to learn to run both sets in parallel.

What do I prefer? 
I use both as required, but if designing something I would almost always prefer metric, just for the ease of use and slightly better low down accuracy. There are times when I would like a bit more of a thread choice on fasteners, purely because of availability, metric fine and superfine are very hard to come by in general model engineering sizes. But I usually cope with what is available.


Now let us see your thoughts on the issue.

Are there definite proveable advantages of one over the other?
Why don't you like one or the other?
Can you work easily with both, and how do YOU do it?
Why do you struggle with the conversion?

If we can get a few answers on this one, maybe we can help a few people cross train on the two systems, and maybe make a bit of a tutorial so people can learn to cope with two totally different systems.
So all you have said in other posts can be brought here into one clear reference point.

Metric & Imperial John


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## rake60 (Apr 5, 2008)

As far as turning maching goes, I don't have a preference.
The measuring devices at work and at home are all Imperial
but the conversion is easy.

A size is a size. 
There's no difference in hitting or missing 1.035" or 26.29mm

Milling is a little different.
Imperial size cutters and end mill are more easily found locally.
That is still not a limiting factor if one is wanting to stay Metric.
ie: To cut a 10mm slot, use a 3/8" end mill then shift .00095" 
in both directions to take the slot to width.
For the purist that WILL make the slot .0003" or .0007mm too wide.
If your measuring skills can show that you are a far better machinist than me!

It may be comparing apples to oranges, but it's not fitting
square pegs to round holes. 

Rick


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## Tin Falcon (Apr 5, 2008)

bogs:
  I think like most here I am most comfortable with imperial measurements because that is whet I learned and What I am used to . Like I mentioned before there was a big push while I was in High School to learn metric because the US was converting. To a certain extent metric is used more in the US than years past. 
I use imperial in the home shop. 
I do run into situations at work when there are mixed hardware on the same piece of equipment it is weird because we have to stock two virtually identical parts the only difference is one is a metric thread the other a UNC. 
I do agree that the metric or SI system has its advantages. for instance 1ml = 1cc = 1 gm of H2O at room temp.So a litre of water = a kilo it is hard to relate such thing with imperial measurements without a bunch of charts or memorization. 
If you think about it most of us have to use both to some extent most tool sets have SAE and Metric sizes in them. 
Tin


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## zeusrekning (Apr 5, 2008)

My input here is only on metric versus imperial linear measurments. Not mass, volume or any other as I rarely use. My mind pictures 1inch better than it does 1cm. I think for what we do it is 1" in one hand 25.4mm in the other  . I do like what I have seen with Michelins prints as far as tolerencing. I am assuming this is a metric thing??? For a certain fit hole you may have an S7 fit. (working from memory here) You look up the fit called out and the range your dimension falls in and it tells you the tolerance you need. 
If a print says 1/4-20 versus m6x1 it matters none. I only think it is of concern if you are designing something. Then you must chose one to go with. Then I choose imperial for availability of material and tooling. I was recently told that alot of error can be made in the conversion from one to the other. but for what we are doing 
I can't understand other than calulating mistakes?
I think it was our way of being different from Europe.
Tim


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## Hilmar (Apr 5, 2008)

Hi Tin


> I do agree that the metric or SI system has its advantages. for instance 1ml = 1cc = 1 gm of H2O at room temp.So a litre of water = a kilo it is hard to relate such thing with imperial measurements without a bunch of charts or memorization.



Hi Tin. I think that is at 4 deg. Celsius
Hilmar


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## Bogstandard (Apr 6, 2008)

So what sort of ratio is it in the US now, between all metric or imperial?

Is major industry still holding onto the imperial system, or is it catering for the metric world and just a little bit for the home market?

What would really happen if your government did as ours did and said say, you have two years to go totally metric?

It has happened twice in my lifetime, once when we changed over to decimal currency, and then inflation spiralled out of control because we got rid of the very low denomination coins, 480 x 1/2 pennies in a pound, instead we ended up with 200 1/2 pence in a pound, so overnight if something went up, it went up by at least double what it used to. We had a time when both pounds/ounces and kilos were displayed on all packaging and loose items for sale. Most of the population didn't know what weight they were buying half the time. Then it went to all kg's, but recently we have just won back a concession from the EU to display pounds and ounces again, but I think it has gone too far now.

Even though we are supposed to be metric, all tooling can be obtained in either, mainly to cater for the older generations.

John


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## steamer (Apr 6, 2008)

Hi Bog,

In my "high tech" company where I work we design with english dimensions and pins but metric fasteners.

This appears to be fairly normative.......at least for me for the last 15 years.

Dave


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## Loose nut (Apr 6, 2008)

On this side of the pond (Canada) the scientific community went metric a long time ago because thats the world standard so did the military because metric is the Nato standard. The automotive industry has been shifting over probably because there is more influence from Asian car companies but for the most part everything else is still imperial. Carpenters still use 2 by 4's even if they are actually 50 by 100 MM, tape measures are in inch's, industry (at least were I am ) still uses imperial. Kids come out of school only taught Metric and when they get into the real world the are lost, they don't know what an inch is. 

The government tried to force metric on us like they did in Britain but they were taken to court and forced to retreat so people use what they want. The government uses metric, mileage is in kilometers, gas is in Liters ( it doesn't have to be but the gas companies had changed there equipment over at great expense and weren't going to do it a second time) but everything else could be either one.

As for the US changing over, don't hold your breath, the average person doesn't see why they should change (I agree with them on this) and they have a big enough portion of the world economy that companies will cater to them. Some Asian companies have changed there fasteners from metric to imperial for the US market and even in the shop equipment area lathes and mills are now made with proper imperial lead screws instead of the kludgey hacks (imperial dials on metric lead screws) that were available years ago. 

The US will have a far higher percentage of Imperial measurements than we do and any change over will be slow. You can get Metric tooling but you have to go to a industrial supplier and it ain't cheap.


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## Powder keg (Apr 6, 2008)

I agree that metrics are easier to use. But me being a full time Machinist in the U.S.A. Inches is what I use every day. The place I work at doesn't supply my tools for me. I have drawers in my tool box that have over $1000 dollars worth of tools in them. It would be tough for me to pitch everything and start over. So for now i'll just convert everything that I need to do in the metric system. Like Rick said, a size is a size.

Wes


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## mklotz (Apr 6, 2008)

Bogstandard  said:
			
		

> What would really happen if your government did as ours did and said say, you have two years to go totally metric?




If the USA forces the metric system on the man in the street, the net result will be that Americans will have two measurement systems they don't understand.

One of the common American counter-metric arguments is that they don't need a new system since they understand the one they have. For most people that simply isn't true. Many people can't read a ruler to closer than a half-inch. Housewives can't puzzle out how to make half of a recipe if it calls for something like 1-1/2 cups of flour. I've had grown men ask me how many feet there were in a (100 yard) football field. Hardly anybody knows how many feet there are in a mile offhand. Consumers happily accept the advertising hype of a 7.5 horsepower shop vacuum that can be plugged into a 115 volt, 15 amp wall outlet.

Americans feel very threatened by any form of standardization - particularly so if it's a system that wasn't invented here. Many feel that some part of their freedom will be stolen if they utilize a denotation that makes sense. It's a bit like the furor raised by the peasants when Pope Gregory decreed that the day after 3 Sept. would be 14 Sept. (in the switchover from the Julian to Gregorian calendar). They were convinced that they'd been robbed of eleven days of their lives.

Fear of standardization if further complicated by the abysmal level of mathematics education here. Americans will do just about anything to avoid having to learn something about math - even the trivial arithmetic involved in day-to-day life. One of the vaunted advantages of the Imperial system is its "more natural" use of power-of-two fractions (1/2, 1/4, 1/8) etc. yet ask someone how much 3/8 + 5/16 inch is and you'll get answers that range all over the map. Even armed with a calculator, few can do such simple computations.


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## Bogstandard (Apr 6, 2008)

I hadn't realised that metrication was so far advanced in the US, even though it is still being rejected.

Marv,



> One of the vaunted advantages of the Imperial system is its "more natural" use of power-of-two fractions (1/2, 1/4, 1/8) etc. yet ask someone how much 3/8 + 5/16 inch is and you'll get answers that range all over the map. Even armed with a calculator, few can do such simple computations.



It was because of the fractions that I mainly went over to metric, what you see is what you get. No converting say 1/4" to 0.250". Fractions just 'got in the way'.

0.63mm + 1.18mm is a straight decimal addition.
3/64" + 7/8" is a nightmare if you're 'not with it'.

I have to agree with you on the way maths is taught. In the schools in my area, calculators are now banned, in the hope it will force kids to use their brains.

John


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## shred (Apr 6, 2008)

IMO USA-ians like me (well, I'm partly British  ) can and do get used to metric this and that no problem-- we buy soda in 2-liter bottles, cars are advertised with '4.6 liter' engines, and so on-- nobody really cares what the milk jug says on it, they know they get the big size and all is well. Speedos read KM/H as well as MPH and nobody really cares for the most part. Building materials are already nothing like the stated size anymore and everybody knows it. Every mechanic has two sets of wrenches, etc, etc, etc.

IMO the biggest day-to-day resistance would be temperature. Fahrenheit has extremely goofy endpoints, but it does one thing well-- the scale is large enough that in the range of normal human existence, five degrees one way or the other doesn't matter much, but ten does. The size of a Celsius degree is a poor fit to weather, psychology, and human comfort levels.


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## mklotz (Apr 6, 2008)

Shred,

With all due respect, what you describe is not "using" the metric system. You're being "exposed" to it, but not in a way that forces you to manipulate it and thus become proficient with it. While exposure is useful, it will never lead to adoption, much less understanding.

The Fahrenheit scale is indeed another Imperial idiocy. And you're correct in saying that the Celsius degree is a bit large. So simply read the Celsius temperature to a half degree. 0.5 degC = 0.9 degF. The idea of dealing with non-integer temperatures should be comfortable. After all, the human body temperature is 98.6 degF, and we don't round it off to 99 degF. 

I am glad to see that some of the responders in this thread are mindful of the fact that the metric-Imperial debate encompasses far more than the linear measurement which is the primary feature in the workshop.

John,

I spent a lot of time in England when you were using the old money. I simply loved the fact that luxury goods were priced in guineas and there wasn't a guinea bill. I used to count my change after each transaction and soon discovered that it was frequently wrong. However, it was just as likely to be an error in my favor as vice versa. I came to the conclusion that the British were just as confused by their system as I was.


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## zeusrekning (Apr 6, 2008)

> I've had grown men ask me how many feet there were in a (100 yard) football field. Hardly anybody knows how many feet there are in a mile off hand.



No matter the system used some people will never be able to comprehend it. I can't say I remember how many feet are in a mile (5280???) but when I played with drag racing I had no problem remembering then. But I can tell you approximately how far a mile from my house is. I seldom use fractions. If I design something I use decimals of an inch. If I am building something structural I use fractions if it is say 1-1/2" angle. I would prefer metric if I was more use to it. But like I said your going to have people who just can't get it no matter the system.



> Americans feel very threatened by any form of standardization - particularly so if it's a system that wasn't invented here. Many feel that some part of their freedom will be stolen if they utilize a denotation that makes sense.



I think that responce is the best answer to Johns question. 
Tim


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## shred (Apr 6, 2008)

mklotz  said:
			
		

> Shred,
> 
> With all due respect, what you describe is not "using" the metric system. You're being "exposed" to it, but not in a way that forces you to manipulate it and thus become proficient with it. While exposure is useful, it will never lead to adoption, much less understanding.


Yeah.. I guess the point there was people really don't care for the most part and don't actually use either system, to use your term. They know the size of the unit they want and get it like that. If they want less, they ask for half that or maybe a quarter of it. People can mentally half and quarter pretty well (it's a half of one half after all), but tenth-ing is much tougher IME. 

Somewhere I have an antique square-shanked drill bit marked with a size of 12/32". Interesting concept there.


> The Fahrenheit scale is indeed another Imperial idiocy. And you're correct in saying that the Celsius degree is a bit large. So simply read the Celsius temperature to a half degree. 0.5 degC = 0.9 degF. The idea of dealing with non-integer temperatures should be comfortable. After all, the human body temperature is 98.6 degF, and we don't round it off to 99 degF.


The problem is with the weatherman. 'highs in the mid 80's' is convenient and accurately represents the variability inherent in weather forecasts and locations. Even the F-experienced Europeans I talked to in France preferred having a finer-graduated scale than C for day to day weather.


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## mklotz (Apr 6, 2008)

That's my point. Americans can only deal with whole numbers (and then not well). Any fraction, no matter how expressed (e.g., 0.5, 1/2) is beyond their feeble ability to deal with anything remotely numerical. Even the bible has pi rounded down to three.

Have you noticed that, on American TV programs, any large dimension must now be converted to "football field lengths" in order to make it understandable to the cretins? And it's never "as long as three and a half football fields". It's always "almost as long as four football fields". I'm surprised that our national unit of measure isn't "one NASCAR track circuit".

We don't live in an integerial world and no amount of farking with measurement systems will eliminate the need to use non-integerial numbers. The world is irrational (both mentally and mathematically) and we need to learn to deal with it.


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## nemt (Apr 6, 2008)

I never understand the discussions on Metric/Imperial. Why not let everyone do what he likes to do but especially enjoy beiing a modelengineer!!! 
I build in metric but sometimes I make things with iomperial threads because it is a casting set from Great brittain. Very difficult and expensive to buy the for us special tools.
Thats why I prefer Metric. 
In the time I was an apprentice in a very big factory, called Stork, I learned to work in Imperial to. Now thats over in Europe. 
It are only older engineers who put these things to discussions over and over again.

Keep building and enjoying, not discussing.

Nemt


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## mklotz (Apr 6, 2008)

Nemt,

I don't think that the intent of this thread is to advise anyone to do anything.

It's patently obvious that each member will do as he wishes in his own shop and that's how it should be. We're not trying to change that.

John started this thread (read the first post in the thread) to provide a platform for discussing the issue with the idea to elicit viewpoints to aid understanding.

I think that was a fine idea because, at least here in the States, most people have only a very narrow view of the problem, and that not well understood.


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## Tin Falcon (Apr 6, 2008)

Marv:
   I have had to use both enough I have a pretty good working knowledge. between practical trade applications and basic science /engineering courses on the metric side. 
A few weeks ago the question came up of how much a tank full of synthetic oil would weigh. Fortunately I knew enough to figure it out given the density of the liquid (in pounds per gallon) and the weight of the empty tank. I knew from training and experience the formula 
for the volume of a cylinder and that there are 231 cubic inches in a gallon. 
 Sad to say you are right that many Americans do not understand either system. I have heard people express a measurement such as 5-1/2 inches plus a line what up with that. At one point I worked in a steel fabrication shop. The unofficial lead man in the shop was a retired dentist. So a doctor that had a 4.0 gpa in college. 
Yet this guy, as smart as he is could not add fractions to save his life without a construction calculator . I usually added in my head then checked on paper. Or soapstone on the steel table. I do not own a construction calculator. 
Also most people have no clue how to convert ounces to decimal pounds. For an experienced machinist it is easy. An once is 1/16 of a pound or .06. 
   One day I was in a home improvement store, the one with lots of blue signs. The manager asked me where he could get a metal yard stick. I should have told him Home Depot LOL. Another time a meat manager of a supermarket asked what level was. Some folks are just plain clueless!!
Nemt:
   Definition: Forum - a public meeting or assembly for open discussion. Also this is the break room the place to talk about whatever. The only stipulation is that the topics are suitable for women, children and pets and that the discussions remain friendly and respectful.
Tin


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## mklotz (Apr 6, 2008)

Ok, here's a test for those of you who love the Imperial system. See how many of the following questions you can answer without consulting any reference sources.

1. When one speaks of a 12 gauge shotgun, what does the "12 gauge" refer to? 

2. Which number comes closest to answering the question, "How many definitions of the unit "barrel" are used in the USA?" - 1,2,5,8,12,22

3. In the USA, energy is measured in ft-lbs and torque is measured in lb-ft. Does that mean that energy and torque are the same thing?

4. How many pounds does a (British) cwt (hundredweight) weigh?

5. True or false: In steel wire gages, the higher the number, the thinner the wire.

6. Does an (American) pint of water really weigh a pound?

7. In the Imperial system, which of the following are names of legitimate units?
	grad, sack, minim, pinch, mil, turn, oscar, point, jereboam

8. What's the major OD of a 0000-160 screw?

9. Is the Imperial pound a measure of mass or of force?

10. Is a fluid ounce (floz) a measure of weight or of volume?


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## rake60 (Apr 6, 2008)

Well Marv I do know one answer off hand.

A shot gun gauge was determined my the number of lead balls the diameter of the
bore that it would take to make 1 pound. 

The rest of them I'd have to look up.
I've never run into any of them in my home or work machine shops, but it's
still interesting reading. 

Rick


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## Bernd (Apr 6, 2008)

The place I used to work built gear cutting machines for the world car makers. Had to work in both imperial and metric. The hard part was the "metric angles". They threw me for a loop.

Prefer to work in imperial since all stock is available in imperial sizes. If, and this is a BIG "if", I build Bog's twin piston steam engine I'll have to give metric a try since it's all dimensioned in metric.

Oh and the other thing that was tough was the electric. 60 cycle imperial and 50 cycle metric.  :

Bernd


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## Bogstandard (Apr 7, 2008)

I am learning a lot here about the way the US system works.

How I understand it now.

The layman in the street has great difficulty because of the fraction system, never having been subjected to the 'other' side of the imperial system of thousandths (millies as I think you call them). If it comes to more than how many fingers and toes, they are out of it.

The engineering side works in both fractions and decimal imperial. So basically the tech minded are working in a basic metric system to begin with, so can swap over easily to full metrication. They understand the metric system, so maybe the stumbling block is the direct conversion between the two different sizes.

--------------------------------------------------------------------------------------

So I will explain how I do the basics, and you can elaborate on my methods.

For rough guesstimations I use the standard - 

1" equals 25.4mm and 1mm equals 40 thou (0.040"), and vice versa.
So 0.1" = 2.54mm and 10mm = 0.40", slightly out but it gets me near enough.

I find that this gets me within striking tolerances of what I am doing, and can easily be done mentally.

If I want to go to much tighter tolerances, I then refer to my little pocket bible.

So I don't have to use a supercomputer of a brain to get to where I am going.

I just remember three things, the two calculations above, and where the hell I left my little book.

So to summerise, I can get near enough with what I have got in my head, with a little bit of extra maths, and to reach final size, twiddle the knobs on the machinery, and measure it.

I could at one time convert large numbers either way in my head to within a thou of where I should be. Now that one of my two brain cells has gone missing, I find that the above is all that I require.

It might seem that I have over simplified things, not true, this is all that is required for getting the job done in what we are doing here.

Now about deg F to deg C. I multiply deg C by 2 and add 29. The other way around, subtract 29 from deg F and divide by 2. If you need it closer than this, you are in the wrong business.

Just like the piece of string for a weather forecast.

Hold it between your thumb and forefinger.

If it is swinging side to side, it is windy.
If there is water dripping from the end, it is raining.
If you can turn your hand the other way up and the string stands up straight, it is freezing.

Don't make life more complicated than what it is.

Do you have any little conversion factors that you use to get the job done?

John


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## Bernd (Apr 7, 2008)

Bogs,

When I worked in the electrical department at work we made up cables for the machines in metric length's. We had an elderly gentlemen who could not do the metrics. He tried to convert the lengths in to feet and inches. He had a very hard time using a metric measuring tape. I finally told him if I gave him a rope with knots in it and told him to cut a length of cable that was 10 knots long, could he do it. He said he could. So I told him not to worry about converting and just to use the metric tape measure and think of it as so many knots in a rope. He had no problems after that. 

Some times a simple solution works. I know I have a hard time visualizing 1 kilometer. But if I convert it to .6 miles I can then visualize the distance. It's just that I was raised on the imperial length and can visualize that unit better than metrics. I can work with either if necessary.

Bernd


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## compound driver 2 (Apr 7, 2008)

Hi
My big objection to metric is being told by the government I have to use it in work.
I run my own machine shop, I take in work thats as a rule steam related and for engines
coming close to 100 years old. 
Why would i even want to convert everything to metric? I dont have the spare hours in the day to do
it or want to do it. 
Working with fractions is as easy as reading a book or eating a sandwich. Once you grasp that 1/32 of an inch is .03125 and 1/8th of an inch is .125 how can you go wrong? Adding fractions was taught to me in school and still comes as easy as it did 40 years ago. Surely kids must still be taught how to add and subtract fractions. No one can tell me fractions have been dropped from education my boys learning them now.

We built an empire on feet and inches why let it go at the whim of a politician in europe.

Cheers Kevin


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## mklotz (Apr 7, 2008)

My set of questions was designed to highlight the sort of problems one encounters when using a hodgepodge like Imperial and to do this without getting into a lot of numerical computations. It was also meant to show that the difficulties with Imperial extend far beyond the simplistic linear measurements we encounter in the amateur shop. Lots of Imperial boosters claim they don't want to switch because they already understand the Imperial system. If that were true, answering the questions should be easy, especially so for anyone calling himself a model engineer.

Rick's answer to Q1 is correct - 12 gauge refers to the number of balls to a pound.
Now, isn't that a sensible way to denote something? The logical measure is diameter (ball OD or barrel ID) and the means to measure such certainly existed if shotguns were being manufactured but no, let's calibrate the gun according to some obscure tradesman's (the lead caster) measure of convenience. If I developed a new type of super drill and decided to label them with a number that represented how many of them it took to make a pound of weight, wouldn't you think me nuts?

Another question I should have added to the list is:

If Imperial fractions (1/4, 5/16, etc.) are so useful, why aren't micrometers graduated in 1024ths of an inch?

Bernd,

What do you mean by metric angles? Some of the Europeans (French particularly) use the 'grad' (90 deg = 100 grad) but, AFAIK, that's never been incorporated into the metric system.


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## gilessim (Apr 7, 2008)

A couple of things here, I may be wrong but I was always told that 12 guage was the _diameter_ of one ball of lead weighing 1/12 of a pound. A pint of water in the UK was said to weigh 1 1/4 pounds x 8 pints =1 gallon =10 pounds, I don't know how accurate that is and I Know that US gallons are smaller but I've always found it curious that linear imperial measurements are quite close to imperial weight standards. Also as Marv points out, dividing an inch into 1000ths was a step towards decimalization, how big a fraction can we cope with? .One more spanner (or wrench!) in the works here is that 1cc of water ,was discovered recently, to weigh slightly less than 1gram ,so that poor physics students in Europe now have to make complicated calculations to compensate!

I have two questions in one here, following on Marvs theme; What is the origin if the inch? and how was the length of a meter determined?.

BTW being a Brit ,I won't say that a hundredweight is 112lbs, but in question 7 ,I don't think any of those are imperial except perhaps, Point and I think that comes from compass divisions, 1 point being approx 1/72".

Giles


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## mklotz (Apr 7, 2008)

A milliliter of water weighs exactly a gram only at 4 degC, the temperature at which water is most dense. For critical chemistry purposes, one must use a temperature compensation at any other temperature. The total effect, though, at any temperature where water can exist as a liquid, is miniscule.


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## zeusrekning (Apr 7, 2008)

> Lots of Imperial boosters claim they don't want to switch because they already understand the Imperial system. If that were true, answering the questions should be easy, especially so for anyone calling himself a model engineer.




I just lost my whole post :'(. 

Marv, I think you could come up with ten similar questions relating to the metric system. I don't see how questions 1,2,4,6,&7 relate to what we do. I forgot half the $#!& I wrote. I can barely remember that there is 11-1/2" in a foot. Much less how many pounds a British CWT weighs. I think a good machinist should be familiar with metric and imperial. A lot less familiar with imperial if in a country that does not use it compared to how familiar an American should be with the metric system. 
I expect the people I buy material from at work to be fluent in there knowledge of materials. I do not expect them to be able to recite ASTM matl codes. I have some salesmen that can. It impresses me as does your knowledge of math Marv. But as long as that salesperson can know where to get the information I need 
I am satisfied. 
There are a lot of members here who came into this hobby with no experience at all in machining and probably some with almost know knowledge of math or measures beyond basic day to day math. Marv's day to day math is different than mine and mine is different than an electrical engineers. Like I said a good machinist needs knowledge of both systems. A better machinist needs to know where to find the information they need with out filling that fileing cabinet in there head with to much info that won't be used. When the time comes to need to know what a Jeroboam is Google it and have some where to put it where it can be pulled up if needed again. I have no problem making parts to a metric print. I am sticky when converting surface finishes to metric. But a lot of these guys are spending what little free time they have trying to learn maching without trying to learn a new measuring language. If you do not know either, learn metric first. Metric is a better system. But unfortunately most of the time there is no choice. I am sure a British machinist is not going to be a better machinist b/c he uses metric than an American using imperial. Oooh, That's an argument I'm not touching :big: 
BTW, A meter is the distance light travels in a vacuum in 1/299792458th of a second. I did not know that but 
I googled it. I'm sure my whole life I will never need to know that but if I ever do GOOGLE. 
To wrap it up , Metric is a better system there is no argument there. If you can't seem to get it, convert when needed and you will get by no problem. If you are stuck there is help here. I wish my English was better so my post didn't sound so ignorant but I try and get by. There is another example look at the language we all use and the flaws in it and how hard it is to understand. It is still the worlds most used language. 
Tim


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## mklotz (Apr 7, 2008)

Tim,

This is no longer a discussion of what system a guy working in his basement shop should use. We've already answered that and the answer was, "whatever is simplest for him and most economical given where he lives." John, the OP, solicited our views on the two systems and, unfortunately, I have some very strong views based on many years of having to deal with both systems.

What I'm trying to convey is that the Imperial system is a complete system of units, not just the linear measures we use in the shop. Furthermore, that system is badly flawed, full of doubly-defined and confusing measures. It's existence and the confusion it's caused have already cost us the loss of two multi-million dollar spacecraft and a number of human lives in air crashes. The longer we keep it alive, the more mistakes, minor and major, are going to be made. Obviously, metric will not eliminate mistakes, but, given an ever dumber population, it will go a long way to reducing the number.

There's more to life than engine-building and intelligent folks like those here should understand more than just what they need to do their immediate task. The key to a long life is to keep learning.

Lots of folks (Americans especially) have made the case that Imperial is as good as or even better than metric. I'm trying to point out that they're saying that without fully understanding just how screwed up the Imperial system is. Perhaps if they understand that they'll come to appreciate that the advantages of metric are far more than the powers-of-ten thing that's always dragged out in these discussions.

The Imperial system could be fixed. Trouble is, to do that right, you'd need to introduce most of the *system* corrections that have already been formalized in the metric system. Since the system has already been worked out (and is used by most of the world - the USA and Mynamar (Burma) are the only countries who haven't adopted it), why not use what's already there?

Finally, let me point out that I do most of my shop work in Imperial - mainly because I live in the USA and that's the most economical way to go. I use metric only when working to a metric print or doing something that will never have to interface with anything Imperial. I'm not sitting in some (metric) scientific laboratory pontificating on what shade-tree mechanics should do. The reason I despise Imperial so much is because I'm forced by circumstance to use it on a daily basis.


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## Bernd (Apr 7, 2008)

mklotz  said:
			
		

> Bernd,
> 
> What do you mean by metric angles? Some of the Europeans (French particularly) use the 'grad' (90 deg = 100 grad) but, AFAIK, that's never been incorporated into the metric system.



Was being a smart a$$ Marv. I wanted to see if anybody was actually comprehending what they were reading. I know I've done it. Read something and then went, What? Usually I can catch somebody. 

And I couldn't answer any of your questions.  Interesting to know they are Imperial. I did learn one thing. The gauge of a shot gun. Very interesting.

Bernd


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## shred (Apr 7, 2008)

The trick with the odd imperial measurements and the reason they hang around is they were all homegrown and thus originally _meant_ something to somebody-- to an old lead-shot-caster, 12-gauge is far more meaningful than ".731" or "18.6mm" or 47/64", so they invented 'gauges' instead of using inches or furlongs or split-hairs, which they no doubt already had. It made their lives easier since they were already whacking up pounds of lead in various fractions to make balls out of them.

The trouble is when people that didn't invent the unit want to use it for a different purpose, or worse yet, compare it to something else entirely. That's where the troubles start and other people's lives get more difficult. To the shotgun barrel-maker, the number of balls-per-pound-of-lead is a lot less interesting than what diameter they have to make the pipe.

But.. as a friend said today.. if metric is so good, why don't we use metric time? 

The average man-on-the-street will have a far easier time approximating half of something than a tenth or any other fraction of it... thus the roots of the fractional system. Take half, then half that, then half that...


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## mklotz (Apr 7, 2008)

shred  said:
			
		

> The trouble is when people that didn't invent the unit want to use it for a different purpose, or worse yet, compare it to something else entirely. That's where the troubles start and other people's lives get more difficult. To the shotgun barrel-maker, the number of balls-per-pound-of-lead is a lot less interesting than what diameter they have to make the pipe.



Exactly, Shred. The Imperial system has had several centuries to mature. Why do they continue to use measures (and there are many of them) that are irrelevant and awkward? A huge reform was in order and the French made that reform.

Incidentally, the French tried 'metric' time. They divided the day into ten 'hours' of 100 'minutes' each IIRC. It was a colossal flop and never caught on.

A very small number of clocks were built to this standard. If you ever run across one, buy it at any price. They're worth a fortune on the antique market.


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## gilessim (Apr 8, 2008)

I perhaps misunderstood the questions here, as the imperial system was originally a set of standards that the Brits who hated the French at the time, decided on .I wasn't aware that French measurements were included later!

BTW the metre was determined in the 1790s I think(by the French!) to be a 10,000,000th part of a meridian from the north pole to the equator.

P.S. I didn't notice sack there! thats definitely English; 1 sack= 364lbs.

Giles


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## Bogstandard (Apr 8, 2008)

The imperial measurements that are used in the US today, are in fact all the old measurements that the English brought across with them when they first turned it into a colony. It was later modified over the years to suit the colonists as they saw fit. Later in the 1800's, the US and English measurements were further split, when England finalised on its standard Imperial system, leaving the American English standards system to be enjoyed and modified as it suited the American people.

Most of the original and later Imperial measurements can be found here, and a bit of history how they both evolved.

http://en.wikipedia.org/wiki/Imperial_units

If you go to all the links in this URL you will find almost everything you need to know about the Imperial, US English standards and metric.

It also states that the US populace, calling it by the Imperial system, are in fact incorrect to be doing so.

Maybe on here we should be differentiating between the two English systems.
But to me totally unnecessary.

John


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## Circlip (Apr 8, 2008)

The two old favourites always guaranteed to generate debate, Metric V Imperial and Carbide V HSS, :big: Nice one John. Back in the early sixties when I was partly forced to become bisexual in the textile machinery manufacturing industry, note I said PARTLY, one of the younger lads in the DO who had just bought a new set of drawing instruments was REALLY pi**ed off when we told him he would have to get a new set of Metric ones : Why partly? With the exception of one machine, the latest design, all the others were made in the brick s**thouse design era of steam technology and the British textile manufacturing owners were famous for their FRUGALITY. Not only that, but due to the quality of the machinery we made, we were supplying spares for some of the machines made in the early 1900's. Many years later, when employed in the Electronics industry, the PCB panels were deigned and manufactured to Metric dimensions but the coordinates for the press tools for punching the component mounting holes although given as Metric sizes were DIRECT Metric conversions of Imperial dimensions. Silicon Valley still made IC's etc at 0.1" pitching, so having to think in conversion dimensions bilaterally became the norm. I work in Metric cos that's what the dials on my Lathe/Miller are marked in, but there are still times when I think "Oh yes 0.1MM is four thou" Having said that, there are times when I think "Twelve and a half P - Oh yes, half a crown" Ian.


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## Loose nut (Apr 8, 2008)

mklotz  said:
			
		

> Lots of Imperial boosters claim they don't want to switch because they already understand the Imperial system. If that were true, answering the questions should be easy, especially so for anyone calling himself a model engineer.


Marv you have to look at your argument from a real world point of view, most people who use the imperial system do understand it, the IT being the part of it they use everyday which is simple measurement and weather temp. Cooks know what a teaspoon or tablespoon is and machinist's can measure using the inch etc. and that's what matters. All the other imperial measures don't really matter because we don't use them. The people who do use them are the only ones who have to worry about it. 

Most people who use metric don't understand any more of the metric system than the same simple measurements and weather temp. because they don't use any more of the metric system than we use of the imperial system.

There are many people in metric countries that still use the imperial and other obsolete metric measurements because SI doesn't satisfy there needs.

P.S. how are shotgun bores measured in metric measurement IE" 12 guage = what?

"How many barrels definitions are there" there is only one that matters, a barrel of oil, which I believe currently is 35 US gallons, but this is subject to chance as it is an economic measurement more so than volume measurement. If OPEC wants more money they just lower the number of gallons in a barrel.


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## Rog02 (Apr 8, 2008)

Sirs:

Having worked in many locations around the world, I understand it is my responsibility to understand the measurement system that is to be used for the job. Arguing continuously which is *THE *best system in an exercise in futility. Any *hack, shade tree mechanic *with any experience in their tool box will tell you that. 

Over the past 4 decades I have spent enough money with Snap-On dealers to put several of their offspring through medical school. I now can claim to own a fairly complete set of SAE, metric, weatherhead, whitworth, and AN wrenches and hand tools. My little fab shop is outfitted with both metric and SAE measuring equipment. The expense to me has been staggering. The options, are however not favorable to me. Failure to purchase the needed tools and acquire the knowledge to work to the required standards would leave me the option of flipping burgers at a fast food joint or becoming a teacher. I think, I will continue to buy the tools.

The metric system is inherently flawed from it's inception, that is a known fact. The "Imperial" system has undergone so many variations and adaptations to fit whatever trade or taxation issue, that it has become over bloated. Simply put, gentlemen, there is no truly accurate or perfect standard of measurement. As technology advances, the problem is expanding as new measurements are required for units of measure never foreseen. Anyone care to hazard a guess as to the definition of a *MICKEY*?

If you want to have some fun, try popping a beer (US), pouring a pint(UK), or cracking a stubby(Aus) and spend some time reading through this site. 
http://www.sizes.com/units/index.htm
Be thankful we only need to argue converting "Imperial/Metric".  :big:

Now I have to go feed my 1 stone tomcat and his 1/2 stone sister their daily 1/2 troy pound ration of cat food before I head out to the store to pick up a wine gallon of milk and 476 grams of butter.


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## mklotz (Apr 8, 2008)

Rog02  said:
			
		

> The metric system is inherently flawed from it's inception, that is a known fact.



Bold statement. Can you explain what you mean?


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## doubleboost (Apr 8, 2008)

Hi
Living in England and being the wrong side of 40 i was tought both the imperial and metric system,
I still use both today (sometimes mixed up).
At work today i asked a 17 year old to take a 16th of the end of a bolt he just looked at me with a blank expression , he really had no idea what i was talking about ,2 mill however made all the sense in the world.
I think it is very sad that we are loosing imperial measurments
John


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## rake60 (Apr 8, 2008)

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


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## Rog02 (Apr 9, 2008)

mklotz  said:
			
		

> 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.
> 
> ...




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.


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## whatsit (Apr 9, 2008)

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


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## mklotz (Apr 9, 2008)

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.


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## shred (Apr 9, 2008)

mklotz  said:
			
		

> 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)  ???


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## mklotz (Apr 9, 2008)

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?


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## Bogstandard (Apr 9, 2008)

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


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## mklotz (Apr 9, 2008)

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.


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## rake60 (Apr 9, 2008)

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


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## Bogstandard (Apr 9, 2008)

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


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## Loose nut (Apr 9, 2008)

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.


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## zeusrekning (Apr 9, 2008)

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.


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## shred (Apr 9, 2008)

Loose nut  said:
			
		

> ...
> 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.


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## gilessim (Apr 10, 2008)

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


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## gilessim (Apr 10, 2008)

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!


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## Circlip (Apr 10, 2008)

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.


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## mklotz (Apr 10, 2008)

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


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## shred (Apr 10, 2008)

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.. )


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## Jadecy (Apr 10, 2008)

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!


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## shred (Apr 11, 2008)

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.. :


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## rake60 (Apr 11, 2008)

Don't tell any else Shred, but the 13MM would have worked just as well on 
a 1/2" bolt. Something like that could make this whole apples to oranges
debate collapse.

13MM is .011" bigger than 1/2" but the bolt head would have been too 
dumb to notice the difference. 

8MM wrench will fit a 5/16 Bolt.
10MM wrench will work on a 3/8" bolt.
12MM will turn a 7/16 bolt but it will be a little sloppy.
Now if you happen to be using six point socket wrenches there's no
problem at all with those interchanges.

Yet these systems are worlds apart and totally incompatible!
(It does make for better reading... )

Rick


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## shred (Apr 12, 2008)

Yeah, I always feel a little bad about using a metric wrench on an imperial bolt or vice-versa even though they fit ok, but I did think it was funny that when faced with a random bolt, I went fishing for the metric wrenches without even thinking about it.


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## Lew Hartswick (Apr 13, 2008)

This discussion brings up a point I always wondered about. In the great "scheme of things" the "UNITS"
are always being brought up as the point of refrence, SO JUST WHY is the "UNIT" of mass in the 
metric system the "KILO" (1000) of something???  
 This was always my first thought when working in physics where the two systems of CGS amd MKS 
just seemed to be inconsistant. If the Pt bar is the standard for the Meter then the standard for masss
should be a Gram chunk of metal not 1000 of something. No problems but an inconsistancy.
  ...lew...


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## mklotz (Apr 13, 2008)

CGS = centimeter - GRAM - second system
MKS = meter - KILOGRAM - second system

So there's no "inconsistancy" (sic).

BTW, the meter standard hasn't been a Platinum bar for a long time.


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## Loose nut (Apr 13, 2008)

The main problem with the metric system meeting resistance is the fact that it was forced on us by our governments that caved into international pressure. What we need is a new system that is truly international and not French. I'm proposing a system based on the beer bottle (long necks). The standards committee would take a couple of cases of each type of beer and what ever one that they like the best then that brand of bottle becomes the new standard measuring system.
The volume of the bottle would be called a beer, 10 beer a case, 10 cases would be a DUI etc. 1/10 of a beer would be a gulp and 1/10 of a gulp would be a sip. The pressure inside a capped bottle would be the standard for pressure measurement and a new temp. scale would be, 0 degrees Beer = temp that a beer freezes and 100 degrees Beer = the temp that beer boils. The standard length meas. would be based on the length of the bottle, 10 bottle would = 1 stagger and so on.
This would be a truly international standard because beer is available everywhere (non-alcoholic for Muslim countries) and people rarely have to have it forced on them and it is a fully integrated system that is completely decimal in concept and as to availability of measuring standards you only have to go to your local beer supplier and buy the "standards" brand to have all the standard bottles you need.



If this sounds a little silly, it is, and if it sounds familiar, it should, it's basically the metric system with different names and values and the metric system had almost as much thought put into it as this one did. Any standard could be used it doesn't have to be one picked out by the French a couple of hundred years ago and forced onto Europe literally at gunpoint by Napoleon. If he wasn't trying to build an empire, metric would never have taken off and we would be using a different system that might be more acceptable to everyone, decimal based or otherwise.


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## Bogstandard (Apr 13, 2008)

LN,

It seems that the system you envisage wouldn't be any good, it would be to volatile to use. Everything is too fluid, it only takes one person to have an extra gulp or sip and your measurement would be being piddled up a wall. Plus everyone, after a bit of measuring wouldn't give a damn about what it was doing there in the first place, they would be too busy falling over (except in Muslim countries, and then they could take over the world, because we would be too drunk to care about anything, then they could impose their own measurement system on us, just like Napoleon did) . ;D ;D

Maybe we should take a look at the German system, where I think it is law that they be allowed to have beer at machineside. If that is the case, I ever wonder as to how they manage to produce such wonderful precision.

But about your theory of having the metric system 'forced' upon us. How else would it be done, because the American people just don't think anything should change. Anything that they come up with, whether it be pineapples or molecules, will still have to be 'forced' on the population, just like Napoleon did. 

But the metric system has survived, and it isn't doing too bad a job.

John


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## Loose nut (Apr 13, 2008)

Maybe, but with my system after you get done collecting your "standards" you won't really care about anything else anyway, that's the beauty of it. We won't care if anything ever gets measured again so there won't be any argument over changing systems or which one is better, we'll all be having an nap.


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## mklotz (Apr 13, 2008)

Loose Nut,

I can't seem to puzzle out whether you're so anti-metric because it wasn't thought up by Canadians/English or because you feel there's something fundamentally wrong with it.

If it's the latter, perhaps you can explain what you think the faults are. Considering the amount of research and refinement that's gone into it (much by non-French scientists), it will be interesting to see if your objections have any validity or whether they're simply I-just-don't-like-it objections.

John's correct. Any change aimed at international standardization is going to have to be forced on people who are only comfortable with their quaint antique tradesmen's measures.


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## John S (Apr 13, 2008)

I don't have a vested interest in Imperial or metric, I have to work to both given that the work I do is spread over a 100 year period of machinery.

One thing I have noticed though is metric has one standard and Imperial has two.

In metric it's aways decimal 8.25mm 124.78 mm etc, one standard.

Imperial has fractions and decimal. OK it's easy on the standard ones 1/4" is 0.250" but when you get a print with 27/64" on it and you have to half that to get a radius to turn to then it's open to error.

The answer is to make prints with decimal sizes on be it imperial or metric but in real life this doesn't happen. 
To me because there is no conversion in metric, it's already in decimal it's easier.

Another point I didn't see in the earlier pages but I may have missed it is threads and tapping sizes.

With metric there is no need for any tables. It can all be done in your head by subtracting the pitch from the diameter so a 10mm x 1.5 thread is drilled 8.5mm, a fine 10mm x 1.25 pitch would be drilled 8.75mm. That simple formula works over the whole of the metric range.

John S.


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## mklotz (Apr 13, 2008)

That formula works just as well for Imperial threads, e.g., 1/4-20 tap...

0.25 - 1/20 = 0.2" tap drill

Now, if the idiots hadn't numbered (or lettered) the drill sizes, you'd be ready to go. No, nothing simple like that. Unless you've memorized the whole farked up drill series, you'll need a table to determine that a #7 drill is 0.201".

With metric designations, everything is straightforward, e.g., 6 x 1 mm tap...

6 -1 = 5 mm

and when you go to the drill index, the drills are labeled 1,2,3,4,5 mm.


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## Loose nut (Apr 14, 2008)

mklotz  said:
			
		

> I can't seem to puzzle out whether you're so anti-metric because it wasn't thought up by Canadians/English or because you feel there's something fundamentally wrong with it.
> 
> 
> John's correct. Any change aimed at international standardization is going to have to be forced on people who are only comfortable with their quaint antique tradesmen's measures.




Well it wasn't thought up in the US either and most Americans don't want anything to do with it either, your the exception Marv not the rule.

John's point hits the nail on the head, IT WAS FORCED ON US, the "us" being all the none metric countries about 30 years ago, most of the people in these countries didn't ask for it or want it, so why did we have to be forced into it. "International standardization", that is not a good enough reason for the lose of our right of free choice. The people that have to deal on the global market could have taken care of it and the rest of us should have been left alone to use what ever system we liked. Don't be under the illusion that Americans would like to pump gas in liter's or drive in kilometer's/hour anymore then I do, I think we both know that wouldn't go down very well.

The English language is the most screwed up conglomeration of words and phrases from all the other language in the world, full of quaint antique words, it is a constant state of flux and the rules of grammar and spelling don't apply from one word to the next because all of the different language's have to be accommodated.

Using your logic we should throw it out and adopt French or Latin because the are more stable. Maybe we should create a new "international" language that can be forced on the whole world, isn't that a good idea in the name of international standardization. How would that go over in the US or any other country. 

Luckily by the time the metric system finally takes over in the work place here I will be long retired, and for as long as I am still able to work in my own shop I will have no trouble sourcing Imperial tools and material. The rest of the world can do what ever they want, but my little corner of this planet will always be Imperial.


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## Seanie (Apr 17, 2008)

I personally grew up with the Imperial system, & first heard about Metric in high school. 

More than 30 years later, I still work in both & truly understand neither! 

All the arguments I've ever heard on the subject can be summed up in one line- 'People don't like change'

My vote is for Metric- sure it has weak points, but imagine how much more advanced the world could be if we all stopped fighting over such things & worked together.


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## Divided He ad (Apr 20, 2008)

I am well and truly lost in most of the discusion here...I struggle with the simplest of maths (ask Marv, he has already given me some lessons!) I just thought this a good place for this to be displayed... It is obviously not just the man in the street who is confusing the issue.... 







If you can't read it ... 9'6" high, 2.5m wide !! :big:

Was behind this last week, just thought it funny after reading a lot of this post  



Ralph.


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## Bogstandard (Apr 20, 2008)

Ralph,

That isn't the only confusing thing, because I live fairly near to the Welsh border, a lot of our roadside signs are like that.

John


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## Divided He ad (Apr 20, 2008)

:big: Tell me about it!! Try living near "Yr Wyddgrug" !! (translated "Mold" !!! ???) I moved up here from the Coventry 20 years ago... Got thrown out of my first ever Welsh lesson because I didn't know the Welsh alphabet!! ??? It all went down hill from there! ;D 
(I can say Quite a few place names now but probably not as well as the nationals would like!  )

Ralph.


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## mklotz (Apr 20, 2008)

Anyone who can spell Welsh should find mastering the intricacies of the metric system a piece of cake.

[Aside for the colonials: As an example,

Llanfairpwllgwyngychgogerychwyrndrobwllllantysiliogogogoch

is a legitimate place name in Welsh.]

Do they have spelling bees (competitions) in Wales? If so, do they ever finish?


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## Divided He ad (Apr 20, 2008)

No spelling bees as far as I know... But quite humorously I drove through Llanfair PG (as it is shortened to!  ) last week and had to laugh at the Volvo dealership that had 90% of the sign dedicated to the area name and 10 to the Volvo part :big: 

Disclaimer... This is an approximation... please do not count all the letters and do the maths to find accurate percentages... I will not be impressed with your efforts. It will not be big or clever! :big:


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