Metric vs Imperial or vice versa

[Bogstandard]

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

 

[rake60]

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

 

[Tin Falcon]

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

 

[zeusrekning]

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

 

[Hilmar]

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

 

[Bogstandard]

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

 

[steamer]

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

 

[Loose nut]

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.

 

[Powder keg]

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

 

[mklotz]

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.

 

[Bogstandard]

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

 

[shred]

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.

 

[mklotz]

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.

 

[zeusrekning]

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

 

[shred]

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.

 

[mklotz]

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.

 

[nemt]

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

 

[mklotz]

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.

 

[Tin Falcon]

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

 

[mklotz]

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?