why is the US not Metric

[Zero999]

Secondly, with AWG, you just go down 3 gauge sizes to double the cross section and halve the resistance. (And you move 6 steps to double/halve the diameter). Every gauge size larger, the diameter of the wire increases by 12.3%. Thus the cross section increases by 1.123^2, or by 26% per step. Going down in size, that is 10.5% decrease in diameter or 20.7% decrease in area. If you know piR^2, you only need to know any one of these numbers. 12.3% is from the 39th root of 92 = 1.122932197. This is because from AWG 36 to 0000, there are 39 steps, and a 0000 wire is 92 times the diameter of a 36 AWG wire.

So e.g.,
If you want double the cross sectional area of an AWG 16 wire, you go to AWG 13.

If you do this by cross section, you go from 1.32mm^2 wire to 2.64mm wire. Then you find out that this doesn't exists. And you select the 2.5mm^2 wire.  In AWG, you can also be aware of and calculate each step up or down without looking at a chart, only knowing your starting point.

You can say it is easier to circumvent AWG and just call it by cross section. But most people probably don't calculate how much cross section they need for a wire, first, then look up the wire, after. Most people probably look a chart or spec sheet to begin with. And naming/buying/selling wires by their cross section isn't necessarily better for your manufacturers and marketplace and engineering codes.

You can all it archaic. I call it reality. These are the sizes we (american companies) make wires in and make engineering codes in. You choose from these sizes; you don't design your own spec as you go, unless you crap money like NASA. And in many cases it is easier to use AWG names/standards than to use cross sectional area as a name. If you're gonna use units, you gotta list the units, somewhere, firstly. And when you get smaller than 30 AWG, watch what happens to your names/numbers.

AWG is not absolutely empirical. But it is based on the 10.5% reduction in diameter which can be achieved by draw dies on copper alloy. That number is empirical, in a way; it's the average of what can be done, practically, using our current manufacturing techniques and dies and lubricants and alloys. After that, it's a matter of designating a reference/zero/calibration point. Then you know what sizes are actually available by this ratio of 1.122932197 : 1, within a very small margin of error. It would be nice it it were a rounder number, but this is the result of what is the biggest step size in practical application. That's where it ended up, and that's fine. This standard contains, in itself, knowledge of the physical universe and know-how of making wire. Why it goes backwards? Probably because this can be done smaller and smaller, if needed. But going larger is/was determined by other factors (which may have been improved/increased at least 3 times in history?  )

That sounds very complicated and only reaffirms my point: it's much easier to use physical dimensions such as cross-sectional area or even diameter. Take a step back. Suppose you've never heard of AWG or SWG. If you saw a drawing with cable cross-sectional area specified, then it would be obvious what it means. No need to look anything up. We're not even talking about metric vs imperial here, but simply defining a physical property vs some complex system. Even wire diameter in inches or thou would be much easier to use.

Here in the UK we use a stupid system for shoe sizes. I wish we'd move over to something more straightforward, based on simple dimensions.

[KL27x]

Tooki, Don't you measure the milk and spirits out separately, sos you dont accidentally pour too much into the cake? Whether by the cup or scale? (You could convert your recipe grams of milk to ml and vice versa, so why not use a metric measuring cup?)

Incidentally, I estimated about 15.5 us fl oz to be about 1 lb of water, calculating from memory, mostly cuz I have been involved with this thread, and doing all the math in my head. Could this be close?

Using a calculator, I come up with 1 US pint of distilled water is 1.04125 lbs. ANS^-1 * 16 = 15.366 us fl oz. Not shabby.

A cup / half pint/ 8 fl oz oz / 8/16ths (pint)         ~ half a lb / 8 oz *
half cup / quarter pint / 4 fl oz                                ~ quarter pound / 4 oz *

*plus 4% extra, for "good measure"

[KL27x]

That sounds very complicated and only reaffirms my point: it's much easier to use physical dimensions such as cross-sectional area or even diameter. Take a step back. Suppose you've never heard of AWG or SWG. If you saw a drawing with cable cross-sectional area specified, then it would be obvious what it means. No need to look anything up. We're not even talking about metric vs imperial here, but simply defining a physical property vs some complex system. Even wire diameter in inches or thou would be much easier to use.

Easier to use...for who, though?
Have you ever had to spec an SIL/DIL PCB connector that comes in multiple numbers of connections? And then you have to use some formula of (n+1)*dimensions/pins/pads on the footprint mechanical drawing to even create the PCB footprint? Wouldn't it be "so much easier" if they just listed the footprint for every single size of connector? (Heck, wouldn't it be easier if they even showed the entire footprint for just one of these components, say the smallest one, just for reference?) But they don't usually do this. And there are communication/clarity/future-proofing reasons for this decision, as well as efficiency/brevity.

If I had never heard of or seen AWG? I would look it up and RTFM. How would that be any worse than just guessing what diameter of wire I need? Or do you suppose you just learn the conductance of copper per square mm per meter in high school and remember it ever after? And then have to do algebra to figure out the minimum diameter you need, including heat dissipation and ambient temp and temp coefficient, and then still have to look up the closest size? (And still not know the actual legal/lawyer ampacity?)

You seem to be concerned with "ease of use" for Jack and Jane, specifically. In America, perhaps we are more concerned that our brighter bulbs have as much info as could possibly be useful to them in making an informed decision and not so very much concerned if Mary Sue Arduino-noob easily can begin to calculate for herself the cheapest possible wire to theoretically do some job and hopefully do it right. We will forgo this 0.0013% of the wire market to better serve the vast majority.

Here in the UK we use a stupid system for shoe sizes. I wish we'd move over to something more straightforward, based on simple dimensions.

You mean more sizes/shapes/combos? Or just a more intuitive way to name them?  The former, yeah. The latter? Well, most people only have to figure that out so many times until their feet stop growing. 

[tooki]

Tooki, Don't you measure the milk and spirits out separately, sos you dont accidentally pour too much into the cake? Whether by the cup or scale? (You could convert your recipe grams of milk to ml and vice versa, so why not use a metric measuring cup?)

You weigh each ingredient separately.

The reason for weighing the liquids is simplicity: why dirty a measuring cup when you already have the scale out to weigh the flour? (Measuring flour by volume is a fool’s errand, and it’s quite telling that professional bakers in USA go by weight, not volume.) So you just add an ingredient, tare the scale, add the next ingredient, tare again, etc.

[SilverSolder]

+1 for weighing ingredients in the kitchen.

When using the bread-bakery machine, I put the pan on the scale, tare it to zero, and start adding ingredients by weight.  There are literally zero extra utensils needed for the job, and hence zero mess / washing up.  The bread is consistent every time.

[Dek]

I use ft and inches for doing rough arse stuff i.e. "about 1 3/4" is near enough.
I use metric when undertaking something needing a jot more precision "that's exactly 44.450mm"
 
 
Dek

[Zero999]

That sounds very complicated and only reaffirms my point: it's much easier to use physical dimensions such as cross-sectional area or even diameter. Take a step back. Suppose you've never heard of AWG or SWG. If you saw a drawing with cable cross-sectional area specified, then it would be obvious what it means. No need to look anything up. We're not even talking about metric vs imperial here, but simply defining a physical property vs some complex system. Even wire diameter in inches or thou would be much easier to use.

Easier to use...for who, though?
Have you ever had to spec an SIL/DIL PCB connector that comes in multiple numbers of connections? And then you have to use some formula of (n+1)*dimensions/pins/pads on the footprint mechanical drawing to even create the PCB footprint? Wouldn't it be "so much easier" if they just listed the footprint for every single size of connector? (Heck, wouldn't it be easier if they even showed the entire footprint for just one of these components, say the smallest one, just for reference?) But they don't usually do this. And there are communication/clarity/future-proofing reasons for this decision, as well as efficiency/brevity.

Fairly simple, because they already give you the pitch, so there's no point in a drawing. I don't have to faff around looking things up. A bit of arithmetic isn't hard and CAD software does most of it for me.

If I had never heard of or seen AWG? I would look it up and RTFM. How would that be any worse than just guessing what diameter of wire I need? Or do you suppose you just learn the conductance of copper per square mm per meter in high school and remember it ever after? And then have to do algebra to figure out the minimum diameter you need, including heat dissipation and ambient temp and temp coefficient, and then still have to look up the closest size? (And still not know the actual legal/lawyer ampacity?)

More often than not, it's unnecessary to worry about the ampacity, because the current is way below the limiting factors of volt drop and insulation temperature rating.

You seem to be concerned with "ease of use" for Jack and Jane, specifically. In America, perhaps we are more concerned that our brighter bulbs have as much info as could possibly be useful to them in making an informed decision and not so very much concerned if Mary Sue Arduino-noob easily can begin to calculate for herself the cheapest possible wire to theoretically do some job and hopefully do it right. We will forgo this 0.0013% of the wire market to better serve the vast majority.

How is a weird gauging system somehow more straightforward than simply specifying a physical dimension?

There are other wire gauging systems than AWG. Suppose a drawing specifies 19SWG, I'd have to Google it, but if it simply said a diameter of 40 thou (I had to look that up), I'd immediately know it's just over 1mm. Not having to refer to charts or Google everything makes designing things such as PCBs much easier.

Here in the UK we use a stupid system for shoe sizes. I wish we'd move over to something more straightforward, based on simple dimensions.

You mean more sizes/shapes/combos? Or just a more intuitive way to name them?  The former, yeah. The latter? Well, most people only have to figure that out so many times until their feet stop growing. 

In the old days it was less of an issue, since one would go into a shoe shop and get their feet measured, but nowadays people more often than not order online, so will have to measure at home. Yes you're right, it's less of an issue for adults, but getting the right size shoes for children is always fun.

[KL27x]

How is a weird gauging system somehow more straightforward than simply specifying a physical dimension?

I didn't say it was more straightforward. I implied/contended that it has the benefits of ease and clarity of communication, that it conveys more and potentially useful information/data to potential customers, and that it may provide future-proofing.

1. Ease of communication: When I run low of "bodge wire," I buy more "30 AWG Kynar." I don't have to remember "0.0231 mm^2" (made up number). If I search for "0.0220 mm^2 wire," and nothing comes up, then I just go up by a thous and try again, 60-70 times?  If I search for a specific type of "0.0231 mm^2 wire," and I get no hits, is it because no one makes the wire in this size, or did I enter that physical dimension/name incorrectly? Does India make 0.0231, or is 0.0233 their standard? The people who enter the wire market can list under the most appropriate gauge, then give the actual physical dimensions of this specific product in the description. Same seller might sell several products of the same gauge wire but with slightly different actual dimensions. Even among American manufacturers, you can expect some variations due to different die manufacturers and die and tool wear and human inputs, let alone manufacturers in different countries.   

2. Conveys more data: I know all the sizes that are available. I know the size of the steps between between each size.

3. Future-proofing: The AWG standard is not dependent on a measuring system. It is equally accessible to either metric or USC. And it will be equally accessible to metric 2.0, whatever that is and whenever that day comes.

[Zero999]

How is a weird gauging system somehow more straightforward than simply specifying a physical dimension?

I didn't say it was more straightforward. I implied/contended that it has the benefits of ease and clarity of communication, that it conveys more and potentially useful information/data to potential customers, and that it may provide future-proofing.

1. Ease of communication: When I run low of "bodge wire," I buy more "30 AWG Kynar." I don't have to remember "0.0231 mm^2" (made up number). If I search for "0.0220 mm^2 wire," and nothing comes up, then I just go up by a thous and try again, 60-70 times?  If I search for a specific type of "0.0231 mm^2 wire," and I get no hits, is it because no one makes the wire in this size, or did I enter that physical dimension/name incorrectly? Does India make 0.0231, or is 0.0233 their standard? The people who enter the wire market can list under the most appropriate gauge, then give the actual physical dimensions of this specific product in the description. Same seller might sell several products of the same gauge wire but with slightly different actual dimensions. Even among American manufacturers, you can expect some variations due to different die manufacturers and die and tool wear and human inputs, let alone manufacturers in different countries.   

2. Conveys more data: I know all the sizes that are available. I know the size of the steps between between each size.

3. Future-proofing: The AWG standard is not dependent on a measuring system. It is equally accessible to either metric or USC. And it will be equally accessible to metric 2.0, whatever that is and whenever that day comes.

There are standard cross-sectional areas for commonly used wire sizes. You don't often get 0.52mm², but convenient sizes such as 0.5mm², 0.75mm², 1mm², etc. unless it's AWG or SWG, converted to meaningful SI units.

AWG does not convey more data than simply stating the cross-sectional are. It means nothing, without looking up the dimensions, unless you're so familiar with it you can remember them. AWG just makes things more difficult. Writing a computer program to work out the resistance of a piece of wire specified by cross-sectional area is easy. Doing the same for SWG or AWG is a PITA. It would require a look-up table or a monster switch case statement.

AWG is not future proof, compared to SI units, which will never go away. Some European suppliers are moving away from AWG, in favour of cross-sectional area. Most suppliers use both in their search engines, but the section of the RS Components catalogue linked below, only lists cross-sectional area.
https://uk.rs-online.com/web/c/cables-wires/wire-single-core-cable/automotive-wire/

[KL27x]

There are standard cross-sectional areas for commonly used wire sizes. You don't often get 0.52mm2, but convenient sizes such as 0.5mm2, 0.75mm2, 1mm2, etc. unless it's AWG or SWG, converted to meaningful SI units.

What makes you think these are the only sizes you will encounter outside of the US? Is there one die maker to supply all the wire manufacturers? Or is this the catalog of standard sizes that every country and every manufacturer within each country outside of the US have decided upon and adhere to within a proscribed tolerance limit, resulting in a standard chart which you have conveniently memorized?

These dimensions are nicely truncated on purpose. Cuz someone made those decisions and everyone agrees. (Like how some countries have 700mL bottle for hard liquor, while others use 750mL; that is sarcasm). If the actual dimensions of the wire match these artificially truncated standards, then you necessarily made your wire manufacturing less efficient by deviating from the 10.5% diameter reduction per die.

E.g., from your link, the list of sizes by cross section is significantly longer than the AWG list. Even though there are essentially an equal number of products (1826 vs 1824; out of 2000 total, so over 90% of wires are happily listed under both categories) between the ones sortable by AWG and those by metric. You will notice lots of sizes that are very close, in the dropdown menu, like 0.22, 0.23, 0.24, 0.25, 0.26 mm^2. Those are less than 5% increases in area each step up. Vs 26% between each AWG size through that same range (through the entire range). This occurs again in several spots on the cross section drop down menu.

And... considering the traffic jam, here, would you confidently design a spec for "0.26mm^2" wire, wondering if that will be an available size in 40 years? Maybe the metric market will consolidate on 0.25mm^2 as a standard to absorb some of those other sizes? America AWG system kinda planned this all out to cover the entire range, efficiently, and in a way that you don't have those questions.

Writing a computer program to work out the resistance of a piece of wire specified by cross-sectional area is easy. Doing the same for SWG or AWG is a PITA. It would require a look-up table or a monster switch case statement.

Then don't do that. Firstly, you could input the actual dimensions for the wire, whether you buy it by cross sectional area or AWG. The actual dimensions and tolerances will determined by the actual product/datasheet, not by the name/standard it falls under for classification. If you make software that goes by gauge, I think the metric version of the software should also have a look-up table, too, so there's  dropdown list of the available metric sizes that are apparently standardized worldwide by every other nation? That increases the utility, no?

The software side is the least of your worries. We're talking a wire manufacturing and distribution and marketing machine. The software is just a tiny afterthought. The ease of use is not a major factor. It's the very few customers who make large repeat order who you want the crystal clear communication and standardization in order to serve. The rest just have to deal with it.

[Zero999]

There are standard cross-sectional areas for commonly used wire sizes. You don't often get 0.52mm2, but convenient sizes such as 0.5mm2, 0.75mm2, 1mm2, etc. unless it's AWG or SWG, converted to meaningful SI units.

What makes you think these are the only sizes you will encounter outside of the US? Is there one die maker to supply all the wire manufacturers? Or is this the catalog of standard sizes that every country and every manufacturer within each country outside of the US have decided upon and adhere to within a proscribed tolerance limit, resulting in a standard chart which you have conveniently memorized?

No one uses SWG or AWG in Europe, for wiring or industrial machinery.  Like everything else, there are standard metric wire sizes. Look up IEC60228. At the moment, only sizes above 0.5mm² are standardised. For smaller gauges we're stuck with a mishmash of SWG and AWG, but it might change in future. I suppose it was more important to standardise larger conductors which are used for safety critical applications, such as mains power. The sooner the smaller sizes are standardised, in SI units, the better.
https://en.wikipedia.org/wiki/IEC_60228

[KL27x]

You weigh each ingredient separately.

The reason for weighing the liquids is simplicity: why dirty a measuring cup when you already have the scale out to weigh the flour? (Measuring flour by volume is a fool’s errand, and it’s quite telling that professional bakers in USA go by weight, not volume.) So you just add an ingredient, tare the scale, add the next ingredient, tare again, etc.

What I meant is that you might sometimes set out some of your ingredients into measured portions in an intermediary container, e.g. a bowl or a cup or even (gasp!) a measuring cup, before adding them into the cake batter. If you pour the milk from the carton into the batter and you overshoot the mark, you can't undo it very easily. 

[SilverSolder]

You weigh each ingredient separately.

The reason for weighing the liquids is simplicity: why dirty a measuring cup when you already have the scale out to weigh the flour? (Measuring flour by volume is a fool’s errand, and it’s quite telling that professional bakers in USA go by weight, not volume.) So you just add an ingredient, tare the scale, add the next ingredient, tare again, etc.

What I meant is that you might sometimes set out some of your ingredients into measured portions in an intermediary container, e.g. a bowl or a cup or even (gasp!) a measuring cup, before adding them into the cake batter. If you pour the milk from the carton into the batter and you overshoot the mark, you can't undo it very easily. 

Be bold - Be confident!  - it rarely goes wrong.

[KL27x]

^That's how I roll, for whenever I do what passes as cooking. I've never weighed anything I later ate. But I assume baking requires high precision, or something.

I have mixed reagents for lab work. After spending 45 minutes mixing a solution, I wouldn't pour the last bit in there over a scale.

[KL27x]

At the moment, only sizes above 0.5mm² are standardised. For smaller gauges we're stuck with a mishmash of SWG and AWG, but it might change in future. I suppose it was more important to standardise larger conductors which are used for safety critical applications, such as mains power. The sooner the smaller sizes are standardised, in SI units, the better.
https://en.wikipedia.org/wiki/IEC_60228

For smaller gauges we're stuck with a mishmash of SWG and AWG, but it might change in future.

Maybe they should standardize them to match AWG sizes? If that sounds weird...

...Americans use area to denote wire larger than half an inch diameter. Gauge for anything smaller. So this would be the same thing, in a way.

It appears the 0.52mm² stuff you find all over is made to the American standard. Per wikipedia, 20 AWG = 0.518mm² Not that this is a shocker.

;;;;
Now, I'm sure SWG will live on for quite awhile. But despite Britain implementing this SWG standard in 1880s, almost thirty years after Brown and Sharp invented AWG, they buggered it. Rather than sticking with a set percentage increase/decrease between steps, the Brits made their system piecewise linear, to make several areas of nice linear steps in while numbers. In imperial inches, of course. This was NOT future-proof and as well thought out, esp considering Britain is 20 miles from France.

[Zero999]

Yes, lots of the seemingly odd wire sizes are really AWG. It wouldn't be so bad if they did standardise to rounded AWG sizes, say 0.33mm², 0.2mm², but the EU probably won't do that.
https://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizes

[tooki]

You weigh each ingredient separately.

The reason for weighing the liquids is simplicity: why dirty a measuring cup when you already have the scale out to weigh the flour? (Measuring flour by volume is a fool’s errand, and it’s quite telling that professional bakers in USA go by weight, not volume.) So you just add an ingredient, tare the scale, add the next ingredient, tare again, etc.

What I meant is that you might sometimes set out some of your ingredients into measured portions in an intermediary container, e.g. a bowl or a cup or even (gasp!) a measuring cup, before adding them into the cake batter. If you pour the milk from the carton into the batter and you overshoot the mark, you can't undo it very easily. 

With practice, you learn how to dispense ingredients without overshooting beyond a reasonable tolerance.

[BU508A]

Edit:
Image attached to message

[tooki]

Please just attach the image here. The content delivery network hosting that image won't allow it to embed on other sites.

[BU508A]

Please just attach the image here. The content delivery network hosting that image won't allow it to embed on other sites.

Thanks, have not seen this. Image is now attached at the posting.

[rstofer]

The answer to this quandary is actually very simple.

They prefer working in feet and inches because there are 12 inches per foot.
And we all know that Americans have 6 toes on each foot so they find this one the easiest to count.


They will catch up with the rest of the world one day.

47 pages of well reasoned arguments and the US STILL hasn't changed.  I'm shocked!

Just remember:  There are two types of countries, those who use metric and those who have left footprints on the Moon.

I don't see us changing any time soon!  If 47 pages won't force a change, what will?

[Gyro]

47 pages of well reasoned arguments and the US STILL hasn't changed.  I'm shocked!

Just remember:  There are two types of countries, those who use metric and those who have left footprints on the Moon.

I don't see us changing any time soon!  If 47 pages won't force a change, what will?

I refer the honourable member to my reply #309. Nothing has changed, least of all, the member's attitude. 

If a bunch of Nazi scientists (with their metric calipers!) had run in a different direction at the end of the war, is search of a clean slate, there wouldn't have been an American footprint on the Moon. It would have been a Soviet, metric one!


EDIT: to quote from my post #309:

Lest you forget (or don't even realize) the father of the US space program was Werner von Braun, a member of the German Nazi Party and the SS, secretly smuggled out of Germany, together with around 1600 fellow scientists and stocks of V2 missiles. In his time as head of the V2 program, he was an active party to the deaths of up to 20 thousand people (slave labour) not to mention the people killed by his weapons. All conveniently swept under the carpet and forgotten in the interests of the US race to the moon. As you say, The Germans always did have the superior scientists!

https://en.wikipedia.org/wiki/Wernher_von_Braun

Presumably von Braun had to convert from the metric system to the American customary system when he was recruited to pioneer the US space program. Now that really is irony!

[bsfeechannel]

I love this thread not only because of its many hilarious arguments but also because I've learned a great deal about the metric system, which made me respect it even more.

So I think it is time for a little quiz to test our knowledge about metrication.

The people you see floating in the pictures below are orbiting around the earth's center of mass (at least at the moment the picture was taken and considering the earth's mass much greater than the orbiting people's). Try to spot which of them is using metric and which is using imperial units.

[rstofer]

Of course we snagged up as many German scientists as possible.  Germany has always had a superb educational system and world class scientists.  They were far ahead of the rest of the world.  There is no debate about that, it is fact.  There's a reason my parents had me take 4 years of German in high school (graduated '63) and perhaps this led to my being stationed in Mannheim, Germany rather than Viet Nam.  It was interesting, the young people in Germany (Boomers) all spoke English.  Or at least the ones I encountered and their English was far better than my German.

The US should keep combing the planet for talent and do whatever is necessary to bring them to the US.  We do quite a bit of that with our Doctoral and Post Doctoral education/research system and the associated visas.  We need to expand that!  And we need to make it easier for those scientists and engineers to bring their immediate families.  The H1B visa is not the way to attract high skill talent.

Need a foreign scientist?  Try a million dollar signing bonus!  It's worth every penny!

We do grow a few of our own at places like Cal Tech, Stanford, MIT and Berkeley but it's probably cheaper to import.

[rstofer]

I love this thread not only because of its many hilarious arguments but also because I've learned a great deal about the metric system, which made me respect it even more.

So I think it is time for a little quiz to test our knowledge about metrication.

The people you see floating in the pictures below are orbiting around the earth's center of mass (at least at the moment the picture was taken and considering the earth's mass much greater than the orbiting people's). Try to spot which of them is using metric and which is using imperial units.

Guess which ones are paying taxes for the other group to take a paid vacation!  In any event, the imperial unit woman is smokin' in any system.