why is the US not Metric

[KL27x]

Instead of 40 gauges and 4 different 0 gauges, you could have 0.01mm .. 1mm in 0.01 steps or 0.025mm steps , 1mm..2mm in 0.1 steps, 2mm+ in 0.25mm steps ... not that hard.

But the size of the wire in diameter doesn't not change in a fixed step size. It changes as the square root of a fixed percentage. So if you measure by diameter, the step size will get larger as the wire gets larger, and it will get smaller as the wire gets smaller.

The discrete sizes we have are determined by the physical properties of wire. The jumps between draw dies are based on how much the wire can be drawn at one time without adverse consequences, like the wire breaking or being less uniform. This ends up something to do with square root 39 or 92 or some weird number. This is to get the maximum useful sizes of wire in the least number of steps/cost from the starting extruded stock materials/slugs.

How is it easier to say 14 gauge... do you keep in your head all the diameters and areas for all gauges?

First off, I do say and think in gauge. I don't keep all the diameters in my head, but I know some key numbers which I commonly use.

Without looking it up, I know 30AWG is about 8.5 thous to just shy of 10 thous in diameter, depending on where you buy it. And I know 16 AWG power cord is very typical for most hand held power tools, which is rated for probably ~10 amps, continuous. I know 22 AWG will be around what most people like to stick in a breadboard. I know modern small components thru hole leads are thinner than that, though. Maybe as little 24-26 AWG.

If you go by diameter, you still have to look things up. When you do your calculation and figure out you need 0.38185 mm2 wire, you can't just order that. You have to look up the closest sizes. Gauge is a standard, not a unit. Once you figure out the gauge, then you can buy it by the standard.

Also, when you calculate everything by square mm, but you call it by diameter, do you not end up having to say diameter? That is already way stupider to say than gauge.

Another thing you can say is that pipe sizes in imperial are dumb. But a "schedule 40" pipe is not just a size. It's a standard which specifies tolerance in composition and a specific manufacturing technique, all of which result in a specific product, which welds a specific way, and will withstand specific pressures and lateral and environmental stresses when fitted and welded to the further standards employed by pipeline construction. It's more than just an arbitrary ID and OD. And if you make it 20% bigger in all dimensions (or physically change the dimensions to match better with metric), your workforce will have to relearn/recertify in the protocols for welding it, and we won't know all the repercussions for another 50 years down the line. AWG is not as complex of a standard, but it is a standard. Drawing a wire changes the structure and physical properties. An extruded or turned wire will not be the same as a wire drawn to the same size. The two wires will not be the same thing. AWG conveys more than just the diameter of the wire, although you could just assume that going by diameter does the same, of course. You just won't get the neat quantum steps you envision, unless you use some new non-linear unit based on the formula used for drawing wire? (And then you would end up with something very similar to gauge; albeit, potentially inverted).

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No. It must be something that appeals to what they are crazy for, something they won't resist or raise objections to.

With a demographic as diverse as the US, maybe this can best be summed by cost. If it reduces our taxes, then we would probably do it. Since the opposite will happen, and the only "inconvenience" to not mandating a change is that we continue to use a system we actually like, in addition to metric, then good luck finding this silver bullet. Using both systems is not a detriment. Using a uniquely different systems in each state would be a detriment. That is why the change to metric was more important in Europe.

[stefan_trekkie]

We don't use diameters for wires. We use the aria of the wire .. 0.5mm² .. 6mm² ... etc .. And the calc is easy and done for a second - there are tables for that and the super fast .. 1mm² - 6 amps current limit (may be more on some specialized cables but in general) .. So if you have 3kw consumer for example .. 240 volts (or 400v 3 phase even at home) That are 12 amps .. That is 2mm² or more .. (0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10 are the standards)
Also for short we don't use mm² .. We just say (how many) squares

[KL27x]

And... those are no longer units. They're standards. Rounded off to certain whole nominal numbers. So now, to make close calculations like what bsfeechannel wants to do, you have to look up the actual areas of the wire. And you also don't know from looking at one catalog, if there are other sizes available between say 4 and 6 or 6 and 10. Unless you look at a chart of the standards.

This is a small improvement in utility and doesn't help too much. At least when I say 12 AWG, I know it's a thing. I don't have to look it up to make sure if it exists or not, like saying 8mm^2  wire. Does this exist (under $10,000 for a custom run)? Is it between steps? If I am using I suppose you will have to refer to your chart. Even in AWG, certain sizes might not be cheap or common, I suppose. Sometimes it's cheaper to skip some gauges, for manufacturing/market reasons. So it's not all that big a problem. But it's a thing. Your 10mm wire might round to 11, irl, but called 10mm, because it sounds better, and the next size up is much bigger than 11, anyway.

[stefan_trekkie]

Nope. There are no standards between that.. Everything is on that chart .. If you need 8mm² by calculation (as was your example) you just now that is no such thing and use next big one - 10mm² .. next is 16, 25, 35 etc... (very big industrial cables) Big ones increase in smaller steps and i don't have used ones above 10mm² that are not 3 phase .. But should exist.

EDIT: the specialized wires for bobbins and transformers have tiny steps

[KL27x]

Isn't that basically what I just said? That you have to refer to a chart, anyway, to source and buy and to look up actual dimensions if doing a close calculation.

If I'm a seller of this wire, can I just put the calipers on it and calculate cross sectional area and list what I measure? No. I might measure the 10mm^2 as 11. And no one will find my listing. You have to look up the standards. The way you make the standard sound like a measurement can be detrimental, in some ways, when it comes to communication.

I'm also curious to see how this system works out at the finer end, say 36-40 AWG. Remember that jumping between mm^2 and micrometers^2 is 6 significant digits, so you are stuck with some zeros or some really large numbers in micrometers.

In truth, you will learn what steps are there, in w/e work you are doing. You're just learning stupider numbers, like you might know 1.5 and 2.5 is wire sizes. But 2, 3, 4 are not (dunno for sure), because you work with those wire sizes.

The AWG system separates the standard from the units, and it can be described in any unit of measurement. This seems like a good idea for this particular thing. Esp when the actual dimensions of the wire are needed. You will be calling it by the standard size and also using the real size, both in "mm^2."

[stefan_trekkie]

You can measure it with calipers (everyone can do that it wants to) and use ..  Пd²/4 and find the aria and it is hard with some multi-core cable cables to do .. But the cables are marked and in sections in stores. (3x2.5mm² CBT ) for example .. power cable with "venelith" isolation (i don't know the word in english )

[KL27x]

^

No. I might measure the 10mm^2 as 11. And no one will find my listing. You have to look up the standards. The way you make the standard sound like a measurement can be detrimental, in some ways, when it comes to communication.

Plus not all wires are marked outside the insulation. Not all wires have insulation, even. Also great, now you need a superscript font to label your power wires.   

[Zero999]

There appears to be come confusion over metric and SI units. All SI units are inherently metric, yet not all metric units are SI. For example the calorie, or more commonly kilocalorie, used for food energy, is a metric unit. It's equal to the amount of energy required to heat a gram of water by 1°C. The SI unit is simply the Joule. The same is true for speeds on road signs, in km/h, which is metric, but not the SI unit for speed which is m/s.
https://en.wikipedia.org/wiki/Calorie

Wire gauges are crap compared to using the cross-sectional area, which does make calculations much easier. Doubling the cross-sectional area, halves the volt, drop, with everything else being equal and I don't need to refer to a table to work out the diameter for a 2mm² or whatever piece of wire. I can easily calculate it, by rearranging a = πr² to make r the subject and multiplying by 2: it's simple high school algebra. Granted, it's a little more tricky, for stranded wire, but adding on 15% gives a close approximation and is normally on the large side, which is good in most applications. I'd love to see the back of AWG and SWG and have all cables specified in mm². It should be a global standard, with no county being the exception.

[CatalinaWOW]

Another point of view on the topic of this thread starts with a question.  We mostly all agree that the metric system was designed from ground up to be self consistent and relatively easy to use.  Esperanto is language designed from the ground up to be self consistent and easy to use (regular verbs and all that stuff).  Why doesn't everyone speak Esperanto?

I would assume that the reasons we haven't leaped to metric here in the US are very similar to the reasons that almost no one on this forum speaks Esperanto.  Arrogance isn't number one on the list.  The only difference between Esperanto and metric is that metric does have the advantage of widespread utilization.  But if widespread utilization is the dominant reason for adopting something, why doesn't everyone speak English?  Or Chinese if you want to go by numbers instead of breadth.

[GeorgeOfTheJungle]

Wire gauges are crap compared to using the cross-sectional area

And are backwards: thicker wires have smaller AWG #

[stefan_trekkie]

The real reason US is not metric is that US is self contained too. For the most part they had everything self produced. That includes resources, machines, goods, energy etc even you can include the culture in that .. They can use totally different 3rd system and called a day.   

[SilverSolder]

These days, the US GDP is what...  24%?  That is a big economy, for sure, but it does need to interact with the other 76%...

[paulca]

But democracy is delivered in US customary units.

You mean 500lb JDAMs?

[GlennSprigg]

I love a sunburnt country,
A land of sweeping plains,
Of ragged mountain ranges,
Of droughts and flooding rains.
I love her far horizons,
I love her jewel-sea,
Her beauty and her terror
The wide brown land for me!   

This is such a beautiful poem.
Between it and the song "Land Down Under", have made visiting Australia one of the objects in my bucket list.

Right now, all I can do is enjoy a Vegemite sandwich.

Now THATS making some sense now!!  (This post is going round & round in circles!!!)
Americans need to be 'edurmicated' about 'Vegemite' !!   
The way I explain it to foreigners is that it is NOT something disgusting like Monkeys brains and Bears Bile
or what ever, and nor are we poisoning you. It is just made from Vegetables. I tell them...
  Do you have vegetable Stock-Cubes, like you would use in soups/stews etc...
  Well, Vegemite is just like a vegetable stock cube, but in the form of a Paste!!
Every Aussie kid (and adult) in Australia can not be wrong, & have it from 1-years old or earlier!!
There's also Marmite & Promite. (Not to mention the English 'Bovrille'...   

[vwestlife]

I would assume that the reasons we haven't leaped to metric here in the US are very similar to the reasons that almost no one on this forum speaks Esperanto.  Arrogance isn't number one on the list.  The only difference between Esperanto and metric is that metric does have the advantage of widespread utilization.  But if widespread utilization is the dominant reason for adopting something, why doesn't everyone speak English?  Or Chinese if you want to go by numbers instead of breadth.

Or, for that matter, why hasn't the rest of the world adopted the English spelling reforms that were pioneered and have become commonplace in the U.S.? I.e., "centre" -> "center", "gaol" -> "jail", "plough" -> "plow", "manouevre" -> "maneuver", "programme" -> "program", etc.

[Zero999]

Another point of view on the topic of this thread starts with a question.  We mostly all agree that the metric system was designed from ground up to be self consistent and relatively easy to use.  Esperanto is language designed from the ground up to be self consistent and easy to use (regular verbs and all that stuff).  Why doesn't everyone speak Esperanto?

I would assume that the reasons we haven't leaped to metric here in the US are very similar to the reasons that almost no one on this forum speaks Esperanto.  Arrogance isn't number one on the list.  The only difference between Esperanto and metric is that metric does have the advantage of widespread utilization.  But if widespread utilization is the dominant reason for adopting something, why doesn't everyone speak English?  Or Chinese if you want to go by numbers instead of breadth.

That's not a very good analogy. Languages are by their nature organic and evolve over time. People pick up their first language during a critical period, rather than being taught it in a structured manner. Moving to Esperanto would require everyone learning it as a second language which is notoriously difficult. The only way it could work to put many people with totally different mother tongues, on an island and teach them all Esperanto so they could all use that to communicate. Such an experiment would probably fail, in the long term, as they'd mix their own languages with Esperanto and the resulting language would be completely different within a couple of generations.

Measuring systems are taught in school and it's fairly easy to learn a new one, compared to a different language.

[paulca]

Or, for that matter, why hasn't the rest of the world adopted the English spelling reforms that were pioneered and have become commonplace in the U.S.? I.e., "centre" -> "center", "gaol" -> "jail", "plough" -> "plow", "manouevre" -> "maneuver", "programme" -> "program", etc.

I think you have that backwards.  US English was branched before the spelling reform in the civilised world.

[bsfeechannel]

The real reason US is not metric is that US is self contained too. For the most part they had everything self produced.     

That doesn't explain why other "self contained" countries decided to go metric long ago. That could be a contributing factor, but I think that the crucial components were perhaps the cultural proximity to England and the economic success of both. Success is a bad teacher. That way they could not assess the the real implications of full metrication. Up to this day many of them treat metric as a mere alternative to imperial, when metric represents a leap forward.

What is ironic is that today the US is everything but self-contained and now even their flags are produced by their economical rivals.

Then


Now

[tooki]

Also, the problem with "pure metric," is for when you are done doing the calculations. When you are building your thingamabob, you might have more than one gauge of wires at your work. It's easier to "Hey Bob, we're running low on the 14 gauge. Can you order some more?" Vs saying "hand me the 0.01787mm^2 wire." So why not use both?

How is it easier to say 14 gauge... do you keep in your head all the diameters and areas for all gauges?

For example AWG 14 is 0.0641 in or 1.628mm diameter,  or 2.08 mm2  ... you could just round it and ask for 2mm2 wire or 2.1mm2 wire

0.01787 mm^2 area would correspond to something between AWG 34 and AWG 35...  0.00561 in , 0.143mm diameter and  0.0160mm2  ... just round it up and ask for 0.15mm diameter  or 0.02mm2 area ?

Instead of 40 gauges and 4 different 0 gauges, you could have 0.01mm .. 1mm in 0.01 steps or 0.025mm steps , 1mm..2mm in 0.1 steps, 2mm+ in 0.25mm steps ... not that hard.

Would be easier to just say directly the area or diameter... or maybe use another parameter like resistance per meter where actual thickness is less relevant (ex use aluminum wires or steel wires vs copper wires)

It doesn’t matter. Ultimately, when you need to choose a wire, you calculate the amps it will carry and then use an ampacity chart to choose the right one. Whether the result is a mm² cross section, diameter, or AWG is irrelevant.

We don't use diameters for wires. We use the aria of the wire .. 0.5mm² .. 6mm² ... etc ..

Except this isn’t true, either: stranded wire is given in mm², but solid wire is given in diameter!

Wire gauges are crap compared to using the cross-sectional area

And are backwards: thicker wires have smaller AWG #

That is intuitively backward until you think of it like this: how many times must the wire be drawn through a die to reach that size? Thinner wire = more dies = higher number.

Or, for that matter, why hasn't the rest of the world adopted the English spelling reforms that were pioneered and have become commonplace in the U.S.? I.e., "centre" -> "center", "gaol" -> "jail", "plough" -> "plow", "manouevre" -> "maneuver", "programme" -> "program", etc.

I think you have that backwards.  US English was branched before the spelling reform in the civilised world.

English has never had a spelling reform, since English has no standards body to define what is and isn’t correct. All of our standards are de-facto, not de-jure.

[Zero999]

It doesn’t matter. Ultimately, when you need to choose a wire, you calculate the amps it will carry and then use an ampacity chart to choose the right one. Whether the result is a mm2 cross section, diameter, or AWG is irrelevant.

No it's not. Want half the voltage drop? Simply double the cross-sectional area. No need to refer to any charts. Quite the voltage drop is the limiting factor, long before the insulation starts to melt.

Except this isn’t true, either: stranded wire is given in mm², but solid wire is given in diameter!

Solid core wire for use in building wiring is normally specified in mm².
https://www.screwfix.com/p/prysmian-6242y-twin-earth-cable-2-5mm-x-10m-grey/82572#product_additional_details_container

That is intuitively backward until you think of it like this: how many times must the wire be drawn through a die to reach that size? Thinner wire = more dies = higher number.

That's only relevant to the manufacturer. The end user doesn't care about that. Cross-sectional area is plain and simple to understand, compared to an archaic gauging system.

[KL27x]

No it's not. Want half the voltage drop? Simply double the cross-sectional area. No need to refer to any charts. Quite the voltage drop is the limiting factor, long before the insulation starts to melt.

Firstly, this is a 1kg per liter of water. How often do you need to do this? Not very. And the easiest way to halve the resistance of your wire is to go take another wire and put two in parallel, lol.

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?  )

[Mattylad]

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.

[KL27x]

Measuring and communicating distance is not equal to counting. And that is weird that you guys count with your toes.

[GeorgeOfTheJungle]

Eeny meeny miny moe...

[tooki]

No it's not. Want half the voltage drop? Simply double the cross-sectional area. No need to refer to any charts. Quite the voltage drop is the limiting factor, long before the insulation starts to melt.

Firstly, this is a 1kg per liter of water. How often do you need to do this? Not very.

Actually it’s quite common: when cooking or baking, it’s often best to go by weight of dry ingredients, and so then you can just tare the scale after each ingredient, including liquids. Water is 1kg/l, milk and spirits are close enough. Only oils and sugar syrups require a different ratio.