why is the US not Metric

[Cerebus]

4' 11" and 1/16 is exactly 1.5 m. 3/8" is approximately 10 cm. Piece of cake: 1.7 m - wide minimum blind.

Want to try that again? 

You're trying to work out: 4' 11 ¹/₁₆" - (2 x ³/₈").  ³/₈" is approximately 1 cm, not 10 cm and the talk of clearance ought to make it clear that the blind is meant to be narrower than the window (recess) not (considerably) wider.

The exact answer is 4' 10 ⁵/₁₆". It's remarkably easy to do in your head as long as one knows 1" = ¹⁶/₁₆" and ³/₈" = ⁶/₁₆"; just re-cast it as:
 4' 11 ¹/₁₆" - (2 x ³/₈")
=> 4' 10 ¹⁷/₁₆" - (2 x ⁶/₁₆")
=> 4' 10 ¹⁷/₁₆" - ¹²/₁₆".

Junior school 'fractions' practice basically.

.

[Simon]

In fact to be more precise 4' 11" is 1.499 m

I forgot the 1/16 so its 1.5m or 1500mm exactly

[bsfeechannel]

4' 11" and 1/16 is exactly 1.5 m. 3/8" is approximately 10 cm. Piece of cake: 1.7 m - wide minimum blind.

Want to try that again? 

You're trying to work out: 4' 11 ¹/₁₆" - (2 x ³/₈").  ³/₈" is approximately 1 cm, not 10 cm and the talk of clearance ought to make it clear that the blind is meant to be narrower than the window (recess) not (considerably) wider.

The exact answer is 4' 10 ⁵/₁₆". It's remarkably easy to do in your head as long as one knows 1" = ¹⁶/₁₆" and ³/₈" = ⁶/₁₆"; just re-cast it as:
 4' 11 ¹/₁₆" - (2 x ³/₈")
=> 4' 10 ¹⁷/₁₆" - (2 x ⁶/₁₆")
=> 4' 10 ¹⁷/₁₆" - ¹²/₁₆".

Junior school 'fractions' practice basically.

.

You see? You prove my point. Imperial is error-prone. Ditch that rubbish.

[bsfeechannel]

In fact to be more precise 4' 11" is 1.499 m

I forgot the 1/16 so its 1.5m or 1500mm exactly

Case closed.

[mansaxel]

In fact to be more precise 4' 11" is 1.499 m

Edit: I also forgot that 1/16".

Code: [Select]

(((4*12+11 )+1/16) - (2*3/8) )* 25.4
1481.1375000000000000000

End edit.

Code: [Select]

treize:Avo mansaxel$ bc -l
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
(4*12+11 ) * 25.4
1498.6
.- (2*3/8)*25.4
1479.5500000000000000000

I spent more time than healthy calculating the result in fractions, but as soon as I understood to convert everything to metric it became quite easy. QED.

OTOH, now that we've got calculators that can do more than one thing in sequence, we can elect to stay in fractions one more step:

Code: [Select]


((4*12+11 ) - (2*3/8))* 25.4
1479.5500000000000000000


But staying in fractions is only sensible for math challenged people like me once we get user-friendly tools like bc or dc.

Also, I have a fundamental understanding how wide a ~150cm window is, but 4' 12"? That requires calculation. Proving that neither system is more natural, it only feels so when you're used to it.  But metric is used by more people, and it is systematic, which means that conversations between for instance distances and volumes are obvious. And base 10 is pretty handy.

[Cerebus]

4' 11" and 1/16 is exactly 1.5 m. 3/8" is approximately 10 cm. Piece of cake: 1.7 m - wide minimum blind.

Want to try that again? 

You're trying to work out: 4' 11 ¹/₁₆" - (2 x ³/₈").  ³/₈" is approximately 1 cm, not 10 cm and the talk of clearance ought to make it clear that the blind is meant to be narrower than the window (recess) not (considerably) wider.

The exact answer is 4' 10 ⁵/₁₆". It's remarkably easy to do in your head as long as one knows 1" = ¹⁶/₁₆" and ³/₈" = ⁶/₁₆"; just re-cast it as:
 4' 11 ¹/₁₆" - (2 x ³/₈")
=> 4' 10 ¹⁷/₁₆" - (2 x ⁶/₁₆")
=> 4' 10 ¹⁷/₁₆" - ¹²/₁₆".

Junior school 'fractions' practice basically.

.

You see? You prove my point. Imperial is error-prone. Ditch that rubbish.

No, imperial can't shoulder the blame here for any error proneness. You made errors in your imperial to metric conversion, understanding the question and not noticing that you had a clear "blind longer than window recess" result. Nothing to do with imperial, all your errors where made in the conversion/problem domain. I think anyone who deliberately chooses imperial if they have a choice of using metric is crazy but you clearly demonstrate that understanding and manipulating the problem is much more important than they units you use to express it in.

I'm lucky, I was educated in an era when the UK was actively using both imperial and metric units so I have no difficulty in thinking in either, although I'll pick metric if I have a choice. It also means that I'm primed to immediately notice that your "3/8" is approximately 10 cm" was off - I instinctively know how big 3/8" and 10cm are. I think it's fairly safe to assume that you're 'metric to the core' and so just don't have the instinctive grasp of imperial units that would allow you to immediately spot you'd made a gross error. Thus I think one ought to be very, very careful if forced to work in an unfamiliar unit system. I suspect an 'imperial to the core' American engineer might be prone to just the same errors as you if working the other way around.

What I'll never do is mix the two systems of units in the same job. Your "4' 11" and 1/16 is exactly 1.5 m" is not strictly correct, 4' 11 1/6" is actually 1.500 187 5 m exactly. For fitting blinds 187.5 microns 'off' is neither here nor there but tolerancing in metric and imperial simultaneously is exactly the kind of thing that can bite you in the unmentionables if you try and combine metric and imperial units. If you're working on everyday things one might choose 1/32" as an imperial tolerance and 1 mm as a metric tolerance as 'natural' units if you're working exclusively in one or the other, but if one is using a mixed unit system what does one pick 1/32" = 793.75 microns, or 1mm = 37.37 thou ~ 5/128" (exact = 5/127")? This way lies madness...

The other thing that any metric weenies need to watch out for if forced to use imperial - nominal imperial sizes of threaded connectors are often very much in name only -  a 1/4" bsp (british standard pipe) thread has nothing that measures in at 1/4". Metric threaded connectors are much saner. If I need imperial threaded connectors for something I check three times to make sure I've got the right variant out of the confusing variety of them. My pet hate is things that combine the two systems and then use similar sized but incompatible threads; PC cases typically use both M3 and 4/20 UNC threads at the same time - M3 for the baseboard standoffs, 4/20 UNC for most other things. An M3 screw will start to fit a 4/20 UNC tapped hole and then jam, a 4/20 UNC screw will fit an M3 tapped hole so that it won't pull straight out, but also so that it won't tighten.

[CatalinaWOW]

The comments on recipes are intriguing.  In the US virtually all units are volume (cups, fluid ounces, teaspoons and tablespoons). The exceptions are usually for things marketed in a standard size, the 1lb can for example. My experience with European cookbooks, confirmed by the examples given above show a mixture of volume and mass units.  Do cooks resort to scales or balances for these?

[Simon]

converting to metric and calculating is not the most accurate way. Not an issue here but it illustrates how scientific calculations can become a nightmare. If the problem is resolved in fractions and the result converted it will be more precise.

I found when doing calculations for my coursework that an error would quikly introduce itself if not enough digits were used and I found myself carrying out the whole calculation in one go on a calculator but breaking the operations down to wirte them out on paper so that the tutor could see the way i had done it. Obviously I never wrote out every last digit and if you calculated in steps like i wrote using the numbers I wrote the result would be different from the one I gave that was carried out in "full resolution" on the calculator with all the digits available.

For example it's not 1500mm exactly but 1500.18mm (and the rest), not worth worrying about for a window blind though.

You can of course just work in inches with decimal point.

[xrunner]

Well I'm in the US and I prefer metric myself. That's all I use on my model railroad projects and since I got a 3D printer it's all metric anyways (length and temp). I do have a box of bolts and nuts which unfortunately I've had all mixed up (imperial + metric), I really should sort all that out.

But if I deal with friends it has to go back to inches and Fahrenheit. They could use meters if they had to but when it comes to temps - nope, has to be Fahrenheit. I gave a soldering iron tip thermometer to a friend as a gift and he really cringed that it only displayed Celsius, but has since come around. Most wouldn't have a clue what an average indoor room temp would be in Celsius. 

[SL4P]

In the US, they have to retain Imperial measures, so they can measure their soft drink bottles and ammunition!

How the 7.62 and 9mm got through I can’t imagine!  Maybe they snuck in after WW2

[mansaxel]

In the US, they have to retain Imperial measures, so they can measure their soft drink bottles and ammunition!

How the 7.62 and 9mm got through I can’t imagine!  Maybe they snuck in after WW2

7.62mm is .300", so it's probably one of those NATOisms.

<tangent type="Tools are just another branch of T.E.A">

One of my best sources of AF spanners is Bundeswehr surplus, who, because they bought so much US military hardware, had to get tools for it, and why should the country where Stahlwille, Gedore, Belzer, Elora, Hazet, Wera and WiHa are sited (to this day with manufacturing in-country) buy overpriced Crap-On as an extra insult? The German tools are so much better. Even in imperial sizes 

</tangent>

Edit: but the big soda bottles are in metric!

[Monkeh]

PC cases typically use both M3 and 4/20 UNC threads at the same time - M3 for the baseboard standoffs, 4/20 UNC for most other things. An M3 screw will start to fit a 4/20 UNC tapped hole and then jam, a 4/20 UNC screw will fit an M3 tapped hole so that it won't pull straight out, but also so that it won't tighten.

6-32 UNC and M3, actually. Generally 6-32 for the motherboard standoffs (but occasionally M3..), expansion cards, also 3.5" HDDs. 2.5" HDDs, 3.5" floppies, and 5.25" optical drives are M3. Standard D-shell connectors for VGA, DVI, serial, and good old gameport, are 4-40.

At least get your facts straight.

[KL27x]

Do cooks resort to scales or balances for these?

Yes, that is weird to imagine, weighing all your ingredients to the gram, lol. 

In the US, they have to retain Imperial measures, so they can measure their soft drink bottles and ammunition!

Most Americans don't have any problem using mL and L. Soda has been sold in 1, 2, and 3L bottles since... well, ever since they stopped selling them in glass bottles. I often think in metric for volumes and it's probably because of soft drink bottles. Also, because "fluid oz" doesn't flow off the tongue. Anything other than cups and pints and gallons, I typically think and express in metric.

Also fun fact: our small plastic bottle of soda are often listed in mL and oz. So we have 12.7 oz bottle of soda or 375mL. Obviously same bottles for the rest of the world just labeled for US.

I often use mm where 1 or 2 is the size I'm trying to express.  But to me, 40mm x 120mm is still not automatic to visualize.

4'11" 1/16"  and 3/8" from either side? That's 3/4" you want to subtract. 11 minus 3/4 is 10 1/4. Add 1/16, and you get 4'10" 5/16, and it's pretty automatic if you do this more than once a year.

We learn fractions in grade school, but unless you actually use this skill, you will forget how to do it in your head.

Someone said that "metric is the ideal measuring system" or something to that effect. The ideal measuring system depends on the application. For crude oil, it's barrels. 55 gallons to a barrel. Or do you want to count the barrels coming off the ship and then multiply by 208.2 to get liters to see if you got what you ordered?

[Cerebus]

PC cases typically use both M3 and 4/20 UNC threads at the same time - M3 for the baseboard standoffs, 4/20 UNC for most other things. An M3 screw will start to fit a 4/20 UNC tapped hole and then jam, a 4/20 UNC screw will fit an M3 tapped hole so that it won't pull straight out, but also so that it won't tighten.

6-32 UNC and M3, actually. Generally 6-32 for the motherboard standoffs (but occasionally M3..), expansion cards, also 3.5" HDDs. 2.5" HDDs, 3.5" floppies, and 5.25" optical drives are M3. Standard D-shell connectors for VGA, DVI, serial, and good old gameport, are 4-40.

At least get your facts straight.

Kind of reinforces my point about checking three times on imperial connector sizes - I could have walked across the room and pulled out the (labelled) packet of spare screws and checked the actual designation. I didn't and consequently I'm screwed (pun intentional). On the other hand the simple straightforward metric designation of M3 came straight to mind and was correct whereas the imperial was misremembered.

[bsfeechannel]

No, imperial can't shoulder the blame here for any error proneness. You made errors in your imperial to metric conversion, understanding the question and not noticing that you had a clear "blind longer than window recess" result. Nothing to do with imperial, all your errors where made in the conversion/problem domain. I think anyone who deliberately chooses imperial if they have a choice of using metric is crazy but you clearly demonstrate that understanding and manipulating the problem is much more important than they units you use to express it in.

My errors are irrelevant. For the record, I know darn well that 3/8" is half a bee's prick from 1cm, i.e. 10mm. I have imperial drill bits, nuts and bolts galore in my shop. And none of my blinds are in recessed windows.

What I wanted to show and you demonstrated quite well is that you have to perform additional number base conversions to calculate what you want, even without the conversion to metric.

Metric doesn't demand that. So yes, imperial is to be blamed for errors.

I'm lucky, I was educated in an era when the UK was actively using both imperial and metric units so I have no difficulty in thinking in either, although I'll pick metric if I have a choice. It also means that I'm primed to immediately notice that your "3/8" is approximately 10 cm" was off - I instinctively know how big 3/8" and 10cm are.

I too received education in the imperial system. But since I don't use it much these days, I confess that I am a little rusty on the use of such units.

I think it's fairly safe to assume that you're 'metric to the core' and so just don't have the instinctive grasp of imperial units that would allow you to immediately spot you'd made a gross error.

I'm trying to wipe imperial out of my brain. Just that. Every time I bump into it, it's a WOMBAT.

Thus I think one ought to be very, very careful if forced to work in an unfamiliar unit system. I suspect an 'imperial to the core' American engineer might be prone to just the same errors as you if working the other way around.

I doubt it. The farad, the ohm, the ampere, the volt, the henry, the watt, etc. are all metric units. And no "imperial to the core" engineer complains about those. 

What I'll never do is mix the two systems of units in the same job.

Good advice. That's what we are trying to show to the "imperial to the core" guys. Since we realized that all units are interconnected somehow, there's no point in using two systems:

V = kg · m²/(C · s²) but feet, pounds and gallons.

[KL27x]

Since we realized that all units are interconnected somehow, there's no point in using two systems:

There are often reasons to use other systems. Example of crude oil by the barrel. No matter if you want to convert it to L or to gallons, it's easier to use barrels when loading/unloading the boat.

[bsfeechannel]

Do cooks resort to scales or balances for these?

Yes, that is weird to imagine, weighing all your ingredients to the gram, lol.

Nope. People have a good idea of what 100g butter or 500g flour means. Some of those quantities are the exact value, multiples or submultiples of what you find in the groceries. But if you need to weigh your food, that's what kitchen scales are for.

[KL27x]

Most wouldn't have a clue what an average indoor room temp would be in Celsius. 

Yup. I use C for soldering. But C doesn't mean anything to me in the ambient temp range. F seems better suited to express ambient temperatures, since anything over 100 is hot and really conveys the amount of discomfort, lol.

We mostly make sense of things by comparison. So units don't really matter so long as they conveniently sized for the application.

[KL27x]

"imperial to the core" guys.

Born and raised in US, and I don't think this guy exists. Other than as a strawman.

Another example where imperial just happens to be good size for the application is in machining and PCB work. Thousandth of an inch just happens to be about spot on for what you need to fine tune physical stuff to fit. It's the smallest unit that you can easily measure without jumping through hoops. All common electric calipers measure to a thous. 0.025mm just isn't that great a number, IMO.

[Cerebus]

"imperial to the core" guys.

Born and raised in US, and I don't think this guy exists. Other than as a strawman.

They definitely existed here in Britain's pre-metric past and for quite some time after official metrication here.

My father couldn't tell a centimetre from a centipede. His final full time job was as an area sales manager for fastener sales for GKN. That's an arena where he ought to have had a good grip of metric units but seemed completely alien to him. He knew what an M10 bolt was on an order form, but if a tape measure came out for a job around the house it was read off in feet and inches; to him coal, sand and cement came in hundredweights, petrol in gallons, beer and milk in pints, and food in quarters and pounds well after all of them had moved to being sold in metric units. I honestly don't think I heard him even mutter a metric unit right up to his death.

[Simon]

some people just want to keep imperial, like Jacob

[KL27x]

Maybe times gone by, yeah. Most Americans under retirement age, let's say, are very comfortable with metric. I think our young people are more inclined to metric and really most folks in college can't use an imperial tape measure for squat. It's the people who build stuff that get accustomed to 1/16".

How many times you get a blank stare and a moment of confusion when your total is 11.37, and you hand over a twenty and two ones? You don't have any preference for either system when all you know to do is punch numbers into a computer.

[tooki]

The comments on recipes are intriguing.  In the US virtually all units are volume (cups, fluid ounces, teaspoons and tablespoons). The exceptions are usually for things marketed in a standard size, the 1lb can for example. My experience with European cookbooks, confirmed by the examples given above show a mixture of volume and mass units.  Do cooks resort to scales or balances for these?

As someone who first learned to cook in USA and then moved to Europe, it also seemed odd to me at first to go by weight. But having become a very good cook, I’ve come to appreciate accurate measuring for the things where it’s critical (read: baking, candy, etc). It makes absolutely no sense to measure compressible powders (like flour) and ingredients with significant density variation between manufacturers (like salt) by volume, since the measurement can be off by a HUGE amount. (For example, when a recipe says to add salt, it absolutely matters what kind of salt it is: Diamond Crystal kosher salt, for instance, is HALF as dense as Morton’s kosher salt or regular granulated salt. For Europeans: it’s like comparing the same volume of fleur de sel vs. table salt vs. coarse pretzel salt.) And some ingredients, like honey and shortening, are just a pain in the butt to measure by volume, even if they can be measured accurately that way.

Cooking is one area where I have more or less abandoned US customary measurements, because weighing is just  so damned convenient, and grams are great for doing it because a digital kitchen scale’s dynamic range is enough to measure both large and small amounts accurately. The fact that water weighs 1g per ml also means that you can just weigh the water too, without even having to change units. (Less measuring cups to clean!) When I make bulgur, for example, I put a glass bowl on the scale and tare it, put in 200g of bulgur, add water to 600g, and then add bouillon powder to 615g. (Black pepper and olive oil added by eye, then it goes in the microwave for 11 mins at 1000W and then another 5 mins at 400W.) Tablespoons and teaspoons are the only non-metric measures I use, since even European recipes use those regularly. However, since most of my favorite cookbooks and cooking channels are in US units, I remain fully comfortable using them.

[bsfeechannel]

I often use mm where 1 or 2 is the size I'm trying to express.  But to me, 40mm x 120mm is still not automatic to visualize.

I developed rules of thumb to convert imperial to metric.

If the temperature in °F is below 300, I subtract 30 and divide the result by two. For instance, 100 °F: (100 - 30)/2 ~ 35°C. Quite warm for an ambient temperature. 40 °F: (40 - 30)/2 = 5°C. Hmm, pretty cold. For temperatures above 300 °F I simply divide by two. For instance, solder melts at about 200 °C. That's around 400 °F for you.

2.2 pounds is 1 kg. I divide the value in pounds by two and subtract 10%. So a 200-pound gorilla weighs about 90 kg. A little fat for 1.75-m tall guy.

1 foot is 0.3 m. 485 ft? It is about 500ft. So multiplying by 0.3 gives me about 150 m. That's about 1.5 the length of a standard city block. 

A mile is about 1.6 km. But I round it to 1.5 km.

A gallon is 3.8 l. So I round it to 4.

There are a little more that 4 inches in each 10 cm. So, 40" is about 1 m. 7 inches? That's something around 17,5 cm.

1/2" is about 13 mm, a little less.

1/4" is little more than 6 mm.

1/8" is little more than 3 mm.

1/16" is little more than 1,5 mm.

40 mm? That about 39 mm, which is about 3 x 13 mm, which is about 1" 1/2. 120 mm? A little less than 5".

That way I can have a rough idea what the "imperial to the core" guys are talking about.

Ounces (fluid or "solid"), pints, and all the rest, however, I don't even touch with a barge pole.

[Simon]

I used that sort of thing a lot with an imperial family. Forget what it should be, best tell dad in the measurements he understands when it's how far frow the wall is he that he is about to back into.