Metric vs. imperial: point in metric's favor - Page 1
Forum section: electronics / general

author: Analog Kid
author_rank: Super Contributor
timestamp: December 13, 2024, 11:06:34 pm
content: OK, another installment in the ongoing metric vs. non-metric feud.Normally I weigh in on the side of non-metric usage, at least for let's call it "domestic" usage, meaning anything outside the realm of scientific or technical measurement: cooking, carpentry, etc.So far as scientific and technical usage goes, metric is not only clearly the winner so far as accepted usage goes, but it's also probably actually superior for those purposes, being a decimal-based system. There's a reason all those pointy-headed scientists use SI units. So let's concede that up front.But there's another area where going to metric usage would clearly be an improvement on a really messed-up system. I'm referring to the printing industry, specifically the classification of printing-paper weights.Now the first thing to know is that for historical reasons, reaching back into antiquity to how the king's scribes worked on their folios or some such thing, different kinds of printing paper come in different sizes. Of course, paper can be cut to any size: what I'm talking about here is what's called the "basis" size for a certain type of paper, which is the size of a full-size sheet of that type of paper before it's cut by the printer into a print sheet or the final printed item. When printers go to the paper supplier, they buy paper by the ream (500 sheets) in big cartons at the basis size. (The paper supplier also sells small reams of bond, index, etc., in "letter" and "legal" sizes for direct printing on a small sheet.)So to take two very common types of paper, bond and so-called "text" (and here I'm going to use the non-metric sizes):The basis size for bond is 17" X 22"The basis size for "text" is 25" X 38"Why are those the sizes for those paper types? Don't ask me; I don't know. Some hysterical reason.OK, so what? Well, it turns out that the way printing paper weights (at least in North America) are measured is by taking the weight of a ream (500 sheets) of that paperat the basis size. So a very common weight for bond--the weight that you'll buy at the office-supply store when you buy a ream of paper for your laser printer--is 20 lbs., so the paper is called "20 lb. bond".But:a ream of "text" paper, which is almost exactly the same thickness (and therefore the same weight) as bond is50 lbs., because the basis size is so much larger. So that paper is known as "50 lb. text".WTF??? I used to be a printer, and it took me a while to absorb that: 20 lb. bond is the same as 50 lb. text. Which really makes no sense.Likewise for all the other different types of paper: cover (thicker, used for book covers, etc.) whose basis size is 20" X 26"; "index" (the stuff index cards are made out of), 25-1/2" X 30-1/2" (!!); and so on.Now that's on the non-metric side. On the metric side, you still have all these different crazy types of paper, each with their own basis size.But, the weight measurement system is much more rational:It's measured ingsm, or grams/meter2.Much more sensible; now we're comparing apples to apples.Now if we could just somehow harmonize sheet sizes: our letter (8-1/2" X 11"), legal (8-1/2" X 14"), etc., vs those A1/A2/A3, etc., sizes. Which are very close but not at all the same ...

author: Benta
author_rank: Super Contributor
timestamp: December 13, 2024, 11:27:53 pm
content: Judging by your location, it's probably US, not Imperial.If you want to talk paper, OKA0 is 1 m2with an x/y ratio of 1/sqrt(2).If you cut it in half, it will be 0.5 m2, still with a side ratio of 1/sqrt(2). (A1)If you halve it again, it will be 0.25 m2also with a side ratio of 1/sqrt2. (A2)I could go on, but you get the idea.Simple, no?

author: TimFox
author_rank: Super Contributor
timestamp: December 13, 2024, 11:29:37 pm
content: The US paper inch sizes (8.5 x 11, 11 x 17, 17 x 22, etc.) can all be cut from the same size sheet, but have different aspect ratios.The "A"-series European sizes (A3 = 297 x 420 mm , A4 = 210 x 297 mm, etc.) all have the same aspect ratio (1 : 21/2) and can be cut from each other (four A3s or two A2s from one A1).If one were allowed by pedants to express area in dB, they would be 3 dB apart.And then there are photographic papers (4 x 5 inch, 8 x 10, 11 x 14, 16 x 20, etc.) that have the same aspect ratio as a traditional film camera, as opposed to the 2:3 aspect ratio of a 35 mm frame.Traditional book sizes are based on the "folio" and its divisions: folio at 12 x 19 inch, quarto at 9.5 x 12, ... , 16mo at 4 x 6.8, etc. Larger sizes include the famous "double elephant folio", approximately 50 inches high.These terms and approximate dimensions started centuries before the adoption of the metric system.A website with a huge set of paper sizes:https://papersizes.io/

author: Analog Kid
author_rank: Super Contributor
timestamp: December 13, 2024, 11:32:09 pm
content: Quote from: Benta on December 13, 2024, 11:27:53 pmYes, I'm in the US.But you raise an interesting point: I used the term "imperial", but I'm not sure that's correct.I've heard our (US/N. American) measurement system referred to as that, but not sure that's right.Is "imperial" what's used in the UK?Anyhow, I mean "non-metric". Which I suppose comes in a few different flavors.

author: Benta
author_rank: Super Contributor
timestamp: December 13, 2024, 11:48:58 pm
content: Just look at petrol (US: gas); US and imperial gallons are not the same. Or pints of beer...

author: brucehoult
author_rank: Super Contributor
timestamp: December 14, 2024, 12:02:32 am
content: Fair enough on paper weights, though the US could perfectly well resolve the issue within their weird system by using something like e.g. oz/sqft.Well, that one is a bit inconvenient as 80 gsm is 0.26 oz/sqft, as Google search was perfectly able to tell me. Or 9.43 oz/sq fathom. Hmm. Or 1142 oz/sq chain. Better. But too big.AHA! 71.4 oz/sq rod. Perfect.Or if you want an Imperial unit, 51 stones/acre.Also, A3/A4 etc paper sizes are nothing to do with the metric system (SI). That's ISO 216.

author: TimFox
author_rank: Super Contributor
timestamp: December 14, 2024, 12:08:46 am
content: Quote from: Analog Kid on December 13, 2024, 11:32:09 pmAs I keep pointing out, the term in the US is "conventional units". US conventional units are not identical to Imperial units. Just ask any beer drinker.In the US, Federal statutes define the conventional units (yard, gallon, pound, etc.); in this modern era, they are defined quantitatively in terms of metric units (meter, liter, kilogram, etc.).

author: jpanhalt
author_rank: Super Contributor
timestamp: December 14, 2024, 12:32:00 am
content: Quote from: Analog Kid on December 13, 2024, 11:06:34 pmDo you really mean just another meaningless and endless thread?QuoteThen why are our computers and MCU's binary? BCD is still binary. The last time I used a decimal computation device was in the 1960's in college. It was called a slide rule.Decimal is simply a choice and may be related more to anatomy than any inherent superiority. I have read that ancient Egyptians used fractions and a sum of fractions. Carpenters and I (I am not a carpenter) do the same. That is, rather than say something is 17/32" they will write that as 1/2 +1/32, which is exactly what binary does too.

author: xrunner
author_rank: Super Contributor
timestamp: December 14, 2024, 12:35:49 am
content: I prefer metric for all my personal projects now, not just electronics or 3D printing. But if I have to deal with contractors - like for oh I dunno, fencing, flooring, plumbing, or whatever they are working on you can forget it - they ain't going to deal with metric at all.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 14, 2024, 12:36:39 am
content: Quote from: brucehoult on December 14, 2024, 12:02:32 amAlert the ISO! We've got the new standard! (For N. America anyhow.)

author: Analog Kid
author_rank: Super Contributor
timestamp: December 14, 2024, 12:46:52 am
content: None other than George Orwell*worked his dislike of the metric system into his1984:QuoteHere's a page with some more context for this.*AKA Eric Blair

author: nctnico
author_rank: Super Contributor
timestamp: December 14, 2024, 01:08:09 am
content: It is very simple. Inches are derived from the size of a sausage while metric sizes come from an actual SI standard.Who would want to measure things in sausage units?

author: brucehoult
author_rank: Super Contributor
timestamp: December 14, 2024, 01:30:37 am
content: [ Specified attachment is not available ]Quote from: Analog Kid on December 14, 2024, 12:46:52 am

author: themadhippy
author_rank: Super Contributor
timestamp: December 14, 2024, 01:31:34 am
content: Quotethought it was bananas

author: brucehoult
author_rank: Super Contributor
timestamp: December 14, 2024, 01:34:14 am
content: 3.11 bananas. 79mm. Weird size.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 14, 2024, 01:35:07 am
content: Must be "engineer's bananas" since they're divided into tenths instead of 8ths/16ths.Oh, and "very near" caliper: ha ha, I get it.

author: brucehoult
author_rank: Super Contributor
timestamp: December 14, 2024, 02:35:56 am
content: Quote from: Analog Kid on December 14, 2024, 01:35:07 amI decided on the 0.01 in the 3.11 bananas by using the "very near" principle.

author: xrunner
author_rank: Super Contributor
timestamp: December 14, 2024, 02:37:59 am
content: Looks like those are only for ripe bananas.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 14, 2024, 03:03:43 am
content: Quote from: Benta on December 13, 2024, 11:48:58 pmWhich leads to a "whinge" of mine;Australia had its own standard beer glass & pot sizes, all Imperial based, after the "sorting out" of some minor State differences.At Metrication, those standards were all metricated to the nearest Metric size, which was very close to the original & peace was upon the landAlong came "de-regulation" & "let the market decide", & some taverns began to sell beer in English style "pints", so all the "little trendoids" could pretend they were in London.For some unknown reason, it "took off" & the scourge of "re-Imperialisation by stealth" spread across the country, till now, you can't buy beer in the traditional sizes.To add insult to injury, there seems to be no regulation on what a "pint" is, so you have no way of knowing whether you are getting a "full- blooded" Pommy pint, or a wimpy US "pintette"

author: TimFox
author_rank: Super Contributor
timestamp: December 14, 2024, 03:10:56 am
content: An article inThe Economistlast summer discussed an American trend to sell canned beer in Imperial pint sizes.It seems that the automated beer-can-making machines come with a discrete set of selectable sizes, including US customary pints, Imperial pints, normal 12 US fl.oz., and various metric sizes.

author: brucehoult
author_rank: Super Contributor
timestamp: December 14, 2024, 03:22:06 am
content: Quote from: vk6zgo on December 14, 2024, 03:03:43 amThere is no good reason -- certainly no legal reason -- that things must be sold in "round number" sizes. It's only ever the units used on the label that is regulated.So 568 ml? Not a problem.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 14, 2024, 03:37:09 am
content: Quote from: brucehoult on December 14, 2024, 03:22:06 amWhen I have had a "pint" of beer recently, there were absolutely no markings on the pot, so I have no idea how much it contains.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 14, 2024, 03:38:32 am
content: Quote from: TimFox on December 14, 2024, 03:10:56 amSurely that is a bonus for beer drinkers.

author: TimFox
author_rank: Super Contributor
timestamp: December 14, 2024, 03:43:37 am
content: Quote from: vk6zgo on December 14, 2024, 03:37:09 amIn the US, all packaged goods must have the size on the label, usually in metric and conventional units.However, apparently US and Australia do not require calibration of glassware for serving beer.I like the German glassware with a calibration line. At a classy restaurant, the line is engraved on the wine glass, but normally it's just a simple label.

author: wraper
author_rank: Unknown
timestamp: December 14, 2024, 04:53:49 am
content: Already posted in other thread, but noticed this which should be more suitable, so will post here as well.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 14, 2024, 05:37:55 am
content: I will stipulate that metric is a better system. Marginally in most areas, but better.But I really lose it when metric fans bring up scores of US conventional units that are barely if ever used and for the ones that are used invent silly ways of using them that no sane person does.Furlongs. Used only to measure horse racing tracks. No other use that I am aware of.Rods. Used in historical documents on surveying, but not really a thing for anyone else.Drams. Same thing. Archaic medicine and for gunpowder historical re-enactments.Carats. Wait, I think everyone uses these.This list can be extended quite a ways.Also, things are usually not broken down into sets of smaller and smaller units. An object roughly four meters long is not described as 3 yards, 2 feet and 3 inches (this construction is often brought up to express the silliness and/or difficulty of US conventional units.) In some industries (framing carpentry for example) feet and inches will be used, I guess because it is tradition in that industry. Not so much for finish carpenters who often stick to just inches. In most engineering settings using non-metric units the work is done in decimal units, with the base unit picked for the size of the application so that only one unit is used. For example when I started in aerospace airframe dimensions were in inches. These were airframes up to about six meters in max. dimension so only 3 digits were required for the largest measurements, and 3 decimal places got you to the precision needed for almost all parts. 999 inches is just over 25 meters so this approach works for pretty good size airframes. If your engineering brain can wrap around 4 digits you start handling all but the largest airframes. Or (GASP), use scientific notation. Just enter it in your calculator or spreadsheet. Calculators don't have keys for pico, nano, micro, milli and so on so those brain cells are memorizing something no matter what system you use.The one area that the metric system really shines is in eliminating the confusion between pounds force and pounds mass (and all of the stand ins like poundals and slugs). The metric system has this well sorted. Unfortunately not so much for metric users. I can't tell you how many times I have seen force expressed in kilograms. Just saw one today on a load cell. So the problem exists in technical people, not just the great unwashed masses.

author: brucehoult
author_rank: Super Contributor
timestamp: December 14, 2024, 06:08:03 am
content: Quote from: CatalinaWOW on December 14, 2024, 05:37:55 amFurrows, obviously.An acre is a furlong long (10 chains) by a chain wide. How else to measure how much ploughing you did today, or have left?QuoteI'll give you rods are not used, but chains are -- or were until we switched to metric in the early 70s.QuoteNot really a problem though, is it, because it's quite clear what is meant. Multiply by 9.80665 (10 for a quick estimate) and you're golden with Mr Newton.

author: m k
author_rank: Super Contributor
timestamp: December 14, 2024, 09:29:22 am
content: Here book is 25 sheets, rice is 500 sheets, so rice is 20 books and pack is 10 rices.Some others'tiu' 20 eggs'kerppu' 31 lampreys, 30 + 1 for binding'kiihtelys' 40 squirrel skins

author: jpanhalt
author_rank: Super Contributor
timestamp: December 14, 2024, 10:37:44 am
content: @CartalinaWOW (and later)Another significant unit still used is the troy ounce and troy pound. The oz troy in grams is more than the avoirdupois ounce in grams, but the troy pound is only 12 ounces. Don't get cheated if you are buying precious metals.As for rods and chains, they were used well into the 1980's for real estate based on personal experience, and probably still are. That may vary by state as they are critical for deeds. A "section" (640 acres) = 1 mile square and is still used in everyday conversation and deeds. As pointed out already, imperial measures wre easy for humans to relate to. In farming areas, one talks of quarter sections, etc. Once we get below 1/4 (or 1/8) section, we usually switch to acres. We also have townships, and the typical size in most of the US is 36 sections (6 miles square). In northeastern Ohio, however, many townships are only 25 sections. That is related to our history as the "Western Reserve" of the state of Connecticut. It's all perfectly logical, Watson.

author: nctnico
author_rank: Super Contributor
timestamp: December 14, 2024, 11:03:16 am
content: Quote from: CatalinaWOW on December 14, 2024, 05:37:55 amActually they do (at least some models from Casio). I have used such calculators since the start of my EE studies (decades ago) and still do today. Everyone working with electronics should have one as it makes life so much easier and less prone to mistakes.

author: dave j
author_rank: Regular Contributor
timestamp: December 14, 2024, 11:19:02 am
content: Quote from: brucehoult on December 14, 2024, 06:08:03 amCricket pitches are still defined as 1 chain long.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 14, 2024, 12:05:46 pm
content: Saying kg and newtons (mass and force) are easily sorted by multiplying by 9.8 ( the metric g), is no different and no better than saying you can sort conventional units by multiplying by 32. In both cases what is meant is usually clear by context. To those bright enough and well enough educated to know why you would do such a thing. But most of the benefits of the metric system are for those that aren't so privileged and need help remembering a few scale factors.And I will stand by the rarity of use of most of the obscure units. Sure, legal documents will preserve old usages. I am sure the same thing exists in metric countries. Land descriptions, water rights and a myriad of other things were defined long before the metric system as I am frequently reminded by folks who tell me that the US doesn't have a long history. My relatives are farmers and none use furlongs to measure furrows.I will grant the widespread use of acre, but will compare it to the metric hectare. Sure it is a nice 100 meter square, but why is it not using one of the standard power of three units. A kilare? So yet another prefix to memorize.

author: themadhippy
author_rank: Super Contributor
timestamp: December 14, 2024, 01:51:35 pm
content: Quotestill very commonly used in scotland were youll often get asked if you fancy a wee dramQuoteBelieve the uks railway still measure fractions of miles in chains

author: SteveThackery
author_rank: Super Contributor
timestamp: December 14, 2024, 08:47:05 pm
content: Quote from: CatalinaWOW on December 14, 2024, 12:05:46 pmActually the hectare is not an ISO standard unit of area. I guess it's a bit like the centimetre: in common use because both are useful units. But not "official" (ISO).

author: Cyclotron
author_rank: Unknown
timestamp: December 26, 2024, 09:31:38 pm
content: I don't know why anyone would consider there to be any contention since the advent of the International System of Units (SI). US, Imperial, and Metrics are all defined by SI.So it comes down to just units, not actual standards.72F is comfortable and easy, but 22.2222C is less easy but the same.Whenever I've heard one was superior to the other, most often someone criticizing the US and most often to me, my UK Director at work, I ask why you have a Pint after work. What day of the week or day of the month is it in Metric?As far as I know, all of these things are defined back to SI.

author: TimFox
author_rank: Super Contributor
timestamp: December 26, 2024, 09:47:11 pm
content: Quote from: themadhippy on December 14, 2024, 01:51:35 pmIt should be obvious why land surveyors used a physical chain as a portable length standard.In imperial and US customary units, it is defined now as 66 feet, or 1/80 of a statute mile, or 1/10 of a furlong.An acre is 4840 square yards, or 10 square chains (which is not a square integer).The US Geological Survey "National Map Corps" has a set of recognitions for amateur volunteers, where the "Order of the Surveyor's Chain" is the lowest level, proceeding through "Society of the Steel Tape", through the "Theodolite Assembly", and ending upward with the "Squadron of Biplane Spectators".https://www.usgs.gov/core-science-systems/ngp/tnm-corps/recognition-program

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 26, 2024, 10:02:10 pm
content: Quote from: Cyclotron on December 26, 2024, 09:31:38 pmYes it does. No, the imperial and US customary are not defined in the SI standard nor part of it.Quote from: Cyclotron on December 26, 2024, 09:31:38 pmThe imperial and US customary units have been defined using equivalents from the SI standard for a pretty long time now, but they are still not part of the SI.

author: TimFox
author_rank: Super Contributor
timestamp: December 26, 2024, 10:12:27 pm
content: Not all metric units are in the SI, but it does recognize 22 units derived from the 7 basic units.There is a long list of "accepted" units that can be used: e.g., 1 minute = 60 sec and the electron-volt.Other units from the "cgs" system seem to be ignored in the current list, such as the Gauss and erg.https://en.wikipedia.org/wiki/Non-SI_units_mentioned_in_the_SISince 1959, US law defines conventional units such as the yard and pound in terms of corresponding metric units.

author: Cyclotron
author_rank: Unknown
timestamp: December 26, 2024, 10:42:35 pm
content: Quote from: SiliconWizard on December 26, 2024, 10:02:10 pmMaybe it's the imperfection of language? As my last statement clearly says, back to SI, not part of SI.

author: .RC.
author_rank: Frequent Contributor
timestamp: December 27, 2024, 02:53:30 am
content: Threads and fasteners are stupid in metric.I have metric bolts here where the bolt heads are smaller then the nuts.Go work on a car that others have bodged up and you will find the same size bolts some with 12mm heads and others with 13mm heads. Some will be 16mm head, others 17mm and others 18mm for the same bolt size.Threads are just bizarre. thread per inch is far more sensible then mm per thread.

author: Monkeh
author_rank: Super Contributor
timestamp: December 27, 2024, 03:03:46 am
content: Quote from: .RC. on December 27, 2024, 02:53:30 amAh, they're stupid because there are options. Just like there always have been..And no, specifying pitch directly isn't stupid. It's justdifferent. Some people are scared by things which aren't familiar to them and they lash out and make themselves look.. you fill in the blank.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 27, 2024, 04:32:05 am
content: Quote from: Monkeh on December 27, 2024, 03:03:46 amThis is the absolute truth. And it doesn't apply only to thread pitch.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 27, 2024, 10:44:42 am
content: Quote from: .RC. on December 27, 2024, 02:53:30 amI have also seen Imperial bolts where the bolt heads are smaller than the nuts, so it isn't a metric "thing".With Imperial & US "inch sized" bolts we had the delightful possibility of:"Whitworth"(BSW), which was sometimes compatible with"UNC", but mostly not, with the latter nominally compatible with the US threads which were formerly known as "SAE" threads.UNF, which was in my experience, compatible with the US ("SAE") fine threads.We also had from "out on left field", "British Standard Fine" (BSF), which was compatible with nothing, "British Standard Pipe", which was also "standalone", not to mention the fairly rare "Lucas" & "GM" threads.But wait!---there's more! "BA" threads were totally incompatible with anything, & "to add insult to injury", were graded inversely as numbers, so that a "0"BA screw was larger in diameter than, say a "4" BA.An interesting side issue is that, although US, UNC, UNF & Metric spanners are identified by the "Across Flats"(AF) dimension, BSW & BSF use the thread diameter.Oh, by the way, the small US screws commonly used in older equipment from Tektronix, HP & the like, have no equivalent in any "Imperial" type of thread.Of course, Metric isn't immune! some small Metric screws of around the common 3.0---3.5mm range are coarse threads (notably Japanese), whereas others are extremely fine (early German), Modern usage seems to have settled on "somewhere in between".

author: guenthert
author_rank: Frequent Contributor
timestamp: December 27, 2024, 12:38:02 pm
content: Quote from: Analog Kid on December 13, 2024, 11:06:34 pmWell ... SI is mandated in trade in Germany (and I'm sure in the EU, but IANAL), but there is no law or other requirement that I'm aware of for its use in science. e.g. nuclear physicist still prefer CGS (as do perhaps less obviously so astrophysicist). Theoretical physicists define their units as they go (in electrodynamics it is common to chose a system where the speed of light in vacuum is dimensionless 1). That just makes some formulas and constants easier and the intended audience is expected to pay attention. It typically just trips undergraduate students accustomed to SI from high school.

author: themadhippy
author_rank: Super Contributor
timestamp: December 27, 2024, 01:18:18 pm
content: Metric and imperial it seems can play nicely together,got some imperial taps ,along side the tap size stamped on them is the recommended drill size,in metric.

author: TimFox
author_rank: Super Contributor
timestamp: December 27, 2024, 02:58:04 pm
content: Similarly, it is easy to find the US conventional size tap drill (either number or fractional) for standard metric taps.

author: themadhippy
author_rank: Super Contributor
timestamp: December 27, 2024, 03:05:21 pm
content: Quoteyou can,but i just find it amusing given the battle that ones better than the other how these taps are stamped ,for example 7/16 unc. drill 9.4mm

author: vad
author_rank: Frequent Contributor
timestamp: December 27, 2024, 04:11:33 pm
content: Quote from: guenthert on December 27, 2024, 12:38:02 pmWait, is using the centigrade units banned in Germany in favor of kelvin? Wow!

author: TimFox
author_rank: Super Contributor
timestamp: December 27, 2024, 04:46:02 pm
content: Obvious confusion here between "SI units" and "metric units".The liter (or litre) is accepted for use alongside SI-units, or for explanatory purposes.Otherwise, we would need to buy beer by the cubic meter.

author: Zero999
author_rank: Super Contributor
timestamp: December 27, 2024, 05:38:10 pm
content: Metric is generally a superior system because the units are all derived from one another, but it doesn't matter to me, as I can work with imperial just as well. The only thing which does confuse me is some people abbreviate millimetres as mil, which the Americans use for1/1000inch, which us Brits call a thou.

author: TimFox
author_rank: Super Contributor
timestamp: December 27, 2024, 06:00:22 pm
content: Quote from: Zero999 on December 27, 2024, 05:38:10 pmAmericans use either "mil" or "thou" for 0.001 inch: mil is common for electronic and electrical applications, thou for machinists.A useful American unit for wire sizes is the "circular mil", which is the area of a circle that is one mil in diameter.Wire tables for transformer winding often use rules-of-thumb for Amperes/circular mil.To confuse foreigners, US machinists also say "tenth" for 0.1 thou = 0.0001 inch.When working in the UK, I encountered confusion when a colleague asked me if "4 mil" wire were sufficient for an application: I assumed he meant 4 mm in diameter, but he actually meant 4 mm2(as specified by the wire vendor).Conventional units are also derived from each other, e.g., 1 statute mile = 8 furlongs. In modern usage, they are all defined from metric units (1 yard = 0.9144 m by definition).

author: Zero999
author_rank: Super Contributor
timestamp: December 27, 2024, 06:21:01 pm
content: Quote from: TimFox on December 27, 2024, 06:00:22 pmTechnically the wire size is 4mm2, but it's abbreviated to mil. Some electricians are clueless about this. I once asked for 1.5mm squared heat resistant cable at an electrical shop and the person at the counter said they don't have any square cable, only round.QuoteNo they're not. pints and gallons are not derived from cubic feet/yards. With the metric system a litre is the same as 1000 cubic centimetres.

author: iMo
author_rank: Super Contributor
timestamp: December 27, 2024, 07:18:50 pm
content: .. a "mil" is also 1/6400 or 1/6000 or 1/6300 of 360degree (a full circle), when talking "mil"itary..https://en.wiktionary.org/wiki/mil#English

author: vad
author_rank: Frequent Contributor
timestamp: December 27, 2024, 07:54:23 pm
content: Quote from: Zero999 on December 27, 2024, 06:21:01 pmThey are:1 imperial pint = 568.26125 milliliters (exactly)1 US liquid pint = 473.176473 milliliters (exactly)1 US dry pint = 550.6104713575 milliliters (exactly)Some people might argue that 1000 is a more natural multiplier number because humans typically have five fingers on each hand. Similarly, 273.15 might be perceived as a more natural offset number by some, though the origin of this perception isn’t entirely clear to me.

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 27, 2024, 08:04:00 pm
content: There's no reason to use the imperial unit, the entire thing makes no sense at all, simply people got used to it and now it's too late."What length is it?""1yrd, 7ft, 15/16in"Metric is so much more natural, it's all made by factors of 10.

author: Zero999
author_rank: Super Contributor
timestamp: December 27, 2024, 08:15:43 pm
content: Quote from: vad on December 27, 2024, 07:54:23 pmNo they're not derived from one another. Metric units have been designed from the ground upwards to relate to one another in powers of 10. Non-metric units are not. An inch and pint are completely unrelated to one another. The customary.imperial units have been standardised to metric, not the other way round.

author: vad
author_rank: Frequent Contributor
timestamp: December 27, 2024, 08:31:04 pm
content: Quote from: DavidAlfa on December 27, 2024, 08:04:00 pmI would argue that there is no reason to have a single system of units.When I studied at university, we learned to use the CGS system in certain fields of physics while sticking to the SI system in other courses. If I am not mistaken, nobody uses meters in astronomy, where parsecs are the standard unit of measurement.As for everyday people, they have grown accustomed to certain units of measurement, and no bureaucratic agency can force them to use Kelvin instead of Celsius, 500 ml instead of a pint of beer, 0.159 cubic meters instead of a barrel of oil, or 9,754 meters for flight level FL320 instead of the more natural 32,000 feet.

author: vad
author_rank: Frequent Contributor
timestamp: December 27, 2024, 08:46:54 pm
content: Quote from: Zero999 on December 27, 2024, 08:15:43 pmThey can be derived from each other - there are fixed conversion factors between a pint and cubic meters (as I provided above), between cubic meters and meters (via the cubic root), and between a meter and an inch (1 inch = 0.0254 m exactly). This means you can derive a pint from an inch in a defined and exact manner.I do agree through that the derivation requires different multiplication coefficients compared to deriving a liter from a meter, where you multiply a meter by the number of fingers on both hands and then raise it to the third power.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 27, 2024, 09:30:51 pm
content: Has any one noted that neither system is oriented to computer operations? Powers of ten are not convenient for binary based systems.

author: TimFox
author_rank: Super Contributor
timestamp: December 27, 2024, 10:02:44 pm
content: In classical history, the cubit and span were units of length that were independent of each other (referring to human anatomy).The origin story of units will give different results from modern definitions.Much later, conventional units of volume (gallons in English) were originally defined in interesting ways, but later defined by statutes in terms of length units.A US gallon is defined by US law as 231 cubic inches; the quart and pint are defined as binary fractions of the gallon.For interesting history, look up the different gallon definitions in English history depending on the fluid being measured.For irregular objects such as apples, it is conventional to measure them by "bushels", but that is not geometrically wise, so for trade bushels are defined as different weights for different products.(Traditionally, bushels are binary divided into 4 pecks or 8 dry gallons, not to be confused with liquid gallons.)For oats, the US bushel weighs 32 lb av, while the Canadian bushel weighs 34 lb, and the British bushel weighs 38 lb.US policy is to replace this with metric mass values directly (kg).Another interesting origin story is the liter.The original metric definition of the gram was the mass of 1 cm3of water, which is equivalent to a kg being the mass of 1000 cm3of water, defined as a liter.Later refinements of the definitions in terms of the artifact meter and the artifact kilogram made this definition no longer accurate.To keep wet chemists happy, the liter stayed defined as the volume occupied by 1 kg of water (at its maximum liquid density), while the m3and cm3stayed defined by the meter.Sometime recently, this was changed to make the liter 1000 cm3again, but it is not a base unit of the SI.Ignore any pedantry about the spelling of meter vs. metre: French and English pronunciations are different.

author: Zero999
author_rank: Super Contributor
timestamp: December 27, 2024, 11:06:49 pm
content: Quote from: vad on December 27, 2024, 08:46:54 pmYou appear to have missed the point. Customary/imperial units have evolved naturally, whilst metric was designed as a complete system in a scientific manner. The conversions you mention, only came into being after metric was invented. Modern imperial/customary units have been standardised with reference to the metric system.

author: .RC.
author_rank: Frequent Contributor
timestamp: December 28, 2024, 12:33:54 am
content: Quote from: Monkeh on December 27, 2024, 03:03:46 amNo once you cut a thread on manual lathes you will see the stupidity of the metric thread system.An imperial thread on an imperial lathe, easy to use the chasing dial.A metric thread on a metric lathe. Nah, we have to change the gear on the chasing dial for x pitches.But it is amusing the ISO standard for pipe threads is BSP.If I buy a M12 metric course bolt in Germany, it will have a different head size to one bought in Japan and one bought in England will have a different head size again.If I buy a 1/2"UNC bolt the head size is going to be 3/4" no matter where I buy it.https://boltdepot.com/Fastener-Information/Bolts/Metric-Bolt-Head-Size?srsltid=AfmBOooerzezf2niANfdO9-feMr6y-krSGl5DdnSkOjGa-xHZw6k-GymIt is one of the only issues I have with the metric system. Although I find centimetres a stupid thing people use, as much as I find people in the US using pounds in the absurd, like the space shuttle weighs 4 400 000 pounds, rather then start using tons once over a certain weight.

author: IanB
author_rank: Super Contributor
timestamp: December 28, 2024, 01:06:12 am
content: Quote from: Zero999 on December 27, 2024, 06:21:01 pmIt should be pointed out that 1 litre of water weighs 1 kg. 1 Imperial gallon of water weighs 10 lb. There is a very parallel way of defining things.Also there is nothing to stop you measuring volume in cubic feet or cubic yards, such as with sand or concrete where you want to fill a measured space.The particular value of SI derived units is when you want to combine force, work, heat and power in a single calculation. At that point, the benefit of avoiding all sorts of irregular unit conversion constants becomes really valuable (e.g. how many foot-pounds in a BTU?). This is good for engineers, but of very marginal value for everyday applications.In reality, Metric units have become prevalent for the same reason that English has become prevalent. If everyone needs to communicate then it helps if they can all use a common language. We can give Metric to France (Napoleon), and keep English as a donation from the British.

author: TimFox
author_rank: Super Contributor
timestamp: December 28, 2024, 03:47:05 am
content: Quote from: IanB on December 28, 2024, 01:06:12 amThemassof 1 liter of water (using the current definition of liter) is very close to 1 kg, but no longer exact. See my discussion above.

author: IanB
author_rank: Super Contributor
timestamp: December 28, 2024, 04:45:46 am
content: Quote from: TimFox on December 28, 2024, 03:47:05 amWhich just goes to show you can be a pedant in any system of measure.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 28, 2024, 05:46:09 am
content: Quote from: vad on December 27, 2024, 08:31:04 pmIn Australia, the things which were formerly packaged as1 pint(Imp),have been "rounded up" to600ml.(except for beer where it is anybody's guess what a"pint"means).There were also things likefluid oz------The "big brown bottles" of beer were traditionally26 fluid oz, & are now750ml.

author: tooki
author_rank: Super Contributor
timestamp: December 28, 2024, 10:07:04 am
content: Quote from: vk6zgo on December 27, 2024, 10:44:42 amBSW and UNC are only cross-matable by accident. They have different thread geometry.Since the UN thread series were significantly based on SAE, and have the same fundamental geometry, it's no wonder they work.UNC and UNF are not competing thread standards, they are tables of preferred threads within the UN thread system, which is what the C and F suffixes mean. That is, "UNC" = UN+C, "UNF" = UN+F.The same C and F suffixes apply to the modified-thread-geometry variants of UN: UNK, UNR, and UNS. (And previously a few more.) So UNK, for example, also subdivides into UNKC and UNKF.The C and F suffixes are, in a sense, completely unnecessary, since the name of the thread fully describes it and unambiguously places it into one of the two tables. E.g. #6-32 is UNC and #6-40 is UNF. So while they're frequently called "#6-32 UNC" and "#6-40 UNF", there's not really any need for the C and F, since a #6-32 UNF" doesn't, and can't, exist.

author: tooki
author_rank: Super Contributor
timestamp: December 28, 2024, 10:21:32 am
content: Quote from: TimFox on December 27, 2024, 06:00:22 pmandQuote from: vad on December 27, 2024, 08:46:54 pmLet's not get sloppy with terminology."Derived from" ≠ "defined in terms of" ≠ "converts to".These all meandifferentthings."Derived from" means the origin of the unit."Defined in terms of" is what we declare a unit to be, by decree, regardless of the origin."Converts to" simply expresses that we can use a factor/algorithm to convert, but says nothing about the origin of the relationship.To be crystal clear: the inch, for example, is nowdefined in terms ofmm, so you canconvert toand from mm. But it isNOT derived frommm.In metric, the units are (or at least originally were) derived from each other, meaning they are designed to have anintrinsicrelationship, not just by definition (decree). That is not the case for most Imperial or US Customary units.

author: Monkeh
author_rank: Super Contributor
timestamp: December 28, 2024, 01:04:16 pm
content: Quote from: .RC. on December 28, 2024, 12:33:54 amOh no, the one niche case! Or maybe your lathe is poorly equipped for the task.QuoteThree bolts to three standards can be different, say it ain't so. What if I need a 1/2" UNC bolt or nut with a smaller head?QuotePeople don't generally hang on to centimetres that far. I'm quite comfortable using any prefix, but if you find shifting the decimal difficult..

author: Zero999
author_rank: Super Contributor
timestamp: December 28, 2024, 01:43:52 pm
content: tooki,Thanks for explaining it better than I did.Quote from: IanB on December 28, 2024, 01:06:12 amThis is precisely why the metric system is used in academia and is so widely used. It's easier to learn because the units are derived from one another and are in multiples of 10, rather than arbitrary ratios.

author: TimFox
author_rank: Super Contributor
timestamp: December 28, 2024, 02:59:31 pm
content: Quote from: IanB on December 28, 2024, 04:45:46 amIn a different context, I have been accused of pedantry because I can count from 1 to 100 without taking my shoes off.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 28, 2024, 11:11:25 pm
content: Quote from: tooki on December 28, 2024, 10:07:04 amI never said that they were "competing thread standards".QuoteIn Australia, & as far as I could see, the UK, the designations "#6-40" & the like were not used, & in fact, they were rarely used outside North America.US projects often called for small screws by such terms, which were gibberish to those of us where small screw sizes were almost universally BSW, with a minority vote for BA & BSF.Losing a few screws from a Tektronix 'scope was not just a matter of "picking some up at a hardware store".

author: TimFox
author_rank: Super Contributor
timestamp: December 29, 2024, 12:39:31 am
content: For UN screws, as discussed above, the first number represents the diameter (in a convenient log series, like resistors, for small sizes and fractional for larger sizes) and the second represents the pitch (in inverse inches).The "C" or "F", for coarse and fine, are a standard list of two possible thread pitches for each diameter.However, there are further pitch lists, especially the UNEF (e.g., 3/8-32 for the standard bushing on a BNC connector or 1/4-inch shaft potentiometer).Note that the ISO thread form (for metric machine screws) and the UN thread form are identical (angles and relief percentage): only the diameter and pitch are different between "metric" and "UN" screws.Due to the huge investment in tooling, threaded fasteners will probably be the last important item to go fully metric.My favorite metric screw size is the standard thread for a small camera mounted on a tripod: M6.3, otherwise known as 1/4-20 UNC.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 29, 2024, 05:21:15 am
content: Quote from: TimFox on December 29, 2024, 12:39:31 amUnlike the 3/8-16 UNC tripod screws on some Yurpeen cameras (specifically the cameras I have from the Soviet Union, FEDs and Zorkis).

author: TimFox
author_rank: Super Contributor
timestamp: December 29, 2024, 03:33:21 pm
content: 3/8-16 UNC is the standard thread for larger cameras (like my 4x5 and 8x10 inch view cameras).Also, for the thread between the tripod leg assembly and the tripod head.Amusingly, I have seen it referred to as the "European thread".One of my tripod heads has a retractable 3/8-16 sleeve around a 1/4-20 core to allow either camera female thread.Also, many large cameras come with a removable thread adapter: a brass insert with a 3/8-16 outer male thread and a 1/4-20 inner female thread.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 29, 2024, 04:14:37 pm
content: The number system for small drills and threads is really inconvenient.

author: xrunner
author_rank: Super Contributor
timestamp: December 29, 2024, 05:13:13 pm
content: Quote from: Kleinstein on December 29, 2024, 04:14:37 pmYea that one is weird and that "system" dates way back to the 18th century. It has something to do with how many times wire was pulled through a die to make a smaller wire.

author: TimFox
author_rank: Super Contributor
timestamp: December 29, 2024, 05:28:10 pm
content: The number system for small drills is actually convenient, since it increases in size from number to number with an approximately constant ratio, as do resistors, for the same reason.I find it more useful than a fractional-inch set (in that range) or similar mm-size sets that are arithmetic sequences.I keep an old-fashioned chart in my garage showing common sizes in ascending order, including metric, number drills, fractional inch, and letter drills.I find I don't need to buy a metric drill set, since my number and fraction sets are close enough to anything I want.(If I really need an exact size, I have a few precision reamers.)

author: Analog Kid
author_rank: Super Contributor
timestamp: December 29, 2024, 08:28:46 pm
content: Quote from: TimFox on December 29, 2024, 03:33:21 pmIt's also the standard thread for many smaller cameras (like the then-"miniature" 35mm ones) made in the former Soviet Union.That's why I have 3/8"-to-1/4" adapters.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 29, 2024, 08:40:58 pm
content: Quote from: TimFox on December 29, 2024, 05:28:10 pmI made this chart for myself some time ago, showing all (common, not exotic) drill sizes from 0.1mm to 1", in inch, metric, numbered and lettered flavors:I think I copied this from a (paper) wall chart of the same format.