There is an ANSI specification as well.
Try this:
for each gauge screw there is only one threadâŚ
Order any gauge and you get what you get, pointless knowing the thread.
Iâm sure I could add metric dimensions to an npt thread too.
I donât make them or sell them or even care about anything other than the length and diameter but you asked and I answered with real world information.
It does matter to people who design industrial mass produced products in modern CAD/CAM programs.
Why do you persist in pretending that everyone on this form hates anything non US?
Even when I say something positive about a US institution you manage to turn it into something negative. WHY??
It wasnât.
The snark and sarcasm were plainly evident.
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Just wanted it to be higher than Fahremheit 451. 
Iâve only one reference for °F and itâs 68 °F (20 °C).
@ombugge; I thought K and maybe °C would be used in cryogeny worldwide.
Funny is that the Chinese flood the European market with electronic thermometers with a annoying protruding °C/°F switch which youâll sooner or later hit inadvertently, or scales with a kg, g/oz fl. oz, lb or whatever switch. I donât get it why such switch is not in the battery compartment or at the rear. Iâve never ever used such feature.
Self-tapping screw sizes are often simply specified by Diameter x Length (e.g. 3.5x16 mm or 3,5x16 mm while I only use the . as decimal separator). There are standards but unless designing for high volume manufacturing most donât care, itâs not like metric screws which are very well defined (mostly regular and fine pitch, left and right).
Metric has also its oddities, liters are commonly used, dm3 (equivalent to one liter) rather for calculations. Also bar is common as unit of pressure (barg is mostly used in the process industry, steam systems,⌠). Some abbreviations are correct but never [Edited rarely] used, pm, TN, MK, cK (not Calvin Klein!!!), pK, daK, dam, Mm, cW, daA, pm, hN are all valid but sort of confusing. A torque in daNdam or a torque in YNym or ist it required to simplify, or maybe just in ENm, mNm (which is common), or zNm? You get it, metric SI can also be confusing (I just made up the examples which are mostly never used but formally correct).
In the industry we use mm but the brick layer will use cm.
The kg is common but using Mg is confusing even if formally correct. Very often I see kelvin * gram (Kg) instead of the correct kg and kelvin * watt (KW) instead of kW (kilowatt) and of course kelvin * volt * ampère (KVA) instead of kVA and the list goes one.
OTOH I canât remember the different definitions of tons or miles. If at least there would be a univoque definition.
More problematic are mechanical drawings if someone mixes up 1st angle projection with 3rd angle projection. Also blueprints are unknown where I live, at least helio copies which died as wide paper plotters became affordable are never in ânegativeâ, lines are dark and the blackground clear.
Some basic unit conversion I can live with but non-decimal fractions of inches and acre-foot Iâll never get used to. AM/PM is odd but can be understood, date formats are a mess, I only use the ISO format since ages (2024-05-30). With DST itâs interesting to check how logged data can be accessed for the hour which existed twice and if QA stats are messed by with the missing hour.
More seriously, I always wondered how one can perform complex computations without SI units. Unit conversion factors can easily lead to program errors.
And dont get me started about IEC vs. North American electrical codes and how wiring diagrams from different regions of the world look. Mostly the only very formal and accurate ones are those from German manufacturers. Where I live weâre strict when it comes to mechanical drawings but electrical diagrams are not the best but still ways better than for example French ones.
(Sadly I tend to always notice even very minor errors in wiring diagrams.)
Quite formal are those of nuclear and hydroelectric power plants and waste incinerating plants if based on the former German KKS. Iâm still wondering why classification companies didnât issue something like a KKS for ships.
And does someone know how many stones Emma is?
metric electrical wire, lost count how many systems there has been over the last 50 years
gauge worked then still works
Metric from 0.14 to beyond 1000 mm2 has been around since a long time but there are still oddities like 0.6 and 0.8 mm massive wires where the sizes refer to the outer diameter of the wires and not the metallic cross section (area) in mm2.
Also when using cable lugs, depending on the conductor structure, special versions (e.g. for extra flexible stranding class 6 conductors) may be required but many donât even know or care about such details and one day thereâs a fire because of non-conform crimping (hint: thermography (thermal imaging) even using a cheap thermal camera can help detecting some faults before they become a problem, also check fuses, there are often contact problems).
Indeed I always wondered how one uses a manual mill to machine parts with non-decimal inch-fractions in the drawings. I only ever used machine tools with verniers in mm.
BTW Iâm not criticizing the Imperial system as such, whatever floats oneâs boat , I just find it unnecessarily complicated and could never ever get used to it; excepted for body heights I must always convert to metric. Usually I sort of âfeelâ if some engineering data is realistic or not in the domains I know, but only if metric.
College science courses, chemistry and physics were taught in metric units when I went. The engineering courses, dynamics and statics were a mix, maybe 80% metric. I much preferred staying in metric. Slugs?
Day to day most people donât spend much time converting units or even interacting with the two systems. Iâd imagine in some industries the two systems are a PIA.
Itâs not on my list of things Iâd write to my representative about.
The question âWhat is stopping youâ doesnât make sense unless one believes that their keyboard is providing a direct link to people with the power to make changes. If the question is why doesnât the U.S change a google search would provide more information than posting the question here.
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Each country remains free to decide which system to use. I just donât find the Imperial system intuitive.
As long as the used units donât lead to confusion like e.g. the various definitions of a ton or a mile we can still convert correctly.
Iâd just appreciate if US datasheets would always also include metric data.
My comment was more about how itâs handled every day, not criticizing at all, just wondering.
I did and posted the result here: What is stopping you? Metric, again - #160 by ombugge
Since Iâm not a US voter it wouldnât do much good for me to write any âcongress critterâ, but you and many other here can, if you want to.
Personally I have used multiple systems all my life, so Iâll manage for the time I have left as well. 
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So what was the point of this extended and tedious discussion?
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Maybe somebody think it worthwhile to spend some time and effort on this âtedious discussionâ, since it has attracted 174 post in 21 days.
Those who find it boring, or offending, can stick to less tedious subjects, which there are enough of for every taste.
You must have read something âbetween the linesâ.
PS> my remark was only one line.
Maybe not converting to all metric is by design to ensure some âmental math agilityâ converting units if required. In the commercial marine industry including US built ships as they collaborate with Korean yards, I have noticed that most common plant process piping is metric and reference size/class/pressure rating conforms to DN standards (with a bit of JIS â Japanese thrown in). There are exceptions such as boiler tubes dimensions in imperial (or converted metric) conforming to ASME, fire hoses, etc.
In the O&G industry it is mostly all imperial due to API. ANSI has plenty of equivalents - ASME and API equivalent are âwork in progressâ.
Good discussion and learnt a bit â especially aircraft parts/machining!
RE: âWhat is stopping you?â
The issue has nothing to do with physical measurement. The USAâs imperial system is a measure of our power in the the world. Itâs proof that America can bend the rest of the world to its will, and not the other way round. Which is an obsession with a lot of Americans. In politics itâs called âAmerican exceptionalismâ and itâs a powerful force.
We can refuse to use the metric system in daily life because our economy is so strong we can force the rest of the world to make extra production lines to accommodate our feet and ounces. If we give up the imperial system for metrics we are admitting that we are weak, and must bow to the rest of the worldâs standardsâthatâs the mindset of many a voter.
The same with currency. Our paper money, without relation to its actual financial strength, looks dowdy and third-world. It is bi-color, when multi-color folding money is the standard in much of the world. Our bills are made from linen and cotton. Really? The same materials as ancient Egyptian mummy wrappings, and high-end ancient Roman TP? Compare to Australia, where bills are made of 21st century polymers. Much better in every way.
But the USA persists in using old-fashioned mummy-wrap money precisely because our dollar is so strong we could print it on bubble-gum and it would still kick-ass internationally. Despite all the predictions that the yuan and bitcoin would replace the dollar as the worldâs currency, the US dollar just gets stronger. Our bills are notes to the rest of the world saying, âWe are so powerful we print our money on ancient Roman ass-wipe and youâre still begging for moreâ.
So, no, we wonât be converting to metric any time soon.
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So what about BSP and Whitworth hardware?
British Standard Whitworth - Wikipedia
British Standard Pipe - Wikipedia
For some odd reason some Japanese cars have BSP threaded fittings.
I thought that Whitworth thread was widely used in aircraft manufacturing because of its strength.