A glimmer of hope

[mklotz]

A recent post on HSM had the following quote...

"The use of gauge number is discouraged as being an archaic term of limited usefulness not having general agreement on meaning." (Specification ASTM A480-10a)

I found it immensely satisfying to see that the folks who arbitrate the quagmire of nomenclature systems have finally had the good sense to say what I've been preaching for many years - the only sensible way to label things is by their sizes as measured using a decimal measurement system.

I don't expect their recommendation to have any effect whatsoever on the dinosaurs who still treasure the inferial nonsense but it's nice to know that a glimmer of intelligence is peeking through the curtain.

[Frank S]

I'm afraid that peeking may be about all though. at least until manufactures of materials normally listed in gauge sizes adopt a decimal measurement system

[mklotz]

The only way to fix the problem is to fully adopt the metric system, teach only that in the schools, and wait for all the dinosaurs to die out.

Nomenclature systems, of which this is an example, are not part of measurement systems but all the countries that use the metric system use sensible, size-based nomenclatures for things like sheet, wire, drills and taps. Adopting the metric system, a good thing in its own right, would naturally lead to use of these sensible nomenclatures once the old Luddites are gone.

[nickyd]

Why is the 'Micron' still in common use?
This was internationally changed to 'Micrometer' in 1969.

[mklotz]

Why is the 'Micron' still in common use?
This was internationally changed to 'Micrometer' in 1969.

The term "micron" isn't the only survivor. The medical community still uses "centimeter" as do many archaeologists. The metric system has numerous derived units, e.g. Newton = 1 kg-m/sec^2. As long as the unit is simply related to the primary units such derived units are acceptable. If we consider "micron" (= 1E-6 m) to be a derived unit, then all is well.

I think the arbiters of the metric system took a step backward when they dismissed such terms as centimeter and decimeter. Why is centi+meter conceptually different from milli+meter? So-called engineering unit steps of 1E3 aren't always convenient in the real world.

A minor quibble..

I don't think micron or micrometer should be capitalized. I believe the rule is that if the multiplier is less than unity it's not capitalized, if greater it is. Thus everything from "deci" to "atto" would not be capitalized and everything from "deca" to "exa" would be. The exceptions are the units named for an individual which are always capitalized. Thus the following forms

micron, millimeter, centimeter, milliliter, nanosecond
Kilometer, Megameter
Newton, Ampere, Pascal, Weber, Tesla

I'm not certain of the rule for applying prefixes to units named for people. I've seen both "GigaPascal" and "Gigapascal" but the abbreviation is usually "GPa" which implies that "GigaPascal" would be a correct spelling.

[Ed Weldon]

I agree with you guys a decimal measurement system is better than a system of numbers and letters with archaic meanings or fractions.
But if you want to argue American (or whatever you want to call it) vs. Metric this is an argument I love. The Metric system is terrible in theory because it is based on a standard that is totally foreign to the human scale and experience (the distance from the equator to the North pole; which when adopted was impossible to measure). OK, we now have standards based on the wavelength of light so the measurement issue is solved as long as humanity retains the technology to make such accurate measurements. But note that it was only a century ago that America had to send a high speed warship to Europe to bring back sets of gauge blocks that insured we made munitions that were measured to the same standards as our European allies. Hopefully the Norwegians have a little cabinet in that seed bank in Spitsbergen where a few lab grade sets of gauge blocks are stored.
I like measuring in mils. Sorry, I just don't want to deal with 3 digit pieces of millimeters when I have to hold close tolerances or tenths of a milimeter when spacing drilled holes. Besides I have only one metric vernier caliper and no such micrometers. (All those cheap digital things are in a box in my shop along with some dozens of corroded Chinese button batteries).
And the metric thread systems? Don't encourage me to get started on that. Or metric construction materials.
Oh yes. I'm a retired mechanical engineer. I trained and grew up in a world where everything we learned was measured in the American system.(1950' and 60's) Now all the engineers are trained in the metric system and that's all they use. Fine. I can handle that. But........... Nobody creates decent conversion charts anymore. They are all on their computers. And search for a decent conversion chart on the net and all you will find is conversion programs that cover the simplest types of measurements one at a time and leaves you to do a derivation if you want to convert some oddball engineering measurement in a product spec.
Ed Weldon

[mklotz]

A long time ago I wrote the following broadside. Whenever the metric vs. inferial discussion arises, I like to throw it up so that we all know what the salient points are and which arguments should be avoided.


SOME THINGS YOU SHOULD THINK ABOUT BEFORE ATTEMPTING TO DISCUSS MEASUREMENT SYSTEMS INTELLIGENTLY

The main advantage of the metric system is NOT just that its units are based on powers of ten. Briefly, the key advantages are:

Only one unit used to measure each fundamental or derived physical quantity.

These fundamental units are, as much as possible, simply related to each other, e.g., a liter of water weighs a kilogram.

All subdivisions of fundamental units are related to the fundamental by the SAME sequence of prefixes, e.g., micro, milli, kilo, mega..., each of which denotes a power of ten multiplier.

Derived units of convenience are simply related to the fundamental units, e.g., a hectare = 10000 m^2, a Newton = 1 kg-m/sec^2, 1 liter = 0.001 m^3, etc..

As much as possible, the standards which define the fundamentals are based on phenomena that can be accurately duplicated in laboratories around the world, e.g. the meter is defined in terms of a certain wavelength of light rather than the distance between marks on a bar kept in Paris. Thus the inevitable errors incurred in transferring a standard can be avoided.

Just because something uses a powers of ten sequence does not automatically make it metric. Your inch micrometer has markings for tenths and thousandths of inches but it isn't metric. Most money is subdivided into a hundred "pence" of some sort but it isn't metric.

The fact that something is expressed in metric units does not make it part of the METRIC MEASUREMENT SYSTEM. European thread standards are naturally expressed in metric units because they originate from nations using that system but you will find no mention of thread standards in the documents defining the metric measurement system. If you have a problem with metric threads, take it up with the agencies that set thread standards; don't use it as an excuse to condemn the metric system.

Some folks want to argue that the metric system is flawed because the length standard it uses is "wrong". The French set out to make the meter one ten-millionth of the distance from the Earth's equator to the North Pole. Their technique for measuring this quantity was inspired and they did an admirable job considering the tools available to them at the time. Still, the value they obtained was very slightly in error. But, NONE OF THIS MATTERS IN THE LEAST. All measurement systems are based on a choice of some arbitrary standard. Whether it's the length of the King's arms or the distance traveled by light in a vacuum in a given period of time, it's the fact that everyone agrees to use that length that's important and the real test of a measurement system is how well it satisfies the criteria outlined at the beginning of this text. THE NOTION OF "ACCURACY" OF A MEASUREMENT SYSTEM IS COMPLETE NONSENSE. Accuracy is a function of the measurement tools and techniques, not the system in which the measurements are expressed.

Another argument to avoid is the "we put a man on the moon using..." farce. Everything was built using the measurement system in force at the time. The ancient Egyptians built the pyramids using the cubit (and had problems with multiple, competing definitions) but that's not an argument for returning to their system. If you doubt me, try working a problem using Egyptian fractions. Building achievements are the product of the genius of their designers and fabricators, not the markings on their rulers, scales and buckets. The fact that you managed to build a corral for your dinosaur using the inferial* system is not a valid argument against the use of the metric system.

An insidious so-called argument to avoid is the exceedingly narrow-minded idea that only the aspect of a measurement system you personally use is a proper basis for deciding which measurement system is best for the society at large. It goes something like this...

I don't need another system to machine my parts. The difference between inferial* and metric is just a factor of 2.54, why bother changing; I can make accurate parts using my present inferial system.

There might be some validity to this approach IF THE JOB OF EVERYONE IN THE SOCIETY INVOLVED NOTHING MORE THAN MAKING LINEAR MEASUREMENTS. People have many jobs involving all the aspects of the measurement system. Using one that's antiquated, un-necessarily complex and confusing leads to inefficiency, lost time and dangerous mistakes.

-------------

Nomenclature systems are not a part of measurement systems but they deserve mention here. A sensible nomenclature system should satisfy the following criteria...

* Should provide information about the thing being named. A #43 or size 'K' drill carries no information about its most important feature, the size hole it will drill. This requirement pretty much means that things be labeled by their size in the measurement system in use. A 6 x 1 metric screw tells you OD and pitch directly; a 6-40 inferial* screw makes you work to get the same information. Labeling wire with a number corresponding to how often it's been through the drawing dies may be useful on the wire mill floor but it should never be let loose in the real world where people only care about its diameter.

Not only are sheet metal gauge numbers meaningless, but there are a prolific number of standards to further muddy the waters. Perhaps the USA is finally waking up to the nonsense it's created. In a recent statement, the ASTM has said,

"The use of gauge number is discouraged as being an archaic term of limited usefulness not having general agreement on meaning." (Specification ASTM A480-10a)

* Should have an intuitive progression. Smaller names should correlate with smaller entries in the progression; larger names with larger entries. A #80 drill should be larger, not smaller, than a #1. Similarly with wire and sheet metal.

* Should be open-ended so that a new item larger or smaller than the original set can be sensibly named. This avoids the idiocy of things like 000-120 screws and AAAA batteries. What do you do if you want to add a drill slightly larger than a 'Z'? Again, labeling by actual size avoids most of these problems.

--

* I live in the USA, the only industrial nation on earth that hasn't adopted the metric system. Usonians will tell you that we use the Imperial system but that isn't strictly true. True, we obtained most of our system from Britain but we further botched and confused it into the mess now known as American Customary Units. That's a mouthful to say or write and few will know what you're talking about.

I decided to make up my own designation for a system that has seven different units all called "barrel". My "inferial" is a portmanteau of "infernal/inferior/infuriating" and "Imperial".

[tonyfoale]

Why is the 'Micron' still in common use?
This was internationally changed to 'Micrometer' in 1969.

i use it because it is easy to say and easier to write.

[Festus]

I thank you also! I just work on simple home DIY stuff but I am forever looking for the correct size, MM, Standard, etc.

[mklotz]

i use it because it is easy to say and easier to write.

Also, "micrometer" used as a dimension in a machine shop setting can be confusing given that the primary tool in that venue has the same name.

One has to be careful with "mil" though since it's one of the common terms for milliradians. an SI unit...

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

Also the artillery setters use it as an angular measure. However, to maintain the spirit of inferial confusion, they've "rounded" the 6283... milliradians in a circle to 6400. I suppose the (admittedly slight) error so induced is compensated with more explosive shells.