I am now retired. I remember a thousands of an inch was often called a 'thou'. Is it true it is also called a 'mil'?
Anybody knows the background to the usage of these two terms. Was one more British and another one more American. And is the term 'thou' still used?
Yes. Richard
The terms seem to have found homes in different industries. If you look at the fine print on a package of plastic garbage bags, you'll find that the thickness of the plastic is typically expressed in mils. That seems to be the standard for that business.
But if you walk around a machine shop, you'll most often hear people talking about "thousandths", "thou", or "tenths". Tenths, of course, are ten-thousandths of an inch.
You'll also hear references to microns, or U's (pronounced "youse"), from the U-like appearance of the Greek letter omicron. Those are the standard terms for thousandths of a millimeter, or millionths of a meter. As the US continues to move slowly toward total metrification, and as manufacturing processes become more and more capable of dealing with micron-level precision, I suspect that youse will become more and more common around many shops.
Which ought to cause a great deal of confusion, and maybe even some interesting humor, here in Philadelphia.
KG
"Mil" is usually used to express the thickness of a film or coating.
"Thou" is simply a slang abbreviation for "thousandth", or "thousandth of an inch" and is very common (US). In contrast to "mil", "thousandths" can be used to refer to much larger dimensions. For example, a machinist would probably refer to 0.100 in. as "one hundred thousandths", or "a hundred thou". Mils tend to be restricted to small single- or perhaps double-digit measurements.
Don Kansas City
The Greek letter omicron doesn't look like a "u", it looks like an "o". Microns are represented by the symbol for the metric prefix "micro-" which is the Greek letter "mu" (µ). It is often represented as a small "u" since mu is not easily typed on many keyboards (particularly the old typewriters).
Don Kansas City
This would make sense as "milli" means one thousandth, but I find that today (in Britain) the word "thou" generally refers to a thousandth of an inch and "mil" to one millimetre.
The influence of metrication I guess.
Chris
Duh...
I knew that. I don't have a clue about why I typed omicron. Of course, there ARE some days when I can't tell the difference between my ohmmeter and my micrometer. They both measure something in Greek, right?
Thanks for waking me up, this morning.
KG
That's what you get for posting before the coffee kicks in, Kirk! At least omicron actually has the word "micron" in it, which is more than we can say for mu.
Don Kansas City
Thanks to all of you for your quick comments.
I have been brought up years ago using 'thou' to stand for a thousandth of an inch, and I now understand it is still very much in use in conversations in workshops and engineering offices.
I notice 'mil' is used mainly in thin film and coating industries to refer to the same measurement. On the other hand, it would cause grave misunderstanding, would it, if as one of you said it is also used in conversations to refer to one mm ?
John, Singapore
Without the boring details, the answers to your Qs are yes, yes n yes.
Brian W
To sum up this greek vocabulary issue, I would like to add that the reason that the word "omicron" has the part -micron, is because "micro" means "small" in greek and the letter omicron means "small o" while the letter omega means "big o" and in anciend greek there was a difference in pronunciation, omicron being a shorter o than omega. Now there is no difference in pronounciation. You can also notice that "Megabyte" for example also uses the greek word "mega" (=big).
By the way, 10^-9 m are called nm which stands for nanometers. "Nanos" in greek means dwarf. And "gigas" (e.g. gigawatt) means giant.
Sorry if this comment was irrelevant.
Stefanos
difference in
"Nanos" in
The omicron/omega thing is interesting. I never thought about that. But what about large omicron "O" and small omega "w"?
Don Kansas City
You are speaking to the deep roots of our civilization. Let's hope it is not irrelevant
Brian Whatcott Altus, OK
"Kirk Gordon" wrote
Do you mean the abbreviation of a micron is not pronounced in US industries as "miu" ? This is the pronounciation of the Greek letter that represents a micron. It looks like u with a long leg in front.
About your last point, it is all right if these only cause confusion. What if they end up as mistakes in works to be done ?
John
Don Gilmore caught my error on the first point. It's the Greek letter mu that looks like an English "u" with a tail on it. That's why some American machinists refer to microns as U's. Regarding your second question: I can only assume that youse have never spent much time in Philadelphia. Here, youse'll hear the word "youse" (pronounced yooooz) used quite frequently. In a machine shop that makes, say, precision parts for universal joints, a sentence like "Youse gotta take a couple more u's offa dem U's, or we ain't gonna be able to use 'em." would make perfect sense.
If I were to use a really small (micro-sized) micrometer to measure the size, in millionths of a micron, of a certain sub-atomic particle, would I then have a micro-micro-micro-mu-mu-meson measurement?
KG
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