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Use of mil
#MISC
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Richard
When I was an apprentice many years ago in the UK we worked with
imperial measurements. An inch was 1.000" a tenth was 0.100", one hundredth was .010", a thou' was 0.001", and a tenth of a thou was 0.0001". I now see our American friends refer to 0.001" as a mil. When did this start and why does the thou' seem to be out of fashion. Given the use of metric measurements on both sides of the pond is the use of mil not likely to cause confusion with the millimetre? Typically over here (as far as I am concerned) a tenth of a mil is 0.1mm not 0.0001" Richard |
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Hi, Richard,
With respect, and just FYI... even 65 years ago, my father commonly referred to 0.001 inches as a "mil". I was surprised a few years ago when John Lindo used it in reference to metric measurements, and I had to ask him exactly what he meant. The Merriam-Webster dictionary defines a "mil" as follows: Definition of?mil?(Entry 1 of 3) 1:?found a salinity of 38.4 per?mil
2:?a monetary unit formerly used in Cyprus equal to ?/???? pound
3:?a unit of length equal to ?/???? inch used especially in measuring thickness (as of plastic films)
4:?a unit of angular measurement equal to ?/???? of 360 degrees and used especially in artillery
In order to avoid confusion, its use should probably be avoided entirely where both metric and Imperial measurements are used.. Regards, Charlie New Jersey, USA ? ANTHONY¡¯S LAW OF THE WORKSHOP: Any tool, when dropped, will roll into the least accessible corner of the workshop. ? THE LINDO COROLLARY: If you have cats, they will promptly hide the tool. |
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Richard
¿ªÔÆÌåÓýThe use of mil is maybe just an American thing then as I certainly never came across it in the UK when we were imperial.Richard On 25/09/2020 12:56, CLevinski wrote:
Hi, Richard, |
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Hi, Richard,
I believe that you are correct. If I look in the Oxford English dictionary, it includes both meanings of 1/1000 of an inch and 1 mm: mil1Pronunciation?/mil/?/m?l/?ABBREVIATIONinformal
?
Main definitions of?mil?in English:?
mil2Pronunciation?/mil/?/m?l/?NOUN
OriginLate 17th century from Latin millesimum ¡®thousandth¡¯, from mille ¡®thousand¡¯.-- Regards, Charlie New Jersey, USA ? ANTHONY¡¯S LAW OF THE WORKSHOP: Any tool, when dropped, will roll into the least accessible corner of the workshop. ? THE LINDO COROLLARY: If you have cats, they will promptly hide the tool. |
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For me, a Russian, born and raised with metric system, learning about these things had been / is a very curious topic!
When it comes to machining, I usually read the Model Engineer forum (UK) and the Practical Machinist forum (USA). I don't recall people on either of the forums using "mil", at least not often (or perhaps I haven't noticed)? The term "thou", though, comes up very often, as well as "tenth". The funny thing is, I have a 1966 USA book "Fundamentals of Dimensional Metrology" by Ted Busch. The book has a rather thoughtful discussion on pros and cons of the metric system and the decimal inch system. It talks about an upcoming (at the time) Decimal Inch standard: Quote: - In 1959 the American Standards Association (ASA) and American Society of Tool and Manufacturing Engineers (ASTME) decided to jointly urge greater use of the decimal inch. ... The committee formed for this purpose was known as ASA Sectional Committee B87. ... This proposal, known as ASA Standard B87, is being considered for approval at the time of this writing. Curiously, outside of this book, I was not able to find some information about it's history or fate! Some more quotes: - The "thousandths" division of the inch is one of the most useful. Unfortunately it is a tongue twister, hard to spell, and easily confused with "thousand". Slang was already shortening it to "thou" which is even more ambiguous. Mil was a much better choice. It is similar to the official international prefix "milli" meaning thousandths. The prefix "mil" is from Latin and widely used by non-technical people. And it is short enough. - In practical work one tenth of a thousandth of an inch is frequently encountered. Alas, it acquired the most unfortunate name possible, the "tenth". Tenth of what? The resulting mistakes that have been made are legend. Furthermore, in the opinion of many who have studied the metric system, if it teaches anything, it is that units that vary only by a factor of ten are an open invitation to trouble. Therefore, this interval is skipped in the decimal-inch system. One-tenth part of one thousandth inch is simply point one mil (three syllables) or one-hundred mike (four syllables). The book suggests, though, that one ten thousandth of an inch is such a useful and needed unit, that it suggests using "tenth mil" to remove ambiguity. - The next unit is one millionth of an inch. Again the word was chosen for much the same reason as was mil. "Micro" of the international prefixes was an obvious choice. In the decimal-inch system it is simplified to mike. Regardless of using a standard that seems to not had gained enough traction, this book is a pretty great (and even entertaining!) read. Funnily, I've never encountered "mike" in contemporary usage on the machinist forums (I've heard micro-inches). Everyone seems to say "tenth" or "thou". FYI: Russian machinists measure in microns or sometimes in 0.01 mm units - called §ã§à§ä§Ü§Ñ (sotka), literally a hundredth, = 1/2.54 of a "thou" or a "mil". If someone has a more or less recent USA book on metrology, what kind of units it suggests? I wonder if UK metrology books still mention decimal inches, considering that UK had *mostly* been metric for a long time now? --Gene |
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The term "tenth" always throws me (of course I am new?to machining). I always think of tenth as being a tenth of an inch .1 but to USA machinists a tenth is ten thousands of an inch .0001. A thou is .001. Ralph On Mon, Sep 28, 2020 at 5:51 AM Gene Pavlovsky <gene.pavlovsky@...> wrote: For me, a Russian, born and raised with metric system, learning about these things had been / is a very curious topic! --
Clausing 8520, Craftsman 12x36 Lathe, 4x12 mini lathe, 14" Delta drill press, 40 watt laser, Consew brushless DC motors and a non working 3D printer |
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A light hearted reply, we all need some of this at this moment, but true.
In and around 1966 , UK changed to the metric system, and was not really a major issue or disaster. I was apprentice toolmaker during the transition and most of the work we produced was in metric units anyway. My father who happened to be a Inspector for a Gage (Gauge) making company Matrix of Coventry, and worked in the standards room, +so he knew all about Metrology, and?was building a storm porch, basically a wooden covering for the front door of the house we lived in. He needed some wooden corner supports and he duly measured his requirements and so off to the local wood yard he went. He was greeted by the typical store clerk, you know the type, hate to sell anything as they think the stocks they have are solely theirs. LOL. So my Dad asked this sales clerk, if they had any 4" x 2" planed wood.? The clerk replied in the normal poor fashion, what do you mean ? 4" x 2" , don?t you know we are a Metric certified company NOW, what we only stock is 100 mm x 50 mm. and how long are the pieces you need. My Dad understanding the metric system replied? I need 4 pieces? x 3 metres long please. The clerk replied, what is that in feet and inches, as we have not got used to the new way of expressing lengths of wood yet. Silly but true. Stay well and safe. ? -- John |
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John,
Thanks for the funny story! Another hilarious bit: A nominal 2"x4" board starts out 1.56 in. x 3.58 in. Then, the edges are surfaced (planed), reducing the actual size to 1-1/2 in. x 3-1/2 in. Supposedly it's because 2x4 of the past (rough-sawn) is not surfaced (planed), thus ending up smaller. Sure sounds like a con to me, though! So the "100 mm x 50 mm" was more like 89 mm x 38 mm, I suppose. Here in Luxembourg, and in neighboring Germany, the nominal size (metric) matches the actual size. --Gene |
John Lindo
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