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Convert mm to inches - easy to remember!!
Convert mm to inches - easy to remember!!
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Old 17th July 2019, 12:40 AM   #51
kevinkr is offline kevinkr  United States
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Convert mm to inches - easy to remember!!
Canada, USA and Mexico...
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Old 17th July 2019, 01:08 AM   #52
PRR is offline PRR  United States
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Quote:
Originally Posted by DF96 View Post
I'm still trying to get my brain around how 0.03937 can be more accurate and easier to remember than 25.4...
Agree. 25.4 is Legally Exact. (the Old Inch was not quite 25.4mm, but we could not agree what it was, so 25.4 was defined by fiat.)

1/25.4 is at least 0.039 370 078 740 157 480 314 960 629 921 259 842 519 685 ... ...

.... ah, it repeats "039 370 078 740 157 480 314 960 629 921 259 842 519 685" forever. Only 42 digits to remember, compared to three "25.4" on the flip-side.

Last edited by PRR; 17th July 2019 at 01:16 AM.
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Old 17th July 2019, 01:17 AM   #53
nigelwright7557 is offline nigelwright7557  United Kingdom
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Originally Posted by PRR View Post
Agree. 25.4 is Legally Exact. (the Old Inch was not quite 25.4mm, but we could not agree what it was, so 25.4 was defined by fiat.)
I use 25.4mm to an inch in my PCBCAD software.
The software often doubles up on metric and imperial when making foot prints. Accumulation of errors can be a real nuisance so I now don't add the next pad to the previous pad position as the previous pad position is rounded up/down.
I now keep a number of how many pads are being used in a row and that is multiplied by original pad distance so no accuracy is lost.
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Old 17th July 2019, 02:16 AM   #54
JMFahey is offline JMFahey  Argentina
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Originally Posted by Duke58 View Post
Where is NA?

Remember, I'm American...
I am also American, so what?

Saying unqualified "American" is not precise enough, since America is 14000 km end to end including some 35 Nations.

Maybe you are a citizen of the Country called "United States OF America"?
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Old 17th July 2019, 02:35 AM   #55
Duke58 is offline Duke58  United States
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Okay- I was referring to the old joke- What do you call someone who speaks 3 languages? Trilingual. What do you call someone who speaks two languages? Bilingual. What do you call someone who speaks 1 language? American.

NA= North America.

Play the song- North American Scum, by LCD SoundSystem
lcd soundsystem north america - Yahoo Video Search Results
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Old 17th July 2019, 10:32 AM   #56
DF96 is offline DF96  England
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Quote:
Originally Posted by takitaj
What number does everyone use for pi?
When I use pi I am almost always doing algebra so it stays as pi. On those occasions when I need a numerical value I will be using my old Casio fx-570 calculator which has a pi key and gives the value 3.141592654 -whether this is a true decimal representation of whatever format is used internally I don't know. The number I remember is 3.14159.

I could never fully understand why it matters that pi is not only irrational but also transcendental. Then one day I was doing some algebra with lots of powers of pi and realised that I could equate coefficients on the left and right of the equation because pi behaves a bit like x, except that pi is fixed and x can vary. In algebra you have to match x with x, x^2 with x^2 etc. because you want your equation to be true for all values of x. When using pi the transcendental property means that you cannot balance pi against pi^2, assuming that the coefficients do not contain pi. A mathematician might be able to poke holes in this argument, but it is good enough for a physicist.
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Old 17th July 2019, 01:26 PM   #57
Galu is offline Galu  Scotland
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Originally Posted by DF96 View Post
I could never fully understand why it matters that pi is not only irrational but also transcendental.
I sometimes use the rational expression 22/7 as an of estimate of pi. It's only accurate to a couple of decimal places, but good enough for a rough pencil & paper calculation.

The big question is - where do you weigh a pi?
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Old 17th July 2019, 01:53 PM   #58
RAndyB is offline RAndyB  United Kingdom
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Originally Posted by Duke58 View Post
Doesn't it seem funny that the English converted to the metric system years ago and the USA still uses the English system?
Not so much pedantic or political as accurate:

the BRITISH (or the UK) converted to metric, the USA uses the IMPERIAL system. If England had converted then Scotland, Wales, Northern Ireland would still be using yards, feet and inches.

I've just looked out the triangular (in cross section) ruler, calibrated in inches, with full size, 3/4, 1/2, 3/8, 1/4 and 1/8 scales which I have kept since my days in a drawing office in about 1965.
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Old 17th July 2019, 02:00 PM   #59
syn08 is offline syn08  Canada
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Originally Posted by Cal Weldon View Post
2.54 is the real magic number for us here in Canada as we use inches and cm for the most part.
Sometimes makes me think it's a govt. plot to force us buy all tools in both systems. Good for the economy.

Even so, you always miss exactly the one tool that fits the d*mned part. Or always pick the wrong tool first. The weight scale is always set to the wrong units. You always get to the wrong side of the ruler.
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Old 17th July 2019, 02:47 PM   #60
tsmith1315 is online now tsmith1315  United States
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Originally Posted by Galu View Post

The big question is - where do you weigh a pi?
Somewhere over the rainbow?
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