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Thread: Why 68 Deg. for inspection

  1. #11
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    Aviation settled on 15c and 29.92 inches as the "standard day".

  2. #12
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    Quote Originally Posted by epicfail48 View Post
    That's said, imperial measurements deserve to die a painful death. 100 centimeters to the meter, 1000 meters to the kilometer makes more sense than 12 inches to the for, 3 feet to a yard 5612 or some such nonsense feet to the mile, its a mess
    Yes BUT With all the hullaboo over the GREAT METRIC system they seem to have something wrong with the factor TEN .
    Tne bloody idiots seem to have forgotten DECI and DECA in their prefixes. SO! if youre so all hipped up on this factors of ten you had better start using the "forgotten" to of them. BAH!
    ...lew...

  3. #13
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    Quote Originally Posted by RB211 View Post
    Aviation settled on 15c and 29.92 inches as the "standard day".
    That 29.92 comes from the standard atmospheric pressure, with a 10 ft adjustment made to represent an approximated height of the altimeter sensor's mounting location in the plane above the runway. Ten feet was reasonable back when the altimeter standard was established, now not so much.

    Don't know about the temperature. Maybe it was the temperature used as the mean in converting station pressure to sea level. ...in fact, that kinda makes sense.

  4. #14
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    Quote Originally Posted by thaiguzzi View Post
    Thankyou.
    Again, the 'Mercans are the odd ones out.
    Most of the Rest of the World is Centigrade.
    Most people in the world would just look at you weird when you say 68 Fahrenheit.
    Fahenwhat?
    Your use of 'Mericans instead of Americans I find highly derogatory.
    You find it weird and have a problem with the name Daniel Gabriel Fahrenheit.
    You apparently are accepting of the name Anders Celsius, possibly because he
    uses ten based numbers for freezing and boiling.
    Are your rationale's based on emotion or selfish needs for fulfillment?

    -Doozer
    DZER

  5. #15
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    Quote Originally Posted by epicfail48 View Post
    ...

    That's said, imperial measurements deserve to die a painful death. 100 centimeters to the meter, 1000 meters to the kilometer makes more sense than 12 inches to the for, 3 feet to a yard 5612 or some such nonsense feet to the mile, its a mess
    Sounds to me that you are too lazy to remember things like one miles is 5280 feet.
    Are you afraid your brain will leak out your ear????

    -Doozer
    DZER

  6. #16
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    Quote Originally Posted by RB211 View Post
    Aviation settled on 15c and 29.92 inches as the "standard day".
    Odd that they didn't settle on either, 59°F and 14.7 lb/in2 or 15°C at 1013.25 hPa.

    What is the "standard" for density?
    Last edited by Willy; 07-09-2019 at 09:18 AM.
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  7. #17
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    Quote Originally Posted by nickel-city-fab View Post
    It goes back to when Johanssen created his gage blocks. The common average temp in European QC labs at the time was 68F or 20C. When Johanssen lapped his first block, he sent it to the Bureau of Weights and Measures in Sevres and asked them to determine the length of it when it was at 20C. He then used the coefficient of expansion to hit his exact number, and create the rest of the blocks in the set.
    That’s interesting. I always wondered also. Now at Eaton before I retired a Gage master needed at least 2 of them, because the master needed 24 hours in the Gage lab to adjust to temperature before calibration could be done. Actually the masters was rotated so as not to disrupt production. Of course some masters was onesies because one failed and the volume was so low they wouldn’t replace them because of the cost, then QC would have to keep them for a day, but since we didn’t need them but maybe once a year it could be scheduled.

    My question would be in shops that outside calibration service does the micrometers etc. They don’t use 68 degrees or do they?


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  8. #18
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    It just occurred to me that I own several micrometers. They do not measure millionths. I wonder if the Metric world uses micrometers. If so, do they call them micrometers?


    Best Regards,
    Bob

  9. #19
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    Quote Originally Posted by Willy View Post
    Odd that they didn't settle on either, 59°F and 14.7 lb/in2 or 15°C at 1013.25 hPa.

    What is the "standard" for density?
    That's because pilots don't care about air density.... At least not directly. They are after a setting for their barometer so they can set "zero" for their altimeters. This is so important for them that pilots are given the local barometric pressure during talks with the tower both before takeoff and again before landing at the destination. The altimeters have a little calibration window that they use to set the value.

    Now the "why inches of Hg instead of Pascals?" question would be a good discussion. Perhaps because so many aircraft had already been made with instruments calibrated for inches of Hg?
    Last edited by BCRider; 07-09-2019 at 11:35 AM.

  10. #20
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    Quote Originally Posted by rjs44032 View Post
    It just occurred to me that I own several micrometers. They do not measure millionths. I wonder if the Metric world uses micrometers. If so, do they call them micrometers?


    Best Regards,
    Bob
    At least for some materials measured in millionths of a meter the term is microns. And I agree that it's rather meaningless at first glance. Micrometers would be a much better tie in to the system.

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