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Machinist level specs seconds vs tenths/10"

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by AGCB97, Jun 24, 2017.

  1. AGCB97

    AGCB97 United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I'm looking at level specs of various levels.
    Starrett gives 0.42 mm/m or 80 to 90 seconds
    How does this compare to .0005/10"
    My math seems to not work

    Thanks
    Aaron
     
  2. T Bredehoft

    T Bredehoft Active User H-M Supporter-Premium

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    equals .0165 per 39.37 inches.

    If your Starrett level is 10 inches long, that would equal ,0042 in 10 inches. Someone please check my math.
     
  3. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    10 seconds of arc equals approximately .0005"/10" or .0006"/12". A second of arc is 1/3600 degrees. The sine of 1 second of arc is 4.848 x 10^-6 (.000004848) That times 10" is .00004848". For very small angles, the sine, tangent, and arc in radians (2π radians equals 360º) are close to equal so 10 seconds of arc = .00048"/10".
     
  4. mikey

    mikey Active User H-M Supporter-Premium

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    Per Starrett, Main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42mm per meter)
     
  5. AGCB97

    AGCB97 United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Should that be .0005" per foot?
     
  6. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    Starrett' 98 Series levels are .005"/ft. Their 199 series level is .0005"/ft.
     
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  7. woochucker

    woochucker United States Active Member Active Member

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    That's correct.
     
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  8. benmychree

    benmychree United States Active User H-M Supporter-Premium

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    The bottom line is that the 98 series is not good enough to precision level a machine tool such as a lathe, but is adequate to level such as milling machines, drilling machines, etc.
     
    Bob Korves and mikey like this.

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