Symmetry of a keyway on a shaft

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  • Symmetry of a keyway on a shaft

    I am having trouble with a getting symmetry of a keyway on a shaft. I am using the shaft as Datum A and a plane perpendicular to the shaft as Datum B. Print report says symmetry is 0.000. Is this wrong or am I doing this right. Any help would be appreciated.

  • #2
    Need more info.

    When you say 'Plane perp to shaft' I assume you mean the mid plane of keyway? Or si this a shouler / end face of shaft?

    What sort of sizes are we dealing with here - I've had very limited success with keyway measurements, especially internal (broached) keyways. Milled keyways tend to be more parallel and I get better correlation with plate inspection that way, BUT only if the keyway is big enough - anything less that 6mm /1/4" is dodgy.

    Also how are you measuring the features (planes / lines / points / feature sets) and how are you dimensioning them? Using legacy dimensions or exact measure? What is the callout on the drawing?

    Automettech - Automated Metrology Technology


    • #3
      It's a 3/8" milled keyway - 4" long on a shaft that is 1.7495 Dia. +.000/-.0005. The plane is a flange at the end of the shaft. I am using legacy dims. symmetry is .002
      Last edited by tiny4d; 02-12-2019, 09:46 AM.


      • #4
        3/8th width isn't so important - how deep is the keyway?
        Automettech - Automated Metrology Technology


        • #5


          • #6
            You're going to struggle. You've got about 5mm of land. You can't probe right to the bottom or right to the top so call it 4mm Max. You're trying to provide timing from a line / plane only a few mm long.

            Use slips and clock instead.
            Automettech - Automated Metrology Technology


            • tiny4d
              tiny4d commented
              Editing a comment
              thank you for your time I will try that instead. Have a great afternoon!

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