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Thread: BSC dimension tolerance

  1. #1
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    BSC dimension tolerance

    I have a BSC dimension (177) in length and there is a profile tolerance of .7 on both ends. One end surface is Datum A. Do I get the +/-.35 on both ends? Or just the end that is not a datum? Its either 177 +/-.7 or 177 +/-.35. I have attached the drawing.
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  2. #2
    Technical Fellow Kelly_Bramble's Avatar
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    That only applies on the surfaces Between Point A and B. Look below the Feature Control Frame.

    But, yes one half the specified Profile Tolerance from the nominal surface.

    Technically, the Profile tolerance also applies to the Datum Surface and is measured from the established datum plane on that surface - works like a flatness.
    Last edited by Kelly_Bramble; 11-09-2022 at 05:50 PM.
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  3. #3
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    Quote Originally Posted by Kelly_Bramble View Post
    That only applies on the surfaces Between Point A and B. Look below the Feature Control Frame.

    But, yes one half the specified Profile Tolerance from the nominal surface.

    Technically, the Profile tolerance also applies to the Datum Surface and is measured from the established datum plane on that surface - works like a flatness.

    Yes, Point A and B are on both ends and one being a datum. So that Datum A surface does have a +/-.35 tolerance also? If so, then the overall length will be 177 +/-.7 then. Unless I'm not understanding you correctly.

  4. #4
    Technical Fellow Kelly_Bramble's Avatar
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    Quote Originally Posted by kreits View Post
    Yes, Point A and B are on both ends and one being a datum. So that Datum A surface does have a +/-.35 tolerance also? If so, then the overall length will be 177 +/-.7 then. Unless I'm not understanding you correctly.
    The limits of size is a different control (+/- .35) and the geometric tolerance is contained within that variability. So, the profile is a refinement of surface variability of the limits of size.

    Tolerances are Hierarchical and the limits of size (+/-) are the outermost tolerance boundary unless otherwise specified in all ASME and ANSI standards.

    You need this book...

    https://www.engineersedge.com/engine...-gdt-p-47.html
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