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Thread: GD&T question

  1. #1
    Associate Engineer
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    GD&T question

    VZW6KWA.jpg

    See picture above(which hopefully links)

    I'm trying to use GD&T to tolerance the flats of the D-hole. What I'm trying to describe is the flats centered on the 1.125 diameter hole.

    I also have to do something similar with the shaft that fits through this hole.

    Position tolerance I have doesn't feel right. What are your thoughts? Can you use symmetry in a hole?

    Thanks,
    Pete

  2. #2
    Administrator Kelly Bramble's Avatar
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    Try Profile of Surface - All Around...

  3. #3
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    your hole is not fully dimensioned.
    please give dimension from centre of hole and any one side of flat and make that dimension basic.
    by doing this your current position tolerance will serve your purp

  4. #4
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    Quote Originally Posted by Rahul_Kamdar View Post
    your hole is not fully dimensioned.
    please give dimension from centre of hole and any one side of flat and make that dimension basic.
    by doing this your current position tolerance will serve your purp
    I couldn't help but feel like I was missing something when I drew this last night. The drawing does seem more complete with that basic dimension added.

    Any other ideas before I close this out?

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  6. #6
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    No... the .438 should not be basic. Basic dimensions establish the "basis" for a geometric tolerance. Your geometric tolerance is position. The only basic dims should be those that help establish position (location). If you were using profile of a surface across the two flats (or even all around), then that basic dim would be needed, and you'd drop any tolerances on the .875, because profile across there would be controlling size as well.

  7. #7
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    To add to my last post...

    In case you're not aware, the position tolerance actually applies to the center plane of the two flats, not the flats themselves. This is why the basic dim of .438 shouldn't be there.

  8. #8
    Administrator Kelly Bramble's Avatar
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    On another look at the geometry it appears that it is punched sheet metal. This is because there are sharp corners designed into an internal cutout feature.

    Since the geometry will require a single action tool to create, Profile of Surface would reflect the best control.

    All of this assumes that this is in fact a sheet metal punched part.

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