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Thread: Company Standards - misapplication of GD&T?

  1. #1
    Associate Engineer
    Join Date
    Sep 2014
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    Company Standards - misapplication of GD&T?

    My company has for years used drawings with a general symmetrical tolerance block and applied GD&T as necessary, to very good success. However, we're recently been pushed by our parent company to adopt their standards. This includes a general note calling all untoleranced dimensions basic, which I know is OK per standards. However, the general drawing notes also contain feature control frames for both profile and position. The values are part dependent, but generally the profile allows a larger variation than the position. And there are normally very few specific tolerances called out on their prints. One of my problems comes in the interpretation of what's profile vs. position. A dimension to a hole is obviously position, but to the edge of a slot? Or a cutout in a piece of sheet metal. Dimension to the first edge of the cutout, profile or position? First edge to second edge? Hole diameters would seemingly all be profile? Not only am I confused, but I'm getting completely inconsistent inspection reports; dimensions are almost always interpreted using all profile or all position. This morning I got report on a sheet metal part where all the bends (indeed all the dimensions) where inspected using the profile tolerance, which seems a misapplication. I've used basic GDT for years, but I don't consider myself an expert. Does this seem reasonable? Am I misinterpreting something? I'm having some consternation both trying to follow the "standards" and producing a print that I believe is acceptable.

    Thanks,
    Dave

  2. #2
    Administrator Kelly Bramble's Avatar
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    Feb 2011
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    Bold Springs, GA
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    You have not stated the specific dimensioning and tolerancing standard therefore I'm going to give you a general ~ specific answer.

    For any ASME or ANSI standards position tolerance is used to locate a feature of size and profile of a surface and line defines tolerance boundaries within which a surface profile feature as-built must lie within.

    For ISO or any of the derivative dimensioning and tolerancing standards, position tolerance may be used to locate an individual planar surface as well as a feature of size and profile any line or surface defines tolerance boundaries within which a surface profile feature as-built must lie within.

    Based on your description your organization needs training to whatever standard being used in order to get everybody on the same page in regards to interpreting dimensioning and tolerancing..
    Last edited by Kelly Bramble; 09-25-2014 at 12:27 PM. Reason: Spelling

  3. #3
    Associate Engineer
    Join Date
    Sep 2014
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    2
    Thank you Kelly. Sorry, should have mentioned that our standard is ANSI Y14.5M-1982.

    Thanks,
    Dave

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