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Thread: How would you tolerance the channels on this part?

  1. #1
    Associate Engineer
    Join Date
    Aug 2019
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    1

    How would you tolerance the channels on this part?

    See attached image / print.

    Hello. The customer has asked for advice on how to modify/improve the characteristics on this print. The features needing control are the seven
    .0255-.0260 long, .0255-.0260 deep channels. The profile controls are completely up for modification and in fact need to be changed.

    This print invokes ASME Y14.5.

    Here is the crux of the issue: The channel size at any 2-point section is critical. However, the overall length of the channels, which is 14 inches, can allow generous straightness deviation, because the mating parts that move through these channels are more like "al dente spaghetti." The same is true for the depth of these channels (any 2-point depth must be .0255-.0260).

    How would you tolerance this print to maintain the 2-point .0255-.0260 channel width and depth requirements while allowing these same channels deviation in form, size and orientation over their entire 14 inch length?

    • 1. Can the independency symbol be utilized here somehow?


    • 2. Is it sufficient to only include the size tolerance and no geometric control since ASME Y14.5 is invoked, so rule #1 applies?


    • 3. Can/should profile of a line be used?

    Any other thoughts?

    Much appreciated.

    Attached Images Attached Images

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
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    Feb 2011
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    Bold Springs, GA
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    The left side of the provided view composite Profile of Surface is incorrectly specified as it indicates to a feature of size as opposed to a surface or surfaces. Profile controls surface variation not FOS location. More correctly you could use position tolerance here as the specification with a feature of size and tolerance +/- .0025.

    To only control the local size and allow notable straightness variations you might indicate a feature of size and tolerance +/- .0025 with the principle on Independency (Circle I) and use a Profile of Surface on only one of the vertical surfaces of the cutout to an amount that is acceptable to control the relative location and wiggle.

    Notes:

    Rule #1 is default unless otherwise specified.

    Datums are not shown so no review for compliance.

    The views right side composite Profile of Surface specification indicates the upper boundaries of +/- .001 bilateral equal and an orientation only specification of .0005 relative to datum A.
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