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Thread: Position of Hole where Primary Datum is Paralell to Hole Axis

  1. #1
    Associate Engineer
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    Position of Hole where Primary Datum is Paralell to Hole Axis

    The attached file shows a position callout for a hole that has an axis that is parallel to the primary datum. I understand that if the primary datum is perpendicular to the axis of the hole, then perpendicularity is controlled. With the primary datum parallel to the hole axis, is parallelism controlled? Is this position callout even valid? If not, what part of ANSI Y14.5 is violated?
    Thanks
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  2. #2
    Project Engineer
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    Yes, it's valid. And yes, by doing that, the axis of the small hole is being held parallel the the primary datum A.
    All the datums are doing is establishing a "reference frame," or a coordinate system in which to locate this hole. Once that datum reference frame has been established, the hole is actually being controlled in all possible directions and orientations.

  3. #3
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by Belanger View Post
    Yes, it's valid. And yes, by doing that, the axis of the small hole is being held parallel the the primary datum A.
    All the datums are doing is establishing a "reference frame," or a coordinate system in which to locate this hole. Once that datum reference frame has been established, the hole is actually being controlled in all possible directions and orientations.
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