Position of a Pattern of Features to a Datum

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  • Position of a Pattern of Features to a Datum

    Position of a pattern of features to a datum (a plane normal to the features in this case) controls location of the pattern to itself (feature to feature) as well as orientation to the datum (perpendicularity). See attachment. Datum A is the underside of the part.

    This is illustrated in the standard in the following figures; 4-22, 4-26, 5-28. Also it is the very definition of position in that it controls both location and orientation. The main confusion with this occurs with people who use position to control the orientation of a single feature to a single datum. For this requirement, perpendicularity should be used. In this instance, both position and perp will mean the same thing. As soon as I have two or more features, then position and perp have two different meanings. Since perp is an orientation control only, the pattern could be located anywhere and still pass the requirement. Position would define the tolerance zones perp to the datum and basically located to each other.
    Last edited by inspector212; 10-17-2007, 11:34 AM.
    sigpic GDTPS - 0584

  • #2
    Originally posted by inspector212 View Post
    Position of a pattern of features to a datum (a plane normal to the features in this case) controls location of the pattern to itself (feature to feature) as well as orientation to the datum (perpendicularity). See attachment. Datum A is the underside of the part.

    This is illustrated in the standard in the following figures; 4-22, 4-26, 5-28. Also it is the very definition of position in that it controls both location and orientation. The main confusion with this occurs with people who use position to control the orientation of a single feature to a single datum. For this requirement, perpendicularity should be used. In this instance, both position and perp will mean the same thing. As soon as I have two or more features, then position and perp have two different meanings. Since perp is an orientation control only, the pattern could be located anywhere and still pass the requirement. Position would define the tolerance zones perp to the datum and basically located to each other.
    And your point is?? LOL





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    Bill Jarrells
    A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain

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    • #3
      Did you get this out of the ASME Y14.5M-1994
      sigpic.....Its called golf because all the other 4 letter words were taken

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      • #4
        This is exactly what I needed for that darn thread that had 100 posts!!! Now I think I need more info.
        Tom

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        • #5
          Originally posted by TommyD View Post
          This is exactly what I needed for that darn thread that had 100 posts!!! Now I think I need more info.
          Tom
          This is EXACTLY what they were arguing about on your thread with 100 posts - LOLOLOL

          PLEASE don't go there!!!
          Bill Jarrells
          A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain

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          • #6
            Originally posted by TommyD View Post
            This is exactly what I needed for that darn thread that had 100 posts!!! Now I think I need more info.
            Tom
            Get yourself a copy of the ASME Y14.5M-1994 standard, study it and apply it.

            Now,

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            sigpic GDTPS - 0584

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