Model point profile tolerance

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  • Model point profile tolerance

    We manufacture castings for the automotive industry and each print has CMM checkpoints with profile tolerances. For instance an individual point has a profile tolerance of 1.0mm. These are single points taken at exact locations on the model, using the model. We have in the past toleranced this as the nominal plus or minus .5mm instead of 1mm. Since this is a single point from a theoretical exact point on the model, I believe we should be tolerancing these to plus or minus 1mm instead of .5 giving us an allowable deviation from the profile of 1mm in either direction from that point.
    What are your thoughts on this and which one is correct?

  • #2
    Profile is a window of allowance. If the profile is 1.00, that is the full allowance and it would be dimensioned as +/-.5
    What authority can you point to that would allow +/-1.00?
    Lately, it occurs to me
    What a long, strange trip it's been.

    2017 R1 (Offline programming)

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    • #3
      Unless otherwise stated, a profile zone is a bilateral tolerance. It is a tolerance zone equally disposed about the true profile. A profile of 1mm would be equally disposed by a 0.5 tolerance zone on each side.

      reference figure 8-4 Application of Profile of a Surface Tolerance to a Basic Contour. ASME Y14.5 - 2009

      B&S CHAMELEON/PCDMIS CAD++ V2011

      There are no bugs, only "UNDOCUMENTED ENHANCEMENTS!"

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      • #4
        My thought here is that profile is similar to a flatness tolerance and did not know it had to be bilateral. For instance with a tolerance of 1.0mm, if you had points at .7 and .8 they would still be within nominal to plus 1mm of the nominal profile, more like a floating tolerance zone. I don't have a copy of ASME Y14.5 - 2009 so that is the reason for the question. Can someone post the section that refers to bilateral profile tolerance?

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        • #5
          They already told you what you needed to know. Profile of 1.0 ABC = +/-0.5, period. You could always buy your own set of books, like we have. whjere we got the answers for you from.
          sigpic
          Originally posted by AndersI
          I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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          • #6
            Now that's a wonderful idea, wish I would have thought of it. duh! Wonder if they sell spelling books?
            Last edited by myrex11; 11-02-2012, 08:47 AM.

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            • #7
              Yep, would have been nice.

              "Oh, answer this question for me." "Answered." "Well, I don't have the book and I think it is THIS instead, can you prove you are right by making an illegal copy of copyrighted material and posting it in a public forum?" "No".

              They do teach this stuff in community colleges all across the nation as well.
              sigpic
              Originally posted by AndersI
              I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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              • #8
                Myrex11. There is a website that has a great deal of info.

                Www.tec-ease.com

                demand your employer to purchase a copy of the ASME Y-14.5 standards. Duh!

                B&S CHAMELEON/PCDMIS CAD++ V2011

                There are no bugs, only "UNDOCUMENTED ENHANCEMENTS!"

                sigpic

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                • #9
                  Originally posted by John Riggins View Post
                  Profile is a window of allowance. If the profile is 1.00, that is the full allowance and it would be dimensioned as +/-.5
                  What authority can you point to that would allow +/-1.00?
                  In some circumstances the 1mm profile tolerance can be applied directionally as +1mm, minus nothing...which is still a 1mm total tolerance.

                  I wonder if that is what he is remembering from somwhere?
                  Poleaxe

                  Beware the environment you live in for it will shape you
                  Be careful the friends you choose for you will become like them.

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                  • #10
                    Originally posted by myrex11 View Post
                    I believe we should be tolerancing these to plus or minus 1mm instead of .5 giving us an allowable deviation from the profile of 1mm in either direction from that point.
                    What are your thoughts on this and which one is correct?
                    If the profile is 1.0 the allowance will never be +/- 1.00. It could be unequally disposed so that more is allowed in one direction but the total allowance will always equal 1.0.
                    If the intent is to have it unequally disposed then that must be indicated on the drawing or in the digital definition.
                    Lately, it occurs to me
                    What a long, strange trip it's been.

                    2017 R1 (Offline programming)

                    Comment

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