U in the FCF

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  • U in the FCF

    Could some one explain, the meaning of" U" in the FCF -Image attached
    Attached Files

  • #2
    Unequal profile
    Darroll
    2018R2

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    • #3
      NB: .006 is the total tolerance.
      So for an FCF with an Unequally disposed profile:
      The .002 after the 'U' allows the feature .002 ADDITIONAL material. And then you subtract of .006 - .002, .which gives you 004 --- the allowed amount of material REMOVED from feature .

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      • #4
        What sealevel said !
        U in ASME is UZ in ISO.
        Unilateral and Unequally Disposed Profile Tolerance [ASME Y14.5-2009 Section 8.3.1.2] - To indicate that a profile of a surface tolerance is not symmetrical about the true profile, this symbol is used. The first value in the feature control frame is the total width of the profile tolerance. The value following the symbol is the amount of the tolerance that is in the direction that would allow additional material to be added to the true profile.


        Some more GD&T info here :
        https://www.tec-ease.com/gdt-terms.php
        https://gdtseminars.com/wp-content/u...Chart_2013.pdf
        http://www.g-wlearning.com/cad/97816...r/pdf/appg.pdf

        Without forgettng the excellent presentation of Rob Jensen :
        https://www.gagesite.com/documents/E...0Standards.pdf

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        • #5
          +0.002/-0.004 from nominal, I believe
          Last edited by vpt.se; 04-23-2019, 06:19 AM.
          PC-DMIS CAD++ 2o19 R1 SP10

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          • #6
            At the moment, PC-DMIS only allows the ASME notation. Watch out for the difference between ASME and ISO - in ASME you tell what the Upper tolerance is (U) 0.002, in ISO you tell how the tolerance zone has been moved from the symmetrical case (UZ -0.002).

            Also note that PC-DMIS FCF will not let you (U) more than the tolerance width, if your tolerance is +/+ or -/- you can only do it with a Legacy dimension.
            AndersI
            SW support - Hexagon Metrology Nordic AB

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            • #7
              (U) in FCF signifies material "on" allowance in an unequal distributed tolerance zone
              .002 is Material "on" Max from nominal .004 material "off" from nominal
              Profile Surface or Line .006 (U).006 -A- is +.006-.000 from nominal-material must be at or plus to nominal
              Profile Surface or Line .006 (U).000 -A- is +.000-.006 from nominal-material must be at or less material than nominal
              Be aware of difference for a material "on" and Material "off" if they are an ID or Outer surface.

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              • #8
                Originally posted by Rich P View Post
                (U) in FCF signifies material "on" allowance in an unequal distributed tolerance zone
                .002 is Material "on" Max from nominal .004 material "off" from nominal
                Profile Surface or Line .006 (U).006 -A- is +.006-.000 from nominal-material must be at or plus to nominal
                Profile Surface or Line .006 (U).000 -A- is +.000-.006 from nominal-material must be at or less material than nominal
                Be aware of difference for a material "on" and Material "off" if they are an ID or Outer surface.
                IN THEORY, the arrow (leader) of the FCF should be pointing TO the side of stock that the U applies to. Also, IN THEORY, the arrow (leader) is NOT TO be passing through the part to point to the side of stock the U applies to.

                U-FCF.jpg
                Last edited by Matthew D. Hoedeman; 04-25-2019, 07:08 AM.
                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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                • #9
                  A simpleton like myself needs pictures to lÔÔk at in the ASME standard....wording alone is just sooooo dry.


                  profile.PNG

                  and personally? I don't care much for the 'Alternate Practice' with that dash line clutter

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                  • SingularitY
                    SingularitY commented
                    Editing a comment
                    Can't dispute the standard.

                • #10
                  Thanks for all great explanations. I am not very familiar with profile FCF tolerance. Now understand clearly going to apply once reach the office tomorrow.

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