GD&T call out question

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  • GD&T call out question

    Hello All,
    I have quick question in regard GD&T call out. In attached picture there is dimension 33 call out profile 0.075U |0
    My understand is the customer want to control the size of the round slot, and it should be 12.4 +0/-0.075 is this correct?

    but my co worker telling me it should be 12.4 +0.075 interpretation.

    I would like to known who is right?

    Thanks
    Attached Files

  • #2
    I don't know, but I want to say you are correct, based on this:

    The number following the circle U designates how much tolerance is displaced to the outside of the basic profile that adds material. This new symbol was first introduced in the ASME Y14.41 standard and is now in effect in the ASME Y14.5-2009 standard. The standard still allows, as an option, the chain line to define an unequal tolerance, but the circle U symbol is certainly preferred.
    Sheffield Endeavor3 9.20.8, Tesastar-SM, Leitz LSP-X1s & LSP-X1M, PCDMIS 2011 MR1

    Comment


    • VinniUSMC
      VinniUSMC commented
      Editing a comment
      You have the right words, but the wrong conclusion.

      Since there is 0 allowed "outside of material", and outside of material means a smaller hole (more material, smaller hole), then the tolerance would be +xxx. And, since it's all around, and the tolerance applies to the surface, and there are 2 surfaces, then the tolerance on the size is xx +.15/-0

  • #3
    Do not look at it like a slot. It has the ALL AROUND SYMBOL on the leaderline. And you have all your Basics. I assume you have cad. Each line and radius can be +0.075 / -.0 Check it with points and create a set, and Profile using Form Only. In reality OAL can be plus .15 if both were exactly .075 outward.
    sigpicSummer Time. Gotta Love it!

    Comment


    • VinniUSMC
      VinniUSMC commented
      Editing a comment
      Opposite words, correct interpretation... +0 for each surface, -.075 for each surface.

  • #4
    Actually, that callout is 'wrong' in that the leader-line & arrow are to be pointing at the side of stock (and ON the side of stock) that gets the value AFTER the (U). Since the arrow is pointing to the 'side' of stock that is inside the part, the meaning is flipped from what you might think. SO, based on a 100% strict interpretation, the size of that hole (and it isn't a size callout!) would be none bigger but 0.15 smaller than the called out size. That leader-line & arrow should be INSIDE the hole, pointing to the INSIDE of the hole, not pointing to the 'outside' of the hole (as in, going through the opening to point at the opposite side of the hole that it is pointing to right now).

    Since it is a profile, if you MUST (and it's wrong) use it to check size, remember, that tolerance is for BOTH sides of the hole, not just one side, so it gets doubled.

    TOL 1.0 (U) 0.0 means that the surface the arrow is pointing to (and the SIDE it is pointing to) gets 1.0 total tolerance, with 0 "added" stock. So, how do you add stock to the side of the hole that is inside the stock already? THIS is why that leader-line & arrow is wrong.
    sigpic
    Originally posted by AndersI
    I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

    Comment


    • Mike Ruff
      Mike Ruff commented
      Editing a comment
      Matt, I'm not saying you are wrong, but I would like to know where you are seeing it have to do with the direction of the leader line. I have ASME Y14.5-2009 (so maybe you are looking at a newer or older version, or ISO?), and it seems pretty specific about the number AFTER the U symbol representing material in the direction that adds material. Specifically, I'm looking at Section 8.3.1.2 of ASME Y14.5-2009. Also, none of the pictures in my version of the standard show the arrow coming thru the part and pointing at a void in material, either. Can you please reference where you got this info from?

    • VinniUSMC
      VinniUSMC commented
      Editing a comment
      I second Mike, this is not something I've heard of. It is explicitly stated "adds material" and "removes material".

      Unlike Mike, I am saying, Matt is wrong.

  • #5
    I can't see your picture.

    All I know is... The number after the U is the amount of IN SPACE tolerance you have. 0.075 is the total.

    So..Imagine you're measuring the OUTSIDE PROFILE of a square block and the nominal width was 1". You'd have to be 0.925-1.000 to comply.

    Comment


    • #6
      According to ASMEY14.5, 2009, this tolerance zone would be +0.075, minus zero from the basic, all around. The width of the slot can technically be +0.150", but not minus 0.0001" from basic.

      8.3.1.2 Unilateral and Unequally Disposed Profile Tolerance. A unilateral and unequally disposed profile tolerance is indicated with an unequally disposed profile symbol placed in the feature control frame. See Fig. 3-11. The unequally disposed symbol is placed in the feature control frame following the tolerance value. A second value is added following the unequally disposed symbol to indicate the tolerance in the direction that would allow additional material to be added to the true profile.

      (a) Unilateral Tolerance in the Direction That Adds Material. Where a unilateral profile tolerance is 0.3 and applies from the true profile in the direction that adds material, the tolerance value would be 0.3 and the value following the unequally disposed symbol would be 0.3. See Fig. 8-1.

      (b) Unilateral Tolerance in the Direction That Removes Material. Where a unilateral profile tolerance is 0.3 and applies from the true profile in the direction that removes material, the tolerance value would be 0.3, and the value following the unequally disposed symbol would be 0. See Fig. 8-2.

      (c) Unequally Disposed Tolerance. Where an unequally disposed profile tolerance is 0.3, 0.1 applies from the true profile in the direction that adds material, and 0.2 applies from the true profile in the direction that removes material, the tolerance value would be 0.3, and the value following the unequally disposed symbol would be 0.1. See Fig. 8-3.
      Last edited by louisd; 11-08-2019, 11:06 AM.

      Comment


      • Mike Ruff
        Mike Ruff commented
        Editing a comment
        +1. This is exactly how I would interpret it per ASME Y14.5-2009

    • #7
      Mike: My info is from the GM 'standard', when they implemented it (and I think they are the ones that got this rolling into the real standards). It's the GM ADDENDUM from 2004, all arrows to be pointing TO the side of stock that is effected, no arrows 'going through the part' to indicate, must be pointing TO the surface that gets the (U) from the side that gets the (U). The 'real' standard appears to be different, but who in their right mind would point THROUGH a part with a leader-line/arrow to indicate the SIDE of stock for the unilateral? This may be due to GM & sheetmetal. Think about it this way, very thin part (say, 0.012") on a 1-1 scale drawing, you'll never be able to tell what side of stock is indicated by the arrow, if ya follow what I am saying. Don't think only cubical parts, very thin stuff is out there as well, and if half the arrow go THROUGH the stock and half don't, you'll never figure out what they want. It would be 'obvious' (but stupid) on a block part, but thin sheet metal, there MUST be something to ensure you are 'adding' the stock to the right side. And in sheetmetal, it isn't really 'added stock', but more a direction in which the part can move. One side get 'added' while the other side 'loses', so, you have to know!
      sigpic
      Originally posted by AndersI
      I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

      Comment


      • Mike Ruff
        Mike Ruff commented
        Editing a comment
        That makes a lot of sense. I occasionally get PDFs that are dimensioned incorrectly because the engineer/drafter responsible grabbed the wrong edge for the dimension. It would be much worse with sheet metal! Especially if you have to deal with scanned drawings

      • VinniUSMC
        VinniUSMC commented
        Editing a comment
        This is a feature of size. It is either internal or external. The surface of the hole doesn't change depending on how you point at it. The print shown is using one of the explicitly defined methods of pointing a leader line at a hole.

    • #8
      I have similar callout on my drawing I am working on. Our former CMM guy still work with us as an engineer and said if we use .030 U 0 for profile without datum, PC-DMIS won't know where to show deviation arrows and may show wrong data. He is insisting to use datum structure. I am currently getting all the arrows pointing INWARDS which satisfies condition asked. Can someone comment on my former CMM GUY's note?

      Attached Files

      Comment


      • #9
        Your former CMM guy is probably going by what he used to work with. That used to be the case with older versions of PCDMIS, specifically legacy dimension. Legacy demanded a Datum before it allowed you to specify unidirectional tolerance on a profile. With Xact measure, that's no longer the case.

        Comment


        • aliptpatel
          aliptpatel commented
          Editing a comment
          Thank you for your input sora5. So the callout is right and my deviation arrows does make sense of having in tolerance profile right?

        • Sora5
          Sora5 commented
          Editing a comment
          Yes, that callout allows +0, -.030. All your arrows pointing inward (within .03) shows an in tolerance deviation.

        • aliptpatel
          aliptpatel commented
          Editing a comment
          Thanks for validation.

      • #10
        Do note that, at least in ISO, the "all around" still doesn't mean that everything should be evaluated as a single set - it would also need "CZ" for that.
        AndersI
        SW support - Hexagon Metrology Nordic AB

        Comment


        • #11
          Originally posted by Matthew D. Hoedeman View Post
          Actually, that callout is 'wrong' in that the leader-line & arrow are to be pointing at the side of stock (and ON the side of stock) that gets the value AFTER the (U). Since the arrow is pointing to the 'side' of stock that is inside the part, the meaning is flipped from what you might think. SO, based on a 100% strict interpretation, the size of that hole (and it isn't a size callout!) would be none bigger but 0.15 smaller than the called out size. That leader-line & arrow should be INSIDE the hole, pointing to the INSIDE of the hole, not pointing to the 'outside' of the hole (as in, going through the opening to point at the opposite side of the hole that it is pointing to right now).

          Since it is a profile, if you MUST (and it's wrong) use it to check size, remember, that tolerance is for BOTH sides of the hole, not just one side, so it gets doubled.

          TOL 1.0 (U) 0.0 means that the surface the arrow is pointing to (and the SIDE it is pointing to) gets 1.0 total tolerance, with 0 "added" stock. So, how do you add stock to the side of the hole that is inside the stock already? THIS is why that leader-line & arrow is wrong.
          I have GM Addendum 2004 and the new one for 2009. Matt, you've read the Addendum wrong.

          See fig NEW 6-56 on page 55 of the 2004 addendum. It describes exactly this scenario, and the figure also points at the feature in exactly the same manner. The number after the U is still "Add material". And, on the previous page, fig NEW 6-55 shows that the number after the U is always "add material".

          I didn't come back to the forum just to tell you that you're wrong, I promise!
          "This is my word... and as such is beyond contestation."

          Comment


          • #12
            Originally posted by VinniUSMC View Post

            I have GM Addendum 2004 and the new one for 2009. Matt, you've read the Addendum wrong.

            See fig NEW 6-56 on page 55 of the 2004 addendum. It describes exactly this scenario, and the figure also points at the feature in exactly the same manner. The number after the U is still "Add material". And, on the previous page, fig NEW 6-55 shows that the number after the U is always "add material".

            I didn't come back to the forum just to tell you that you're wrong, I promise!
            The "only" problem with that is that there is NO 'added stock' possible in sheetmetal. You have a thickness tolerance (per a print I am looking at, 2.3 to 2.7, thinning not to exceed 25%), then you have a prof 3 (U) 0 ABC, and you can't add 3mm of stock to either side of the part as that is more than the maximum stock thickness. So you absolutely have to know which direction the entire part is allowed to move as one side can get 'heavy' by 3 while the other side can get 'lighter' by 3. If the arrow is just randomly pointing "here", which direction can it go? And keep in mind, you may or may not be able to check the part on the 'called out' side of stock, so you may have to use +3/-0 or +0/-3. The only way to ensure that you are tolerancing correctly is if the arrow IS pointing to the correct side of stock from the correct direction (as in, not through the part). It may have been a BMW 'clarification' of this addendum I am thinking of, but "added stock" is not a possibility in sheetmetal.
            sigpic
            Originally posted by AndersI
            I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

            Comment


            • VinniUSMC
              VinniUSMC commented
              Editing a comment
              No, added stock is not possible in sheet metal. That doesn't invalidate the standard. Most of my customers either specify on the print which side of material is the surface in question, or give us a general guideline like, "if in doubt, outside of car".

              Sheet metal can't really be "add material", but you can still tolerance in the direction of add material, regardless of what side of material you measure on, one side is the side being referenced.

          • #13
            BUT without a guidline, you can't know which direction is which. Like I said, it may have been a BMW (or Merc, or even GM) that gave out the 'clarification' on the arrow use for direction of movement.
            sigpic
            Originally posted by AndersI
            I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

            Comment


            • VinniUSMC
              VinniUSMC commented
              Editing a comment
              That's fine. But you're trying to tell someone to ignore ASME Y14.5 based on a single customer (maybe?) because of sheet metal, when his question likely doesn't involve that customer, and isn't related to the thickness of sheet metal anyways.

          • #14
            Actually, he IS trying to measure a sheet metal part.
            sigpic
            Originally posted by AndersI
            I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

            Comment


            • VinniUSMC
              VinniUSMC commented
              Editing a comment
              No, he's measuring a slot. That has nothing to do with it being sheet metal. A slot is a slot is a slot.

              Whether some other method is needed to identify side of material for sheet metal is entirely irrelevant.

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