Position of an angle?

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  • Position of an angle?

    Good morning,
    Something new here, a position call out for an angle to be .001 to datums A and B. Anyone here experience this before and how would that even be possible?
    Thanks

  • #2
    Can you attach the print?

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    • #3
      Actually I am not allowed to copy prints and distribute. Sorry. This is basically a machine cut within the cavity of a circular section of the part and it has an angle of 40 degrees +/- .5 degrees from the x axis centerline of part which is a bore and datum A. B is the bottom flat of the part. It is a medical implant so it is quite small, about 1/2 inch in overall length. Checking the angle is no problem but not sure what to do with a true position of that angle.

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      • #4
        Machine cut within a cavity? Is it a notch? If it is a feature of size, at a particular angle, it would make sense. If it is just the clocking of a surface, then TP would not be legitimate and should be instead called as angularity or profile.

        How exactly is the FCF shown in relation to the dimension in question? Is it tagged directly to the angle? To the surface? If you can't provide a snippet of the print, can you provide a hand-drawn pseudo-print replicating the conditions? I'm having trouble even picturing this.
        "This is my word... and as such is beyond contestation."

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        • #5
          Originally posted by VinniUSMC View Post
          If you can't provide a snippet of the print, can you provide a hand-drawn pseudo-print replicating the conditions? I'm having trouble even picturing this.
          I can't picture it either.

          Hopefully it's Position of a feature whose nominal location is defined with Polar/Cylindrical coordinate system basic dims: RAH instead of cartesian XYZ. We can do that, because we can convert it to XYZ.

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          • #6
            I am trying to attach a small sectional view of the print area but am having no luck posting a doc. What am I doing wrong?

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            • #7
              Doc3.pdf

              This is the best I can do. Hope this explains a little better

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              • #8
                To me, it looks like the 40° is to the tangent line of the circle detail E witch i think means that the position tolerance is for the circle, or even maybe to the tangent point of the line going through center of datum -A- and just touching the circle detail E. I'm leaning more towards the tangent point.

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                • #9
                  Nano, thanks for your input so far. I know it looks like a tangent line but it is actually a machined linear surface that steps down from a higher flat to a lower flat. It has enough surface for me to establish a line which I am using as one leg of the angle for the 40 call out. It just happens to be coincidental to where a tangent point would fall.

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                  • #10
                    Oh wow that really is a bad callout. Another one for my collection...

                    My best guess is that the designer wants the machined flat to be cut in the correct "position", but is not aware that we can only measure and report the position of geometric features that have bounded centerpoints or central axis... which flat planes do not have. Planes are mathematically infinite.

                    I would recommend getting written permission from the customer to report the Profile of that plane instead.

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                    • #11
                      Thanks Josh, my thoughts exactly. As to profile, that area is included in the profile of .001 shown on the top of the detail as reaching from x-y. So why the additional call out that I agree is not proper. As for permission from the customer, that function is always left up (unfortunately) to the discretion of the salesman who seldom follows through because he doesn't understand GD&T as well.

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                      • #12
                        Jim,
                        That is an invalid callout.
                        A position must be tied to a feature of size.

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                        • #13
                          If you folk mfr'd the part, talk to the machine shop foreman. They could not have made the part without getting an answer from the designer.
                          Pat McSwain
                          President
                          Quality Inspection, Corona CA

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                          • #14
                            Originally posted by Chris Carlson View Post
                            Jim,
                            That is an invalid callout.
                            A position must be tied to a feature of size.
                            Not if its an ISO drawing.
                            Lately, it occurs to me
                            What a long, strange trip it's been.

                            2017 R1 (Offline programming)

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                            • #15
                              look like some was trying to use polar coor.
                              sigpic
                              A proud Vietnam Veteran. 1973-1974

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