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True Position in 3 axis???

1CMM4ME
Ok, I have read the post regarding this so called argument that my boss and I got into today. He told me that you cannot measure true position in 3 axis, as I told him he was wrong. I know it depends on the way the FCF calls it out, but I tried to explain to him that it is possible to measure TP in 3 axis.
I have seen the formulas, so I know it's possible. I just wish I could get one of you gurus to reply back explaining that it is possible and why. I see the picture but he does not. I do not like to get into pissing matches with upper management, but I have learned a h**ll of alot from you guys, and I know this is possible. So if one of you fine gentleman can back me up on this, I would very much appreciate it. Thank you very much.
Now I am going to get a cold beer.Smiley
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  • I have had numerous prints where features have a TP callout to all three
    axis and I am given Basics to all three axis. When that is the case I call
    the TP to all three axis. This calculation makes a spherical Tolerance zone.
    Even if the S is not in the Feature Control Frame using the third axis makes
    it spherical.

    My biggest pet peeve is a TP callout to a surface. I say that a TP to a surface is a 'Profile'.

    Actually I posted an example where the tolerance zone is not spherical even though three axis are used. Guys, tolerance zone shape is not dictated by the number of axis constraining the feature's location/orientation. Tolerance zone shape is dictated by the shape of the feature. Axial features have an axial tolerance zone not a spherical one.

    BTW you can not TP a surface a surface is not a FOS so that is actually an illegal callout.

    Bill, here is another example where a cylindrical feature is adequately constrained using one basic dimension and a FCF.




  • in reply to craiger_ny
    You are correct that it is adequately constrained using "one" EXPLICIT basic dimension. However, as you pointed out the axial features having a cylindrical tolerance zone, there becomes an IMPLICIT (unspecified) basic dimension limiting perpendicularity deviation to not exceed the allowed positional tolerance. For the "one" basic dimension, you are omitting the perpendicular implicit requirement. Also, the axis (so far as one might have setup a DRF with X,Y,Z axes is necessarily unreferenced. In essence, the single basic dimension will not necessarily be in any axis except a polar radius.
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  • in reply to craiger_ny
    You are correct that it is adequately constrained using "one" EXPLICIT basic dimension. However, as you pointed out the axial features having a cylindrical tolerance zone, there becomes an IMPLICIT (unspecified) basic dimension limiting perpendicularity deviation to not exceed the allowed positional tolerance. For the "one" basic dimension, you are omitting the perpendicular implicit requirement. Also, the axis (so far as one might have setup a DRF with X,Y,Z axes is necessarily unreferenced. In essence, the single basic dimension will not necessarily be in any axis except a polar radius.
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