True Position in 3 axis???

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.

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craiger_ny over 16 years ago

I disagree to a point. You MUST have three to have a spherical zone. When it is diametric tolerance zone you MUST have at least two BASIC Dims to locate it. You can have only one BASIC if it is a single axis tolerance zone.

That said, I have seen points with spherical zones. Same with circles in sheet metal.

Actually you can constrain a feature to a spherical tolerance zone with one basic dimension provided it is a spherical feature (see P 155 fig 5-62). What I am saying is that just because you have 3 basic dimensions locating a feature that does not necessarily mean it is a spherical tolerance zone. I am saying you can have 3 basic dimensions locating a feature with an axis which means that you have a diametric (or cylindrical) tolerance zone (see attached picture). And yes you can locate a diametric (or cylindrical) feature with only one basic dimension for true position purposes. Actually, when specifying coaxiality you have zero basic dimensions.
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craiger_ny over 16 years ago

I disagree to a point. You MUST have three to have a spherical zone. When it is diametric tolerance zone you MUST have at least two BASIC Dims to locate it. You can have only one BASIC if it is a single axis tolerance zone.

That said, I have seen points with spherical zones. Same with circles in sheet metal.

Actually you can constrain a feature to a spherical tolerance zone with one basic dimension provided it is a spherical feature (see P 155 fig 5-62). What I am saying is that just because you have 3 basic dimensions locating a feature that does not necessarily mean it is a spherical tolerance zone. I am saying you can have 3 basic dimensions locating a feature with an axis which means that you have a diametric (or cylindrical) tolerance zone (see attached picture). And yes you can locate a diametric (or cylindrical) feature with only one basic dimension for true position purposes. Actually, when specifying coaxiality you have zero basic dimensions.
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