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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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  • Maybe it's too early in the morning but I still see NO way to locate a spherical tolerance zone with one BASIC unless as you illustrated there are ASSUMED dimensions as in coaxiality. The point I am trying to make is that you have to LOCK three Axis in place somehow to be able to use a spherical tolerance zone. You have to LOCK two axis in place for a diametric tolerance zone etc. No way around it. I don't see the shape of the feature as having any special significance. Example: A tooling Ball. Put it in space in any reference frame. Give it a locator in one axis ONLY and there is no way you can tolerance it with a spherical tolerance zone. The center point of a spherical tolerance zone MUST be pinpointed in all three axis. Unless all three axis converge on a theoretical center point there is no way to determine deviation from that point. Same goes with a diametric. It has to be locked in two axis in a given workplane to be able to determine deviation from the theoretical center.

    I do agree that there are times that there are three BASIC Dims locating a feature and there is only a diametric zone. However, you cannot USE all three to axis deviations calculate the vector deviation. With a diametric zone you can ONLY use two axis to calculate deviation OR you are constraining the feature to a spherical zone.

    That said, what is your criteria for determining workplane when performing diametric TP tolerancing when there are three or even four BASIC Dims?
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  • Maybe it's too early in the morning but I still see NO way to locate a spherical tolerance zone with one BASIC unless as you illustrated there are ASSUMED dimensions as in coaxiality. The point I am trying to make is that you have to LOCK three Axis in place somehow to be able to use a spherical tolerance zone. You have to LOCK two axis in place for a diametric tolerance zone etc. No way around it. I don't see the shape of the feature as having any special significance. Example: A tooling Ball. Put it in space in any reference frame. Give it a locator in one axis ONLY and there is no way you can tolerance it with a spherical tolerance zone. The center point of a spherical tolerance zone MUST be pinpointed in all three axis. Unless all three axis converge on a theoretical center point there is no way to determine deviation from that point. Same goes with a diametric. It has to be locked in two axis in a given workplane to be able to determine deviation from the theoretical center.

    I do agree that there are times that there are three BASIC Dims locating a feature and there is only a diametric zone. However, you cannot USE all three to axis deviations calculate the vector deviation. With a diametric zone you can ONLY use two axis to calculate deviation OR you are constraining the feature to a spherical zone.

    That said, what is your criteria for determining workplane when performing diametric TP tolerancing when there are three or even four BASIC Dims?
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