Datum Shift

I received a report from a vendor where they are showing everything on a part 100% in tolerance. I have checked the part myself and show quite a few things out of tolerance. On their report I noticed a term "DATUM SHIFT" and some variables "X,Y,Z", etc. just before each dimension is reported. My question is this, What exactly is "DATUM SHIFT" and what is it doing? Is there some kind of data manipulation going on here?

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cmm-measurer over 14 years ago

I understand the concept of MMC. But I don't understand what is happening with the "rotations" within that shift. Now this shift is not actually moving the datums around, but moreso it is applying this "allowable bonus" tolerance to the feature in some form or another. Is that a correct statement? I'm just curious as to how this might stack up when reporting on a group of several holes. Theyll all look good relative to the Datums, but to each other could potentially have some problems, with no exact numbers to relate to a tool correction. Am I trying to play hockey on a basketball court with that approach?
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cmm-measurer over 14 years ago

I understand the concept of MMC. But I don't understand what is happening with the "rotations" within that shift. Now this shift is not actually moving the datums around, but moreso it is applying this "allowable bonus" tolerance to the feature in some form or another. Is that a correct statement? I'm just curious as to how this might stack up when reporting on a group of several holes. Theyll all look good relative to the Datums, but to each other could potentially have some problems, with no exact numbers to relate to a tool correction. Am I trying to play hockey on a basketball court with that approach?
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