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Tangent Point - actually Cosine Error from incorrect IJK vector

I've a question about how the CMM calculates hits on tangent points. In the attachment I have a picture showing the issue.
I have 2 lines. Y is vectored with straight on hits. X is also vectored with straight on hits.
Since X- is not a 0/45/90 degree angle, but at a 20 degree angle form a straight on hit, will the ball calculate slightly off as it thinks it makes contact at 0 degrees, but actually hits earlier at 20 deg. thus creating the line 0.096mm sooner than it should have?

It obviously figures this out with circles/cones/cyliders, but it doesn't seem to do this with lines and points.
Should this be planned for and the measurement offset in calculation, or can it be corrected with some really specific (and tedious) vectoring so the probe knows where it should be hitting?



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  • Your diagram is showing what is usually referred to as "cosine error".

    This will always be present on points that do not vector normal to the surface.

    It should not be an issue for a measured line if the software is working properly. If you measure points and construct a line using BF, the error will be present in the line. If the line is constructed using BFRE, there will be no cosine error in the line.
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  • Your diagram is showing what is usually referred to as "cosine error".

    This will always be present on points that do not vector normal to the surface.

    It should not be an issue for a measured line if the software is working properly. If you measure points and construct a line using BF, the error will be present in the line. If the line is constructed using BFRE, there will be no cosine error in the line.
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