First Article Inspection and Basic Dimensions

[kelroy]

Does anyone know of a standard, specification, or industry best practice reference that addresses basic dimensions in first article inspections? I've checked AS9102 and haven't found any guidence.

The question is whether the basic dimension must be referenced in the FAIR (First Article Inspection Report), or if the verification/reporting of the locattion of the feature (controlled by the tolerance in the feature control frame) is sufficient? Example provided:

Drawing Req't: Hole with True position of .005 RFS, Basic dims are 1.000 and 2.000 from the planar XY datums (RFS).

FAIR: True position reported as ".003 RFS"

I contend that the only contractual requirement is that the true position is reported, since it's value is calculated based on the reference datums and basics, even though general "best practice" would be to report the measurement of the location used to calculate the location of the feature. Looking for hard industry standards though.

 

[MikeHalloran]

I don't know what the standards say or don't say.

From the perspective of a person who occasionally tries to use the information in a FAIR, I'd prefer to just see what the measuring instruments showed, without any potential calculation or transcription errors superimposed, and without any information (like the direction of the deviation) removed.

I.e., IMHO, the 'true position' of the hole is its X,Y coordinates from the datums, not a calculated deviation from where it's supposed to be.
If you feel you must report the deviations, please report them as X,Y signed coordinates.




Mike Halloran
Pembroke Pines, FL, USA