Default procedure for using the uncertainty when making statements of compliance with a specification.
Calibration laboratories that are accredited to ISO/IEC 17025 are required to take the uncertainty of measurement into account when making a statement of compliance with a specification (ref. 17025 section 18.104.22.168).
The procedure given is the default procedure used by our technicians when a client has not provided one. Other procedures may be used when required by the customer and we are notified before carrying out the contracted work.
Simple acceptance and rejection is done when the expanded uncertainty doesn’t exceed 25% of the tolerance zone. When this requirement can’t be held, the expanded uncertainty is added to the tolerance to create a new acceptance zone, this is also called “guard banding”. Measurement results are evaluated using the acceptance zone and are indicated by an (*) placed next to the feature on the certification.
The standard used for procedural reference is ASME B22.214.171.124-2001, Guidelines for Decision Rules: Considering Measurement Uncertainty in Determining Conformance to Specifications.
If there are any questions please feel free to contact The Tool & Gage House.