Johnson Gage’s accredited laboratory provides precision inspection, calibration, and certification services for dimensional and screw thread gaging equipment used throughout the aerospace, defense, automotive, medical, and industrial manufacturing sectors. The laboratory operates in accordance with ISO/IEC 17025 requirements and maintains accreditation through A2LA, demonstrating technical competence, controlled processes, and traceable measurement capability for critical thread and dimensional inspection applications. For specifics about our Calibration services please click this link (coming soon) or visit Calibration under our Services Section on the website.
ISO/IEC 17025 is the internationally recognized standard specifically developed for testing and calibration laboratories. While ISO 9001 focuses on quality management systems and organizational processes, ISO/IEC 17025 expands those requirements to include demonstrated technical competence, validated measurement methods, uncertainty evaluation, traceability to national standards, personnel competencies, environmental controls, equipment management, and ongoing verification of laboratory performance. Accreditation under ISO/IEC 17025 provides customers with confidence that calibration and inspection results are technically valid, repeatable, and independently verified through regular external assessments and internal audit programs.
Johnson Gage originally achieved ISO 9001 certification in 1997 as part of its long-standing commitment to quality management and process control. Building upon that foundation, the company developed and implemented the additional technical and laboratory requirements necessary to achieve ISO/IEC 17025 laboratory accreditation for screw thread and dimensional screw thread gaging and systems. The accreditation process required the establishment of documented laboratory procedures, controlled calibration methods, traceable standards, competency training programs, equipment verification systems, measurement uncertainty analysis, and continual improvement processes specific to precision metrology and thread inspection.
The Johnson Gage accredited scope includes the calibration and inspection of analog, digital, and test indicators; plain ring and plug gages, straight threaded ring and plug gages, External and Internal thread gaging roll contacts, and External and Internal thread gaging segment contacts.
The accredited scope supports multiple thread forms ranging from 4 to 80 threads per inch and metric thread pitches from 0.3 mm through 8.0 mm pitch.
These capabilities are critical for industries where thread geometry directly impacts assembly performance, structural integrity, interchangeability, and product safety. In aerospace and defense manufacturing environments, for example, thread lead, flank angle, taper, and functional pitch diameter characteristics must often conform to stringent requirements defined by standards such as ASME and various military and aerospace specifications. Johnson Gage’s accredited laboratory supports these applications through controlled measurement methods designed to verify the functional characteristics of precision threaded components and thread gaging systems.
A key aspect of the Johnson Gage accreditation effort is the laboratory’s focus on traceability and repeatability. All measurements are performed using calibrated standards and controlled procedures within a documented quality system. Personnel performing inspections and calibrations are trained and qualified for the specific methods within the accredited scope, and laboratory processes are routinely reviewed through internal audits, equipment verification activities, proficiency evaluations, and continual improvement initiatives.
For customers, A2LA accreditation provides an additional level of assurance beyond a standard certificate of compliance or non-accredited calibration. An accredited calibration demonstrates that the measurement process itself has been independently assessed for technical validity, traceability, competency, and procedural control under ISO/IEC 17025 requirements. This is particularly important in regulated and high-reliability industries where objective evidence of measurement competence and traceable calibration data are required as part of supplier quality, auditing, or contractual compliance programs.
Johnson Gage’s accredited laboratory services are intended to support manufacturers and quality organizations requiring reliable, repeatable, and technically defensible inspection and calibration results for precision dimensional and screw thread gaging systems.
DECISION RULE and GUARDBANDING METHODOLOGY
Decision Rule and Guardbanding Methodology
The following decision rule is utilized for commercial multi-brand ANSI/NCSL Z540.3 calibration services and may also be applied to commercial multi-brand ISO/IEC 17025 calibration services when specified by contract, customer requirement, or calibration program requirements.
Unless otherwise specified, statements of conformity are based upon Guardbanded acceptance limits designed to achieve a Probability of False Accept (PFA) of 2% or less (PFA ≤ 2%). Johnson Gage seeks to maintain a Test Uncertainty Ratio (TUR) greater than 4:1 whenever reasonably attainable; however, calibration services may be performed at TUR values less than 4:1 and not less than 1:1 when technically justified.
Decision Criteria
1. In-Tolerance
If the measurement result and its associated expanded measurement uncertainty are entirely within the Guardbanded acceptance limits, the measurement result shall be reported as In-Tolerance (Pass).
2. Indeterminate Pass Region
If the measurement result falls outside the Guardbanded acceptance limits but remains within the specified tolerance limits, the result shall be reported as Pass*. In this condition, conformity to specification cannot be established solely through application of the standard guard banded decision rule. The measured value and associated uncertainty shall be reported for customer evaluation.
3. Indeterminate Fail Region
If the measurement result falls outside the specified tolerance limits, but the associated expanded measurement uncertainty overlaps the tolerance limit, the result shall be reported as Fail*. In this condition, conformity to specification cannot be conclusively determined. The measured value and associated uncertainty shall be reported for customer evaluation.
4. Out-of-Tolerance
If the measurement result and its associated expanded measurement uncertainty are entirely outside the specified tolerance limits, the measurement result shall be reported as Out-of-Tolerance (Fail).
5. Additional Risk Analysis
Where applicable, results identified as Pass* may be further evaluated using established Probability of False Accept (PFA) and Probability of False Reject (PFR) criteria. If the calculated measurement risk remains within established acceptance criteria, the item may be determined to conform to specification and reported as In-Tolerance, with appropriate explanatory remarks included on the calibration certificate.
For specifics about our Calibration services please click this link (coming soon) or visit Calibration under our Services Section on the website. To request contact from an account manager please email info@johnsongage.com