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Definition · Calibration Traceability · ISO/IEC 17025 · AS9100

What Is NIST Traceability for Thread Gauges?

// Direct Answer
NIST traceability means there is a documented, unbroken chain of calibrations linking a thread gauge measurement back to NIST (National Institute of Standards and Technology) or an equivalent national metrology institute. Each link in the chain must have a calibration certificate showing measurement uncertainty. For a thread gauge supplier to claim NIST traceability, their calibration laboratory must be accredited to ISO/IEC 17025 by a recognised accreditation body such as CNAS, UKAS, or A2LA. A certificate claiming NIST traceability without an accreditation number is unverifiable and does not satisfy AS9100 or ISO 9001 requirements.

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What the NIST Traceability Chain Looks Like

Traceability is a chain — every link must be documented with a calibration certificate showing measurement uncertainty. A break anywhere in the chain means traceability is lost.

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Level 1 — BIPM (International)Definition of the SI metre — the foundation of all dimensional measurement worldwide
↓ calibration certificate
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Level 2 — National Metrology InstituteNIST (USA) · PTB (Germany) · NPL (UK) · CNAS NMI (China) — maintains national standards
↓ calibration certificate
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Level 3 — ISO/IEC 17025 Accredited LaboratoryCalibrates working gauges using NMI-traceable reference standards — issues your certificate
↓ calibration certificate (supplied with your gauge on request)
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Level 4 — Your Thread GaugeCalibrated and certified — NIST traceability documented — accepted by AS9100 auditors

How to Verify the Traceability Claim in 2 Minutes

Any supplier can print “NIST-traceable” on a certificate. Verification takes two steps:

  • Find the accreditation body named on the certificate — e.g. CNAS, UKAS, A2LA, DAkkS
  • Go to that body’s public online registry and search for the laboratory name or accreditation number shown on the certificate

If the laboratory does not appear in the registry, or if the scope does not include dimensional measurement of thread gauges, the traceability claim is unverifiable. For CNAS verification: cnas.org.cn. For UKAS: ukas.com. For A2LA: a2la.org.

Why CNAS certificates are accepted by US and European customers: CNAS is a signatory to the ILAC Mutual Recognition Arrangement (ILAC MRA). This means CNAS-accredited calibration certificates are internationally recognised and accepted by aerospace customers in the USA (AS9100), automotive customers in Germany (IATF 16949), and engineering companies worldwide. CNAS accreditation number verification is available at cnas.org.cn.

What a NIST-Traceable Certificate Must Show

  • Name and accreditation number of the ISO/IEC 17025 accredited laboratory
  • Name of the accreditation body (CNAS / UKAS / A2LA / DAkkS)
  • Actual measured values — not just PASS or conforms to specification
  • Measurement uncertainty stated at k=2 (95% confidence)
  • Statement of traceability to NIST/PTB/NPL through named reference standard
  • Calibration date and temperature (20°C is the ISO reference temperature)
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