A tangle of formal documents concerning the verification and calibration of torque tools

Two standards documents currently apply to the metrology of torque tools:

  1. NF EN ISO 6789-1 – Hand torque tools – Part 1: Requirements and methods for design conformance testing

Part 1 of the standard describes the verification procedure for torque tools and the declaration of conformance with defined classes.

  1. NF EN ISO 6789-2 – Hand torque tools – Part 2: Requirements for calibration and determination of measurement uncertainty

Part 2 describes the calibration procedure, with more extensive characterization of parameters of influence (e.g. point of load application, geometrical effects of interfaces, etc.) in order to provide more thorough substantiation of the estimated measurement uncertainty.

Attention must be paid to how results are interpreted, depending on the standard used!

ISO 6789-1 leads to quantification of a ‘measurement deviation’ –

(measurement standard value) – (value shown on tool): (Xo-Xt);

ISO 6789-2, on the other hand, leads to quantification of a ‘measurement error’ of the opposite sign –

(value shown on tool) – (measurement standard value).

Therefore, for reasons of harmonization between accreditation bodies, the Laboratory Committee (LC) of European Accreditation (EA) decided in 2022 that it would not authorize referencing to NF EN ISO 6789‑1 as a method of measurement in the scopes of accreditation of calibration laboratories.

Verifying and calibrating my tool with CERIB

In accordance with these requirements, and given the desire of the majority of our customers to include a conformance decision in metrology services for torque tools, at CERIB* we offer:

– either verification services as per the 2003 version of NF EN ISO 6789 (cancelled version) which takes account of measurements and conformity and which can feature in the scope of our accreditation;

– or services as per our in-house method and conformance in relation to paragraph 5.3, ‘Conformance testing during use’, of ISO 6789‑1.

* Cofrac Calibration accreditation No. 2.1019 – scope available at www.cofrac.fr

This activity has applications in many industrial sectors: automotive and aeronautical industries, testing laboratories, agriculture, large-scale retail sector, etc.

To meet the needs of some customers we also offer services on-site (not under Cofrac accreditation terms).

NB: In 2025 CERIB Océan Indien equipped its laboratory with a torque tool verification system, enabling it to reduce the immobilization of customers’ equipment in its geographical area to the shortest possible time.

For any additional information you might require, do not hesitate to contact us.