ISO 6789-2:2017

Overview

ISO 6789-2:2017 - Assembly tools for screws and nuts - Hand torque tools - Part 2 - specifies methods for the calibration of hand torque tools and the calculation of measurement uncertainty for those calibrations. It applies to both step-by-step (static) and continuous (quasi‑static) calibrations of torque measurement devices whose torque is derived from elastic deformation or another variable proportional to torque. The standard covers indicating torque tools (Type I) and setting torque tools (Type II) and defines minimum requirements where a traceable calibration certificate does not already provide the relative measurement uncertainty interval (W′md).

Key topics and requirements

• Calibration method and system: Defines how to set up and perform calibrations using a torque measurement device and loading system (the calibration system).
• Measurement error and reporting: Procedures for calculating relative measurement error and documenting calibration results.
• Uncertainty evaluation:
  • Type A (statistical) and Type B (non‑statistical) evaluations.
  • Identification and quantification of uncertainty sources such as display resolution, repeatability, reproducibility, interface geometry and loading point variation.
  • Determination of relative standard uncertainty (w), expanded uncertainty (W) and relative measurement uncertainty interval (W′).
• Examples and calculation aids: Informative Annex A and B provide worked examples for Type I (indicating) and Type II (setting) tools.
• Minimum requirements for reference devices: Annex C specifies minimum requirements for calibrating the torque measurement device when a traceable uncertainty statement is not available.
• Documentation: Requirements for information to appear on the calibration certificate.

Applications and users

ISO 6789-2:2017 is intended for organizations that need reliable torque results and comparable calibration services:

• Calibration laboratories and metrology labs performing hand torque tool calibrations.
• Manufacturers of hand torque tools and torque measurement devices.
• Quality, maintenance and production departments in automotive, aerospace, electronics and industrial assembly where controlled bolting torque is critical.
• Purchasing and compliance teams assessing supplier calibration claims.

Practical benefits include consistent calibration procedures, traceable uncertainty statements, and easier comparison of calibration results between laboratories.

Related standards

• ISO 6789-1:2017 - Design, manufacture and declaration of conformance for hand torque tools.
• ISO/IEC 17025 - General requirements for the competence of testing and calibration laboratories.
• ISO guides referenced for uncertainty evaluation (e.g., GUM / ISO/IEC Guide 98-3 concepts).

Keywords: ISO 6789-2:2017, hand torque tools, calibration, measurement uncertainty, torque measurement device, Type I, Type II, calibration certificate.