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10. Torque

Siegfried Herbold

The Technical Committee ʺTorqueʺ examines questions relating to the realisation and measurement of the physical quantity torque – on the one hand, there is the concept of ʺpure torqueʺ (generated by a force couple) and on the other hand, ʺtorque with cross forcesʺ (to be seen as moment of a single force).
Pure torque, for example, occurs
in drives with a negligible influence of cross forces or bending moments. A typical application of torque with cross forces would be a torque wrench where a transverse force is used to generate a torque on the lever, but in addition to the torque, there is also the applied force and usually an additional bending moment.

The tasks of the Technical Committee include the development of calibration standards and guidelines for the quantity of static torque, the technical coordination on issues regarding torque measurement, the organisation and evaluation of interlaboratory comparisons as well as the exchange of experience among its members. The members of the Technical Committee are usually accredited calibration laboratories for this measurand. The Committee also develops drafts for DKD guidelines.

In addition, the members of the Technical Committee also support standardisation bodies, such as DIN and VDI, with their expertise. The expert reports serve to collect and disseminate expertise regarding the realisation and dissemination of the unit of torque. Comparison measurements are an important component in the evaluation of the calibration capabilities of accredited laboratories in the field of torque.

The Technical Committee currently has 41 members, including almost all the laboratories accredited for torque calibration (which are more than 30). At present, the Technical Committee is working on revising the guidelines DKD-R 3-7 and DKD-R 3-8 for the static calibration of indicating torque wrenches and of calibration devices for torque wrenches.

In addition, an interlaboratory comparison for the calibration of indicating and clicking torque wrenches according to DIN EN ISO 6789 is about to be completed. A report on the previous interlaboratory comparison for the calibration of torque transducers according to DIN 51309 is ready for publication. In February 2014, and for the first time in the DKD, the Technical Committee held a seminar on measurement uncertainty for employees of accredited laboratories (276th PTB Seminar – Measurement uncertainties in the realisation and measurement of torque).

The Technical Committee has already published the following calibration guidelines:

  • DKD-R 3-5: Kalibrierung von Drehmomentmessgeräten für statische Wechseldrehmomente
    (Calibration of torque measuring devices for static alternating torque – currently only in German)
  • DKD-R 3-7: Statische Kalibrierung von anzeigenden Drehmomentschlüsseln
    (Static calibration of indicating torque wrenches – currently only in German)
  • DKD-R 3-8: Statische Kalibrierung von Kalibriereinrichtungen für Drehmomentschraubwerkzeuge
    (Static calibration of torque tool calibration devices – currently only in German)