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Revisiting the BS EN ISO 6789:2017 standard

It’s been nearly a year since the revised BS EN ISO 6789:2017 standard was released. With this in mind, Philip Brodey, Sales Director at Norbar Torque Tools, the first laboratory in the world to be accredited to perform hand torque calibrations to the standard, explores the key changes, and also some of the challenges these have brought.

What does the revised standard involve?

Previously, the BS EN ISO 6789:2003 divided the requirements into three sections: design conformance testing, quality conformance testing and recalibration. The intention was to allow different groups of users to identify the relevant clauses to meet their needs. Taking this logic even further, the 2017 edition divides the standard into two distinct parts. As a rule, Part 1 relates to manufacture and conformance, and Part 2 focuses on the calibration of torque tools.

For Part 1, most of the requirements from the 2003 edition are carried over, but there are new design and quality conformance requirements to be aware of. Manufacturers will now need to state that the tools adhere to these requirements by supplying a Declaration of Conformance, which will typically include actual readings taken from the tool during its manufacture or subsequent re-testing. Most torque wrench manufacturers and test houses would previously have called such a document a Calibration Certificate; however, under the 2017 version of the standard, this is no longer the case. Instead, Part 2 defines the requirements for the calibration of torque tools, including the establishment of uncertainty budget. Should a manufacturer therefore also wish to produce a Calibration Certificate, they must issue it in accordance with Part 2 of the standard and the conditions that go with it.

This means for torque wrench users there is now a choice; will they accept a Declaration of Conformance produced under Part 1 of the standard, or do they require a Calibration Certificate from Part 2 and the greater level of confidence in the torque wrench evaluation process that this should bring?

What have the challenges been?

From April 2019, all UKAS accredited laboratories will have to be ISO 6789-2:2017 compliant or they will not be allowed to perform calibrations. However, one of the key challenges currently faced is that despite not making it known to their customers, many providers are not offering the same service. In fact, many laboratories and torque wrench repair companies are continuing to call the document they produce a Calibration Certificate even if it would not be regarded as such under the new standard. It may not necessarily be that these companies are trying to be deceitful as they could be mistakenly working to an earlier, now obsolete, issue of the standard, however, the problem is that many customers will not understand the distinction. In addition, even those that claim they are working to Part 1 and / or Part 2 of the revised standard may not be and because the standard is still relatively new, internationally there is a shortage of auditors to monitor and check this.

Another challenge is that it takes a considerable amount of time to gather the readings that are now required to build an uncertainty budget. For ISO 6789:2003 only 20 actuations were required, but for ISO 6789-2:2017 the minimum amount of readings is 59 (where there is no adaptor and no ratchet) or up to a maximum of 139 (where both an adaptor and ratchet are present). This has meant that the average calibration time has increased on average by 2.5 times that of the original time taken. The question therefore is how does a laboratory recover the cost of this additional time when they are competing with other businesses who are not adhering to the latest version of the standard.


The solution?

The answer therefore has to be to educate customers about the difference and the importance of working with those that are compliant with the new standard. Some may see it purely as a piece of paper on file, or a price hike, but most customers will care that the calibration of their torque tools is done correctly and that a calibration truly is a calibration. Operators in the Norbar laboratory are able to calibrate all makes of torque wrenches and screwdrivers within its scope of UKAS accreditation from 0.1 N·m to 3,000 N·m with the lowest uncertainty of 0.17%, the lowest uncertainty currently available in the UK.

In addition, for customers and laboratories wanting to perform their own calibration to the standard, Norbar’s latest Torque Wrench Calibrator Auto (TWC Auto) can help. The system enables accurate and efficient testing and calibrations of click, dial and electronic torque wrench designs in accordance to the ISO 6789:2017 and can calculate the uncertainty figure, while also boasting a calibration job management system for booking calibrations and recording the progress of previous jobs. This has the potential to save businesses time and ultimately money in the long run helping to ensure calibration certainty day-to-day.

Media Enquiries:

Tom Leatherbarrow / Anna Hughes

WPR Agency

0121 456 3004 /

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