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27Mar

Understanding ISO 6789 – Automotive, Truck & Bus Aftermarket

The 2017 edition of the standard is considerably modified from the 2003 edition. The five Norbar articles are designed to explain the key differences and how the new standard is intended to be used. They are an overview, not a replacement for studying the standard. If you have questions we will be happy to try and help. Please follow the email link at the end of each article.

This fourth article of five has been written with users in the general automotive and other road vehicle aftermarket in mind. The fifth article for general industrial users will follow. It will help to first read article one on the general reason for change. 


AUTOMOTIVE, TRUCK AND BUS AFTERMARKET USERS

The following examples represent some types of users for whom this article may be useful.

• Service bays for tyres, brakes or general servicing, where torque tools are owned either by the company or by the individual. 
• Mobile operators providing tyre fitting, routine servicing or emergency repairs at a place of the customer's choice.
• Mobile “calibration” services providing a range of repair, documentation or calibrations to the first two user groups.

Why is it important?

The above group of users have been selected for this article because they represent a significant proportion of the hand torque tool market. In the developed world it is unthinkable that even small garage businesses would not have one or more torque wrenches. In the developing world, very small businesses may still rely on skill or guesswork, but larger organisations and franchised dealers will be equipped with the necessary torque tools.

The reasons for applying the correct torque will be obvious to many, but applying incorrect torque values, too high or too low, can cause a bolted joint to fail.

• If applied to wheel nuts on a bus or truck it can lead to wheel separation at speed and cause serious injury or death to those in the path of the wheel/tyre set weighing 60-70 kg and travelling at speed.
• If applied to a brake caliper or suspension joint it is most likely to fail under load, perhaps when cornering, braking or accelerating with loss of control and potential collision.
• In the case of engine rebuilds, the result may just be expensive or it may cause catastrophic engine failure at speed on a highway.

Assessing risk

Essentially then, the owner of the service company and the user of the torque tool wish to know that the torque applied is what they expected it to be, within a reasonable tolerance. They should also be concerned about the condition of the tool. A slipping ratchet or broken drive square for example, can cause injury to the operator or damage to the customer’s vehicle.

There are several ways in which the performance and condition of the tool can be assessed.

• Self-assessment by the business, preferably documented, that checks the torque readings through the usable torque range. This should be done on a regular basis related to the care taken of the tools and their frequency of use. Torque checking devices, such as the Norbar 
TruCheckTM can be purchased to give such peace of mind. The condition of the tool should also be noted, including worn or slipping handles, missing components and ratchets that slip or have deformed square drives.
• Mobile “calibration” services are popular as they hopefully utilise a trained technician who is familiar with torque tools and understands what to look for in particular models. The new standard does alter the documentation that they offer.
• “Return to base” services are used by larger businesses that can hold a few spare tools to be used as part of an inspection rota. Tools are sent away on a regular basis to a remote location and returned once assessed, repaired and documented. This allows the service provider to use their trained technicians for inspection and checking rather than driving from business to business. The service provider also can carry more spare parts and can deal with larger tools more easily in the remote location than in a van.

To perform a visual inspection of a torque tool, test the ratchet and record readings using the procedure in ISO 6789-1:2017 takes about 20 minutes. To strip a tool; replace worn or defective items; lubricate and assemble; then perform all of the steps needed to issue a calibration certificate required in ISO 6789-2:2017 will take about 90 minutes. At an example chargeable rate of £($/€)30 per hour that means a cost of £($/€)10 for the first option and £($/€)45 for the second. Users are invited to insert their own chargeable rates and consider the result.

What level of assessment do I need?

Whether the business has chosen to do the assessment themselves or pay for someone to do it, the next question is “What level of confidence is required?”

Different businesses will, have their own answers to that question. One thing that is clear. If they operate a quality management system that requires traceable calibration certificates, a procedure is required that follows ISO 6789-2:2017. Even without the servicing element, a calibration will probably take about 60 minutes.

If the business just wants a piece of paper that confirms that the torque tool is in good order, then a declaration of conformance can be generated in about 20 minutes, using the procedure in ISO 6789-1:2017

To reconfirm the statement from previous articles, the only way to produce a calibration certificate in accordance with ISO 6789 will be to follow Part 2. Part 1 only allows a declaration of conformance to be issued. The measurement method is the same, but other requirements are different.

If you have questions we are happy to help where we can. Please email ISO6789@norbar.com 

Neill Brodey
Member of ISO working group on ISO6789

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