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Torque - The Power of Precision Part 2

My previous article explained what torque is and how you can calculate it. This article goes deeper to explain why torque is important.

Torque is important because if it’s not correct i.e. the clamping force is improper, catastrophic failure can occur. To the layperson, improper torque might mean a fixing is not tight enough and therefore works loose over time but engineers know that ‘too tight’ could mean a component breaks. Ultimately the result is the same, so it’s critical the correct torque is applied to fasteners. Production, maintenance and repair applications benefit from applying correct torque to optimise process conformity, quality and safety for employees of the manufacturer or end-user customers.

According to the Federal Aviation Administration, between 2009 and 2015 more than 45 aircraft incidents and accidents resulted from improper torque applied to engine fasteners. In 2019 a research article by Saleh,J et al, stated that 14-21% of helicopter accidents in the U.S where flawed maintenance and inspection were factors, 57% were attributed to “improper or incomplete (re)assembly or installation of a part” and that “incorrect torquing” was prevalent within those errors. So, applying the correct torque is crucial in most production/MRO environments.

In order to achieve the correct torque, the engineer needs to use the correct tools. There are many brands and models of torque application tools and instruments in the market and any decent supplier should be able to guide you in purchasing the right tool for your project. The ISO organization has developed a torque tool standard (ISO 6789-1:2017) to help ensure tools made to this standard meet the required performance and repeatability needed for safe assembly procedures. Here is an overview of how the standard classifies torque tools along with some of the GEDORE torque tools available that fit in those classes:

Tool Diagram Info Graphic

This video shows the different mechanisms used in torque tools, it’s good to see them in action:

When choosing the right tool for what you need, consider this quick process created by Gedore Torque Ltd:

For more information about the Gedore Tool Selector visit www.gedore-torque.com and click the Tool Selector button.

From tiny torque screwdrivers used in cleanroom environments to lightweight industrial torque wrenches, choosing the right tool for the job can save your business time and money, so it’s worth asking the experts if you’re not sure.

Torque Myth Alert: A common mistake made by users of torque tools is the ‘one for luck’ action. You know, when the torque wrench has clicked indicating it’s reached the set torque and you do a quick turn to be sure? When this happens, in most instances the user has just applied too much torque albeit the wrench has been set to the correct torque. This creates inconsistent torque results as the problem is replicated each time the user does it. A tool with a slipping mechanism is the only torque tool to combat this as once the tool has reached the desired torque it slips and no matter how many more times the tool is turned on that fastener the tool will just spin meaning the fastener cannot be over tightened. Users of torque tools need to be confident their equipment is accurate and consistent.

As you can see in the chart above, there are many ways to classify Torque tools. However, one which is probably most useful to users is the adjustment method:

  1. Pre-set – Set by the factory or qualified users. Usually has no scale.
  2. Adjustable – Set by user. Usually has a scale

Pre-set tools are ideal for production lines and environments where repetition from users is required. The manufacturer or distributor sets the tool to the user’s desired torque and provides a calibration certificate to validate the setting. Pre-set tools can be adjusted by engineers qualified to do so and validated with a DoC or calibration certificate.

Adjustable tools are perfect for changing scenarios and environments where differing torque is required, whether it is a Maintenance and Repair application or an onsite installation application. These tools will have visible scales and instructions on how to adjust the torque to the desired level.

Using either pre-set or adjustable, it’s always best if the engineer understands how torque tools work and how to use them correctly.

To summarise, torque is important but proper torque for the job is critical to achieve optimum clamping force for a fastener and by not applying it could result in catastrophic failure in safety, production output and quality. Precision and accuracy are determining factors for standards that exist for torque tools and the next article will explain more about them and how they help you.

The next article will dive deeper into the difference between clicker and slipping (cam-over) torque wrenches.

As always, if you have any torque questions please feel free to get in touch and I (or the team) will do our best to help.

I'm not an Engineer but am fascinated by tools that are designed to improve output and safety for the user.
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