A prevalent phenomenon within the automotive and aerospace industries is prevailing torque during fastening applications. So, what is prevailing torque? Prevailing torque, also known as running torque, is the driving torque needed to overcome friction in a threaded fastener.
This value reveals how much friction is left over when operators continue to turn the bolt with a torque wrench. Prevailing torque, or running torque, is often inevitable and a part of the fastening process. However, it does still need to be addressed and overcome during tightening. In this article, we’ll discuss prevailing torque compensation strategies.
Challenges that prevailing torque creates
Though it’s a normal part of the tightening process, operators need to have intuitive, powerful resources to avoid possible complications when running torque goes undetected or ignored. Without reliable compensation strategies, prevailing torque can stop the tightening process in its tracks or cause operators to prematurely move to the next tightening sequence without sufficiently completing prior steps. It can lead to damaged threads, missing components, and incorrect torque data and results.
To compensate for prevailing torque, we suggest using the PVT compensate strategy on the Power Focus 6000 (PF6000) controller and incorporating torque wrenches that have the power to overcome running torque and provide a properly seated fastener.
PVT compensate – a Power Focus 6000 tightening strategy
PVT compensate is a basic tightening strategy that comes on our PF6000 tightening controller. Compensating for the prevailing torque in a joint ensures consistent clamp load despite variations in the level of prevailing torque. PVT compensate will calculate the running torque during the rundown portion of the fastening and then drive the target and running torque. By doing this, operators provide a consistent level of torque to the clamp load, instead of applying an undefined amount of torque to the friction between the threads of the fastener and the workpiece.
PVT compensate is most commonly specified in aerospace applications with running torque fasteners. However, it can be used in any application where fluctuations in friction and prevailing torque in the joint are causing assembly issues.
Torque wrenches with the power to overcome prevailing torque
Another option for compensating prevailing torque is to use a torque wrench with sufficient power to overcome it. We recommend the use of our STwrench or our Tensor STR Electric Nutrunner. The STwrench is a part of our Quality Assurance – QA Platform 4.0 product line. It’s more than a standard transducerized handheld wrench and fully integrates with the PF6000 controller platform. This versatile wrench is lightweight yet powerful, capable of conducting a wide range of quality control tests, including residual torque and joint analyses, which encompasses joint behavior and stiffness checks.
The Tensor STR Electric Nutrunner is another manual torque wrench option that can overcome running torque with its patented and proven TurboTight technology. Also fully integrated with the PF6000 platform, the Tensor STR provides operators with essential feedback during the tightening process, and it handles angle-controlled tightening with very high precision, thanks to its integrated gyroscope with the TrueAngle function. This function eliminates operator influence.
Helping you avoid serious production issues
Without sufficient compensation strategies, prevailing torque can cause a handful of serious issues during production. It can also negatively affect power tools that cannot properly account for or overcome running torque. Possible effects on power tools can include reduced rundown RPM because of added friction, increased torque reaction on operators, and reduced tool life. With all of this in mind, we recommend using our Power Focus 6000 PVT compensation strategy in conjunction with a manual torque wrench that has the power to overcome running torque, such as our STwrench or Tensor STR.
Now that you know what prevailing torque is and why it’s essential for secure fastening, are you using the right tools? Explore our detailed Pocket Guide to Tightening Technique, browse our selection of torque solutions to ensure your projects stay locked in place, or contact one of our experts today to learn more!
