The Importance of Proper Torque

Many manufacturers do not utilize a torque wrench to fasten bolts and nuts in their assembly process. Yet, experiments have shown that the vast majority of them fail to get the exact amount of torque that they want. Applying exactly the right amount of torque is important to ensure proper clamping between parts. There can be serious consequences if you apply either too much or too little torque, as we’ll discuss below.

Torque is defined as a twisting force that tends to cause rotation.  When a socket is applied to a nut and turned, the force rotates the bolt.  As the bolt is tightened, tension stress stretches the bolt.  The bolt is resistant to this flexing and becomes spring-like. Danger can occur in severely over-tightening or pushing too hard, as this runs the risk of bending the bolt. Once this occurs, the bolt no longer applies the correct amount of clamping pressure and is increasingly likely to fail, either by loosening or completely breaking.

To make sure failure does not occur, it is important to understand how to measure torque and what the proper amount for the application is. Torque is measured in force multiplied by distance.  Think about a lug nut that has a torque value of 45 foot pounds.  Imagine having a wrench 1 foot in length with a 45 pound weight at the end, the resulting force is equal to a torque of 45 ft lbs.  A 2 foot wrench with a 10 pound weight at the end would have a torque value of 20 ft lbs on the nut or bolt.  In the assembly process, your hand applies the force and length of the wrench creates the distance.  This is how torque is transferred to a nut or bolt: force multiplied by distance.

Each application of torque is unique. There is even a difference between things of the same size. The torque required for a ¼” bolt has a different torque value of a ¼” nut.  This is because a nut has less surface area in contact with the threads than a bolt shank does with the mating surface.  These differences in surface areas create different friction values which influence the final torque value.  The more friction that is present, the larger the torque required to properly fasten it.

Other factors of determining a torque values are considered such as the material of the bolt. Bolts have different metallic properties requirements for each location of use.  Knowing the specifics of your assembly processes metallurgy will help you understand what the proper torque values are.

Martin Fastening has created a guide to show you the general values needed to properly clamp a bolt. The guide can be downloaded here. Our experts can come in and work with your engineers to make sure that you are being consistent in how you apply torque and that you are using the proper fasteners for your process.

To learn more about the importance of torque and to learn about training your workers to in applying proper torque Snap On offers a torque certification  that will prove valuable to your team. Martin Fastening Solutions specializes in coming on site and helping our customers operate better, so click here to learn more about us or give us a call today.