Controlling torque is a critical element for tightening threaded fasteners. Validating that a screw or bolt is properly installed ensures quality performance and reduces failures. The process to measure torque is relatively easy. It can be conducted either dynamically during the fastening process or statically during a post torque audit.
Auditing is a process used to substantiate consistency and uncovers inaccuracies within the fastening and torque process. After fasteners are tightened, engineers should perform torque audits from a random sample to verify that the proper amount of torque was applied. It’s an opportunity to catch loose fasteners and discover if any relaxation occurred in the joint.
There are three universal torque testing methods that were established to provide a reference to the applied torque. The video below will demonstrate the “Marking” test method using a torque analyzer and torque sensor. It can also be performed using a dial torque wrench, a digital torque wrench or a dial torque screwdriver.
Marking Torque Test
With this testing method, mark the surface of the tightened fastener and continue that mark onto the surface that is being clamped. Next, loosen the fastener and retighten until the marks are aligned. The torque required to return the fastener to its original location is the reference to the original torque applied to the fastener.
The marking test may not always be the best and practical method. If the measuring equipment might block the visual inspection of the mark, such as a socket, then it’s not suitable to use this test method. It also may cause cosmetic damage to a part. Knowing how to properly utilize each test method is important for an engineer to know. The first movement test method is often the preferred method, but the loosening or marking methods are adequate options as well. Which torque measurement method to use depends on the product and the manufacturer.
Overtime, torque tools will drift out of tolerance. An auditing technique to detect and prevent fastening failures is essential. Torque auditing validates the fastening process, the torque tool, the product design and the materials used for the application.
Using a quality torque testing method makes a safer world through accuracy and precision. Measuring torque is essential for companies to ensure their product’s quality, safety and reliability isn’t compromised. The failure of a three-cent fastener that isn’t properly tightened can lead to catastrophic or latent failures. Fasteners that are insufficiently fastened can vibrate loose and excessive torque can strip threaded fasteners.
Fastening errors can never be eliminated if proper torque testing and tools are not used. Establishing a torque testing program is good practice for any manufacturer. Check out our selection for torque measuring equipment.
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