An installation tech locks a wrench against a loose fastener nut. On the other side, another wrench turns steadily. The bolt tightens because the correct amount of torque has been applied. Of course, powered hand tools perform this operation faster, but they still need to apply adequate turning force. Otherwise, the bolt will fail. By the way, doesn’t that last bolt look a little loose?

Assessing Loose Nuts and Bolts

If we were to gauge the applied tightening force with a hand, the secured nuts and bolts would seem tight. The tech would put down the tools, tucking them away in his toolbox, then grab the nut with two fingers to check for fastener tightness. Well, this reckless methodology just doesn’t work, does it? Sure, the nut has stopped its travel up the threads of the bolt, but it’s not secure. Left like this, the fastener will loosen and the anchoring action will fail. Obviously, therefore, more torque is required to properly ensure a secure lock.

Applying Too Much Tightening Force

What about too much torque? What happens when a distracted and possibly overmuscled technician applies too much locking force to a nut? Overtightened fasteners wear quickly. They stretch and strain, then they fracture when a transient force is experienced. Alternatively, the metal threads become stripped. They’ve sheared away because the installer has exceeded the bolt’s rated metallic endurance. If the threads on the nut are softer, then they’re the set that fails. Without these sharply formed threads, nuts and bolts simply cannot tighten.

The Importance of Proper Fastener Torque

Think about a car, about its spinning wheels. Rolling down a highway at close to 1000-RPMs, proper bolt and nut tightening practices are essential here. Locked properly to the wheel axle, wheel nuts cannot loosen. Furthermore, the wheel bolt shanks can’t fracture if they’re tightened properly. That’s an axiom that applies to every fastener. Installed in a moving machine or a housing that contains moving parts or simply on a surface that holds two or more weighty loads, proper nut and bolt tightening practices ensure a secure structural lock.

Correct locking torque, as used in the fastener industry, goes far beyond what can be felt by touch. It’s the last half turn, the direct stress experienced by the bolt shank as it elongates very slightly until the applied force offsets the rated torsional stress that engages the shank threads, nut, and bolt head. Dropped into the sweet spot that exists between a loose coupling and an over torsioned one, properly tightened nuts and bolts won’t disengage, nor will they fracture.

Get in touch

TCI Fasteners – Topcope
13 Slater Parade, Keilor East VIC 3033 Australia

Telephone: (03) 9336 0155