Torque is used to create tension. Bolts are used to affix two components so that they can resist tensile (pulling apart) and shearing (sliding apart) forces. After the nut has been turned onto the bolt, additional torque causes the nut to turn and stretch the bolt.

Why do you torque a bolt?

In simple terms, you need torque to create tension in a bolt. You use torque to turn a nut onto a bolt and then to stretch the bolt, making it a solid spring that clamps the two materials together.

What happens if you don't torque bolts?

Insufficient torque

Alternatively, the engine's vibrations can cause the bolt or nut to come undone, displacing the tensioner. This, in turn, will lead to incorrect belt tension and, eventually, to belt and/or engine damage.

What is the purpose of torquing?

Torquing is the most commonly used way to achieve fastener preload with bolted joints. Torquing produces this load through rotational force on a nut or bolt head.

Why is torque Tightening important?

those nuts that keep your wheel fastened to the studs on your axle and the bolts that secure and keep your engine assembled were installed at the proper torque to keep them from coming loose. When accurate torque is not applied to the bolts and nuts, they wear out quickly and can cause failure.

how to calculate bolt tightening torque

22 related questions found

What happens when a bolt is over torqued?

Typically, an under torqued bolt will deform and be unable to provide as much clamping force as needed. An over torqued bolt will break.

Should bolts be lubricated before torquing?

So, torque isn't the true measure of bolt tightness—it's tension. But lubrication on the bolt threads—and a whole host of other factors—can cause fluctuation in torque readings. So once you add a lubricant of any kind to the threads, all bets are off as to whether the same torque setting will truly secure the bolt.

What is the purpose of bolt tightening?

Tightening the bolt puts the shank in tension, counteracted by compressive forces on the contact surfaces of the head and the nut, transferred from the parts.

Do you really need to torque bolts?

That's why most owner's manuals have a torque specification for lug nuts. If you plan to do any major work on your engine or on some major powertrain components, you absolutely need a torque wrench. Overtightening cylinder-head bolts, for instance, can easily cause expensive damage and catastrophic coolant loss.

Is it OK to loosen bolts with a torque wrench?

A torque wrench is a tightening tool.

It is a very sensitive and precise tightening tool, and should never been used to loosen bolts.

Is it bad to leave a torque wrench set?

Storing your torque wrench

However, when storing a torque wrench for an extended period of time, users should always wind it down to the minimum scale setting and never to zero. A fully loaded torque wrench, left in storage for a long period, can cause a 'set' in the spring, causing it to weaken over time.

Can you over tighten bolts?

Everyone who has ever worked with fasteners has accidentally messed one up at some point. One of the most damaging ways to do that is by over-tightening, or over torquing the fastener. This can result in stripping screws, snapping screw heads and damaging pre-tapped threading.

Should I torque the nut or bolt?

There is no simple answer to this as in some instances, it is perfectly acceptable to tighten the bolt head while holding the nut in place. In other situations, it's acceptable to tighten the nut. It all depends on the application and the condition of the product or material being worked with.

Can you torque a bolt twice?

A bolt that has already been used in a given application may or may not be reused, depending on the grade, application, and recommendation of the “Engineer of Record”. ... Touching up or re-tightening bolts that may have been loosened by the installation of adjacent bolts shall not be considered to be a reuse.”

How do I know if my torque is loosening?

To conduct this test, take a screw or bolt that is tightened down and begin to loosen it. When the fastener breaks loose, record the torque reading. The torque value to loosen the fastener is the approximate torque that was applied to the joint.

What is the difference between bolt tensioning and torquing?

“Torque” is simply a measurement of the twisting force required to spin the nut up along the threads of a bolt, whereas “Tension” is the stretch or elongation of a bolt that provides the clamping force of a joint. ... This is the most common form of providing load to a bolt.

What happens to a torqued bolt if the threads are not properly lubricated?

If that lubricant isn't applied generously/properly, the dry parts of the fastener will increase your Nut Factor and result in different bolt loads on each of your fasteners.

Does wd40 affect torque?

By applying oil, grease, or an anti-seize preparation to the threads, you run the risk of over-torquing them when you tighten up your wheels. WD-40 tends to be more of a band-aid fix than anything.

Should you put grease on bolts?

As the friction is reduced, the bolt will turn and stretch more for a given amount of applied torque. The more stretch it has, the tighter it is squeezing the assembly together. Oil or grease also keeps the threads from galling or pressure welding.

How much does a bolt stretch when torqued?

With regard to torque specs, the ARP approach is to establish a torque that will stretch the bolt to 75-percent of the fastener's yield strength. This is also the rod bolt stretch number.

Should you double click a torque wrench?

Double checking your torque is never a bad thing.

By double clicking, you are allowing the fastener to rest for a second, then you are back at it to get the proper amount of torque there.

Why do you zero a torque wrench?

A torque wrench in regular use doesn't need to be wound back. ... If you expect to store a torque wrench for more than a few weeks, always wind it down to the lowest scale setting (never to zero). Storing a fully loaded torque wrench can result in a set in the spring, weakening the spring over time.

Does temperature affect torque wrench?

How does heat affect torque? It increases as temperatures get higher, like in the 400 to 500 deg. C range. So a beam-type torque wrench will read a bit lower than it should at a lower temperature.