What Is a Bolted Joint?

Three bolted joints on a piece of concrete.

While simple in design, the bolted joint is one of the most common ways in which objects are joined. By definition, a bolted joint is a combination of a fastener and a nut. A long bolt with a nut, for example, is classified as a bolted joint. The bolt is placed through a pre-cut hole in the objects, after which a nut is twisted and secured onto the mating thread at the end of the bolt. The combination of the bolt and nut is known as a bolted joint.

Advantages of Bolted Joints

Bolted joints offer several advantages, one of which is high tensile strength. Of course, tensile strength reflects the maximum amount of stress or tension the bolted joint can sustain at any given time without breaking. Bolted joints have a naturally high tensile strength. Furthermore, the tensile strength of a bolted joint can oftentimes be increased by changing the fasteners or clamp load.

Another reason why bolted joints are so popular is because they are simple and easy to create. It typically takes less than a minute to slide a bolt through two or more objects and cap it off with a nut. And even if you’re unfamiliar with bolted joints, you shouldn’t have trouble creating one.

Disadvantages of Bolted Joints

While strong and easy to create, bolted joints have a few disadvantages. Overloading, for instance, may cause a bolted joint to fail prematurely. If the operating force exceeds the bolted joint’s clamp load, it will fail.

Bolted joints can also fail from corrosion. if the nut or bolt begins to corrode, the nut may loosen to the point where it’s no longer able to support the operating force.

Locking Solutions for Bolted Joints

There are several locking solutions available for bolted joints. With a locking solution, the nut is less likely to come off the bolt — even when exposed to excessive vibrations. Jam nuts offer an effective solution for bolted joints. Jam nuts are thicker than traditional nuts, so they are able to apply greater force to the joint.

Adhesive compounds may also be used as a locking solution for bolted joints. The bolted joint is first created by combining the bolt and nut, after which an adhesive compound is applied. The purpose of the adhesive compound is to hold the nut on the bolt. Other locking solutions for bolted joints include friction-locking threads, screw-locking inserts and lockwire holes.

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