The Beginner’s Guide to Coupling Nuts

Coupling nut by MonroeWhen shopping for aerospace fasteners, you may come across coupling nuts. Coupling nuts are commonly used in airplanes and other aerospace vehicles. They aren’t the same as traditional nuts, however. Coupling nuts live up to their namesake by connecting or “coupling” the parts with which they are used.

What Are Coupling Nuts?

Also known as extension nuts, coupling nuts are threaded fasteners that are used to connect two parts. They are typically used to join two rods together. Assuming the rods are threaded — or at least threaded on one end — a coupling nut can join them. With that said, coupling nuts can also be used to join small pipes. Whether it’s a solid rod or a hollow pipe, the end can be secured to a coupling nut.

How Coupling Nuts Work

With their internal threading, coupling nuts can connect two parts with external threading. Coupling nuts have a threaded interior. You can twist the end of a threaded rod or pipe into a coupling nut. The external threading of the rod or pipe will grip the interior threading of the coupling nut.

There are also reducing coupling nuts. Reducing coupling nuts look like most other coupling nuts from the outside. And like their counterparts, reducing coupling nuts are used to connect two parts. Reducing coupling nuts simply have different-sized threading. The internal threading on one end of a reducing coupling nut is smaller than that of the other end.

Standard coupling nuts have the same size threading on both ends. Reducing coupling nuts are different in the sense that they have threading in different sizes on their ends.

Choosing the Right Coupling Nuts: What You Should Know

When choosing coupling nuts, pay attention to the size. Coupling nuts must be sized to fit the rods or pipes with which they are used.  In addition to the nut height and length to shoulder, check the thread size when choosing coupling nuts.

The thread direction of coupling nuts may vary as well. Some of them have right-hand threading, whereas others have left-hand threading. Right-hand threading is the most common.

You can find coupling nuts in different materials. Some of them are made of stainless steel. Other coupling nuts are made of carbon steel or brass. Stainless steel coupling nuts offer a superior level of protection against corrosion. Carbon steel coupling nuts, on the other hand, are typically stronger. You can also find carbon steel coupling nuts with a corrosion-resistant finish.

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