Extension Nuts

Nuts Used to Join Two Male Threads

Extension nuts are threaded fasteners used to join two male threads, most commonly threaded rod. The outside of an extension nut is typically a hex to be driven with a wrench. Extension nuts are also used to make up long rod assemblies from shorter lengths of rods. Extension nuts come in two types: Coupling Nuts and Reducer Nuts.

Coupling Nuts

Coupling nuts are the standard form of extension nuts, connecting two male threads of the same thread diameter. They can be used to tighten a rod assembly inward or to press a rod assembly outward. The industrial fastener institute describes coupling nut dimensions in standard IFI-128. Coupling nuts come in stainless steel (304 & 316), aluminum, hot-dipped galvanized steel, and zinc-plated steel finishes.

Reducer Nuts

Coupling reducer nuts, sometimes just referred to as reducer nuts, are very similar to traditional coupling nuts. Where they differ is in the threading. Reducer nuts have different thread diameters on each side, allowing the connection of two different sized male threads. They are often used in threaded rod assemblies where each rod is of a different size, in which they tighten they rod assembly inward or press the rod assembly outward. Reducer coupling nuts come in zinc plated steel.

Not sure what material to use? Check out our Materials guide.

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Extension Nuts Overview: Coupling & Reducer Nuts

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FAQs

What is an extension nut?

An extension nut is a kind of fastener nut that is used to join two male threads together, such as multiple pieces of threaded rod. Extension nut is a much broader name for coupling nuts, which connect two male threads of the same thread size, and reducer nuts, which connect two male threads of different sizes.

What are coupling nuts used for?

Coupling nuts are used to connect two male threads together, usually threaded rod or pipes. Typically hexagonal in shape to be grabbed by a wrench, they tighten rod assemblies or extend them further outward.

What are reducer nuts used for?

Reducer nuts, or reducer coupling nuts, are used to connect two different sized male threads together, usually threaded rod or pipes. Typically hexagonal in shape to be grabbed by a wrench, they tighten rod assemblies or extend them further outward, even if the rods have different thread sizes.

How do you join two threaded rods together?

Join threaded rod together by using coupling nuts. You can join any two externally threaded rods or bolts with coupling nuts, so long as they are of the same body diameter and pitch. If the body diameter and pitch are different between the two, use reducer coupling nuts to connect them together.

What are long nuts called?

Long nuts are another name for extension nuts, otherwise known as coupling nuts or coupling reducer nuts.