What Are Hex Coupling Nuts And How Are They Used?

Coupling nuts are useful tools that often don't get enough attention—especially hex coupling nuts. They can help complete many different types of projects. And learning more about these useful tools can help anyone, from purchasing managers to design engineers, finish their next job. 

Hex coupling nuts are defined by their elongated hexagonal shape that accommodates wrenches that can tighten or loosen them. They are called extension nuts because they can convert small male threaded rods into more extended tie rod assemblies.

If you’re using hex coupling nuts regularly or just finding out how valuable they can be, let’s take a look at hex coupling nuts, what types of materials they’re made from, and get a glimpse into the many shapes and sizes you can get them in.

What Is a Hex Coupling Nut?

Hex coupling nuts are metal fasteners used to connect two pieces of threaded material. They work by screwing the coupling nut into the outside of another component, typically a threaded rod. Hex coupling nuts also feature left-handed threads that enable rods to be put into both ends of the nut to form a single, long rod. 

There are several variants of the typical hex coupling nut. First, the length of the nut might range from less than an inch to 14 inches or even more for specific uses. Second, the coupling nut's polish might differ. They may be plain, galvanized, plated with another material, colored, or coated.

The Unique Shape of Hex Coupling Nuts

Most coupling nuts are hex-shaped on the exterior to allow for the use of a wrench, and most are open in the middle on the top and bottom to enable a rod to thread through the nut. 

A cap nut has a dome on top, used for a coupling rod end. An acorn nut is like a cap nut, but with a cone-shaped dome. Both have a hexagonal outer shape.

What Types of Materials Are Hex Coupling Nuts Made From?

Coupling nuts can be made from any material. However, metal coupling nuts are the most common type owing to the strength of the material and the versatility of their uses. Coupling bolts and nuts are often made from ASTM A108-grade material, although they are also available in 4140, 1045, stainless steel, and structural grades. It would be best if you opted for a bolt made of a strong enough substance to sustain your specific project.

The Standards That Hex Nuts Are Manufactured By

The Industrial Fasteners Institute describes the coupling nut dimensions in standard IFI-128. Their mechanical and chemical properties conform to ASTM and SAE nut specifications. The IFI-128 standards define an optional cross hole called a sight hole. It is on the nuts' exterior and travels through the material. The sight hole allows visual inspection that the threads are fully functional.

Hex Coupling Nuts Come In Various Strengths

Hex coupling nuts meet the chemical and mechanical requirements of ASTM A563 grade A. When high-strength rods are specified, ASTM A563 grade DH and A194 grade 2H or grade 7 coupling nuts can be provided since they have all the necessary chemical and mechanical qualities. The rods must be threaded into the coupling nut for a distance that is at least equal to the thread's diameter. This will ensure that it is strong enough.

Threading Matters With Hex Nuts

Hex coupling nuts operate by the use of metal threads or grooves. On their inside, a continuous male groove runs down their length. One continuous male groove extends along the outside of the part to be fastened. It intertwines with a female groove to create the connection. It can then be tightened by hand or with a tool - this is known as threading.

Find All Types of Nuts To Finish Any Job

Hex coupling nuts are essential fastener tools for any project. If you're ready to use them regularly, turn to Big Bolt for all your fastener needs. Big Bolt manufactures and sells nothing but high-quality fasteners and can turn them around for you in a day. 

Contact us and let us know about your next project, or get a quote for any custom or special fasteners.