Barrel Nuts

What are Barrel Nuts?

Barrel Nuts provide an alternative method for combining two pieces of material instead of using a traditional screw and nut. These fasteners go by various names such as  inter screw, sleeve nut, chicago screw, cross nut, furniture nut, sex bolt, cylindrical nut, insert nut, connector nut, socket nut, tube nut, binding post screw, female nuts, binding barrels, and so on. Nomenclature varies across different industries and application but the basic fasteners are much the same – featuring a drilled-out barrel with a threaded centre.

They are designed for use with a male machine screw, sometimes called a mating screw or connector bolt, which is threaded inside the barrel. Although a barrel nut can be used with any machine threaded fastener, they are typically supplied as a set, where the male screw shares the same head style and drive type as the female nut.

Why use Barrel Nuts?

One of the main benefits of these fasteners is their effectiveness at hiding installation details compared to using standard fasteners. When clamping material with a screw and nut, the exposed nut will be visible on one side, reducing the aesthetic appeal of an application or assembly. Sex bolts resolve this issue by replacing the nut with a fastener that matches the opposite side for a clean and decorative finish.

Barrel nuts can also be hidden entirely which is often desired in the furniture industry. The most popular types of inter screws feature a low-profile head – often a truss, countersunk or mushroom (like our 6 Lobe TX Mushroom Barrel Nuts. These types are ideal for applications that require a flush fitting, as well as those with limited clearance. Barrel nuts with a button head and hex head are also popular choices, while they can all be supplied in a wide range of sizes, materials and finishes to meet your requirements.

Measuring up

If you are using a barrel nut that is not part of a set, then you will need to ensure that the thread diameter of the female barrel matches that of the male fastener. The length of the barrel nut should also be shorter than the thickness of the installation material – typically measured from underneath the head to the end of the barrel.

Some head styles are measured differently, however. For example, the length of a countersunk barrel nut is measured from the top of the head to the end of the barrel, while the length of raised countersunk variants are measured from under the raised portion of the head to the end of the fastener.

One of the most important things to consider is the thickness of the installation material. The maximum thickness that a barrel nut and sex bolt can clamp is often referred to as the “grip range”. In most cases, we recommend using a shorter male screw length to prevent it threading too deep within the barrel nut.

Installing Barrel Nuts

These components provide a strong and secure fixing if they are installed correctly. To begin, a hole should be drilled through the first piece of material where the barrel nut is going to be placed. The barrel diameter needs to be slightly smaller than the hole to ensure a snug fit.

Another hole should be drilled through the second piece of material that corresponds with the hole of the female barrel. The male screw is then placed through the hole and fastened into the barrel nut. Connector bolts sometimes feature a shoulder below the head which should be considered during installation.

Choosing the right Barrel Nuts

Every fastener offers something different and with so many types to choose from, selecting the right one for the job can be difficult. Some feature an oversized head to provide a larger bearing surface. This can be seen with our Phillips Oversized Truss Head Barrel Nuts, which also feature serrations under the head to prevent turning and reduce the effects of vibration.

T Head Barrel Nuts offer a rectangular head shape for additional strength, while Low Profile Socket Sex Bolts provide a low style head for situations where space is a concern. Furniture Connector Caps and Furniture Connector Bolts are primarily designed for use in furniture, but can be utilised in a range of applications where panels require clamping.

Security barrel nuts and sex bolts are a popular choice for applications that require an additional layer of protection. These are available with various drive types that offer medium to high levels of security – with the most popular featuring a Pin Hex drive or 6 Lobe Pin TX drive. For example, our 6 Lobe Pin TX Button Barrel Nuts are now available from stock in M12 and M16 threads. 2-Hole, Clutch Head and Wave barrel nuts offer the highest levels of tamper-resistance due to their unique designs.

In contrast, some barrel nuts don’t have a drive at all. For example, Architectural sex bolts are designed for one sided installation, featuring a knurled barrel which prevents the nut from turning when tightened from the other end. They are often used for architectural applications and door hardware such as closers, hinges and kickplates.

Need more guidance?

Our full range of barrel nuts and sex bolts can be found above which list the standard sizes, materials and finishes that we offer. If the fittings you require are not listed, or you are still unsure of the best fastener for the job, please get in touch – our team will be happy to help.