Finding the right fastener for a project requires more thought and deliberation than you would expect. Finding the right fastener can seem impossible, especially when trying to fasten thin or brittle materials together. This is where rivet nuts shine. From use in aerospace and automotive manufacturing to furniture and consumer goods, rivet nuts are an innovative and easy fastening method that’s both revolutionized and simplified how products are assembled. In this article, we dive deeper into rivet nuts and discuss everything there is to know about them – from what they are and how they’re used to different types of rivet nuts and their advantages.
What are Rivet Nuts?
Rivet nuts, alternatively known as RIVNUTs®, were developed by the BF Goodrich Company in the late 1930s. Also called blind rivet nuts or threaded inserts, rivet nuts are internally threaded components that are completely anchored on one side. Originally used to secure deicing boots to aircraft wings, rivet nuts have since been adapted into many different forms and types for various fastening applications.
Rivet nuts are derived from standard rivets and are paired with standard sized bolts. Rivet nuts can have round, square, splined, or hexagonal bodies. Because it’s considered a blind fastener, rivet nuts are used in applications where only a single side of the workpiece is accessible. This makes rivet nuts one of the most versatile fastening devices that exist.
How do Rivet Nuts Work?
Like a normal rivet, rivet nuts are punched into a workpiece to fasten two or more materials together. The difference between a rivet and a rivet nut is that the rivet nut is only punched into a single piece of material, not all the constituent materials to be joined. Once the rivet nut is installed into one material, the remaining materials to be joined can be fastened with an externally threaded fastener, like a bolt, to the rivet nut. It’s that simple.
The simplicity in how rivet nuts are used to fasten materials together is what makes them so versatile. It can be argued that rivet nuts are easier to use and better at joining materials together than self tapping screws or pressed inserts.
How to Install Rivet Nuts?
To install a rivet nut, have a drill, appropriately sized drill bit, and a rivet nut tool available. Installing rivet nuts is as easy as following the 5 steps below:
- Drill a pilot hole with the same diameter as the rivet nut to be used in the workpiece.
- Take the rivet nut and thread it until flush onto the mandrel of the rivet nut tool.
- Pull the opposite end of the mandrel as far back as allowed and thread the adjuster back to contact it.
- Install the rivet nut using the rivet gun by inserting the rivet nut into the drilled pilot hole and squeezing the handles of the tool until it reaches a stop.
- Remove the rivet nut tool by unscrewing the mandrel from the rivet nut.
Be careful not to apply too much force on the rivet nut during installation as this may ruin the internal threads of the rivet nut.
When are Rivet Nuts Used?
Rivet nuts can be used to fasten a variety of materials together – including different types of metals, plastics, fiberglass, and carbon fiber. Like a normal rivet, rivet nuts are blind – as in, only one side of the workpiece is visible when installing the rivet nut. While the rivet nut will be permanently fixed to the material it is attached to, materials assembled to the rivet nut via a bolt, pin, or other devices can be removed.
Because of their light weight, small size, and easy installation, they are often used in applications where weight reduction is critical (i.e. aerospace and automotive). Additionally, rivet nuts can have high shear and tensile strengths, making them ideal for load bearing applications. This makes them also great for use in furniture, certain consumer goods, and electronics. While weight reduction and load-bearing are certainly advantages of using rivet nuts, manufacturers can also benefit from reduced costs due to faster assembly. Rivet nut installation can even be automated through 6-axis robots or other automotive processes.
Different types of Rivet Nuts and Their Advantages
1. Round Rivet Nuts
These nuts are made for circular holes and have a smooth or knurled surface on the shank of the nut. While both smooth and knurled surfaces can provide spin-out resistance, knurled surfaces provide better resistance since the knurled surfaces “bite” into the workpiece. Round rivet nuts can be made either with open or closed ends. Closed-ended rivet nuts are great for preventing the trickling of unwanted gasses or liquids through the rivet nut and out the installation side. The 3 biggest advantages of round rivet nuts are:
- Strong, internal threads on round rivet nuts allow fastening to be completed on thin materials which cannot be tapped.
- Simple installation makes round rivet nuts ideal for assembling parts together when compared to other fastening methods.
- Easy, but labor intensive, installation can be automated to reduce overall costs associated with the fabrication of parts and assemblies.
2. Hexagonal Rivet Nuts
Hexagonal (hex) rivet nuts, like round ones, provide great spinout resistance and are used for hexagonal shaped holes. Hexagonal rivet nuts have hexagonal shaped shanks and are usually designed for more load bearing applications. Hydro-pneumatic tools are usually recommended when installing hexagonal rivet nuts. Semi-hexagonal rivet nuts are a subtype of normal hex rivet nuts and feature a hexagonal shank that gradually tapers to a round shank. Semi-hex rivet nuts are typically used in lighter-duty applications and can be used with standard rivet nut tools. 3 advantages of hex rivet nuts are described below:
- Excellent spinout resistance compared to round rivet nuts.
- Several different sizes of hex rivet nuts allow for a variety of mating applications.
- Corrosion resistant finishes can be added to hexagonal rivet nuts to make them more environmentally stable.
3. Slotted Rivet Nuts
Slotted, plus, or cross rivet nuts have a slotted body and a straight shank. These types of nuts have a large footprint on the non-blind side of the workpiece which adds pullout resistance. Alternatively, a shank may also be pre-bulbed for added spin-out resistance. Slotted rivet nuts offer an extensive grip range ideal for fastening varying thickness materials. The advantages of slotted rivet nuts are described below:
- Corrosion resistant surface finishes allow slotted rivet nuts to be used in a variety of environments.
- Simple and easy installation of slotted rivet nuts can be completed with standard rivet nut tools.
- Surfaces are not distorted when a slotted rivet nut is installed in plastic workpieces.
4. Swaged Rivet Nuts
In thicker materials that have reduced clearance requirements, swaged rivet nuts provide strong, durable internal threads for fastening. The design of these nuts allows a segment of the nut to deform during installation. This deformation causes the walls of the rivet nut to extend outwards into the fastened component which leads to a firm hold. 3 advantages of swaged rivet nuts are described below:
- Swaged rivet nuts have a shorter profile which allows them to be used in applications that have reduced clearance.
- Improved shear strengths due to increased wall thicknesses present in the nut.
5. Floating Rivet Nuts
Floating rivet nuts allow for flexible fastening of workpieces. In these types of nuts, internal threads of the nut “float” within the nut body which allows for the angled installation of bolts. This provides both accurate and efficient assembly of products and eliminates the risk of both spinout and cross-threading. Floating rivet nuts can be made in a variety of lengths and sizes to fit different thicknesses and clearance specifications. Advantages of floating rivet nuts include:
- Easily fasten off center or misaligned workpieces with floating rivet nuts.
- A hydro-pneumatic installation tool is recommended when installing floating rivet nuts.
- Excellent replacements for both riveted nut plates and cage nuts.
6. Rivet Nut Studs
Composed of two pieces, rivet nut studs contain the rivet nut and an externally threaded stud. When the rivet nut is installed, the stud protrudes beyond the workpiece. This allows conventional fasteners, like standard hex nuts, to be mated onto the threaded stud. Advantages are described below:
- Cost effective fastening method compared to weld or clinch studs.
- Easier placement of components makes final assembly processes easy when using a rivet nut stud.
While finding the right fastener for your project may be a challenge, it doesn’t have to be. Rivet nuts provide an innovative and flexible fastening method that rivals traditional methods such as the use of bolts or welds. Rivet nuts are easy and cost effective to install, have exceptional tensile and shear strengths, and enable the function of many of the goods and modes of transportation we use every day. Contact an Albany County Fasteners sales representative today to discuss which rivet nut is right for your project.