What is a Blind Rivet Nut? An Introductory Guide

Rivet nuts, blind rivet nuts, rivets, blind rivets, POP® rivets… this fastener family has many different names for its members. Fortunately, they all serve the same basic purpose: to fasten two surfaces together with superior strength than a bolt or screw. However, there are significant design differences between the varying types of rivets. Here, we will focus on one of the most popular options: the blind rivet nut. 

What is a Blind Rivet Nut?

First, it is helpful to know what a rivet is. A rivet is a fastener with a head and a shank that fastens two or more surfaces together. The shank is inserted through two aligned holes in the mating materials, with the head fastening the front side of the application while the shank collapses or mushrooms out to fasten to the back side. These come in many different types.

A blind rivet nut is a type of rivet that only requires access to one side of the application to install. Its distinguishing factor is the shank design. More specifically: 

Blind Rivet Nuts: Also known as blind threaded inserts , threaded inserts , or simply rivet nuts , blind rivet nuts feature a hollow body with a partially threaded, collapsible shank. A rivet nut tool threads into the shank from the open head and pulls up until the shank mushrooms into the designated collapsed position, which is either bulged or swaged: 

Once they collapse into their locked position, a bolt (or screw) threads through the hollow shank to complete the material connection. Thus, the rivet acts as a nut receiving the fastener. They are the only type of rivet that creates a reliable mounting point for a second, independent fastener to connect the two mating materials. 

Blind rivet nuts are ideal for connecting thin sheets of material, because the bolt or screw will not make direct contact with the metal (which may become distorted if it is thin, or may be too thin to feature its own threads to accept the bolt). Additionally, the rivet nut is collapsed in place with a controlled clamping force from a rivet nut tool, which distributes the clamping pressure across the mushroomed shank and takes pressure off the joint area. 

Types of Blind Rivet Nuts

There are several different types of blind rivet nuts based on varying characteristics of the head, shank, and threads. Common variations include: 

• Sealed heads: Seal off the head from water and fluids.

• Closed/open ends: Refers to the end of the shank, which is either open or sealed.

• Head profiles:Wedges: Increase torque capacityReduced or heavy duty flange: Accommodate different mating material thicknesses

• Shank wall profiles:Thick/thin: Accommodates different material strengthsKnurled: Ridges located on the collapsible section of the shank to provide “biting” power when installed, which is particularly helpful with soft materialsSlotted: Feature four pre-bulbed slits along the collapsible section of the shank that span out beyond a normal bulge to provide better pull-out resistanceHex-Shaped: Either half or fully hex-shaped; provides spinout resistance

• Floating threads: Feature a floating internal nut to accommodate for bolt misalignment.

• Stud-style: Features a protruding threaded head to install a nut instead of a bolt.

Huyett’s guide to rivet nuts and tools gives a more in-depth explanation of the different types.

What is a Rivet? A Quick Overview

Blind rivet nuts are commonly confused with other rivet-type fasteners, which necessitates a quick explanation of what exactly a rivet and its purpose is. 

Rivet: A broad term referring to fasteners that feature a head and a shank of varying shapes and designs. Rivets fasten two or more surfaces together when a bolt or screw is either not sufficient on its own or would damage the material. The fastening is made possible by the head securing one side and the end of the shank widening to secure the other side. 

Each type of rivet will share this basic design and function. The nature of the head and shank and how the fasteners are installed is what differentiates them and makes them suited for specific applications. 

We can delineate this basic group into further categories. The two main categories are solid rivets and blind rivets ; solid rivets require access to both sides of the application for installation, while blind rivets only require access to one side. There are many different subtypes within these two categories, but they mostly derive from one of these descriptions.

Blind Rivet Nuts vs. Blind Rivets

Part of understanding what a blind rivet nut is is knowing what it isn’t . They should not be confused with blind rivets, which have a markedly different design. While blind rivet is a broad term that refers to any rivet that can be fastened without access to the back of the application, it also refers to a specific type of fastener. 

In simple terms, the biggest difference between the two is that blind rivet nuts require an independent fastener (bolt or screw) to complete the connection – making it easy to disassemble – while blind rivets accomplish this feat as one full component but create a permanent connection. In fact, the rivet nut design is unique enough that they are usually set apart in their own category (like a self-retained nut), rather than as a subcategory of blind rivets. 

Blind Rivet Nut Installation

As the image shows, rivet nuts are threaded with the end of a rivet nut tool (usually a power or pneumatic tool for industrial use, but hand tools for small or custom applications are available) and are placed through a pre-drilled hole in the mating material. The tool then pulls up on the shank with electric power or pneumatic pressure. 

The pressure created by the tool collapses the body of the rivet nut on the blind side of the parent material, resulting in a threaded fastener ready to be joined with a mating fastener. For swaged rivet nuts, the end of the shank breaks off and is pulled into the top of the shank to create a bulge on the blind side of the parent material.

Blind Rivet Installation

Blind rivets, commonly referred to as POP® rivets, have a distinctly different design. They house a thin internal dowel rod (a mandrel) that protrudes above the head and attaches to the bottom of the inside of the shank. The dowel also features two notches about halfway down. 

When the shank is inserted through the holes of two mating surfaces, a blind rivet tool pulls up on the mandrel, which pulls up the bottom of the shank. The force of the pull will break the mandrel at the notches and lock the mushroomed rivet shank in position. 

Application Considerations: Pros and Cons

Each type of rivet has its own set of pros and cons, but a given advantage of both is their blind nature. Here are other main points to consider when choosing your fastener type. 

Blind Rivet Nuts

Pros

• Quick Installation: Electric Powered or pneumatic tools in industrial settings take about one second per rivet nut to install.

• Reusable Components: The mating bolt can easily be replaced or removed from a single rivet nut installation, as opposed to single-use blind rivets.

• Versatility: If the bolt protrudes beyond the end of an open-end rivet nut, other threaded components can be attached.

• Vibration Resistance: Rivet nuts are commonly used in applications that are exposed to high vibration – like the aerospace industry – because they are far less likely to jostle loose than a bolt on its own.

• Cost-Effective Application Maintenance: Since the bolts are replaceable, the connection maintenance is convenient and does not require a complete replacement.

Cons

• Requires Specific Tools: Rivet nuts have to be installed with rivet nut tools, even in small, custom settings. Industrial tools can be expensive, often require an air compressor, and can have limited mobility. Manual tools are more affordable, but are not ideal for quick, repetitive installations. 

Blind Rivets

Pros

• Permanent Installation: Blind rivets create permanent connections between materials in demanding industries, like aerospace and marine equipment.

• Single-Piece Component: Unlike rivet nuts, blind rivets do not require other fasteners to complete a connection.

Cons

• Protrusion: After the mandrel breaks off, it leaves a small head that protrudes above the connection, which could catch or cause additional issues.

• Difficult Removal: Because it's a permanent installation, replacing or disassembling the connection is difficult.

• Installation Risk: Sometimes, the mandrel does not break easily or at all after it is pulled.

• Higher Application Maintenance Costs: If the application needs a new connection, the blind rivet will need to be completely replaced, which may cause damage to the mating material and will require a new fastener.

The Bottom Line

Overall, blind rivet nuts offer simple, cost-efficient, and secure connections between thin materials. The surfaces are reinforced with the holding force of threaded fasteners while staying protected from the torque force of a bolt or screw. Additionally, their design facilitates easy disassembly and replacement of the connection. 

Huyett offers premium, high-quality rivet nuts and blind rivet nuts from trusted industry suppliers like Sherex and AVK. To learn more about these products, visit our product FAQ page and our complete product line.