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The Threaded Insert Buyer’s Guide

Fasteners are durable, critical components used universally to hold together various assemblies and machines. It is necessary, however, to pick the appropriate fastener design for your specific application. Since these elements vary in size, material, and compatibility, it is essential to have a sufficient understanding of the various designs prior to purchasing. One popular category of fasteners that encompasses several designs are threaded inserts, which are designed to accept bolts or other threaded fasteners. In this blog, we will discuss the various threaded insert designs you may encounter while shopping, enabling you to make the right decision based on your individual needs.

When discussing threaded fasteners and inserts, most people immediately think of screws, which commonly create their own inserts as part of the drilling process. While screws work for a large number of applications, they provide nowhere near the stability that comes from a dedicated threaded insert and associated fastener. These versatile assemblies perform better under higher loads and may be secured at any time from production to after installation. As such, threaded inserts are the number one choice for high-performance products in several industries, including automotive, aerospace, military, and medicine.

We are now going to cover some of the most common types of threaded inserts:

Slotted Body Inserts

These inserts are designed with walls that expand upon accepting the bolt. As the walls expand, a very tight and secure connection is produced between the two fastener elements and the surrounding material.

Rivet Nut Inserts

Rivet nut inserts are the most widely used of any design listed, particularly in the context of aviation. They are commonly used to bind two thick pieces of material together, such as aircraft body pieces. Rivet nuts are also commonly referred to as blind threaded inserts since they only need to be accessed from the installation side of the material. Additionally, they were designed with strict tolerances to fit into a compatible hole, avoiding damage to the peripheral material surrounding the assembly.


These unique fasteners feature a round external body with one of several designs on the interior, which may be hexagonal, square, or semi-hexagonal. They are commonly used to ensure interchangeability between standard and metric threading systems.

Molly Jack Inserts

Popular in assembly line applications or for use in brittle materials, Molly Jack inserts feature an inner thread and a body composed of four collapsible elements. After installation, the body collapses and forms a tight fit with the wall of the insert. This design may be thought of as the inverse of a slotted body insert.


Unlike other examples, which are generally made from pure metal or metallic alloys, wellnuts use softer materials or rubber in their composition. Like the slotted body design, the walls of the wellnut inserts swell upon fastening, creating a tight seal with the surrounding material.


Regardless of the threaded insert you decide to use, it is always necessary to ensure size and shape compatibility with both the bolt and the surrounding material. Moreover, if your application is likely to experience harsh operating conditions, such as corrosion and heat, it is critical to choose a material that can withstand these stressors. Finally, it is important to choose a reputable source to ensure you are receiving authentic components.

At Fasteners 360, we specialize in providing customers with a diverse selection of thread inserts and many other assembly types. With an inventory of over 2 billion ready-to-purchase items, we are confident that we can help you find the exact component needed for your operations. To begin the procurement process for any product listed on our website, simply submit an Instant RFQ form, and one of our account managers will reach out to you with a customized solution in 15 minutes or less.


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