There are many occasions when you encounter material that is either too thin or too soft to accommodate a conventional tapped hole, or a tapped hole that has stripped. Rivet nut threaded inserts solve the problem quite elegantly, but you need to understand what type of threaded insert is best for a particular job. A rivet nut threaded insert is basically a cylindrical or hex shaped sleeve that is internally threaded to accommodate a mating bolt or other type of threaded fastener, creating a threaded hole. The sleeve itself fits securely in the tap hole using various methods so the fastener won’t turn. Once installed, rivet nut threaded inserts provide a strong receptacle for a threaded fastener. In fact, they often are used in joints that are frequently assembled and disassembled to prevent stripping the bolt hole.
Rivet Nut Threaded Inserts Have Multiple Designs
There are different types of rivet nut threaded inserts for different types of materials and applications, each designed to create a solid, lasting threaded joint:
- Thick-wall rivet nut threaded inserts are frequently used to repair stripped bolt holes. As the name implies, they have thick walls and insert snugly into a pre-drilled hole. Many thick-walled inserts have a hexagonal exterior to prevent turning in the hole. They come with either flat or countersunk heads and they are typically blind inserts that can be installed from one side of a hole. They also are available with open-and closed-end sleeves and are made of different materials, and they can have different coatings to prevent corrosion. Some inserts can incorporate locking threads and a raised key under the head and are often specified for military and aerospace applications.
- Thin-wall inserts are available with round, hexagonal, semi-hexagonal, and knurled external body and usually have a wider head for stronger load bearing. They also come in various materials with different coatings and are usually closed-ended. A Nutsert® is a specific type of thin-wall insert that works much like a blind fastener; when the fastener is tightened, the nutsert creates a flange on the blind side to lock it in place.
- Slotted body rivet nut threaded inserts use a different approach for a secure joint. Rather than using a shaped sleeve, slotted body inserts have slots cut into the sleeve so when the fastener is tightened, the sleeve collapses outward on the blind side, forming a flange to hold it firmly in place. These inserts work well in plastic and other brittle materials.
- Euro-style rivet nut inserts are used in holes that are prepared with exact metric dimensions. Euro-style inserts come in round, hexagonal, semi-hexagonal, and square shapes to prevent them from turning in the hole.
- Well-Nuts® are a specific type of rivet nut threaded insert usually made of rubber or some other soft material. They are commonly used to create sealed joints or to prevent loosening from vibration. The Well-Nut is flanged at one end where the bolt is inserted, and as the bolt is tightened, the insert expands to hold the insert securely in place while creating a seal.
- Jack-Nuts® are commonly used with especially thin or brittle material. They are slotted and have a wide head to prevent pull-through. When they are installed, they create a large umbrella-like footprint on the blind side of the material. The look similar and perform like sheet rock anchors sometimes referred to as Molly® anchors. The Jack-Nut is ideal for use in an assembly line and can be installed by hand or using power tools without affecting thinner materials.
- Riv-Float® inserts are made by Sherex Fastening Solutions and are designed to accept the threaded fastener that may not be perpendicular to the face of the installed insert. They have a unique "floating" internal threaded sleeve that pivots to accomodate misaligned parts.
Different Inserts Accommodate Different Materials
The reason there are so many types of rivet nut threaded inserts is that they are used for a wide range of applications with different types of materials.
Plastics, for example, tend to be soft and brittle, but often need a fastener that can withstand assembly and disassembly multiple times. Jack-Nut inserts are commonly used because they have a wide footprint and create a strong insert without damaging the plastic. Fiberglass presents a similar challenge; Jack-Nuts are frequently used for thin sheets of fiberglass, but for thicker sheets, such as those used in boatbuilding, knurled inserts provide a solid joint and Well-Nut inserts create a vibration-proof and waterproof joint.
Tapped holes in soft woods such as pine tend to strip, but using a rivet nut threaded insert can repair a stripped hole or create an anchor for a firm joint. Stud inserts, such as those used in making furniture, are also used to create a secure threaded stud that can accept a nut.
Thick-wall inserts are often used with metal, though slotted body inserts are typically used for thin sheets of metal. For softer metals such as aluminum, aluminum inserts and slotted body inserts are frequently used.
Rivet nut threaded inserts are used in concrete for construction applications. You will usually find thick-walled inserts and stud-style inserts used in concrete foundations and structures.
When buying rivet nut threaded inserts you will likely encounter the four most popular insert brands: Atlas Engineering, Avdel/Stanley, Sherex Fastening Systems and AVK Inudstrial Products. These four vendors manufacture a variety of rivet nut threaded inserts for all applications and have proven track records of quality and reliability. They also offer a complete line of installation tools that are paired with each specific style of insert to ensure correct installation.
If you need assistance choosing the right insert, Bay Supply offers one of the most comprehensive line of fasteners and installation tooling available. Our experts are available to help you choose the right fasteners and inserts for your needs.