The Essential Guide
to Threaded Rivet Nut Inserts

A threaded insert, sometimes referred to as a rivet nut, is a type of insert that is secured into material to provide a threaded hole. Rather than drilling a threaded hole directly into the material, the threaded insert provides a more durable fastening, especially when it is used in soft materials or in a work surface that is too thin to accommodate a conventional tap hole. Many threaded inserts have threads or ribs on the exterior for a more secure join that won’t turn in the hole. They are ideal for manufacturing applications because they provide a standardized way to apply fasteners and they address issues such as switching from metric to standard threads or vice versa.

A rivet nut, sometimes called a blind rivet, threaded insert, or rivnut, is a one-piece, tubular insert that is threaded and counterbored so it can be anchored from one side, just like a blind bolt. The RivNut® brand was originally developed by Bollhoff but has become synonymous with blind rivet nuts, just as Kleenex® is used to refer to facial tissue. There are two basic rivnut designs: one that creates a bulge on the blind side when a bolt is tightened in the insert, and one that is drawn into the sleeve when the bolt is tightened to create a strong bond.

There are five primary categories of threaded rivet nut inserts:

• Thick-wall inserts: Traditional thick-wall inserts, sometimes called nutserts, are the original rivnut design developed in the 1930s for use in airplane manufacturing. They are single tubular inserts with internal threads and usually come in round or hexagonal body types. Heavy wall inserts are available in different sizes, thicknesses, and materials for applications across industries, and they remain popular in aerospace and defense because they are ideal for high-strength metalworking applications.

• Thin-wall inserts: Thin-wall rivet nut inserts, also called threaded bushings, are similar to thick wall inserts and come in round and full-hexagonal designs. They come with closed-end designs and knurled bodies, and some even come with weather-resistant plating.

• Slotted-body, wide-tail formation inserts: Slotted-body inserts have slots in the cylinder and are designed to bulb or collapse on the blind side when tightened to form a strong connection. They come in both straight shank for soft materials such as plastics and composites and pre-bulbed body configurations for use in plastics and thin-gauged metals.

• Euro-style or hard metric inserts: Euro-style inserts are offered in round, semi-hex, full-hex, heavy-hex body, and square body configurations in various metric sizes.
  
  
• Stud-style inserts: Sometimes, you want to use a nut rather than a bolt, and stud-style inserts are designed just for that purpose. They have the same types of insert bodies as thin-wall inserts and include semi-hex or knurled shafts to prevent turning. Once installed, they offer a secure stud that protrudes to accept a nut to complete the joint.

In addition to the four primary threaded rivet nut insert designs, there are specialty designs, as well.

• Wellnut inserts: Wellnut threaded inserts are made of rubber or similar materials and are useful for sealing holes or reducing vibrations. The wellnut insert is passed through one end of the workpiece and the nut is inserted from the flanged end. The non-flanged end is inserted into the second piece of material so that as the bolt is tightened, the flange expands and the bushing is compressed, forming a tight seal around the bolt hole.

• Molly Jack nut inserts: Molly Jack nut threaded inserts are designed for use with thin, brittle, or soft materials. These inserts are perfect for the assembly line, or they can be installed by hand without distorting thin materials. They are available in steel, brass, and coated steel, and when tightened, the sides collapse to form a permanent, reusable threaded insert.

• Riv-float inserts: Riv-Float® threaded inserts are manufactured by Sherex Fastening Solutions and are used for unique situations in which the two pieces of material that need to be joined are off-center or the holes fail to properly align.

Round and hexagonal body inserts

Both round body and hexagonal body inserts are available in standard or metric threading. They also come in open- and closed-end configurations with either flat or countersunk heads. The inserts are available in a range of materials, including steel, stainless steel, alloy-hardened steel, and aluminum. The alloy-hardened steel inserts are available with a thread locking feature. All of these units are also available with a non-keyed or keyed head.

The round body inserts also come in both ribbed and smooth body designs, with both open and closed shanks:

• Open-end smooth shank round inserts – Open-end smooth shank inserts are blind threaded rivet nut inserts specifically designed to provide load-bearing joins in thin sheet materials. There is a large flange version that provides a greater load-bearing surface for the thin sheet nutsert.

• Open-end ribbed shank round inserts – These blind rivet nuts are designed for high-torque applications with ribs along the shaft for a better grip. They also have countersunk features so they can be installed flush with the material surface.

• Closed-end smooth shank round inserts – These threaded inserts are designed for heavy-duty applications with a thicker head profile and increased wall thickness in the collapse area. This particular threaded insert is ideal for applications requiring heavy push-out loads, such as leg-leveling screws on heavy equipment. They also offer superior thread strength thanks to an internal rolled thread manufacturing process. These inserts are corrosion-resistant because the threaded area is enclosed, which eliminates leaks getting past the threads from either side.

• Closed-end ribbed shank round inserts – Designed with a rib feature for high-torque applications, these blind rivet nuts have a countersink feature that allows them to be installed flush with the surface of the workpiece.

Thin-wall rivet nut inserts

There are a few types of thin-wall rivet nut inserts:

• Thin-wall threaded rivet nut insert – Like thick-wall rivet nut inserts, the thin-wall inserts come in both round and hex body designs, and they typically have a wide-bearing head for a stronger bond. The round body inserts also have a low-profile head available.

• Nutserts – Nutserts are a type of round thin-wall threaded insert with a low-profile flange for near-flush installations. They are designed so the inner body pulls into the outer body for a tight seal. Nutserts come in configurations for various specialty applications. For example, a standard splined nutsert is designed for applications in which you want a minimal protrusion on the blind side. A “W” Series nutsert is a knurled threaded insert designed for applications in thick fiberglass, such as boat building, and it can be installed prior or after finish. Superserts are structural locking threaded inserts.

• Stud-style locking rivet nut inserts – Stud-style locking inserts include the bolt; once they are installed in a predrilled or punched hole, they can accept a nut for fastening. Stud inserts are available in various styles, thread sizes, head types, body materials, and stud lengths.

Bay Supply stocks four popular types of thin-wall inserts: L-style round body inserts that can be used in drilled or punched holes; K-style round body inserts, which are smaller with a smaller head for near-flush mating part assemblies; O-style round body inserts with reduced profile heads; and H-style hex body inserts, which are designed for maximum torque strength.

Slotted body with wide tail formation

Slotted body threaded rivet nut inserts are available with round bodies that feature slots that collapse as the bolt is tightened. They are available in both a straight shank body design, in which the outer body pulls into the body of the nut for a strong connection, and pre-bulbed body design, in which the body collapses and grips the blind side when tightened. There are a couple of different types of slotted body inserts:

• The straight slotted body threaded insert features a wide grip range with an extra-large grip on the blind side. It was specifically designed for use with soft materials, such as composites and plastics, and is easy to install. Using simple hand tools, it can be installed with only blind-side access in less than three seconds. The extra-large blind side area resists pull-out and offers higher torque-to-turn resistance in brittle materials. It is typically used in auto trim moldings, domestic appliances, handles, and plastic fabrications.
  
  
• The pre-bulbed shank body insert also works well with plastics and thin-gauge steel where you need additional resistance to prevent pull-out. When it’s installed, four segments fold onto the blind side of the workpiece, creating a strong join. It features a very wide grip range and has four high-load-bearing legs when tightened. It can be used in single, variable, or multiple thickness materials.

Slotted body threaded inserts are available in both standard and metric thread sizes, and they come in steel and aluminum in various body styles.

Other threaded inserts used for specific applications include Euro-style, wellnut, Jack nut, and riv-float inserts:

Euro-style or hard metric threaded inserts

If you need metric threaded rivet nut inserts, the Euro-style or hard metric inserts are right for you.

Euro-style inserts are available in steel, stainless steel, and aluminum. They come in the same body styles as the thin-wall inserts, but with metric threads. They also come with flat, low-profile countersunk heads.

You can choose from round body, semi-hex body, full-hex body, heavy-hex body, and square body Euro-style insert types.

Stud-style inserts

Unlike a threaded rivet nut insert, which accepts a bolt, a threaded stud-style insert is designed to accept a nut. The round body shape is similar to that of a thin-wall insert. Stud-style inserts have a knurled or semi-hex body to prevent the insert from turning. Upon installation, you have a secure stud that can accept a nut to complete the joint.

Stud-style inserts are available in standard and metric threads and come in various lengths. They also come in different materials and can be coated to prevent corrosion.

Wellnut inserts

Wellnut threaded inserts are designed to create a seal at the same time they create a join. They are designed as neoprene bushings with a machine nut molded into one end. Tightening the machine screw causes the insert to expand, creating a watertight, vibration-resistant join. Wellnut inserts are especially useful in automotive and industrial applications, such as for motor and shock mountings, as well as in boat building and waterproof applications.

The most common wellnut inserts are made of neoprene and EPDM rubber with a brass internal nut. They are available in standard and metric threading.

Jack nut inserts

Jack nut or Molly threaded inserts are an economical type of blind fastener typically used in assembly line applications. They are made of thin, soft, or brittle materials. When tightened, the legs collapse on the blind side of the parent material, leaving a firm, reusable threaded insert. They come in steel, brass, and steel with PVC or Raintite coating for added protection against corrosion.

Jack nut inserts are normally used in blind holes and won’t deform soft plastics or thin sheets of metal. They also are not sensitive to hole size and will fasten securely, even if there are burrs or an uneven substrate. They can be set using manual tools or using pneumatic tools for fast setting.

Riv-float inserts

Riv-float threaded inserts are used to connect off-center or misaligned holes and can compensate for tolerance stack-up in manufacturing. The floating nut aligns with the bolt to accommodate the angle of the screw for a strong join. These inserts were designed to replace cage nuts, clinch nuts, floating nut plates, and weld plates.

Riv-float inserts are made of steel and available in standard and short body lengths with both standard and metric threading.

• Atlas – thick-wall rivet nut inserts, thin-wall rivet nut inserts, Euro-style inserts, nutsert inserts, slotted body inserts, stud-style inserts
• Avdel – thick-wall rivet nut inserts, thin-wall rivet nut inserts, Euro-style inserts, nutsert inserts, slotted body inserts
• AVK – thick-wall rivet nut inserts, thin-wall rivet nut inserts, nutsert inserts, stud-style inserts
• Bayfast – thin-wall rivet nut inserts, Euro-style inserts, wellnuts
• Gesipa – thick-wall rivet nut inserts
• Goebel – thick-wall rivet nut inserts, thin-wall rivet nut inserts, nutsert inserts, stud-style inserts
• Marson – thick-wall rivet nut inserts, thin-wall rivet nut inserts, nutsert inserts, Molly jack nut inserts, stud-style inserts, wellnuts
• Pop – Molly jack nut inserts, wellnuts
• Sherex – Thick-wall rivet nut inserts, thin-wall rivet nut inserts, Euro-style inserts, nutsert inserts, slotted body inserts, riv-float inserts

The rivet nut was first used in the 1930s, when BF Goodrich used them to mount rubber deicing boots to aircraft wings. They then came into wide use in airplane manufacturing and were adapted for static dischargers and inspection covers, among other applications. They proved an ideal alternative to weld nuts because they didn’t warp the base materials and eliminated splatter, fumes, and other problems associated with welding. Over time, rivet nuts were adapted for use in steel, plastics, thin metals, composites, and fiberglass.

For plastics, threaded rivet nut inserts are ideal for applications that require a lasting connection or that can be assembled and disassembled without fear of stripping the bolt threads. Common applications for plastics include mobile phones, electronics, medical prosthetics, automotive, aerospace, transportation, industrial, and recreational equipment.

Threaded rivet nut inserts also are ideal for wood assembly, especially for soft woods such as pine, plywood, and composites. Inserts are commonly used in construction, furniture building, boat making, and a variety of wood repairs.

Fiberglass is a challenging material to work with, and threaded inserts can be invaluable in the manufacture of hot tub, automotive bodywork, satellite dishes, boat building and repair, and other applications.

Threaded rivet nut inserts are especially useful when working with metal. They are ideal for attaching parts to tubes, castings, extrusions, or housings. They also are useful for connecting disparate materials, such as plastic and metal. Inserts also are commonly used as a long-lasting solution to repair stripped threads. They can be used in any metalworking application, but are especially useful when working with thin metals, such as in auto body work, or applications that require repeated assembly and disassembly.

Aluminum is a softer metal that also requires threaded inserts for a strong bond. Inserts are typically used in manufacturing of aluminum boats, aircraft, and equipment, as well as for repairs.

For construction, threaded inserts are an ideal solution for concrete, providing a hole or a secure stud that can be used for a lasting join.

Among the power tool options available are “spin-spin” tools, with which the rivet insert is threaded onto a mandrel, fitted in place, then driven home. As the mandrel spins, it pulls the threaded shank to form a bulge on the blind side around the unthreaded portion. Once in place, the mandrel spins in the opposite direction to complete the installation.

There also is a “spin-pull off” tool that threads the insert on a mandrel for insertion in a predrilled hole. Once the insert is in place, pressure is applied to form the bulge on the blind side of the workpiece, and the tool then reverses its spin to complete the connection. This approach is ideal for plastic workpieces and similar applications.

The third type is “pull-to-pressure,” which is similar to the spin-pull tool, but instead of pulling to a preset distance, it pulls to a preset pressure to release. This type of tool is commonly used with metals and hard plastics.

Depending on whether you are working in a shop or at a remote location, you can use either a power tool or a hand tool. If you are using the tool in a plant or shop, a pneumatic tool may meet your needs. If you are working on a job site or doing remote repairs, you might prefer a handheld, battery-operated tool. You also should determine how quickly you want to install inserts and if you need a heavy-duty tool for ongoing daily use. Here is a basic overview of available rivet nut insert tools:

1. Hand-powered rivet nut insert tools – If you are only installing rivet nuts occasionally, then handheld tools will be your least expensive option. You add the insert to the end of the tool, squeeze the handles, and then loosen the tool to complete installation. Although these tools are inexpensive, they do require a lot of muscle strength, and they certainly are not fast.
   
   
2. Pneumatic rivet nut insert tools – For heavy-duty applications such as an assembly line or repair shop, pneumatic rivet nut insert tools are ideal for fast, consistent applications. Of course, you do need an air compressor, but the tools are easy to use and powerful.
   
   
3. Battery-powered rivet nut insert tools – These handheld tools are cordless but powerful, making them extremely versatile so you can install rivet nuts from practically any angle. They are basically point-and-shoot tools that let you install inserts quickly and efficiently. They may cost a little more, and you may want to pick up extra battery packs, but the convenience outweighs the cost.

No matter what tool you choose, you should have a range of mandrel sizes to choose from. Your choice of the right rivet insert tool should be dictated by application, ease of use, and, of course, safety.

Installing the rivet nuts themselves is relatively easy. Some rivet nuts are self-tapping, but most require a predrilled hole. Using the right tool, you drive the rivet nut through the hole until it is properly sealed, either by creating the appropriate bulge on the blind side or by pulling into the sleeve for a tight fit. There are different rivet nut choices depending on the application, and each is installed differently:

• Wide front-side flange – This style of rivet nut features a large load-bearing surface that both reinforces the hole and keeps the rivet nut from being pushed through.
• Thick flange – This type of rivet nut provides spacing and extra push-out strength.
• Countersunk/low-profile head – This is the rivet nut to use if you want the installation to be completely flush.
• Wedge head – This type of rivet nut has wedges under the head to keep it from turning by “biting” into the parent material, making it ideal for soft materials such as plastic, fiberglass, and aluminum.
• Shape – As noted above, rivet nuts come in splined, square, and hexagonal shapes as well smooth cylinders. Each shape is designed to prevent the insert from turning, especially at high torque.
• Open or closed – Most rivet nuts come in open-ended styles, but closed-end nuts are available for applications that need to prevent water or dirt from entering the assembly, such as automotive installations.
• Thin or thick wall – We talked about thick and thin wall rivet nuts; however, the thick wall or standard style rivet nuts have keyed heads, and the thin wall rivet nuts do not.

These are just some of the threaded rivet nut insert options that are available on the market. Depending on your industry and application, there are going to be threaded rivet nuts that are ideal for your needs, whether those needs include extra strength, easy installation, non-conductivity, corrosion-resistance, or any number of other characteristics.

If you aren’t sure what type of threaded rivet nut insert is right for your next job, consult the experts. Bay Supply stocks rivet nuts in all shapes, sizes, and materials, and our in-house fastener specialists will be delighted to assist you.