Countersunk Rivet Nuts: Flush Threaded Inserts for Aircraft, Automotive, and More

Introduction to Countersunk Rivet Nuts

Countersunk rivet nuts, also known as counterbore rivet nuts, are a type of threaded insert designed to provide strong and reusable machine screw threads in materials too thin for standard nuts. With their low-profile heads, countersunk rivet nuts are ideal for applications where a flush surface is needed.

Countersunk rivet nuts consist of a cylindrical barrel threaded on the inside and a conical countersunk head on the top. The heads come in various angle degrees to match standard countersunk holes. Common angles are 82°, 90°, and 100°.

Benefits of Using Countersunk Rivet Nuts

Here are some of the benefits of using countersunk rivet nuts:

Flush Fit

The countersunk head allows the rivet nut to sit flush with the surface of the host material, providing a smooth finish. This avoids protrusions that could snag or get damaged. It also contributes to the streamlined look desired in many applications.

Strong and Reusable

Countersunk rivet nuts are made from steel and provide excellent holding strength while allowing for repeated use. The threads on the inside barrel grip screws tightly while resisting vibration and shock loads. You can remove and reinsert screws many times without wearing out the threads.

Wide Material Compatibility

Countersunk rivet nuts can be installed in a range of materials, including metal, plastic, fiberglass, and composites. The low profile heads let you use them even in thin sheets. Flexible installation methods allow fastening to flat or curved surfaces.

Speedy Installation

Installation of countersunk rivet nuts is quick and simple using standard riveting tools. The nuts can be quickly secured in existing counterbored holes or installed in new holes made with a counterbore cutter. Minimal access is needed behind or around the workpiece.

Types of Countersunk Rivet Nuts

There are two main types of countersunk rivet nuts:

Blind Rivet Nuts

Blind rivet nuts are designed for installation where access is limited to one side of the material. They use a rivet stem that pulls a built-in mandrel to flare out the nut body and clamp it in place. The stem snaps off after installation.

Through Hole Rivet Nuts

Through hole rivet nuts require access to both sides of the material. They use a threaded center rod and washer to compress the nut body. The rod and washer remain in place after installation.

Key Applications of Countersunk Rivet Nuts

Here are some of the most common applications for countersunk rivet nuts:

Aircraft and Aerospace

Countersunk rivet nuts are extensively used in aircraft for installing screws that hold down access panels, attach brackets, and secure component mounts. The flush heads prevent air disturbances.

Automotive and Transportation

In automotive applications, countersunk rivet nuts provide strong threaded mounting points for inside panels, undercarriage components, and body accessories. Their tight grip resists vibration.

Appliances and Electronics

Countersunk rivet nuts allow easy screw attachments for brackets, covers, controls, and displays in appliances, computers, instruments, and other electronics. They accommodate frequent disassembly.

Furniture and Cabinetry

Flush rivet nuts provide an invisible way to assemble furniture and cabinet components. They are also used to attach hinges, slides, handles, and hardware.

Installation of Countersunk Rivet Nuts

Proper installation is key to achieving optimal performance from countersunk rivet nuts. Here are some tips:

Prepare Precise Counterbores

Accurately machined counterbores with dimensions matched to the rivet nut are essential. The holes should be perpendicular to the surface and deburred.

Use Recommended Tools

Quality riveting tools in good condition help ensure proper compression and seating of the rivet nut. Use any special mandrels or stems specified.

Follow Setback Guidelines

Observe the recommended setback distance from material edges. This avoids distortion or tear out around the hole under riveting force.

Confirm Full Compression

Inspect each installed rivet nut to verify the head is seated flush and the body is fully compressed. Re-compress any loose nuts.

Deburr Threaded Holes

Use a thread deburring tool to remove any burrs from the nut threads. This allows screws to thread in smoothly without binding.

Conclusion

With their unique combination of low-profile heads, excellent strength, and easy installation, countersunk rivet nuts are an indispensable solution for creating flush permanent threads. They deliver reliable performance in demanding applications across aviation, transportation, industrial machinery, electronics, and anywhere strong, concealed mechanical fastenings are needed. Following recommended practices for hole preparation, tool selection, and installation helps harness the full capabilities of these popular threaded inserts.

FAQs

What materials can countersunk rivet nuts be installed in?

Countersunk rivet nuts can be installed in a wide range of materials including metal, plastic, fiberglass, composites, and more. The flush low profile heads allow use even in thin panels or sheets.

What tools are required to install countersunk rivet nuts?

Standard riveting tools like squeezers or rivet guns are used to compress and flare the rivet nut body. Blind rivet nuts require special stems and mandrels. Through-hole rivet nuts use a threaded center rod and washer.

How are countersunk rivet nuts secured in place?

The riveting action compresses and deforms the rivet nut body to flare out against the hole edges. This creates strong mechanical retention comparable to rivets. Thread locker or adhesive can provide additional security.

What screw sizes can be used with countersunk rivet nuts?

Countersunk rivet nuts are available in a range of thread sizes to accept screws from #2 to 1/4" or larger. Metric threads are also available. The nuts grip screws tightly while allowing repeated use.

Can countersunk rivet nuts be removed and re-used?

In most cases, countersunk rivet nuts are considered semi-permanent fasteners. However, with care they can be drilled out and replaced if needed. New nuts may then be installed in the same holes.