By Frank Genovese
Sherex Applications Engineer

For installing rivet nuts into flat materials, the solution is usually rather simple when it comes to geometry. It usually just comes down to making sure there’s sufficient clearance for installation and the right hole size to properly fit the rivet nut. Since the material is flat, the only thing to worry about is ensuring the rivet nut is suitable for use with the thickness of that material.

With curved materials, the options may be narrowed down, and a solution may become more complex.

Rivet Nut installed in curved surface

Installing Rivet Nuts in Curved Surfaces

The options depend specifically on the curvature of the material. Since the entire circumference of a rivet nut collapses onto the material, the geometry of the rivet nut’s crimping bubble will possess the same curvature as the material it’s mating to.

If the base thickness is in the middle of a rivet nut’s grip range, the curvature may not have a significant effect, as the grip range would cover all of the effective thicknesses that rivet nut is crimping onto. However, if a rivet nut is installing into a base thickness toward the upper edge of its grip range, it may have trouble properly installing if the curvature is at all substantial. To account for this, there are two main options.

Testing Rivet Nuts in curved surface

Material thickness plays a big role in determining whether a rivet nut can be installed in a curved surface

The first option, sometimes preferable for thicker curved material, would be a swaging-style rivet nut. These rivet nuts expand into the installation pane rather than crimp onto it, and thus only have to meet a minimum thickness requirement. Swaging styles are recommended for high (or variable) thickness applications where high joint strength is not an option.

For improved spin-out, pull-out, and torque-out performance, pre-bulbed and slotted rivet nut styles are the recommended option for variable thicknesses. These rivet nuts are typically suitable for large thicknesses, but also a wide range of them. This is because the slots of the rivet nut fold over to collapse onto the material, rather than a significantly smaller counterbore region found in other body styles.

Rivet Nuts in Curved Surfaces

Typical round body rivet nut in curved material

If installing tin to curved surfaces and have questions, feel free to reach out to Sherex’s engineering team with application details and performance requirements. Whether for standard round or hex body rivet nuts, swaging, slotted, or pre-bulbed, Sherex will help guide to users to a recommendation we have the tools to determine the best solution for you.

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