Products + Tools

Here Sherex Fastening Solutions^®, a PennEngineering^® company and global specialist in engineered fasteners, tooling, and automation, discusses the benefits of combining a compression limiter with a rivet nut to create a compression limiting rivet nut, as well as how its Optisert^® round body rivet nut performs comparably versus a half hex body rivet nut.

Compression limiters fill a gap for a metal on metal load transfer as to not deform the material. So when the fastener, such as a screw or bolt, is tightened, the compression limiter is compressed between the fastener head and the metal parts being joined for a compact assembly. 

Compression limiters are typically integrated with a fastener, such as a rivet nut, to provide metal to metal transfer of forces during the joint assembly. However, there is an even simpler solution available – combining a compression limiter with a rivet nut to create a compression limiting rivet nut. A compression limiting rivet nut integrates both a rivet nut and a compression limiter into a single piece with a unique part number.

This offers several advantages as it is a single component instead of two separate parts, streamlining assembly time and simplifying the ordering process for purchasers, as they only need to consider one part. It is also cost-effective as a compression limiter and a rivet nut combined would likely cost more than a specially designed compression limiting rivet nut.

How does it work?

With a compression limiting rivet nut, it pretty much acts as a rivet nut with a bigger shoulder or spacer combined on top of the rivet nut. When the compression limiting rivet nut installs, it installs into the base material, but the spacer or compression limiter then sits above it as to not distort the material sitting on top.

Like all compression limiters made and designed by Sherex, they are all unique to the application and the same applies with these compression limiting rivet nuts. They are very popular in automotive applications with pretty much limitless designs – round body, hex body, underhead seals, knurls, etc. Sherex engineering works with the application design engineers to come up with a design that will surpass performance expectations while also being the most cost-effective solution compared to other fastening options.

So, if considering a compression limiter, a compression limiting rivet nut might be a better solution that delivers the same performance with less parts. 

Optisert^® round body rivet nut 

Sherex has been working for over five years on a round body rivet nut that can perform comparably versus a half hex body rivet nut. Rivet nut best practice is to still recommend a full hex body rivet nut if you can make a hex hole – especially in harder material like steel and stainless steel. However, if a round hole is the only hole that can be produced, especially in softer materials like plastic, fiberglass, and aluminium, Optisert^®’s performance is recommended.

“We’ve had over five years of product development to get the performance where we want it,” says Sherex Engineering Manager John Knechtges. “We’ve done similar wedgehead, knurled rivet nuts as specials for projects, but this standard part has unmatched performance. We’re really proud.”

Optisert^® spin out performance in aluminium is closer to the performance of a full hex rivet nut than a normal, round body CAL rivet nut, and actally greater than a half hex rivet nut.

With knurls underneath the flange that bite into the material, resistance to spin out is very extraordinary. Spin out occurs when the rivet nut spins into the hole it’s installed into. Spin out would potentially occur in applications that experience heavy vibration or in applications that experience a lot of strain force.

For industries that are continuously looking for lightweighting options, such as the automotive and heavy truck sectors, Optisert^® is an ideal option for a threaded insert fastener. Optisert^® also comes in a closed end option with a seal that comes standard. The seal does not compromise grip and helps keep dust and water out of the base material.