Zero-risk Assembly For Rivet Nut Installation

Louise Smyth

Designed with a closed end and a large flanged head with a cylindrical groove and O-ring seal mounted underneath, Dejond’s cold-formed HX blind rivet nuts in steel and stainless steel offer a worry-free, watertight fastening solution in many critical applications.

During rivet nut installation an axial crimping action performed with a setting tool the O-ring seal slides into the groove and is compressed between the flanged head and the plate or profile the rivet nut is installed in. The hex-shaped shank prevents spin out, resisting a torque-to-turn force of at least 30Nm in M8.

After setting, the special head design ensures metal-to-metal contact on either side of the O-ring, that firmly remains in the conically shaped recess, resulting in an optimal seal compression. This guarantees a well-functioning seal, ideally positioned away from possible burrs or sharp hole edges and protected against UV light.

The under-head seal provides excellent protection against ingress of fluids, moisture, oil or dirt, even under high pressures up to at least 10 bar. The HX design is IP 68 guaranteed under Dejond test conditions, and is available in thread sizes M5 to M8. Standard O-ring seal material is NBR (Buna-N), but when a specific pressure, temperature resistance or chemical compatibility is required, other O-ring materials (Viton, EPDM, silicone, etc.) can be offered. 

Originally designed to prevent leaks in a boot hinge assembly in a premium car make, the watertight HX Tubtara is a trusted solution in many other challenging applications too.

demanding applications

As application requirements become increasingly complicated, other watertight rivet nut solutions had to be conceived. Therefore Dejond developed the (H)DPX series, involving a non-reactive peripheral seal, made of flexible, organic-based material, applied to the under-head bearing surface of a flat head Tubtara rivet nut.

The polyurethane seal compound is resistant to many automotive oils, antifreeze and transmission fluids, and has a sealing capacity exceeding 150 bar. The material offers a temperature resistance from -40°C to 100°C for continuous usage (150°C peak temp), and is gap filling, forming a robust seal between mating surfaces. Slight variations in seal thickness may influence head height and grip range, but a correctly installed Tubtara (H)DPX ensures an IP 67 waterproof assembly.

This seal can be applied under the flat head of stocked standard parts, in all materials and shank shapes, offering OEM customers very short delivery times. It is the preferred solution for numerous applications such as in roof rack assemblies, battery packs or enclosure covers.

New HX developments focus on their outstanding sealing properties rather than on fastening. The new designs feature connection options such as male or female threads, or a hose connection, offering zero-risk assembly solutions in HVAC and fluid control applications.

Marc Drossaert is with Dejond

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