Aerospace rivet nuts

Rivet nut setting

This is the most common method of joining sheet materials in aircraft. A hole is drilled through the parts to be joined. A properly sized SS304 rivet nuts is put into the hole and set - the tail of the SS304 rivet nuts is deformed so that it expands sideways and grips the sides of the hole, clamping the material together. They may be set by hand, but more often a powered riveter is used.SS304 rivet nuts are available with a type of head shapes, including mushroom, snap SS304 rivet nuts and countersunk head rivets.

Where access is available to only one side, steel rivet nuts are employed. These are hollow steel rivet nuts, which are set by drawing a mandrel through the hollow steel rivet nuts from the same side as the head,the mandrel then breaks off.
Because steel rivet nuts are hollow, they must generally be sealed separately. The steel rivet nut is pushed into the drilled hole, then set - the tail is deformed so that it expands laterally. The deformed tail clamps the sheets together and retains the steel rivet nuts in the hole. The steel rivet nut may be used when access is restricted to one side. Pulling the mandrel through the steel rivet nut expands the rivet to set it, and the mandrel breaks off to leave a neat fastener. Steel rivet nuts are hollow, and need to be plugged after setting, if sealing is required.

Type of rivet nuts

There is a wide variety of special stainless steel rivet nuts, each for a specific application. Aerospace stainless steel rivet nuts may be made from any deformable material, but light alloy stainless steel rivet nuts are almost universal. An exception is the high-shear rivet, which uses a steel stem for very high shear strength, with an aluminium alloy collar that is deformed during setting to hold the stainless steel rivet nut in place. All stainless steel rivet nuts are designed to be used in shear, and have limited strength in tension.

This is most useful where high shear loads or significant tensile loads will happen at the joint. Aluminium bolts are available for shear applications, but commonly steel bolts are preferred for most applications. In most airframe applications, the fasteners must be locked to make sure that the nut and bolt don't loosen under vibration or temperature changes. A wide variety of methods can be used, including split pins, wire locking and clinch nuts. For bolts fitted to blind holes, wire locking is the most common method.