How Structural Blind Fasteners Work
The shear strength of structural blind fasteners is generated by the combined resistance against failure of the pin and sleeve. This takes place along the joint’s shear line between fastened plates.
The tensile strength of structural blind fasteners differs to that of LockBolts, as they form a blind side positive lock either by bulbing or expanding of the sleeve. The sleeve, assisted by the permanently secured pin, therefore resists failure along its centre line.
The sleeve of the fastener is compressed, causing it to fold outwards to form a bulb. This forms itself tightly against the joint material. Once the pin is permanently locked into place the pintail will break off, completing the installation.
Pulling on the pintail causes the head of the pin to draw into the sleeve. This expansion causes a foot print to form against the joint material.
Note: The pre-load of blind rivets is generally not published, as it varies widely depending on the application.
- Pin placed into prepared hole
- Tool is placed over the fastener pintail
- Tool activated
- Deforming of blind side begins
- Joint tightened
- Internal locking mechanism formed
- Pintail breaks
- Installation complete
How LockBolts Work
Clamp Force or Pre–Load: In the initial stages of the installation process, the tool engages and pulls on the pintail. The joint is pulled together before the conical shaped cavity of the nose assembly is forced down the collar. This progressively locks (swages) it into the grooves of the harder pin. The pin and swaged collar combine to form the installed fastener.
The squeezing action reduces the diameter of the collar, increasing its length. This in turn stretches the pin, generating a clamp force over the joint.
Shear strength of LockBolts vary according to the material strength and minimal diameter of the fastener. By increasing the diameter or the grade of material, the shear strength of the fastener can be increased.
The tensile strength of LockBolts is dependent on the shear resistance of the collar material and the number of grooves it fills.
- Pin placed into prepared hole – Collar placed over pin
- Tool is placed over the fastener pintail and activated
- Pin head pulled against material
- Anvil pushes collar against joint
- Initial clamp generated
- Tool swages collar, increasing clamp
- Pintail breaks, installation complete
How a Recoil wire thread insert works
LRecoil inserts are rolled from high quality stainless steel wire with a diamond shaped cross section, wound to the shape of a spring thread. Once the insert is installed into a tapped hole, it provides a permanent and wear resistant thread in the parent material designed to be stronger than the original thread.
The inserts are greater in diameter than the corresponding tapped hole and compress as they are installed. This allows maximum surface contact area with the tapped thread, safely and permanently anchoring the inserts into place.
The insert’s compensatory action shares the load over the entire bolt and hole, increasing holding or pull out strength. With a Recoil insert in place, load and stress are more evenly distributed.
Recoil inserts are installed in four easy steps…