Mythbusters: If the clamp length is at least five times the bolt’s diameter, then the joint will not loosen from vibration
The Myth: If the clamp length is at least five times the bolt’s diameter, then the joint will not loosen from vibration.
The Truth: A long clamp length generally increases the elasticity in the bolt. This improves the resistance against fatigue and loosening because the bolt is subjected to less dynamic stress and can follow the movements of the joint. However; the resistance against vibration induced loosening also relies on friction conditions, which often vary significantly. The elasticity alone may not be sufficient to keep the fastener from rotating loose. A long clamp length may instead result in increased cost and weight but not provide sufficient safety for critical applications.