ISO 7040 specifies the characteristics of prevailing torque type hexagon regular nuts with a non-metallic (nylon) insert. Designed for reliability in dynamic environments, this standard ensures that the nut maintains its position on the bolt even when subjected to intense vibration or fluctuating loads, without the need for additional locking washers.

As an essential part of the ISO metric mechanical system, ISO 7040 regular nuts provide a standardized height and locking torque performance, making them the preferred choice for automotive, aerospace, and heavy machinery assemblies where safety and anti-loosening are paramount.

Le Prevailing Torque mechanism in ISO 7040 is achieved through the elastic deformation of a nylon collar located at the top of the nut. As the bolt enters the collar, the nylon is displaced, creating a high-friction radial compressive force. This internal friction, or "prevailing torque," prevents the nut from rotating freely, providing a permanent locking effect that is independent of the axial clamping force.