Feststellmutter

Feststellmutter is a German term for a locking nut, a fastener used to fix the position of a nut or component on a threaded shaft. Its main purpose is to prevent loosening of a nut under vibration, dynamic load, or temperature changes by increasing friction or by mechanically jamming the parts in place.

Common implementations include a second nut, known as a jam nut, tightened against a standard nut to lock it in position; as well as locking nuts that incorporate features such as a nylon insert or serrated surfaces to resist loosening. In practice, Feststellmutter designs range from simple jam configurations to commercially produced locking nuts used in a variety of industries.

Applications span machinery, automotive, construction, and consumer products, where precise adjustment must be retained. Typical uses include securing adjustable collars, clamps, linkage joints, and steering or alignment settings. Installation generally follows the manufacturer’s torque specifications to achieve the required clamping force, and may involve thread-locking compounds or specific finishes to enhance security. The term is often used interchangeably with emergency or general references to Sicherungsmutter (locking or securing nuts) in German technical contexts, though regional or technical distinctions can apply between a jam nut and a purpose-built locking nut.