I. Friction-based anti-loosening: Maintaining a tight fit using friction.
Loosening is prevented by generating continuous friction between the threaded parts, suitable for normal vibration environments.
1. Spring Washer: The washer generates spring force when flattened, maintaining preload between the nut and screw. During installation, ensure the opening direction is opposite to the tightening direction.
2. Double Nuts (opposite nuts): Two nuts are tightened together, forming two friction surfaces. Even if one loosens, the other maintains a locking effect.
3. Self-locking Nuts (Nylon Insert Nuts): Nuts with embedded nylon rings create an interference fit with the screw when tightened, providing continuous frictional resistance. They are reusable and widely used in electronic equipment and automotive parts.
4. Toothed Locking Washers: Washers with a serrated structure embed into the contact surface when tightened, increasing friction and preventing loosening.
II. Mechanical anti-loosening: Directly restricting rotation through locking elements. High reliability, often used in strong vibration or critical structural connections.
1. Cotter Pin + Slotted Nut: After tightening the nut, insert the cotter pin into the nut slot and bolt end hole and pry it open to completely prevent relative rotation. Widely used in machinery and aerospace fields.
2. Locking Washer: After tightening, bend the ear of the washer to fit tightly against the nut and the side of the connector, forming a mechanical lock. Suitable for multi-point array fastening.
3. Serial Steel Wire (Wire Anti-Loosening): Pass a steel wire through the small holes in the heads of multiple screws and pull it tight, causing the screws to restrain each other. Any tendency to loosen is immediately tightened. Commonly used in high-reliability scenarios such as engines and weaponry.
III. Structural Anti-Loosening: Self-Locking Achieved Through Special Structural Design
Does not rely on external components, resulting in more stable anti-loosening performance.
1. Tang's Thread (Double-Direction Thread): Uses a combination of right-hand and left-hand threads, combined with a two-way nut. Under vibration, it automatically enhances the locking force, a typical example of structural anti-loosening.
2. Spitec Thread (30° Wedge Thread): The thread root features a 30° wedge-shaped bevel, increasing normal pressure and significantly improving anti-loosening friction, resulting in superior anti-loosening performance compared to traditional threads.
3. Flange Face Toothed Nut: The nut's bearing face has serrations that embed into the surfaces of the connected parts during tightening, increasing contact friction and preventing rotation.
IV. Chemical Anti-Loosening: Curing threaded pairs with adhesives. Easy to use, suitable for mass assembly and non-removable connections.
Thread Locking Adhesive: Applied to the thread engagement area, it cures to bond the screw and threaded hole together, providing both sealing and anti-loosening functions.
Available in three strength grades:
Low Strength: Easy to disassemble, suitable for parts requiring frequent maintenance;
Medium Strength: Most commonly used, balancing disassembly and reliability;
High Strength: Used for permanent connections; disassembly requires heating or tool damage.
⚠️ Usage Tips: When assembling blind holes, apply adhesive to the bottom of the hole first, then apply screws to ensure full filling; when disassembling, use a wrench with impact force or local heating (about 250℃) to soften the adhesive.
