What Is A Double Fold Self Locking Washer?

A Double Fold Self Locking Washer (also called a double-layer anti-loosening washer) is an advanced fastener component engineered to maintain bolt or nut tightness under extreme vibration, dynamic forces, and thermal fluctuations. Unlike conventional washers, its two-layer design creates a self-reinforcing locking mechanism through friction differentiation and wedge effects, eliminating the need for adhesives or secondary locking devices.

Appearance and Structural Features

Each washer in the pair has two distinct surfaces:

1. Low-Friction Side: Smooth inclined tooth surface (angled teeth with polished finish).

2. High-Friction Side: Textured radial convex (raised ridges or knurled patterns).
   Key Design Parameters:

• Tooth angle > Bolt thread angle (typically 5°–15°).

• Convex roughness (Ra 3.2–6.3 μm) for enhanced grip.

• Material: Manufactured from high-strength steel, stainless steel, or corrosion-resistant alloys.

• Asymmetric Design: The inner teeth and outer ridges are engineered with specific angles and surface roughness to optimize locking performance.

Working Principle

The anti-loosening mechanism operates through four synergistic effects:

1. Friction Differentiation

• The textured radial convex surface has higher friction against the mating surface or fastener.

• The smooth inclined tooth surface has lower friction, allowing controlled micro-movement between the two layers.

2. Relative Displacement

When vibration or rotational forces attempt to loosen the fastener:

• The inner inclined teeth undergo controlled slippage due to their lower friction.

• The outer convex纹面 maintains fixed engagement with the contact surfaces.

3. Wedge Angle Effect

• The inclination angle of the inner teeth is designed to be greater than the bolt thread angle.

• Slippage between the inner layers forces the washer to expand vertically, increasing thickness and generating upward tension to compensate for bolt elongation or relaxation.

4. Mechanical Interlocking

• The outer radial convex creates a bite-in effect with the contact surfaces, preventing overall rotation of the washer assembly.

These combined actions create a dynamic self-compensating system that actively resists loosening.

Installation and Usage

Critical Installation Guidelines:

1. Orientation:

   
   

• Place two washers together with their low-friction inclined teeth surfaces facing each other.

• Ensure high-friction convex contact bolt/nut and workpiece (see diagram).

Torque Application:

• Tighten to the specified torque to activate the wedge effect without over-compressing the teeth.

2. Reusability:

• Discard and replace if significant tooth deformation or wear is observed after disassembly.

Applications

This technology excels in scenarios requiring active vibration resistance:

1. Heavy Machinery: Mining equipment, crushers, and hydraulic systems.

2. Transportation: Engine mounts, wheel assemblies, and rail track fasteners.

3. Energy Infrastructure: Wind turbine generators, pipeline flanges.

4. High-Temperature Systems: Exhaust manifolds, turbine casings.

Advantages Over Traditional Locking Washers

Conclusion

The Double Fold Self Locking Washer represents a paradigm shift in fastener security. By combining friction gradients, geometric wedge effects, and mechanical interlocking, it provides adaptive resistance to loosening forces unmatched by traditional methods. Proper installation orientation and torque control are critical to harnessing its full potential in mission-critical applications.