1. Standards and types
Standard system: German Industrial Standards (DIN), metric (millimeter) specifications, designed specifically for high anti loosening requirements.
Core features: Hexagonal flange face, integrated flange plate below the head (with serrations or rolling patterns), providing anti loosening and anti vibration performance without the need for additional gaskets.

2. Structural characteristics
Flange design:
The flange diameter is larger than the standard hexagonal head, increasing the contact area and dispersing pressure.
Sawtooth/Rolling Pattern: The bottom of the flange surface has radial saw teeth or rolling patterns, embedded in the surface of the connected part to prevent bolt loosening.
Thread type: metric coarse thread (M series, such as M8 M12）， The thread length can be selected as full thread or half thread according to the requirements.

3. Material and grade
Common materials:
Carbon steel (such as 8.8 grade, 10.9 grade), surface galvanized, Dacromet or phosphated treatment.
Stainless steel (A2-70, A4-80), suitable for corrosive environments.
Strength grade: 8.8 grade (tensile strength 800MPa), 10.9 grade (tensile strength 1000MPa), etc.

4. Application scenarios
High vibration environment: automotive chassis, engine components, railway equipment, and other scenarios that require anti vibration and anti loosening measures.
Automation equipment: fixed conveyor belts and motors to reduce maintenance frequency.
Steel structures: bridges, towers, and other connections that require long-term stability.

5. Advantages and Comparisons
Compared to regular hexagonal bolts:
Replacing gaskets with flanges simplifies the installation process and reduces costs.
The serrated design significantly enhances the anti loosening ability and is suitable for dynamic loads.
International benchmark: Similar to ISO 4162 standard, but DIN 6921 serrated design has more anti loosening features.

6. Precautions
During installation, it is necessary to ensure that the flange serrations are fully pressed into the contact surface to avoid serrated failure due to excessive surface hardness.
Tighten according to standard torque, excessive tightening may crush flange serrations or damage the connected parts.
Stainless steel material (such as A4-80) is preferred for humid or corrosive environments.

Summary: DIN 6921 bolts, with their integrated anti loosening flange design, are an ideal choice for high vibration and high load scenarios, combining ease of installation with long-term stability.