DIN 6921 Hexagon Flange Bolts represent a critical advancement in fastening technology, engineered specifically to optimize surface pressure distribution. By integrating a circular flange directly under the hexagonal head, these fasteners function as a built-in washer, significantly increasing the bearing area to prevent the bolt from digging into soft metal surfaces while maintaining a compact, low-profile design.
Designed for high-performance industrial environments, LONGZE DIN 6921 bolts are the preferred choice for automotive frames, engine mounts, and structural steelwork. These components eliminate the need for separate washers, which drastically reduces assembly time, simplifies inventory management, and provides superior resistance to vibration-induced loosening compared to standard hex bolts like DIN 931.
Detailed Parameters
| Standard Specification | DIN 6921 / ISO 4162 / EN 1665 | Metric Size Range | M5 to M20 |
|---|---|---|---|
| Property Classes | 8.8, 10.9, 12.9 (High Tensile) | Stainless Steel Grades | A2-70, A4-80 |
| Flange Type | Smooth or Serrated (Locking) | Manufacturing Process | Cold-Formed Transition |
| Surface Finishes | Zinc-Nickel, Dacromet, Geomet | Core Application | Surface Pressure Optimization |
| Primary Benefit | Eliminates Separate Washers | Industry Benchmarks | Automotive & Renewable Energy |
Key Advantages
Load Distribution
Increased bearing area (dc) reduces contact pressure, preventing surface damage on clamped parts.
Faster Assembly
Integrated flange removes the need for separate washers, accelerating production line speed.
Vibration Resistance
Superior grip and stability minimize the risk of loosening in high-vibration automotive environments.
Fatigue Resistance
Cold-formed flange-to-head transitions eliminate stress risers for maximum component longevity.
Anti-Corrosion
Available in Geomet and Zinc-Nickel coatings to withstand harsh global environmental conditions.
Inventory Efficiency
Consolidating bolts and washers into one part reduces SKU counts and logistics complexity.
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Management Platforms
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Automated Supply Chain
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Investment Return Comparison
| Metric | Standard Hex Bolt (DIN 931) | Flange Bolt (DIN 6921) |
|---|---|---|
| Assembly Speed | Slower (Bolt + Washer) | Faster (Integrated) |
| Part Count | 2 Parts per Joint | 1 Part per Joint |
| Surface Stress | Higher Concentrated Load | Optimized Distributed Load |
| Vibration Stability | Requires Locking Washers | Inherent Stability/Serrated Grip |
| Inventory Cost | Higher (Multiple SKUs) | Lower (Single SKU) |
Frequently Asked Questions
DIN 6921 features an integrated circular flange under the head, which acts as a built-in washer. This eliminates the need for separate washers and increases the load-bearing surface area.
Serrated versions should be used when maximum locking grip is required, as the serrations bite into the mating surface to prevent rotation under extreme vibration.
They are commonly available in high-tensile carbon steel property classes 8.8, 10.9, and 12.9, as well as stainless steel grades A2-70 and A4-80.
Yes, ISO 4162 (Small Series) and EN 1665 (Heavy Series) are the modern equivalents, though DIN 6921 remains a widely used industry benchmark.
For high corrosion resistance in automotive and renewable energy sectors, we recommend Dacromet, Geomet, or Zinc-Nickel finishes.
You must verify the flange diameter (dc) against your housing or structural ribs. Refer to our technical data tables for exact dc measurements for each bolt size (M6-M20).
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