Hexagon Flange Bolts
ISO 6921 (With Washer Face)
Integrated Load Distribution & Anti-Loosening Solution
Manufacturer & Exporter: Super Industries India
1. What Is Hexagon Flange Bolts?
ISO 6921 specifies hexagon head bolts with an integral flange (washer face under the head).
The flange replaces a separate washer and is designed to:
- Distribute clamping load
- Protect the joint surface
- Improve resistance to loosening
- Reduce assembly time
These bolts are widely used in automotive, machinery, structural frames, and OEM assemblies.
Super Industries
Global Manufacturer of Heavy & Custom Engineered Fasteners & Flanges
2. Why Engineers Prefer ISO 6921 Flange Bolts
ISO 6921 bolts offer multiple engineering advantages:
✔ Built-in washer → fewer components
✔ Larger bearing surface → reduced surface pressure
✔ Better preload retention
✔ Faster assembly on production lines
✔ Reduced risk of washer loss
3. ISO 6921 vs Standard Hex Bolts (ISO 4014 / ISO 4017)
| Feature | ISO 4014 / 4017 | ISO 6921 |
|---|---|---|
| Separate washer | Required | Not required |
| Load distribution | Washer-dependent | Integrated flange |
| Assembly speed | Normal | Faster |
| Loosening resistance | Moderate | Improved |
4. Flange Design & Engineering Logic
The flange:
- Acts as a washer
- Has a larger contact area
- Often includes serrations (optional variant)
- Reduces localized stress
This is especially useful on:
- Thin plates
- Painted or coated surfaces
- Soft materials
Super Industries
Global Manufacturer of Heavy & Custom Engineered Fasteners & Flanges
5. Dimensional Range
Typical sizes:
- Thread: M5 to M24
- Length: 10 mm to 200 mm
- Thread type: Metric coarse (fine thread on request)
Custom lengths available at Super Industries India.
6. Strength Grades (ISO 898-1)
Common grades supplied:
- 8.8
- 10.9
- 12.9 (project-specific)
Grade selection depends on:
- Load
- Safety factor
- Fatigue requirement
7. Materials Offered
- Carbon steel
- Alloy steel
- Stainless steel (A2 / A4)
- Special materials for OEM projects
8. Surface Finishes
- Zinc plated (white / yellow)
- Black oxide
- Phosphate
- Hot dip galvanized
- Stainless steel natural finish
Finish is selected to:
- Match corrosion environment
- Maintain friction coefficient
9. Applications Across Industries
ISO 6921 flange bolts are widely used in:
- Automotive chassis & engines
- Heavy machinery
- Structural frames
- Agricultural equipment
- Pumps & compressors
- OEM production lines
10. Serrated vs Plain Flange Bolts
| Type | Application |
|---|---|
| Plain flange | General load distribution |
| Serrated flange | Anti-loosening / vibration |
Serrated variants bite into the mating surface and improve joint security.
11. Torque & Preload Behavior
Integrated flange:
- Provides consistent friction
- Improves torque-to-tension accuracy
- Reduces preload scatter compared to loose washers
12. Manufacturing Process
At Super Industries India:
- Cold forging
- Precision flange forming
- Thread rolling
- Heat treatment
- Surface coating
- Dimensional & hardness inspection
13. Quality Control & Testing
- Head geometry check
- Flange diameter & thickness
- Thread gauges
- Mechanical property testing
- Coating thickness verification
14. Export & OEM Supply
We supply ISO 6921 bolts for:
- OEM contracts
- Export distributors
- EPC & industrial projects
With:
✔ Mill test certificates
✔ Batch traceability
✔ Customized packaging
15. Custom ISO 6921 Bolts
Available customizations:
- Special flange diameter
- Serrated flange
- Fine thread
- Special coatings
- Project markings
16. Buyer FAQ (SEO)
Q: Can ISO 6921 replace bolt + washer assemblies?
Yes, in most applications it is superior.
Q: Are ISO 6921 bolts suitable for vibration?
Yes, especially serrated flange variants.
17. Engineering Mistakes to Avoid
❌ Using flange bolts on soft materials without validation
❌ Mixing flange bolts with separate washers unnecessarily
❌ Ignoring torque recalculation
18. When to Choose ISO 6921
Use ISO 6921 when:
✔ Assembly speed matters
✔ Washer loss is a risk
✔ Load distribution is required
✔ OEM production consistency is critical
19. Standards & Compliance
- ISO 6921
- ISO 898-1 (mechanical properties)
- ISO 965 (threads)
20. Conclusion
ISO 6921 hex flange bolts offer efficient assembly, improved joint reliability, and reduced component count.
Super Industries India manufactures ISO 6921 flange bolts for high-performance industrial and export applications worldwide.