Hex Flange Head Bolts / Flange Screws (DIN 6921) – Serrated & Plain Face – Grade 8.8 / 10.9 – Manufacturer Direct

Premium Hex Flange Head Bolts: The Ultimate Anti-Vibration Fastener

At Handan Bolt, we are a leading manufacturer of high-performance Hex Flange Head Bolts (often referred to simply as Flange Bolts or Frame Bolts). Produced in our advanced cold-heading facility in Yongnian, China, these fasteners are engineered to eliminate the need for separate washers while providing superior locking capabilities. We supply millions of DIN 6921 and SAE J429 flange bolts annually to the automotive, solar energy, and heavy machinery sectors.

What is a Hex Flange Bolt?

A Hex Flange Bolt is a one-piece fastener that consists of a hexagonal head and a built-in washer-like base (the flange). This design innovation serves two critical functions:

1. Load Distribution: The integrated flange acts like a heavy-duty Washer (Read more on Wikipedia), spreading the clamping force over a larger surface area. This protects the base material from damage and prevents the bolt from pulling through oversized holes.
2. Efficiency: By combining the bolt and washer into a single unit, assembly time is significantly reduced. Workers no longer need to fumble with separate flat washers or lock washers, speeding up production lines.

Serrated vs. Non-Serrated (Plain) Types

Based on your specific application, we manufacture two distinct types of flange faces:

• Serrated Flange Bolts (Locking): As seen in your product image, these bolts feature “teeth” or serrations on the underside of the flange. When tightened, these teeth bite into the mating surface, creating a powerful mechanical lock that resists loosening caused by vibration. This makes them ideal for engine mounts, exhaust systems, and conveyor belts.
• Non-Serrated / Plain Flange Bolts: These have a smooth bottom surface. They are used when the surface finish of the part must be protected from scratches, or when an external nut will be used for tightening.

Technical Standards and Grades

We manufacture flange bolts to meet rigorous international standards listed in your specifications:

1. DIN 6921 / ISO 4162 (Metric Series)

This is the global standard for metric hex flange bolts.

• Grade 8.8: The most common high-tensile grade, suitable for structural steel connections and automotive frames.
• Grade 10.9: Heat-treated alloy steel for critical high-stress applications requiring exceptional yield strength.

2. SAE J429 (Imperial/Inch Series)

For the North American market, we produce “Frame Bolts” or “Hex Flange Screws” in inch sizes.

• Grade 5: Equivalent to Metric 8.8.
• Grade 8: Equivalent to Metric 10.9, identifiable by 6 radial lines on the head.

Surface Treatments for Longevity

Flange bolts are often used in chassis and undercarriage applications where corrosion is a major threat. We offer:

• Zinc Plated (Clear/Blue): The standard finish for indoor or protected outdoor use.
• Black Zinc / Black Oxide: Provides a sleek, stealthy look often required in automotive engine bays or motorcycle fairings.
• Hot Dip Galvanized (HDG): For solar panel mounting structures and outdoor construction, our HDG coating ensures decades of rust-free performance.
• Dacromet / Geomet: Advanced coatings available upon request for high salt-spray resistance (1000+ hours).

Common Applications

Our Hex Flange Bolts are the fastener of choice for:

• Automotive Industry: Securing vehicle frames, transmissions, and suspension components.
• Solar Mounting: Fastening solar panels to aluminum rails (often used with stainless steel flange bolts).
• Industrial Plumbing: Joining pipe flanges where a secure seal is critical.
• Truck & Trailer: Body assembly where vibration resistance is mandatory.

Why Source from Handan Bolt?

Cost Savings: By eliminating the need to buy and stock separate washers, our flange bolts save you money on inventory and labor.
Customization: We can produce flange bolts with specific serration patterns or extra-wide flanges (Big Flange series) according to your drawings.
Quality Assurance: Every batch undergoes torque-tension testing and serration hardness checks.

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