introduction to products：
Black Hex Flange Head Bolts (DIN 6921, non - fully threaded) are hex - headed fasteners with an integrated flange. The built - in flange serves to evenly distribute the load, significantly reducing the risk of loosening, especially in applications with high vibration or stress. Made from carbon steel (strength grades such as 8.8, 10.9, 12.9) or alloy steel, these bolts feature a black surface treatment, which can be black oxide for wear resistance or black zinc for enhanced corrosion protection.
Complying with the DIN 6921 standard, the non - fully threaded design makes them ideal for applications where only part of the bolt needs to engage with the threads of the mating component, providing greater strength and stability in the non - threaded section. Sizes typically range from M5 to M30. They are widely used in automotive manufacturing (chassis and engine mounting), heavy machinery assembly (industrial equipment, construction machinery), and transportation equipment (trucks, trailers), where reliable and secure fastening is crucial.
Instructions for Use：
When installing, use a matching hex wrench to tighten the bolts to the recommended torque value. The torque should be adjusted according to the strength grade of the bolt (e.g., Grade 12.9 bolts require higher torque than Grade 8.8). The serrated underside of the flange helps to grip the workpiece firmly, preventing it from rotating during tightening.
For maintenance, regularly clean the bolts with a dry cloth to keep the black surface free from dirt and debris. If the black coating gets scratched, apply anti - rust paint or a suitable protective coating promptly to maintain the corrosion - resistant or wear - resistant properties. Periodically inspect the bolts for any signs of damage, such as thread stripping, flange deformation, or cracks in the non - threaded section, and replace them as needed.
| Screw Thread | M5 | M6 | M8 | M10 | M12 | M14 | M16 | M20 | ||||
| d | ||||||||||||
| P | Pitch | Coarse thread | 0.8 | 1 | 1.25 | 1.5 | 1.75 | 2 | 2 | 2.5 | ||
| Fine thread-1 | / | / | 1 | 1.25 | 1.5 | 1.5 | 1.5 | 1.5 | ||||
| Fine thread-2 | / | / | / | 1 | 1.25 | / | / | / | ||||
| b | L≤125 | 16 | 18 | 22 | 26 | 30 | 34 | 38 | 46 | |||
| 125＜L≤200 | / | / | 28 | 32 | 36 | 40 | 44 | 52 | ||||
| L＞200 | / | / | / | / | / | / | 57 | 65 | ||||
| c | min | 1 | 1.1 | 1.2 | 1.5 | 1.8 | 2.1 | 2.4 | 3 | |||
| da | Form A | max | 5.7 | 6.8 | 9.2 | 11.2 | 13.7 | 15.7 | 17.7 | 22.4 | ||
| Form B | max | 6.2 | 7.4 | 10 | 12.6 | 15.2 | 17.7 | 20.7 | 25.7 | |||
| dc | max | 11.8 | 14.2 | 18 | 22.3 | 26.6 | 30.5 | 35 | 43 | |||
| ds | max | 5 | 6 | 8 | 10 | 12 | 14 | 16 | 20 | |||
| min | 4.82 | 5.82 | 7.78 | 9.78 | 11.73 | 13.73 | 15.73 | 19.67 | ||||
| du | max | 5.5 | 6.6 | 9 | 11 | 13.5 | 15.5 | 17.5 | 22 | |||
| dw | min | 9.8 | 12.2 | 15.8 | 19.6 | 23.8 | 27.6 | 31.9 | 39.9 | |||
| e | min | 8.71 | 10.95 | 14.26 | 16.5 | 17.62 | 19.86 | 23.15 | 29.87 | |||
| f | max | 1.4 | 2 | 2 | 2 | 3 | 3 | 3 | 4 | |||
| k | max | 5.4 | 6.6 | 8.1 | 9.2 | 11.5 | 12.8 | 14.4 | 17.1 | |||
| k1 | min | 2 | 2.5 | 3.2 | 3.6 | 4.6 | 5.1 | 5.8 | 6.8 | |||
| r1 | min | 0.25 | 0.4 | 0.4 | 0.4 | 0.6 | 0.6 | 0.6 | 0.8 | |||
| r2 | max | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.9 | 1 | 1.2 | |||
| r3 | min | 0.1 | 0.1 | 0.15 | 0.2 | 0.25 | 0.3 | 0.35 | 0.4 | |||
| r4 | ≈ | 3 | 3.4 | 4.3 | 4.3 | 6.4 | 6.4 | 6.4 | 8.5 | |||
| s | max=nominal size | 8 | 10 | 13 | 15 | 16 | 18 | 21 | 27 | |||
| min | 7.78 | 9.78 | 12.73 | 14.73 | 15.73 | 17.73 | 20.67 | 26.67 | ||||
| t | max | 0.15 | 0.2 | 0.25 | 0.3 | 0.35 | 0.45 | 0.5 | 0.65 | |||
| min | 0.05 | 0.05 | 0.1 | 0.15 | 0.15 | 0.2 | 0.25 | 0.3 | ||||
| Length of Thread b | - | - | - | - | - | - | - | - | ||||
Hebei Duojia Metal Products Co., Ltd. was formerly known as Yonghong Expansion Screw Factory. It has over 25 years of professional experience in manufacturing fasteners. The factory is located in the China Standard Room Industrial Base - Yongnan District, Handan City. It conducts online and offline production and manufacturing of fasteners as well as one-stop sales service business.
The factory covers an area of over 5,000 square meters, and the warehouse covers an area of over 2,000 square meters. In 2022, the company carried out industrial upgrading, standardized the production order of the factory, improved the storage capacity, enhanced safety production capacity, and implemented environmental protection measures. The factory has achieved a preliminary green and environmentally friendly production environment.
The company has cold pressing machines, stamping machines, tapping machines, threading machines, forming machines, spring machines, crimping machines, and welding robots. Its main products are a series of expansion screws known as "wall climbers".
It also produces special-shaped hook products such as wood tooth welding sheep eye ring screws and machine tooth sheep eye ring bolts. In addition, the company has expanded new product types from the end of 2024. It focuses on pre-buried products for the construction industry.
The company has a professional sales team and a professional follow-up team to safeguard your products. The company guarantees the quality of the products it offers and can conduct inspections on the grades. If there are any problems, the company can provide professional after-sales service.
Our export countries include Russia, South Korea, Britain, France, Germany, Italy, Canada, Mexico,Brazil, Argentina, Chile, Australia, Indonesia, Thailand, Singapore, Saudi Arabia, Syria, Egypt, Tanzania.Kenya and other countries. Our products will be spread all over the world!
WHY CHOOSE US?
1.As a factory-direct upplier,we eliminate middleman margis to offer you the most competitive pricing for high-quality fasteners.
2.our factory pass the ISO 9001 and AAA certification .we have the hardness testing and the test of zinc coating thickness for galvanized products.
3.with full contrl over production and logistic,we guarantee on-time delivery even for urgnt orders .
4.our engineering team can customize faseners from prototype to mass production , including unique thread designs and anti-corrosion coatings.
5.From carbon steel hex bolts to high-tensile anchor bolts ,we provide a one-stop solution for all your fastener needs.
6.If any defect is found ,we’ll reship replacements within 3weeks of our cost .
