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Handan - sourced Hot Dip Galvanized (HDG) DIN7991 CSK Flat Head Hex Socket Bolt Screws are countersunk - head fasteners with internal hex sockets, supplied directly by manufacturers in Handan (a leading fastener production hub in northern China). Crafted from carbon steel (grades 4.8, 8.8, 10.9, 12.9), alloy steel, or stainless steel (A2 - 70, A4 - 70), they feature a HDG coating — a thick zinc layer formed by dipping in molten zinc, providing exceptional corrosion resistance (ideal for outdoor, marine, and industrial environments). Compliant with the DIN7991 standard, the CSK (countersunk) head sits flush with the workpiece, eliminating protrusions. Available in sizes from M3 to M36, they are widely used in construction (steel structures), automotive (chassis mounting), marine equipment, and industrial machinery, delivering secure fastening and long - lasting anti - corrosion performance.

Instructions for Use：

Install using a matching hex socket wrench, tightening until the CSK head is completely flush with the workpiece (follow torque guidelines based on the material grade — for example, Grade 10.9 requires higher torque than Grade 4.8). For maintenance: Clean regularly with a dry cloth; the thick zinc layer of HDG resists rust, but avoid scratching the coating. If the coating is damaged, repair it with zinc - rich paint to maintain corrosion resistance.

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 .