introduction to products：

Brass Copper DIN7991/931/933 Bolts include two types: DIN7991 (CSK flat - head with internal hex socket) for flush - fitting installations, and DIN931/933 (hex head with partial/full threading) for load - bearing connections. Crafted from brass/copper, they offer natural corrosion resistance, excellent electrical conductivity, and an attractive golden finish. The DIN7991 countersunk head ensures a snag - free surface; DIN931 has partial threads (ideal for thick workpieces), while DIN933 features full threads (suited for through - holes). Available in sizes from M2 to M24, they are widely used in furniture (decorative fastening), electrical equipment (conductive joints), architectural hardware (ornamental mounts), and precision instruments (low - profile fixing), balancing aesthetics and functionality.

Instructions for Use：

DIN7991: Install using a matching internal hex wrench, tightening until the CSK head is fully flush with the workpiece (avoid over - tightening to prevent material warping).

DIN931/933: Use an external hex wrench, following the recommended torque guidelines (note that brass has lower strength than steel, so avoid excessive force).
For maintenance: Clean the bolts regularly with a dry cloth. Brass naturally develops a patina over time; if polishing is desired, use brass - specific cleaners. Avoid long - term exposure to strong acids or alkalis to preserve the finish.

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 .