introduction to products：

DIN 433 HV Head Mark High-Strength Washers：These are circular flat washers with a central hole, marked with an HV hardness grade (e.g., 140HV, 250HV) on the surface. Crafted from high-strength carbon steel, they often feature surface treatments like black oxide (for corrosion resistance) or zinc plating (for rust protection). Designed to work with medium-to-high-strength bolts (e.g., 4.8, 5.8, 8.8 grades), their key roles are to evenly distribute bolt pressure, protect connected surfaces from damage, and ensure stable fastening—especially in tight-clearance applications (thanks to their compact outer diameter). Widely used in machinery, automotive assemblies, and industrial equipment to secure components like cheese-head screws and socket-head screws.

Instructions for Use：

1. Match specs: Select a washer size (e.g., M8 for an M8 bolt) and HV grade that matches your bolt and application.
2. Clean & install: Wipe debris from contact surfaces, then place the washer between the bolt and the component.
3. Tighten carefully: Use recommended torque to avoid deforming the washer or parts. Regularly check for wear, corrosion, or damage—especially in high-vibration environments.

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 .