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Help CenterFactory Direct Double Coil Spring Washer With Free Samples and Quality Assurance
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Introducing the Factory Direct Double Coil Spring Washer – a premium fastening solution engineered for demanding industrial applications. As a manufacturer with over two decades of experience (since 1998), Anping County Boli Hardware Wiremesh Products Factory offers these washers directly from our factory, ensuring competitive pricing, consistent quality, and fast lead times. We are pleased to provide free samples for quality evaluation, backed by our rigorous quality assurance system. Our double coil design delivers superior spring force and load distribution, making it the ideal choice for bolted joints that require long-term reliability under vibration, shock, and dynamic loads. Whether you are in automotive assembly, heavy machinery, or structural construction, this washer helps maintain clamp load and prevent loosening over time.
Key Features & Technical Specifications
- Double Coil Design – Two complete coils provide increased spring tension and a larger contact area, offering up to 50% more deflection than standard single-coil washers, ensuring better load retention.
- Premium Spring Steel – Manufactured from high-grade 65Mn or 60Si2Mn spring steel, heat-treated to achieve optimal hardness and elasticity, resulting in excellent fatigue resistance.
- Corrosion Resistance Options – Available in multiple surface finishes: zinc plated (yellow/blue passivation), black oxide, or oiled, to suit different environmental conditions and aesthetic requirements.
- Precision Manufacturing – Produced with advanced CNC coiling and heat treatment equipment, ensuring consistent dimensions, uniform hardness, and a smooth surface without burrs.
- Wide Size Range – Standard sizes from M6 to M30, with custom diameters and thicknesses available upon request for non-standard applications.
- Compliance with Major Standards – Designed to meet DIN 7980, GB/T 93, and ASME B18.21.1 (optional), ensuring compatibility with international bolting systems.
- Anti-Loosening Performance – The spring action of the double coil creates a powerful axial force that resists rotational loosening caused by vibration, thermal cycling, or shock loads.
| Size (M) | Inner Diameter (mm) | Outer Diameter (mm) | Thickness (mm) | Free Height (mm) |
| M6 | 6.2 | 12.0 | 1.5 | 3.0 |
| M8 | 8.2 | 16.0 | 2.0 | 4.0 |
| M10 | 10.2 | 20.0 | 2.5 | 5.0 |
| M12 | 12.5 | 24.0 | 3.0 | 6.0 |
| M16 | 16.5 | 32.0 | 3.5 | 7.0 |
Benefits for Your Applications
- Enhanced Joint Security – The double coil design ensures that even under severe vibration, the washer maintains adequate spring force, reducing the risk of fastener loosening and subsequent assembly failure.
- Longer Service Life – High-quality spring steel combined with precise heat treatment results in superior fatigue life, making these washers suitable for high-cycle or maintenance-critical applications.
- Cost Savings – Factory-direct pricing eliminates middleman markups, and the free sample program allows you to test the product before committing to large orders, minimizing procurement risk.
- Versatile Compatibility – Available in metric sizes and standard configurations, these washers can be used with bolts, screws, and nuts of corresponding grades, simplifying your inventory.
- Environmental Adaptability – With multiple surface finish options, you can select the appropriate level of corrosion protection for indoor, outdoor, or marine environments.
Why Choose Boli Hardware? Since 1998, Anping County Boli Hardware Wiremesh Products Factory has been a trusted name in the fastener industry. We export to global markets including North America, South America, Europe, Southeast Asia, Africa, and Oceania, with an annual export value of US$5 Million - US$10 Million. Our products are shipped from major ports such as Tianjin, Qingdao, Shanghai, and Foshan, ensuring efficient logistics. We implement a strict quality assurance system: every batch of double coil spring washers undergoes dimensional inspection, hardness testing, and spring load verification. Combined with our free sample policy, we invite you to experience the reliability of our washers firsthand. Contact us today to request your free samples and discover how Boli can support your fastening needs with factory-direct quality and value.
Frequently Asked Questions
1. What materials are your double coil spring washers made from?
We primarily use high-quality spring steel grades such as 65Mn and 60Si2Mn, which are heat-treated to achieve optimal hardness and elasticity. For special requirements, other materials can be discussed.
2. What surface finishes are available?
We offer zinc plating (yellow/blue passivation), black oxide, oiled finish, and plain (as-rolled). Custom finishes such as Dacromet or hot-dip galvanizing are available upon request.
3. Do you provide free samples? How can I get them?
Yes, we offer free samples for quality evaluation. Simply contact us with your required size, quantity, and surface finish, and we will arrange shipment. You only need to cover the shipping cost.
4. What is the minimum order quantity (MOQ) for regular orders?
Our standard MOQ is 5000 pieces per size, but we are flexible for first-time orders or small trial batches. Please consult our sales team for details.
5. What is the typical lead time?
For standard sizes in stock, we can ship within 7-10 days after order confirmation. Custom sizes or finishes may require 15-25 days, depending on the quantity and complexity.
6. How do you ensure the quality of your washers?
We have an in-house quality control system that includes incoming material inspection, in-process monitoring, and final testing. Each batch is checked for dimensions, hardness, spring force, and surface condition. We also provide a certificate of analysis upon request.
7. Can you produce washers to non-standard dimensions or special specifications?
Absolutely. We have a strong R&D and tooling department that can customize the inner diameter, outer diameter, thickness, and coil geometry to meet your specific requirements. Please provide a drawing or sample for quotation.
8. What industries commonly use double coil spring washers?
These washers are widely used in automotive suspension systems, agricultural machinery, construction equipment, railway fastening, and any bolted joint that experiences vibration or dynamic loading. They are also popular in the oil and gas, mining, and power generation sectors.
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