Premium Carriage Bolts China Factory and Wholesale Suppliers | DIN 603 ISO 8677
Longze Carriage Bolts, also recognized as Coach Bolts or Cup Head Square Neck Bolts, are precision-engineered fasteners manufactured to rigorous DIN 603, ISO 8677, and ASME B18.5 standards. Specifically designed for high-security and aesthetic applications, these bolts feature a smooth, domed mushroom head and a specialized square neck that anchors firmly into timber or pre-punched metal holes, ensuring a secure, rotation-free installation during tightening.
Ideal for timber construction, security fencing, and public infrastructure, our Carriage Bolts offer a professional, anti-tamper finish that eliminates external drive points. Whether you require the corrosion resistance of Marine-grade SS316 or the structural strength of Grade 8.8 Carbon Steel, Longze provides versatile fastening solutions that balance industrial durability with a safe, streamlined profile for public and commercial environments.
Detailed Parameters
| Compliant Standards | DIN 603 / ISO 8677 / ASME B18.5 / BS 4933 | Metric Size Range | M5 to M24 |
|---|---|---|---|
| Inch Size Range | 1/4" to 1" (UNC / UNF) | Property Class | Grade 4.8, 8.8 / SS A2, A4 |
| Material Options | Carbon Steel, SS304, SS316 | Neck Style | Square Neck / Custom Ribbed |
| Surface Finishes | Zinc Plated, Hot-Dip Galv, Black Oxide | Head Design | Smooth Mushroom / Extra Large |
| Tensile Strength | Up to 800 MPa (Grade 8.8) | Certification | ISO 9001 Certified Production |
Key Advantages
Anti-Tamper Design
The smooth, drive-less rounded head prevents unauthorized loosening from the exterior, making it perfect for security applications.
Self-Locking Neck
The integrated square shoulder "bites" into wood or metal, allowing for efficient one-sided installation without bolt rotation.
Pull-Through Resistance
Extra Large Head variants distribute clamping force over a wider area, protecting soft woods and composite materials from damage.
Aesthetic & Safe Finish
Low-profile mushroom heads reduce snagging hazards in public spaces like playgrounds, parks, and wooden decks.
Extreme Durability
Available in Marine-grade SS316 and Hot-Dip Galvanized coatings to withstand coastal salt spray and harsh outdoor environments.
Global Compatibility
Fully compatible with both Metric (DIN/ISO) and Imperial (ASME) sizing for seamless international project integration.
Product Gallery
Management Platforms
Quality Assurance
ISO 9001 certified production ensures precise square neck dimensions for a perfect locking fit every time.
Mechanical Testing
Rigorous head strength testing ensures the transition can withstand extreme clamping forces without failure.
Coating Verification
Standardized salt spray testing verifies long-term corrosion resistance across all surface treatments.
Export Logistics
Secure 25kg bulk export cartons and fumigation-free pallets for safe global shipping.
Custom Packaging
Available in custom retail kits including matched Nuts and Washers for immediate project deployment.
Rapid Response
Dedicated technical support team providing factory-direct quotes and recommendations within 12 hours.
Material Performance Comparison
| Material Grade | Tensile Strength | Primary Application |
|---|---|---|
| Carbon Steel 4.8 | 420 MPa | General Woodworking / Interior |
| Carbon Steel 8.8 | 800 MPa | Structural Machinery / Heavy Loads |
| Stainless SS304 | ≥ 700 MPa | Outdoor Decks / Modern Furniture |
| Stainless SS316 | ≥ 800 MPa | Marine Structures / Coastal Fencing |
| Zinc Plated Steel | Varies by Grade | Indoor Shelving / General Purpose |
Frequently Asked Questions
Yes, as long as the first metal plate has a square hole punched or laser-cut to accommodate the square neck, preventing the bolt from spinning.
Ensure the hole is the correct diameter. In timber, gently tap the head with a mallet to seat the square neck before tightening the nut.
We strongly recommend Hot-Dip Galvanized or Stainless Steel, as chemicals in pressure-treated wood can rapidly corrode standard zinc plating.
SS304 is suitable for most outdoor uses, while SS316 contains molybdenum, providing superior resistance to chlorides and saltwater in marine environments.
Using a large flat washer under the nut prevents the nut from sinking into the wood, ensuring maximum clamping force and surface protection.
Yes, we manufacture bolts to ASME B18.5 standards with size ranges from 1/4" to 1" (UNC/UNF) for the North American market.
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