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Carriage bolts (also known as coach bolts) are characterized by a domed round head and a square neck beneath the head. The square neck embeds into the material during installation, providing a self-locking feature that prevents rotation while tightening the nut. This eliminates the need for a separate wrench on the head, enabling single-sided assembly.
Zhejiang Chance & Union supplies carriage bolts in carbon steel, alloy steel, and stainless steel, with plain, zinc-plated, or hot-dip galvanized finishes. They are available in metric and inch sizes, with rolled threads for consistent fit and fatigue resistance.
At a Glance
- Head: Domed round head
- Neck: Square or ribbed neck (self-locking)
- Thread: Rolled · coarse or fine
- Grades: 4.6 · 4.8 · 8.8 · stainless
- Finish: Plain · zinc · HDG · phosphate
Typical Specifications
Key Design Features
Square Neck
The square neck beneath the head embeds into the material, preventing rotation during nut tightening. This enables single-wrench installation and ensures consistent clamp load.
Domed Head
Smooth, rounded head profile reduces snagging and provides a finished appearance. Ideal for applications where the head remains visible or exposed to contact.
Rolled Threads
Threads are rolled rather than cut, resulting in improved fatigue strength, consistent class fit, and a smoother surface finish for reliable torque control.
Production & Supply Chain
Manufacturing Capability
- Multi-station cold headers for high-volume production
- Automated heading and threading lines
- Heat treatment for grade-specific properties
- Coating lines for consistent finish quality
- Support for both prototyping and mass production
Logistics & Inventory
- Permanent stock of 5,000+ specifications
- Storage capacity exceeding 2,000 tons
- 24-hour order processing
- 3-day rapid shipping for standard sizes
- Lead time for custom orders: 7–25 days
Quality Assurance & Testing
Testing Capabilities
- Optical sorting for 100% dimensional inspection
- 72-hour salt spray test per ASTM B117
- Tensile testing per ASTM E8
- Hardness testing per ASTM E18
- Ex-factory pass rate: 99.9%
Quality Systems
- ISO 9001 certified
- IATF 16949 certified
- Full traceability with heat numbers
- Material test reports (MTR) provided
- ≤30-minute factory response time
Common Applications
- Wood construction: Timber framing, decking, pallets, and wooden bridges
- Sheet metal assemblies: HVAC equipment, electrical enclosures, and metal building components
- Furniture manufacturing: Industrial shelving, workbenches, and modular systems
- Agricultural equipment: Grain bins, fencing, and livestock equipment
- General industrial: Conveyor systems, machine guards, and structural supports
R&D & Engineering Support
With nearly 20 years of industry experience, our R&D team has developed over 1,000 custom fastener solutions for clients across 25 countries. We invest 5% of annual revenue into R&D, focusing on:
- Joint design analysis: Evaluation of material compatibility and clamp load requirements
- Custom development: Non-standard head dimensions, neck configurations, and materials
- Prototyping: Rapid sample production for fit and performance validation
- Coating advisory: Selection based on corrosion resistance and aesthetic requirements
Selection Guide for Carriage Bolts
When selecting carriage bolts for your application, consider these factors:
- Material compatibility: Carbon steel for general use; stainless steel for corrosion-resistant or hygienic applications; alloy steel for higher strength requirements.
- Neck type: Standard square neck for most wood and metal applications; ribbed neck for softer materials where additional grip is needed.
- Finish: Plain for painted or coated assemblies; zinc plated for moderate corrosion protection; hot-dip galvanized for outdoor exposure.
- Length: Ensure sufficient thread engagement beyond the nut; consider material thickness and clamping requirements.
