Metric Carriage Bolts

In the field of industrial connections, standard hexagonal bolts are not always the ideal solution. When connecting wood to metal, or when working in confined spaces where a second wrench cannot be used to hold the bolt in place, ordinary fasteners are often unsuitable. In these situations, Metric Carriage Bolts, also commonly known as square-neck bolts, become the optimal solution due to their unique design.

We are a source factory with over 15 years of experience in fastener research and development and manufacturing. For more than a decade, we have collaborated extensively with thousands of construction companies, agricultural equipment manufacturers, and wood processing plants worldwide. We understand that in heavy machinery, outdoor fencing, and timber structures, connectors must possess both high tensile strength and secure anti-loosening properties.

Core Technological Advantages

1. Unique Square Neck Anti-Loosening Design: Stable and Efficient

More reliable self-locking and anti-loosening: The square neck design is the core advantage of metric carriage bolts. The square neck below the bolt head tightly grips the hole wall of the connected part (mostly wood or soft metal) when the nut is tightened, generating strong friction. This fundamentally prevents the bolt shaft from rotating with the nut, avoiding loosening and stripping problems caused by vibration, and ensuring long-term connection stability.

Efficient and cost-effective installation: Only one wrench is needed to tighten the nut during operation, eliminating the need for a second wrench to hold the bolt on the other side. This feature is particularly advantageous in high-altitude work, single-sided operations, or confined spaces, significantly improving construction efficiency and saving considerable labor costs.

Adaptable to complex connection scenarios: Whether it's cross-material connections between wood and metal, or adapting to worn mounting holes in the repair of old equipment, the square neck design perfectly adapts, solving connection problems that ordinary fasteners cannot handle.

2. Mushroom Head Safety Design: Aesthetic and Practical

Safe and scratch-resistant:  The rounded hemispherical (mushroom head) design has a smooth surface without sharp edges, preventing clothing from snagging or skin from being scratched during use. This makes it extremely safe, especially suitable for amusement facilities, park benches, livestock fences, and other scenarios involving frequent contact with people or animals. Anti-theft and anti-vandalism: The screw head design without screwdriver slots makes it difficult for unauthorized personnel to disassemble with ordinary tools, providing a certain degree of anti-theft and anti-vandalism protection, better safeguarding the security of outdoor facilities, public equipment, and other assets.

3. Excellent Mechanical Performance, Strict and Controllable Standards

High-quality materials:  Made from high-quality medium-carbon steel or alloy steel such as Q235 and Q345, and processed through rigorous cold heading and heat treatment processes, precisely balancing the toughness of the bolt core and the surface hardness, ensuring that the bolts have extremely high tensile strength and impact resistance, and are not easily broken or deformed.

Precise adaptation to multiple standards: Strictly manufactured in accordance with DIN 603 (German standard, large mushroom head), GB/T 14 (Chinese standard, large semi-circular head), and GB/T 12 (Chinese standard, small semi-circular head), with layered control of dimensional accuracy and interchangeability, ensuring perfect compatibility with accessories of the same specifications, meeting the standardized assembly needs of different regions and industries.

Core Technical Parameters

Typical Application Scenarios

With years of industry service experience, our metric carriage bolts have been successfully applied in numerous demanding environments, becoming a trusted choice for many customers:

1. Agriculture and Animal Husbandry: Used for pasture fences, livestock sheds, and feed trough fixation. The unique anti-loosening design effectively resists impacts and pulling from livestock, and the hot-dip galvanized version can withstand corrosion from manure and humid environments, ensuring a long service life and significantly reducing maintenance costs and workload for farmers.

2. Infrastructure and Guardrails: Suitable for fixing key facilities such as highway guardrails, bridge crash barriers, and municipal fences. The square neck anti-loosening design ensures that the bolts will not loosen under conditions such as vehicle vibration, making them an important connecting component for ensuring public safety.

3. Outdoor Landscaping and Woodworking: Used for connecting heavy timber beams, villa terraces, gazebos, park benches, and other outdoor wooden structures. They are both aesthetically pleasing and sturdy, unlike ordinary nails that can easily loosen and pull out, combining practicality and decorative appeal.

4. Industrial Maintenance and Heavy Equipment: Used for fixing machine guards, conveyor belt supports, etc., especially in the maintenance of old equipment. The square neck design perfectly adapts to worn mounting holes, allowing for quick repair and assembly, ensuring the normal operation of the equipment.

Company Strength and Quality Assurance

We are Ningbo Gangtong Zheli Fasteners Co., Ltd. Since our establishment in 2001, we have built a mature full-chain system for fastener research, development, production, and sales. Our factory is located in the Zhenhai Chemical Zone of Ningbo, and our headquarters and foreign trade sales department are located in the Ningbo Jiangdong Eastern Business Center. The factory covers an area of 15,000 square meters, with a stable monthly production capacity of 2,000 tons and annual sales exceeding US$15 million. The company is equipped with a professional R&D team, a full-process supply chain management system, and large-scale warehousing facilities, focusing on the production of various fasteners and providing integrated MRO procurement and distribution services for metal fasteners, comprehensively meeting customers' diverse procurement needs.

In the fastener industry, quality is life. Through rigorous control throughout the entire process, we ensure that every metric carriage bolt is reliable and durable:  During the raw material warehousing stage, each batch of raw materials undergoes spectral analysis to precisely control the chemical composition, eliminating material defects from the source; during the production process, the dimensional accuracy and thread quality of the bolts are fully inspected to prevent unqualified semi-finished products from entering the next process; in the finished product stage, we conduct rigorous salt spray tests (hot-dip galvanized products can withstand over 72 hours without red rust), tensile strength tests, and other tests to comprehensively verify corrosion resistance and mechanical strength. The company fully implements the ISO 9001 quality management system standard and can provide material reports (MTC) according to customer needs, ensuring that the product's chemical composition and mechanical properties fully meet the standards. At the same time, the products comply with the RoHS environmental protection directive, do not contain harmful substances, and are harmless to the environment and human body.

Our product range is extensive, covering heavy-duty hexagonal bolts, heavy-duty hexagonal nuts, threaded rods, studs, washers, screws, etc., with materials including carbon steel, alloy steel, and stainless steel. We strictly adhere to international standards such as DIN, ISO, EN, JIS, ASTM/ANSI/ASME/SAE, BS, and AS. Our products are exported to North America, Europe, Australia, Southeast Asia, the Middle East, Latin America, and many other regions, and are suitable for various fields such as building steel structures, bridges, oil pipelines, mechanical equipment, ships, and railways.

Reasons to Choose Us

1. Direct supply from the source factory, superior quality and price: As a physical manufacturer located in Ningbo, the fastener capital of China, we have advanced cold heading, heat treatment, and surface treatment production lines, achieving independent production throughout the entire process from raw materials to finished products. Without intermediaries, we can provide customers with highly competitive ex-factory prices, while controlling quality throughout the process. We have sufficient stock of standard specifications and can quickly respond to delivery needs.

2. Technology-driven, rapid response: Our engineering team has rich industry experience and is familiar with the standard requirements of different regions around the world. We can provide professional non-standard customization (OEM/ODM) services based on drawings or samples provided by customers; we can quickly respond to and provide targeted solutions to technical problems encountered by customers during use. 3. Global Service Experience, Hassle-Free Cooperation: Our products have been exported to North America, Europe, Australia, and Southeast Asia, and we have a comprehensive logistics and after-sales service system. We can accurately match the procurement needs of global customers and are committed to establishing long-term and stable cooperative relationships with our clients.