Overview of Bolt Standards

Bolts, known as the “rice of industry,” rely on standardization to ensure the reliability and interchangeability of mechanical connections. Globally, bolt standards are primarily divided into three major systems: ISO (International Organization for Standardization) , GB (Chinese National Standards) , and regional standards such as ASTM (American Society for Testing and Materials) .

Standard systems generally cover three aspects: dimensional specifications, mechanical properties, and acceptance criteria.

1. Chinese National Standards (GB/T)

China has been actively updating its fastener standards to align with international advanced levels. According to the 29th National Standard Announcement (October 2025), many bolt standards have been updated and will come into effect in February 2026.

• Product Dimension Standards: Include general hexagon head bolts such as GB/T 5780 (Product grade C) and GB/T 5782 (Product grades A and B), as well as fine pitch thread series like GB/T 5785.
• Mechanical Property Standards: Primarily follow the GB/T 3098 series. For example, GB/T 3098.1 specifies the hardness and property classes (e.g., the classic classes 8.8, 10.9) for carbon steel and alloy steel bolts.
• Specific Type Standards: Include standards for hexagon socket head cap screws ( GB/T 70 series) and threaded rods ( GB/T 15389 ).

2. International Standards (ISO)

ISO standards represent the most universal technical language in global trade. Technical work on bolts is primarily handled by ISO/TC 2 (Fasteners Technical Committee) .

• Core Property Standard: ISO 898-1 is a landmark standard specifically specifying the mechanical properties of bolts, screws, and studs made of carbon steel and alloy steel. It defines core indicators such as hardness, tensile strength, and yield strength.
• Product Standards: The ISO system includes numerous detailed specifications for specific bolts, such as ISO 4014 (Hexagon head bolts — Product grades A and B) and ISO 4762 (Hexagon socket head cap screws).

3. American Standards (ASTM)

In international trade, ASTM standards also hold an important position, often required for specific market applications.

• Nonferrous Metal Standard: ASTM F468 specifies the technical requirements for nonferrous metal bolts (e.g., copper, aluminum alloys) for general use, distinguishing them from standard steel bolt specifications.

Conclusion

From GB/T 5780 to ISO 898-1, bolt standards continue to evolve with industrial demands. By strictly defining material, dimensions, and mechanical properties, these standards ensure the safety and uniformity of connections across all fields, from aerospace and heavy machinery to everyday furniture.