Key Findings
Global fastener standards fall into two non‑interchangeable systems: metric and imperial (inch‑based). ISO and EN push metric‑system harmonization, while US standards combine ANSI and multiple association specifications including ASTM, ASME, SAE and IFI‑8. Export‑oriented fastener users must distinguish international, regional, national and association‑level documents to guarantee part interchangeability.
| Standard Level | Representative Codes | Main Features |
|---|---|---|
| International | ISO | Global metric‑system baseline for fasteners |
| Regional (Europe) | EN | EU harmonized standards, widely adopted by European nations |
| National | DIN, BS, ANSI, GB | Local adoption / modified versions of ISO‑EN documents |
| US Association | ASTM, ASME, SAE, IFI‑8 | Inch‑system core specifications; IFI‑8 is US inch‑fastener manual |
Metric fastener specifications under ISO‑EN have achieved high global unification; many countries such as China convert ISO standards into their national GB standards with minimal edits. The inch‑based imperial system prevails across USA, UK, Australia and parts of the Middle East, and cannot mechanically interchange with metric fasteners.
US fastener rules are complex due to overlapping association‑issued standards. IFI‑8 (2011 8th edition) integrates ASTM, ASME and SAE requirements and is known as the “Bible of American Inch Fasteners”. For cross‑border fastener procurement and export work, clarify system type (metric vs inch) and standard source to avoid assembly mismatch caused by incompatible dimensions and threads.
Fastener standards are among the most highly standardized, complete, and fundamental product standards.
On the one hand, international and national fastener standards pursue simplification through standardization; on the other hand, due to the continuous improvement of quality requirements and the pursuit of technological progress, more products, newer technologies, higher quality clauses, and more rigorous basic technical standards are bound to emerge, making the standards more complex.
Both trading parties hope that international and national fastener standards can tend to be unified, ensuring universality and improving interchangeability.
However, due to the differences in the imperial and metric measurement systems, the two major international standard systems cannot be interchanged, especially the form and size of fasteners and basic technical conditions cannot be completely unified.
Moreover, the complex relationship between American fastener product standards and basic technical standards, the nesting of standards within standards, and the interweaving of basic technical standards from various associations make the content of the standards completely different from metric standards.
The American Industrial Fastener Institute (IFI) released the eighth edition of the “IFI Inch Fastener Standards Compilation Manual” (commonly known as the “IFI-8 Inch American Standard”) in April 2011. Compared with the seventh edition, over 50% of the content in the IFI-8 manual has been updated, with some being major updates.
The manual version has also been completely redesigned. It collects all the latest fastener standards issued by the American ASTM, ASME, SAE, and IFI associations, effectively guiding the production, technology, and quality inspection of American fasteners. Americans refer to it as the “Bible of Fasteners”.
The number of fastener standards in Germany and the United States is vast. It is neither economical nor practical for fastener enterprises to collect and organize standards from various countries on their own.
This article mainly collects and briefly describes the technical quality and interrelationships among standards in the latest European and American fastener standards, including form and size, shape and position tolerances, thread inspection, mechanical properties, testing methods, inspection procedures, surface defects, and surface treatment, and recommends them to colleagues engaged in fastener production, research, inspection, export trade, and management for reference.
1. Fastener Standard System
International and national fastener product and basic technical standards have detailed requirements and provisions, forming a very complete and serialized standard system.
Internationally, there are two relatively independent standard systems for fasteners: metric standards and imperial standards. The imperial standard system can be further divided into two categories: countries mainly using the inch system, such as the United States and the United Kingdom, as well as Australia and the Middle East.
These two major standard systems (metric fasteners and imperial fasteners) cannot be unified or interchanged in terms of form and content. They are relatively independent and can only be used as references for each other.
The ISO International Organization for Standardization and EN European Community Harmonized Standards strive to unify and harmonize standards through standardization. Currently, the product and basic technical standard systems for metric fasteners have been unified.
All metric countries generally directly adopt ISO standards, or make minor modifications without changes, converting them into their own standards. China is a representative country that has basically adopted or equated to ISO standards.
2. Fastener Standards
Fastener standards are classified by hierarchy into international standards, regional standards, national standards, and association standards.
2.1 International or Regional Standards
International Standards: ISO
Regional Standards: EN (European Community Standards)
2.2 National Standards
Germany: DIN, DIN ISO, or DIN EN ISO
For example: DIN ISO – German standards that directly use international standards or European Community standards. American ANSI
British BS, BS ISO or BS EN ISO
For example: BS ISO – British standards that directly adopt international standards or EC standards
Japanese JIS
Italian UNI
French NF
Australian AS
Chinese GB
Indian IS
2.3 Association standards (quasi-national standards)
American Society for Testing and Materials ASTM
American Society of Mechanical Engineers ASME
Society of Automotive Engineers SAE
Industrial Fasteners Institute IFI
Federation of Japanese Industrial Standards FIJ
If you are looking for quality fasteners, please visit us here https://hktl-fastener.com/.
