英制螺纹标准手册（Unified English Screw Thread Standards）

Unified English Screw Thread Standards

Introduction

The Unified English Screw Thread Standards (UN) is a widely accepted system of thread design used mainly in the United States and Canada. The UN system was developed by the Society of Automotive Engineers (SAE) and became the official American National Standard in 1949. This article will provide an overview of the UN system, its advantages, and how it compares to other screw thread standards.

Advantages of the UN System

The UN system has several advantages over other screw thread standards. Firstly, it provides a single system that can be used across a range of applications and industries, simplifying manufacturing and reducing costs. Secondly, the standardized dimensions of the UN system make for a better fit and greater stability than other standards. Finally, the UN system minimizes the likelihood of thread failure due to vibration or other stresses.

Comparison to Other Screw Thread Standards

The most commonly used screw thread standard outside of North America is the Metric system. While both the UN system and Metric system are based on the same fundamental concepts of pitch and diameter, they differ in several key ways. For example, the UN system uses a 60-degree angle for the thread, while the Metric system uses a 55-degree angle. In addition, the two systems use different units of measurement, with the UN system using inches and the Metric system using millimeters. Another frequently used standard is the British Standard Whitworth (BSW), which was the first standardized system of screw threads in the world. While the UN system and BSW share some similarities, such as the use of a 60-degree angle for the thread, the BSW system is largely outdated and has been replaced by more modern standards.

Conclusion

The Unified English Screw Thread Standards are a well-designed and widely accepted system of thread design. The UN system provides many advantages over other screw thread standards, most notably its standardized dimensions and greater stability. While there are other standards available, such as the Metric system and the BSW system, the UN system is the most commonly used in North America and remains a reliable choice for a variety of industrial applications.