Metric,ANSI／ASME,BS In machining and maintenance, many people run into the same problem:Two fasteners look similar in size and even thread in, but they won’t tighten, and when you remove them, the threads are already damaged. In most cases, it’s not poor machining or low-quality screws—it’s simply the wrong thread system from the start. In practice, most screw threads come from three major systems: Metric threads, Unified threads (ANSI/ASME), and Whitworth threads (BS). Their

Global Fastener Standards When searching for screws, nuts, washers, retaining rings, or dowel pins, you may encounter a long list of standards: DIN, ISO, JIS, ANSI, ASTM, CNS, GB, BS, AS…Why are there so many? What’s the difference? How do you choose the correct one? This article breaks down the origins, differences, and real-world uses of global fastener standards in a clear and easy-to-understand way. --- 1. Why Do We Need Fastener Standards? Fasteners are mating parts —scr