The AN thread ensures bombproof connections

If you've ever been asked to name various types of threads off the top of your head at 3 a.m., how many would you manage to recall? A handful, perhaps, but the AN thread might not immediately spring to mind unless you're involved in motor sports. The AN thread is one of those distinctive thread types with a rich history and very specific applications. For most craftsmen, it’s a thread you might never encounter in your career, but when you do, understanding it becomes crucial. That’s where we step in—here’s everything you need to know about the AN thread.

Origins of the AN Thread

The AN thread isn’t something you’d typically associate with this part of the world since it’s deeply rooted in American culture. The letters A and N stand for Army Air Corps and Navy, respectively. During World War II, these two divisions of the U.S. military developed the AN thread to meet the demands of the aerospace industry. Initially confined to the military sector, the AN thread has since found applications far beyond its original scope.

What Makes the AN Thread Special?

The AN thread is primarily used for fittings, specifically connecting flexible hoses to rigid pipes. It’s particularly popular in situations involving heavy loads, vibrations, or high-pressure environments. One common application is in flared fittings, where the pipe ends are shaped to create a tight seal. These fittings feature a 37° cone angle, ensuring a secure connection when tightened.

Color Coding and Key Specifications

Historically, AN thread fittings came in red and blue to symbolize the collaboration between the Air Corps and Navy. While this added a touch of flair to workspaces, modern fittings no longer follow this convention. Instead, the sizing of AN threads is based on dash sizes, denoted by a dash followed by a number. For example, an AN thread might be labeled as -2, -6, or -24. Each dash size corresponds to the outer diameter in 1/16 inches. To calculate the dash size, multiply the outer diameter in inches by 16. For instance, an AN thread with an outer diameter of 5/8 inch would have a dash size of -10 (since 5/8 × 16 = 10).

Challenges with Inner Diameter

One potential source of confusion lies in the fact that the diameter specifications listed in AN thread tables refer to the outer diameter. Depending on the material and intended use, the ratio between the outer and inner diameters can vary significantly. To address this, AN threads are accompanied by a separate designation system, appending a number to the abbreviation AN. For example, the AN6 thread matches the -6 AN thread, but their actual dimensions may differ slightly.

Applications of the AN Thread

While the AN thread remains prominent in the aerospace industry and certain industrial sectors in the U.S., it’s also well-known in Germany through its role in the automotive industry, particularly in motorsports. Flare fittings with AN threads are widely used for creating robust, leak-proof connections in vehicle fluid systems. These fittings come in countless variations, including different colors and shapes, and are often identified by their Dash sizes.

Alternatives to the AN Thread

Though the AN thread hasn’t changed the game entirely, it does face competition, especially in motorsports. Its dimensions align closely with those of SAE flare fittings, which also feature 37° angles. However, it’s essential to exercise caution here. Even though the threads themselves match, the fittings are not interchangeable due to differences in design. Similarly, JIC flare fittings share the same 37° angle but aren’t always compatible with AN threads. Always check compatibility before combining components, especially in critical applications like aviation.

Still curious about threads? We’ve got you covered! Our BAER online store offers a wide selection of threading tools for every standard and application. If you have any lingering questions, our friendly customer service team is just a message away.