The AN (Aerospace Standards) thread is a particular type of fitting used to connect flexible hoses and rigid metal tubing that carry fluid. It is manufactured to MIL-F-5509 per AN (Air Force - Navy Aeronautical Standard) and AND (Air Force Navy Aeronautical Design Standard). AN fittings are a flare fitting, using 37° flared tubing to form a metal-metal seal.
SAE thread is Industrial 37-degree flare fittings are manufactured to meet SAE J514/ISO-8434-2. Straight threads are per MIL-S-8879C now SAE-AS8879. The differences between AN and SAE thread relate to the thread class and shape (how tight a fit the threads are), and the metals being used. As follow:
AN thread Fitting: 1/2-20 UNJF-3B
SAE Industrial fitting: 1/2-20 UNF-2B
NPT Pipe Threads: NPT pipe threads are your traditional tapered thread fittings and have been used for 100 years. They are available in low-pressure black iron and brass, and high-pressure steel and stainless steel. This connection style is used in pneumatic and process systems and hydraulic systems.
Note that 37° AN and 45° SAE fittings and tooling are not interchangeable due to the different flaring angles. Mixing them can cause leakage at the flare.
|
AN size |
-2 |
-3 |
-4 |
-5 |
-6 |
-8 |
-10 |
-12 |
-16 |
-20 |
-24 |
-28 |
-32 |
|
Tube OD (inches) |
1⁄8 |
3⁄16 |
1⁄4 |
5⁄16 |
3⁄8 |
1⁄2 |
5⁄8 |
3⁄4 |
1 |
1 1⁄4 |
1 1⁄2 |
1 3⁄4 |
2 |
|
Nominal hose ID (inches) |
1⁄8 |
3⁄16 |
1⁄4 |
5⁄16 |
3⁄8 |
1⁄2 |
5⁄8 |
3⁄4 |
1 |
1 1⁄4 |
1 1⁄2 |
1 3⁄4 |
2 |
|
Actual hose ID (inches, approximate) |
1⁄16 |
1⁄8 |
3⁄16 |
1⁄4 |
5⁄16 |
7⁄16 |
1⁄2 |
5⁄8 |
7⁄8 |
1 1⁄8 |
1 3⁄8 |
1 5⁄8 |
1 3⁄4 |
|
SAE thread size |
5⁄16-24 |
3⁄8-24 |
7⁄16-20 |
1⁄2-20 |
9⁄16-18 |
3⁄4-16 |
7⁄8-14 |
1 1⁄16-12 |
1 5⁄16-12 |
1 5⁄8-12 |
1 7⁄8-12 |
2 1⁄4-12 |
2 1⁄2-12 |
|
Pipe thread size (NPT) |
1⁄8-27 |
1⁄4-18 |
3⁄8-18 |
1⁄2-14 |
3⁄4-14 |
