AN thread
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The AN thread is a particular type of fitting used to connect flexible hoses and rigid metal tubing that carry fluid. It is a US military-derived specification stemming from a joint standard agreed upon by the Army and Navy, hence AN.
AN sizes range from -2 (dash two) to -32 in irregular steps, with each step equating to the OD (outside diameter) of the tubing in 1/16" increments. Therefore, a -8 AN size would be equal to 1/2" OD tube (8 x 1/16 = 1/2). However, this system does not specify the ID (inside diameter) of the tubing because the tube wall can vary in thickness. Each AN size also uses its own standard thread size.
Size comparison
| AN Size | - 2 | - 3 | - 4 | - 5 | - 6 | - 8 | - 10 | - 12 | - 16 | - 20 | - 24 | - 28 | - 32 |
| Tube OD | 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" |
| SAE Thread Size | 5/8-24 | 3/8-24 | 7/16-20 | 1/2-20 | 9/16-18 | 3/4-16 | 5/8-14 | 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 |