What is AN fittings
AN fittings, defined by the MIL-F-5509 and AS4841 standards. The AN thread (also A-N) 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 that dates back to World War II and stems from a joint standard agreed upon by the Army and Navy, hence AN. The Army-Navy involvement is also the origin of the red/blue color combination that was traditionally used in the anodized finishing process.
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-inch increments. Therefore, a -8 AN size would be equal to 1⁄2-inch OD tube. 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.
AN fittings are a flare fitting, using 37° flared tubing to form a metal-to-metal seal. They are similar to other 37° flared fittings, such as JIC, which is their industrial variant. The two are interchangeable in theory, though this is typically not recommended due to the exacting specifications and demands of the aerospace industry. The differences between them relates to thread class and shape (how tight of a fit the threads are), and the metals used.
What is JIC fitting
JIC fittings, defined by the SAE J514 and MIL-DTL-18866 standards, are a type of flare fitting machined with a 37-degree flare seating surface. JIC (Joint Industry Council) fittings are widely used in fuel delivery and fluid power applications, especially where high pressure (up to 10,000 psi) is involved. The SAE J514 standard replaces the MS16142 military specification, although some tooling is still listed under MS16142. JIC fittings are dimensionally identical to AN (Army-Navy) fittings, but are produced to less exacting tolerances and are generally less costly.
AN fittings are made to a much higher standard than JIC/SAE fittings. Also, AN fittings are much more expensive. Using these interchangeably is not recommended.
QC Hydraulics can make both AN and JIC fittings, if you are interested in them, please contact me.