When Can AN Fitting be Substituted for JIC?

JIC and NPT fittings are based on different standards. Main differences between JIC and NPT are in thread specifications and flare angles.

Photo of three Titan Stainless Steel JIC Fittings on white background
Image Description:JIC Fittings

Proper thread identification can be a real cause for concern in hydraulic and automotive applications. This is because there are various standardized ways of expressing the thread sizes of fittings and other components. Moreover, nowadays, most people that understand thread sizes in AN terms tend to be unable to convert from other size references.
Being unable to convert between different ways of expressing thread measurements can be a costly problem. If thread sizes of various components in a hydraulic or automotive application are incompatible with one another, this could cause leakage of hydraulic fluid and subsequent damage to the system.

What is the Difference Between AN and JIC?

AN and JIC are two different standards by which thread sizes are measured. While it is possible to substitute AN fittings for JIC, there are ways in which this could go wrong.
AN stands for Air-Navy and represents design standards agreed upon by the Air and Naval Forces for military-grade applications. AN fittings hence became the standard in military and aviation applications. However, when land and sea applications began to adopt AN fittings, confusion between AN and SAE 37° became more common.
JIC stands for Joint Industries Council, which cleared the confusion by introducing their own standardization for the specifications of this fitting. Although lower in terms of quality than AN fittings, JIC became widely used for hydraulic applications, and soon the SAE adopted this new standard as well.
AN and JIC are different in the way the union between the male and female parts is described. JIC describes the thread diameter in imperial units (inches). The number quoted as a fraction of an inch is followed by ‘JIC’ to confirm the method. For example, 3/4 JIC.
AN, on the other hand, describes the thread diameter as a dash size with numbers that range from -02 (dash two) to -32 (dash thirty-two) in irregular increments. For example, -08 AN.
Importantly, 3/4 JIC and -08 AN are the very same thing. They are just different standards of expressing the thread size or diameter.

Substituting AN Fitting for JIC

If you are going to substitute an AN fitting for a JIC component, you will have to use a JIC or AN union, which is a UNF thread in which the male has a convex seat and the female has a concave seat. Importantly, the seat on both AN and JIC is 78°.
The table below lists AN thread and size information along with conversions into the corresponding JIC thread sizes. Although the outside measurement is considered to be the correct way to measure thread size, the table also includes the inside measurements, in case you only have access to a female AN thread for reference.