JIC vs SAE 45 Degree Flare Fittings: How to Tell Them Apart
Sep 20th 2023
JIC and SAE 45 degree flare fittings are both flare-style connections, but they are not the same seal. JIC uses a 37 degree flare seat. SAE 45 degree flare fittings use a 45 degree seat.
That angle difference is enough to create a leak or damage the seat. A thread that starts smoothly does not prove that the flare surfaces match.
What Hydraulic Flare Fittings Do
A flare fitting seals when two angled metal surfaces meet. The threads provide clamping force, while the flare seat makes the fluid seal.
Because the seal is made at the cone and seat, the flare angle must match. If a 37 degree cone is tightened into a 45 degree seat, the contact area is wrong and the fitting may leak under pressure.
JIC Fitting Basics
JIC fittings are SAE 37 degree flare fittings used widely in hydraulic hose assemblies, tube connections, and industrial fluid power systems. They are common on mobile equipment, agricultural machines, construction equipment, and hydraulic power units.
JIC fittings are typically chosen for higher hydraulic pressure service when the system is designed around 37 degree flare connections. Steel and stainless steel versions are common, with brass used in more limited applications.
SAE 45 Degree Flare Basics
SAE 45 degree flare fittings are also flare connections, but the sealing angle is different. They are often associated with lower-pressure fluid, fuel, refrigeration, air-conditioning, and some automotive-style service.
They should not be substituted for JIC hydraulic fittings just because the threads appear similar. The angle and intended pressure range must be checked first.
The Main Differences
The first difference is the flare angle: JIC uses 37 degrees, while SAE flare uses 45 degrees. The second difference is typical application. JIC is a hydraulic standard; SAE 45 degree flare is often found in lower-pressure or non-hydraulic service.
The third difference is compatibility. A JIC male end and an SAE 45 degree female end may partially thread together, but the seal faces do not match. That kind of mismatch can damage both parts.
How to Identify the Fitting
Use calipers to measure thread diameter and a thread pitch gauge to confirm pitch. Then inspect the flare angle with a gauge, reference fitting, or known drawing.
Do not identify the fitting by thread size alone. Thread size, dash size, and flare angle all need to agree before a replacement is selected.
Common Selection Mistakes
The most common mistake is mixing JIC and SAE 45 degree flare because both are straight-thread flare fittings. Another is ignoring the application pressure and using a lower-pressure flare style where a hydraulic JIC connection is required.
Material can also be misapplied. Brass may be acceptable in some lower-pressure systems, but hydraulic pressure, vibration, fluid compatibility, and corrosion exposure may require carbon steel or stainless steel.
When to Use Each Connection
Use JIC when the hydraulic system calls for SAE 37 degree flare hose ends, tube adapters, or serviceable hydraulic connections. Use SAE 45 degree flare only where the component, equipment manual, and pressure range specify that style.
If the system must transition between different standards, use a properly rated adapter with the correct geometry on each side. Never use torque to make mismatched flare angles seal.