JIC 37° Fittings & Adapters

In JIC 37° connections, sealing is achieved by the 37° conical surfaces of the male and female parts seating against each other; the UNF thread only holds the parts together. This connection type is defined in SAE J514 and ISO 8434-2. It is widely used on machines built to American standards, in mobile hydraulics, and in aviation ground support and test equipment. The parts searched for in the field as "JIC fittings" or 37° flare fittings are in this group.

Types of JIC fittings

• JIC male x male adapters: connect two hose or tube ends with female swivel nuts.
• Conversion adapters: join a JIC 37° male end to an NPT or BSPP male end.
• 90° female swivel elbows: route the hose to the port without twisting it.
• ORB port adapters (SAE O-ring boss): UNF straight thread and O-ring on the port side (ISO 11926 / SAE J1926).
• Plugs and caps: sealing off lines, pressure testing and maintenance.

JIC fitting sizes: dash size and UNF thread

JIC sizes are usually referred to by their "dash" number. The dash number gives the tube OD in sixteenths of an inch: -8 means 8/16, i.e. 1/2 inch tube. The threads for common sizes are as follows:

Connections commonly confused with JIC

• 45° SAE flare: 45° flare connections used on refrigeration and low-pressure lines share the same thread in some sizes, but because the cone angle is different, they will not seal against a JIC fitting.
• ORFS: sealing is provided by an O-ring on the flat face; it does not mate with a JIC cone.
• Port side: if the pump or valve port is UNF, an ORB port adapter is usually required; a JIC male end does not fit directly into the port.

Assembly and tightening

The conical surface must be clean and free of scratches; no sealing tape or liquid sealant is applied to JIC threads or cones. Tightening is done to the table torque or by the flats-from-wrench-resistance method (FFWR), turning a specified number of hex flats past the hand-tight position. Overtightening crushes the cone and causes a leak at the next assembly; a connection forced into place with misalignment also loosens under vibration. To prevent galling on stainless-to-stainless threads, keep the threads clean and use a suitable anti-seize compound where necessary.

Which industries use them?

Mobile hydraulics and compact power units in the defense industry, ground support and hydraulic test equipment in aviation, American-made deck machinery and cranes, and the hydraulic circuits of imported machines in rolling mills and board mills. Stainless steel JIC fittings are preferred where carbon steel equivalents of the same size rust in salty, humid environments.