JIC 37° Flare Fittings

What it is

The JIC 37° flare fitting is defined in SAE J514 and internationally in ISO 8434-2. A male fitting has a 37° cone-shaped nose (measured from the center line) and a straight UN/UNF thread. The female has a swivel nut and a matching 37° seat. Tightening the nut draws the two cones together, and they seal by metal contact. No O-ring, tape or sealant is used. On tube, the end is flared to 37° and held with a sleeve and nut. On hose, the fitting is crimped or reusable. Sizes use dash numbers in sixteenths of an inch of tube outside diameter.

How to identify

1. Look for a cone-shaped male nose with no O-ring.
2. Measure the thread outside diameter with calipers and the pitch with a thread gauge. See the JIC 37° thread size chart for each dash size.
3. Check the seat angle with a seat angle gauge. The gauge should sit flat on a 37° flare.
4. If the angle is 45°, it is an SAE 45° flare fitting. If the nose has an O-ring, it is not JIC.

JIC 37° vs look-alikes

Key points

• JIC seals on the flare only. Thread tape or sealant does nothing for the seal and can contaminate the system.
• Some SAE 45° and JIC parts share threads and will screw together but will not seal. Always check the angle.
• Assembly uses a torque value or a flats-from-wrench-resistance method. Get the values from the fitting maker.
• Use carbon steel, stainless or brass fittings as the system and media require. Do not mix materials without checking galvanic and pressure limits.

Common mistakes

• Mixing JIC and SAE 45° parts because the nut threaded on.
• Over-tightening to stop a leak, which cracks the flare or the nut. A damaged seat must be replaced.
• Reusing a scratched or dented flare.
• Calling every swivel nut fitting "JIC" without checking the seat.

Governing standards: SAE J514 (hydraulic tube fittings); ISO 8434-2 (37° flared connectors); fitting manufacturer assembly data.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.