What type of flared fitting is used in hydraulic systems?

• A. JIC 37 degrees
• B. NPT 90 degrees
• C. JIS 60 degrees
• D. SAE 45 degrees

Answer: (A)

In hydraulic systems, the flare fitting type that creates a tight seal with a specific cone angle is the JIC flare, which uses a 37-degree seating. The tube end is flared to 37°, and when the nut is tightened, that flare presses against a matching 37-degree seat in the fitting. This metal-to-metal contact forms a reliable seal that can handle high-pressure hydraulic service.

This is different from NPT, which relies on tapered threads (not a conical seating) to seal. It’s also different from a JIS 60-degree system, which uses a 60-degree cone and is a separate standard, and from an SAE 45-degree flare, which uses a 45-degree seat and a different style of flare/seating. So the 37-degree JIC flare is the correct type for typical hydraulic hose fittings.