What Is a JIC Fitting, Anyway? The Meaning and the Standard

Let's start with the basics. JIC (meaning Joint Industry Council) is the common name for a specific type of flare fitting. The entire design is officially defined by one rulebook: the SAE J514 standard. In today's world, the terms "JIC fitting" and "SAE J514 fitting" mean the exact same thing.

So, what is it? It's a tough, reusable fitting that creates a metal-to-metal seal. There are no O-rings or gaskets. The magic is in the design: a 37-degree flared cone on the male end mates perfectly with a 37-degree seat in the female end. It's a simple, robust connection that's become the workhorse of North American hydraulics for a reason.

The Nuts and Bolts: How the JIC Seal and Thread Works

Understanding this is the key to preventing leaks. A JIC connection works on one simple principle:

• The male fitting has an external 37-degree cone (the JIC flare angle).
• The female fitting has a matching 37-degree seat inside a swivel nut.
• The JIC thread itself is a standard UNF (Unified National Fine) straight thread. Its only job is to provide the clamping muscle to pull the two 37° cones together with incredible force. The threads do not form the seal. The seal happens only on that thin line where the two metal faces meet.

The Blueprint: JIC Fitting Dimensions, Sizes & Pressure Ratings

The SAE J514 spec is what guarantees a JIC fitting from one good manufacturer will work with another's. It lays out all the critical JIC dimensions, from the flare angle to the thread sizes.

JIC Fitting Sizes and Thread Chart (Based on SAE J514)

A common point of confusion is JIC fitting sizes. The "dash size" tells you the TUBE size, not the thread size. The JIC thread dimensions are unique to each dash size. This chart breaks it down.

Dash Size	Nominal Tube OD (inch)	UNF Thread Size	Male Thread OD (approx. inches)
-02	1/8	5/16-24	0.31
-03	3/16	3/8-24	0.38
-04	1/4	7/16-20	0.44
-05	5/16	1/2-20	0.50
-06	3/8	9/16-18	0.56
-08	1/2	3/4-16	0.75
-10	5/8	7/8-14	0.88
-12	3/4	1-1/16-12	1.06
-16	1	1-5/16-12	1.31
-20	1-1/4	1-5/8-12	1.63
-24	1-1/2	1-7/8-12	1.88
-32	2	2-1/2-12	2.50

JIC Fitting Pressure Rating: What Can it Handle?

JIC fittings are built for high-pressure work, but the pressure rating depends on the size. A bigger fitting can't handle as much pressure as a smaller one. As a rule of thumb for steel fittings:

• -04 (1/4") is typically rated for 5,000 PSI.
• -12 (3/4") is typically rated for around 3,500 PSI.
• -24 (1-1/2") might be rated for 2,000 PSI or less.

Always check the manufacturer's spec for the exact size you're using. This pressure drop at larger sizes is why engineers often switch to SAE flanges for big lines.

Real World Use: JIC vs. SAE and How Not to Wreck Them

The JIC Advantage

• It’s Reusable: You can service a line and put it back together again without issue. This is a huge advantage over NPT.
• It’s Everywhere: JIC is the undisputed standard in North America for mobile and industrial equipment.
• It’s Strong: The metal-on-metal design is tough and reliable when installed correctly.

How JIC Fittings Fail (And How to Avoid It)

• Over-tightening is the #1 Killer. Don't put a cheater bar on it to stop a drip. You will crush the cone, crack the nut, and make the leak permanent. Get a copy of the JIC torque specs or learn the "flats from wrench resistance" method.
• A Damaged Sealing Surface. That 37-degree cone is a precision surface. A deep scratch will cause a leak. Inspect it before you install.
• JIC vs SAE 45° Flare: A JIC fitting is a 37-degree SAE fitting (per SAE J514). But there's another common fitting, SAE 45° flare, used in automotive and HVAC. NEVER mix them. They will not seal, and you will destroy both parts.

The Bottom Line: JIC Fittings Explained

A JIC 37° flare fitting is the workhorse of the industry. It’s a simple, strong, metal-to-metal connection defined by the SAE J514 standard. Its reliability is 100% dependent on the quality of the part and the skill of the installer. When you start with a well-made fitting and tighten it right, it's a connection you can absolutely count on.