JIC Fittings Guide: 37° Flare Sizes, Identification & Torque

JIC fittings are one of the most widely used hydraulic and fluid-power connections in industrial, agricultural, and mobile equipment. Their 37-degree flare seat creates a metal-to-metal seal that withstands high pressure without thread sealant—but only when mated correctly. Misidentifying a JIC fitting and pairing it with an SAE 45-degree flare or AN fitting can cause dangerous leaks. This guide explains what JIC fittings are, how to identify them, how they compare to look-alike standards, and how to assemble them correctly.

Apex Flow Solutions stocks flareless (bite-type) JIC fittings and SAE 45-degree flare lines. Whether you are building a hydraulic circuit from scratch or replacing a field fitting, understanding flare angles and dash sizes is the starting point.

What Is a JIC Fitting?

JIC stands for Joint Industry Council. JIC fittings conform to SAE J514 (and the equivalent ISO 8434-2 standard) and are defined by a 37-degree included half-angle flare seat. The male fitting has a cone ground to 37 degrees from the centerline; the female swivel nut has a matching 37-degree seat. When the nut is torqued, the two metal cones mate and cold-weld slightly, creating a leak-free seal at pressures up to 10,000 psi depending on tube size and material.

Key characteristics of JIC fittings:

• Flare angle: 37 degrees (measured from the fitting centerline, not the face)
• Thread form: Unified National Fine (UNF)
• Seal mechanism: Metal-to-metal flare-seat contact—no O-ring, no sealant
• Standard: SAE J514 / ISO 8434-2
• Common materials: Carbon steel, stainless steel, brass
• Typical applications: Hydraulic lines, fuel systems, lubrication circuits, instrumentation tubing

JIC fittings are sized by dash numbers that correspond to tube outside diameter in sixteenths of an inch. A -8 JIC fitting connects to 1/2-inch OD tubing. The same dash-number system is used across hydraulic fitting families, which is one reason cross-standard confusion is so common in the field.

JIC vs. SAE 45° Flare vs. AN Fittings

Three fitting families share similar geometry and even identical thread dimensions at some sizes, yet they must never be interchanged. The difference is the flare angle: 37 degrees for JIC/AN, 45 degrees for SAE flare. A 37-degree male seated in a 45-degree female (or vice versa) contacts only at the lip of the cone rather than across the full seating surface. The resulting line contact cannot hold pressure reliably and will leak or blow out under vibration.

JIC and AN are thread-compatible at matching dash sizes—the threads will engage and the 37-degree seats will mate. In practice, AN fittings are manufactured to tighter tolerances and are used in aerospace and motorsport. JIC is the industrial standard. Do not mix them in safety-critical systems without engineering review, but a JIC -6 and an AN-6 will form a usable seal.

JIC and SAE 45-degree flare cannot be mixed under any circumstance. Even though threads may start to engage at some sizes, the seat geometry mismatch makes every such connection a failure waiting to happen.

JIC Dash-Size & Thread Chart

The table below covers the most common JIC dash sizes per SAE J514. Thread sizes are UNF (Unified National Fine). Tube OD is measured with calipers on the outside of the tube wall—not the bore.

Working pressures are guidelines for seamless steel tubing. Stainless steel and brass ratings differ; always consult the fitting manufacturer's pressure-rating tables for your specific material and wall thickness.

How to Identify a JIC Fitting

Identifying an unknown fitting in the field requires three tools: a thread pitch gauge, a caliper, and a seat-angle gauge (or a known JIC fitting used as a reference).

1. Measure the thread OD. Use calipers on the male thread's major diameter. Cross-reference against the dash-size chart above. For example, a 3/4-inch major diameter suggests -8 JIC (3/4-16 UNF).
2. Confirm thread pitch. Use a thread pitch gauge to verify the thread count per inch. JIC uses UNF (fine) threads. If you measure a coarser pitch, the fitting may be metric or BSPP—see our NPT/BSPP/JIC Thread Identification Guide for details.
3. Check the seat angle. Hold the fitting next to a known 37-degree gauge or reference fitting. The 37-degree JIC seat looks more shallow and gradual than the 45-degree SAE flare, which has a steeper, sharper cone. A protractor or angle gauge confirms the difference precisely.
4. Look for the swivel nut. JIC female fittings almost always have a free-spinning swivel nut. The nut captures the flared tube end or the female seat and spins freely before tightening. This is a useful quick identifier.
5. Check for an O-ring groove. Standard JIC has no O-ring. If you see an O-ring groove behind the flare seat, the fitting may be an ORB (O-ring boss) or ORFS (O-ring face seal) hybrid—different standards with different sealing methods.

When you have both a caliper measurement and a confirmed seat angle, you can select the correct replacement from the dash-size chart with confidence.

No Sealant on Flare Seats

JIC fittings seal metal-to-metal. Applying PTFE tape, pipe dope, or any thread sealant to the flare seat will prevent proper metal-to-metal contact and cause leaks. The sealant compresses unevenly under torque, leaves a gap in the seating cone, and can introduce contamination into the fluid system.

The rule is simple: no sealant on the flare seat, ever.

The one exception involves JIC-to-pipe adapters: the NPT pipe thread on the back end of the adapter does require sealant (PTFE tape or anaerobic pipe dope applied correctly). For guidance on which sealant to use on NPT threads, see our guide: Teflon Tape vs. Pipe Dope.

Light machine oil on the threads (not the seat) can reduce galling on stainless steel fittings during assembly.

Assembly & Torque Guidance

SAE J514 specifies torque values for JIC fittings, but the preferred assembly method in production and MRO environments is the FFWR (Flats From Wrench Resistance) method, which accounts for variations in lubrication and plating.

FFWR Assembly Procedure

1. Inspect both seating surfaces for nicks, burrs, or contamination. Any damage to the cone face will prevent a proper seal.
2. Hand-tighten the fitting until you feel the flare seat make contact and resistance increases—this is the Wrench Resistance (WR) point.
3. Mark the nut position with a marker or paint pen.
4. Apply the final torque by turning the nut the additional flats specified in the table below.

Torque values above are for dry carbon steel. For stainless steel, reduce torque by 15–20% and apply a light coat of anti-seize to threads (not the flare seat) to prevent galling. For brass, reduce torque by 30–40%. Always follow the fitting manufacturer's published values when available.

Do not re-torque a JIC fitting that has already been tightened and then loosened. The flare seat cold-welds slightly on first assembly; subsequent re-torquing can crack or deform the seat. Replace the fitting or tube end if the joint is disassembled.

Standards & References

• SAE J514 — Hydraulic Tube Fittings (the primary JIC standard; defines 37-degree flare geometry, thread dimensions, pressure ratings, and material requirements)
• ISO 8434-2 — Metallic tube connections for fluid power and general use: 37-degree flared fittings (international equivalent of SAE J514)
• SAE J513 — Refrigeration Tube Fittings (defines the SAE 45-degree flare; do not confuse with J514)
• SAE J1231 — Formed tube ends for hose connections and their mating fittings
• MIL-F-18866 / AN/MS specifications — Aerospace flared fitting standards (37-degree AN geometry)

Frequently Asked Questions

Are JIC and AN fittings interchangeable?

In most cases, yes—JIC and AN fittings share the same 37-degree flare angle and UNF thread dimensions at matching dash sizes (e.g., JIC -6 and AN-6 use the same 9/16-18 thread and 37-degree seat). They will form a functional metal-to-metal seal. However, AN fittings are manufactured to tighter aerospace tolerances. For safety-critical systems—aircraft, racing fuel cells, high-pressure hydraulics—do not mix the two without engineering approval. For general industrial and fluid-power applications, JIC and AN at the same dash size are routinely used together.

What angle is a JIC flare?

A JIC flare is 37 degrees, measured from the centerline of the fitting (the half-angle). The full included angle of the cone is 74 degrees. This is the defining characteristic of the JIC standard (SAE J514) and what distinguishes it from the SAE 45-degree flare (SAE J513), which has a steeper, sharper 45-degree half-angle cone.

Do JIC fittings need thread sealant?

No. JIC fittings seal metal-to-metal at the flare seat and require no thread sealant on the cone. Adding PTFE tape or pipe dope to the flare seat will prevent proper contact and cause leaks. The only exception is when a JIC fitting has an NPT (tapered pipe thread) end on the back side—that NPT thread does require sealant. See our guide to Teflon Tape vs. Pipe Dope for NPT sealant selection.

How do I measure JIC fitting size?

Measure the major (outside) diameter of the male thread with calipers, then confirm the thread pitch with a thread gauge. Match both values to the JIC dash-size chart: for example, a 9/16-inch major diameter with 18 threads per inch is a -6 JIC fitting, which connects to 3/8-inch OD tubing. Finally, confirm the 37-degree seat angle visually or with a gauge to rule out SAE 45-degree flare fittings, which share similar thread dimensions at some sizes.

JIC vs NPT — what's the difference?

JIC and NPT are completely different connection types. JIC uses a straight (parallel) UNF thread and seals at the 37-degree metal-to-metal flare cone—no sealant on the seat. NPT (National Pipe Taper) uses a tapered thread that seals by thread engagement with the help of PTFE tape or pipe dope to fill thread-spiral leak paths. JIC is used for tubing connections in hydraulic and fluid-power lines; NPT is used for pipe connections in plumbing, process piping, and instrumentation. They cannot be directly mated. JIC-to-NPT adapters exist that have a JIC swivel on one end and an NPT thread on the other—in that case, no sealant on the JIC side, sealant on the NPT side. See our full comparison in the NPT/BSPP/JIC Thread Identification Guide.

Related Resources

• NPT, BSPP & JIC Thread Identification Guide
• Flare Fittings: SAE 45° vs. Inverted Flare
• Compression Fitting Sizing Chart
• Technical Resource Center

Shop Related Products

• Flareless JIC Fittings
• SAE 45° Flare Fittings
• Inverted Flare Fittings