How do you properly tighten a steel JIC fitting?

The main cause of leaks is over-tightening. The correct method is to tighten until finger-tight, then use a wrench for a final 1/4 to 1/2 turn (the 'flats method'). This ensures a secure seal on the 37-degree cone without cracking the flare nut.

An array of forged carbon steel JIC 37-degree flare hydraulic fittings on a factory workbench, showing the precision-machined conical sealing faces.

Steel JIC Fittings (37° Flare, SAE J514)

Q: Are AN and JIC fittings interchangeable?

No. While they share the same 37° flare angle, AN (Army-Navy) and JIC (SAE J514) fittings have different thread classes and tolerances. Mixing them is not recommended in high-pressure or critical industrial systems.

Q: What is the difference between JIC and NPT fittings?

JIC fittings create a reusable mechanical seal on a 37° metal cone, ideal for high vibration and pressure. NPT fittings use tapered threads that deform for a seal, making them less reliable after disassembly. For most hydraulic lines, JIC is the superior choice.

The workhorse hydraulic connector for North American equipment. Forged, plated, and manufactured for the distributors and OEMs who build and maintain the machines that do the work.

A Metal-to-Metal Seal That's Built to Work.

The JIC 37-degree flare is the standard for North American mobile and industrial hydraulics for one reason: it's a simple, strong, and field-serviceable metal-on-metal seal. Governed by the SAE J514 standard, its reliability comes down to two things: the quality of the steel and the precision of the machining.

A poorly made flare fitting will crack under torque or leak under pressure. That's why we forge ours from high-grade carbon steel for maximum strength, then apply a robust zinc plating for corrosion resistance in demanding field conditions. These are the fittings built for construction sites, farms, and factory floors. For applications requiring extreme corrosion resistance (e.g., marine, chemical), see our 316 Stainless Steel JIC line. For all other high-pressure hydraulic systems, this is your reliable, cost-effective solution.

JIC 37° Flare Fitting Catalog (Steel)

37° JIC SAE Flare Male Tube Union

Part #: 2403

Connects two flared tubes or female JIC swivel fittings of the same size in a straight line. Male JIC 37° flare ends.

37° JIC SAE Flare Male Tube Large Hex Union

Part #: 2403LH

Similar to 2403 union but features a larger hex body for easier wrench access or higher torque applications.

37° Male JIC x NPTF Male Pipe Connector

Part #: 2404

Connects a female JIC swivel fitting or flared tube to a female NPTF port. Male JIC x Male NPTF ends.

37° Male JIC x Long Male NPTF Pipe Connector

Part #: 2404L

Similar to 2404 but with an extended length NPTF male thread for reaching deeper ports.

37° Male JIC x Extra Long NPTF Male Pipe Connector

Part #: 2404LL

An extra-long version of the JIC to NPTF connector, providing maximum reach for specific applications.

37° Male JIC x Female NPTF Pipe Connector

Part #: 2405

Connects a female JIC swivel fitting or flared tube to a male NPTF pipe/fitting. Male JIC x Female NPTF ends.

37° Female JIC x JIC Male Tube Expander / Reducer

Part #: 2406

Adapter to connect JIC fittings of different sizes. Typically female JIC swivel x male JIC flare, reducing or expanding size.

37° JIC Male Tube Plug

Part #: 2408

Seals the end of a female JIC swivel fitting or port. Features a male JIC 37° flare sealing nose.

37° JIC Tube Nut

Part #: 318

Female nut used with a tube sleeve (319) to connect a flared tube end to a male JIC fitting.

37° JIC Tube Sleeve

Part #: 319

Used in conjunction with a tube nut (318) to support the flared tube and create the seal against a male JIC fitting.

37° JIC Male Union 90° Elbow

Part #: 2500

Changes flow direction by 90°. Connects two female JIC swivel fittings/flared tubes. Male JIC ends.

37° JIC Male to NPTF Male Pipe 90° Elbow

Part #: 2501

90° adapter elbow connecting a female JIC swivel/tube to a female NPTF port. Male JIC x Male NPTF ends.

Male JIC x Male Pipe 90° Long Elbow

Part #: 2501L

A 90° elbow adapter (JIC Male x NPTF Male) with an extended length on one or both ends for added clearance.

Male JIC x Male Pipe 90° Extra Long Elbow

Part #: 2501LL

Extra long version of the 90° JIC Male x NPTF Male elbow adapter, providing significant reach.

Male JIC x Male Pipe 90° Extra Extra Long Elbow

Part #: 2501LLL

Maximum length version of the 90° JIC Male x NPTF Male elbow adapter for specialized applications.

37° JIC Male to NPTF Female Pipe 90° Elbow

Part #: 2502

90° adapter elbow connecting a female JIC swivel/tube to a male NPTF pipe/fitting. Male JIC x Female NPTF ends.

37° JIC Male to NPTF Male Pipe 45° Elbow

Part #: 2503

45° adapter elbow connecting a female JIC swivel/tube to a female NPTF port. Male JIC x Male NPTF ends.

37° JIC Male to 37° JIC Male 45° Elbow

Part #: 2504

Changes flow direction by 45°. Connects two female JIC swivel fittings/flared tubes. Male JIC ends.

37° JIC Male to NPTF Female 45° Elbow

Part #: 2505

45° adapter elbow connecting a female JIC swivel/tube to a male NPTF pipe/fitting. Male JIC x Female NPTF ends.

37° JIC Male to NPTF Male Pipe Branch Tee

Part #: 2601

Tee adapter connecting two female NPTF ports and one female JIC swivel/tube. Male JIC branch, Male NPTF run ends.

37° JIC Male to NPTF Female Pipe Branch Tee

Part #: 2602

Tee adapter connecting two male NPTF pipes/fittings and one female JIC swivel/tube. Male JIC branch, Female NPTF run ends.

37° JIC Male Union Tee

Part #: 2603

Connects three female JIC swivel fittings or flared tubes in a tee configuration. All ends Male JIC.

37° JIC Male to NPTF Male Run Tee

Part #: 2605

Tee adapter connecting two female JIC swivel/tubes and one female NPTF port. Male NPTF branch, Male JIC run ends.

37° JIC Male to NPTF Female Run Tee

Part #: 2606

Tee adapter connecting two female JIC swivel/tubes and one male NPTF pipe/fitting. Female NPTF branch, Male JIC run ends.

37° JIC Male to NPTF Male Service Tee

Part #: 2607

Special tee configuration, likely for gauge ports or test points, adapting JIC to NPTF.

37° JIC Male to NPTF Male x NPTF Female Tee

Part #: 2611

Complex tee adapter connecting JIC, male NPTF, and female NPTF ports.

37° JIC Male Cross

Part #: 2650

Connects four female JIC swivel fittings or flared tubes at 90° angles. All ends Male JIC.

37° JIC Bulkhead Straight Union

Part #: 2700

Connects two female JIC swivel/tubes through a panel or bulkhead. Straight union with locknut. Male JIC ends.

37° JIC Bulkhead 90° Elbow

Part #: 2701

90° elbow fitting designed to pass through a panel or bulkhead, connecting JIC lines. Male JIC ends, includes locknut.

37° JIC Bulkhead Union 45° Elbow

Part #: 2702

45° elbow fitting designed for bulkhead pass-through, connecting JIC lines. Male JIC ends, includes locknut.

37° JIC Bulkhead Branch Tee

Part #: 2703

Tee fitting where one connection passes through a bulkhead. Typically Male JIC ends, includes locknut.

37° JIC Bulkhead Run Tee

Part #: 2704

Tee fitting where the straight-through ('run') connection passes through a bulkhead. Male JIC ends, includes locknut.

NPTF Female Pipe x 37° JIC Bulkhead Straight

Part #: 2705

Bulkhead adapter connecting a female JIC swivel/tube outside the panel to a male NPTF pipe/fitting inside. Includes locknut.

NPTF Male Pipe x 37° JIC Bulkhead Straight

Part #: 2706

Bulkhead adapter connecting a female JIC swivel/tube outside the panel to a female NPTF port inside. Includes locknut.

37° JIC Short Flare Nut

Part #: 302

Shorter length female JIC nut, used with a sleeve (319) for connecting flared tubes.

37° JIC Long Flare Nut

Part #: 304

Standard/longer length female JIC nut, used with a sleeve (319) for connecting flared tubes.

37° JIC Female Tube Cap

Part #: 304C

Seals the end of a male JIC 37° flare fitting. Female JIC swivel nut with a sealing cap.

37° JIC Bulkhead Locknut

Part #: 306

Nut used to secure a JIC bulkhead fitting (like 2700 series) to a panel or bulkhead wall.

37° JIC to Flareless Compression Convert-A-Flare Nut

Part #: 418

Special nut used with sleeve 419 to adapt a flareless tube directly to a male JIC fitting without flaring the tube.

37° JIC to Flareless Compression Convert-A-Flare Sleeve

Part #: 419

Compression sleeve (ferrule) used with nut 418 to connect a flareless tube to a male JIC fitting.

37° JIC Male to JIC Female Swivel 90° Elbow

Part #: 6500

90° elbow with a male JIC flare end and a female JIC swivel nut end for easy alignment.

NPTF Male Pipe x 37° JIC Female Swivel 90° Elbow

Part #: 6501

90° adapter elbow connecting a male NPTF pipe/fitting to a female JIC swivel hose/tube end.

37° JIC Male x 37° JIC Female Swivel 45° Elbow

Part #: 6502

45° elbow featuring one male JIC flare end and one female JIC swivel nut end.

NPTF Female Pipe x 37° JIC Female Swivel 90° Elbow

Part #: 6503

90° adapter elbow connecting a female NPTF port to a female JIC swivel hose/tube end.

37° JIC Male x 37° JIC Female Swivel Connector

Part #: 6504

Straight adapter connecting a male JIC flare fitting to a female JIC swivel hose/tube end.

NPTF Male Pipe x 37° JIC Female Swivel Nut Adapter

Part #: 6505

Straight adapter connecting a male NPTF pipe/fitting to a female JIC swivel hose/tube end.

NPTF Female Pipe x 37° JIC Female Swivel Nut Adapter

Part #: 6506

Straight adapter connecting a female NPTF port to a female JIC swivel hose/tube end.

37° JIC Female Swivel x 37° JIC Female Swivel Nut Union

Part #: 6565

Straight union connecting two male JIC flare fittings or flared tubes using female JIC swivel nuts on both ends.

JIC Adapters to Other Port Types

Most hydraulic systems mix JIC with other port types. When you tie JIC lines into valves, manifolds or legacy pipe work, you usually need one of these transitions:

SAE O-Ring Boss (ORB) fittings — for straight-thread O-ring ports on manifolds, pumps and cylinders.
O-Ring Face Seal (ORFS) fittings (SAE J1453) — when you need leak-free performance under high vibration.
NPT/NPTF pipe thread fittings — for tying into existing North American pipe work and threaded ports.
BSPP British hydraulic fittings — when the equipment comes with G ports from European or imported machinery.
Stainless 316 JIC fittings — for marine, chemical or washdown areas where corrosion resistance is critical.

The Engineer's Guide to Steel JIC Fittings

Understanding the fundamentals of the SAE J514 standard is key to preventing leaks and ensuring system reliability. Here’s what every technician and buyer should know.

How It Seals: The 37-Degree Mechanical Lock

The JIC connection is purely mechanical. The straight threads provide the clamping force, but the seal occurs on the small contact band where the 37° male cone meets the female flare seat. This design is highly resistant to vibration and can be reassembled multiple times, unlike NPT threads.

Why Forged Carbon Steel is the Standard

Strength & Durability: Forging aligns the steel's grain structure, making the fitting highly resistant to cracking under high pressure and torque.
Cost-Effectiveness: For most industrial and mobile hydraulic applications, zinc-plated carbon steel provides the best balance of performance and price.
Machinability: Allows for precise cutting of threads and the critical 37° sealing surface.

Common Causes of Leaks (And How to Prevent Them)

Overtightening: This is the #1 cause of failure. Excessive torque will crack the female flare nut or deform the male cone, creating a permanent leak path.
Damaged Sealing Surfaces: Nicks, scratches, or contamination on the 37° cone will compromise the seal. Always inspect and clean both surfaces before assembly.
Misalignment: Cross-threading can damage the threads and prevent the sealing surfaces from mating correctly. Always start the nut by hand.

Installation Best Practice: The "Flats" Method

Ensure both male and female sealing surfaces are clean and free of damage.
Lubricate the threads of the swivel nut with a light hydraulic oil.
Tighten the nut by hand until it is snug (finger-tight).
Mark a line on one flat of the nut and the fitting body.
Using two wrenches (one to hold the fitting, one to turn the nut), tighten by the specified number of "flats" (typically 2-3 flats, or about 1/4 to 1/2 turn past finger-tight). This ensures proper torque without over-stressing the flare.

For a detailed guide, see our article: How to Tighten JIC Fittings Without Leaking or Cracking.

Straight Answers to Common JIC Questions

How do you properly tighten a JIC fitting to prevent leaks?

The most common cause of JIC leaks is over-tightening, which cracks the flare. The correct method is to tighten until finger-tight, then use a wrench for a final 1/4 to 1/2 turn. This "flats method" ensures a secure seal without damaging the fitting's conical seat.

Learn the detailed technique in our guide →

Are AN and JIC fittings interchangeable?

No. While they look identical with the same 37° flare angle, AN (Army-Navy) and JIC (SAE J514) fittings have different thread classes and tolerances. AN threads have a tighter tolerance for military and aerospace use. While they might thread together, mixing them in high-pressure or critical systems is not recommended.

Read the full comparison of AN vs. JIC →

What is the difference between JIC and NPT fittings?

JIC fittings create a mechanical seal on a 37° flared metal cone, making them reusable and excellent for high-pressure systems. NPT fittings use tapered threads that deform to create a seal, making them prone to leaks with reuse and vibration. JIC is superior for most hydraulic connections.

See how JIC compares to other fitting types →

Need JIC Fittings You Can Actually Count On?

A good JIC fitting is an inventory essential. A bad one is a warranty claim waiting to happen. We manufacture these parts in volume for OEMs and distributors who can't afford to take chances. For a factory-direct quote on parts that are built right, talk to us.

Get a Wholesale Quote on JIC See Our Stainless Steel JIC Line