AN Fitting Size Chart: JIC 37° Flare Thread Specifications & Standard Dash Sizes (J514/J518)
Engineering Authority Note: This AN Fitting Size Chart adheres to the SAE J514 and ISO 8434-2 standards for 37-degree flare fittings. As a critical reference for high-performance fluid dynamics, this data is verified for aerospace, automotive, and industrial hydraulic applications. For customized integration, consult our Male vs Female Fitting Identification Guide.
Quick Navigation
| AN Dash Size | Thread Size (UNF) | Tube O.D. (Inch) | Tube O.D. (mm) | Typical Application |
|---|---|---|---|---|
| AN -3 | 3/8-24 | 3/16" | 4.76 mm | Brake Lines |
| AN -6 (Critical) | 9/16-18 | 3/8" | 9.52 mm | Fuel Lines / EFI |
| AN -8 | 3/4-16 | 1/2" | 12.70 mm | Oil Coolers |
| AN -10 (Critical) | 7/8-14 | 5/8" | 15.88 mm | Turbo Oil Return |
Introduction
You may have heard of the fitting called the AN fitting if your hands have ever been dirty with cars, planes, or anything that moves fluids. These little connectors are the unsung heroes of high-performance systems, and if you know how to use them, you will save yourself a headache or two.
So, what exactly is an AN fitting? This article will cover what an AN fitting really is, how the sizes work, what its materials are, and what its applications are. You will be all equipped with confidence on your next project.
"Use the comprehensive AN size chart below to cross-reference dash sizes with UNF threads, torque requirements, and maximum operating pressures for both aluminum and stainless steel fittings."
| AN Dash Size | Thread Size (UNF) | Tube O.D. (Inch) | Tube O.D. (mm) | Max PSI (Alum.) | Max PSI (S.Steel) | Torque (in-lbs) |
|---|---|---|---|---|---|---|
| AN -2 | 5/16-24 | 1/8" | 3.17 mm | 2000 | 5000 | 50 - 80 |
| AN -3 | 3/8-24 | 3/16" | 4.76 mm | 1500 | 4500 | 70 - 105 |
| AN -4 | 7/16-20 | 1/4" | 6.35 mm | 1000 | 4000 | 100 - 140 |
| AN -6 ★ | 9/16-18 | 3/8" | 9.52 mm | 750 | 3000 | 150 - 195 |
| AN -8 | 3/4-16 | 1/2" | 12.70 mm | 750 | 2500 | 270 - 350 |
| AN -10 ★ | 7/8-14 | 5/8" | 15.88 mm | 500 | 2000 | 360 - 430 |
| AN -12 | 1-1/16-12 | 3/4" | 19.05 mm | 500 | 1500 | 460 - 550 |
| AN -16 | 1-5/16-12 | 1" | 25.40 mm | 400 | 1000 | 700 - 840 |
*Note: Maximum PSI ratings are guidelines for static systems at ambient temperature. Always include a safety factor for high-vibration or high-heat environments.
2. How to Use an AN Fitting Size Chart (The Engineer’s Roadmap)
An AN fitting size chart serves as the definitive technical reference for ensuring compatibility between hoses, tubes, and adapters. Instead of guesswork, the chart provides a precise cross-reference between three critical variables: Dash Size, Tube Outer Diameter (O.D.), and UNF Thread Specifications.
Key Technical Parameters
In a standard AN fitting chart, each size is categorized to ensure a leak-proof mechanical fit:
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Dash Size: The standardized nomenclature (e.g., -8 AN).
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Tube O.D.: The physical measurement of the mating tube.
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Thread Size (UNF): The Unified National Fine thread pitch (e.g., 3/4-16 UNF), where the first number represents the diameter and the second represents threads per inch (TPI).
The Critical Importance of Accuracy
Why is this data indispensable? In high-pressure applications like custom oil cooling systems or fuel delivery lines, utilizing the incorrect fitting size leads to catastrophic results:
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Hydraulic Turbulence: Misaligned diameters cause flow restriction and pressure drops.
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Seal Failure: Incorrect thread engagement results in immediate leaks or thread stripping under vibration.
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System Integrity: Standardized charts ensure that components from different manufacturers—whether for aerospace or industrial hydraulics—maintain a universal interchangeability.
By adhering to the AN thread size chart, engineers can guarantee that every connection meets the rigorous safety factors required for high-performance fluid dynamics.
3. Material Selection: Aluminum, Stainless Steel, and Brass
The performance of an AN fitting is defined not only by its geometry but by the metallurgy of its construction. Choosing the correct material is a trade-off between weight, pressure capacity, and chemical compatibility.
Aluminum (6061-T6 / 7075-T6)
Aluminum is the industry standard for high-performance automotive applications where weight reduction is paramount.
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Key Advantage: Exceptional strength-to-weight ratio and natural corrosion resistance when Anodized (typically in blue, red, or black).
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Best For: Fuel systems, cooling lines, and low-to-medium pressure racing applications.
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Limitation: Lower fatigue strength compared to steel; may deform under extreme, sustained high-pressure hydraulic spikes.
Stainless Steel (303, 304, or 316 Grade)
Stainless steel is the "heavy-duty" choice for critical environments where failure is not an option.
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Key Advantage: High tensile strength, extreme temperature resistance, and virtually impervious to oxidation.
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Best For: Brake lines, high-pressure turbo oil feeds, and marine environments where saltwater corrosion is a factor.
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Limitation: Higher cost and increased weight compared to aluminum; more challenging to machine with precision.
Brass & Carbon Steel
While less common in modern performance setups, these materials serve specific niche roles.
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Brass: Highly affordable and easy to machine. Best suited for low-pressure fuel or water lines where weight is not a primary concern.
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Carbon Steel: Frequently used in industrial hydraulics for its sheer strength, though it requires plating (Zinc or Cadmium) to prevent rust.
4. Industrial Applications: Where Do AN Fittings Excel?
The application of an AN fitting has expanded far beyond its military origins, becoming the gold standard in any industry where fluid containment is critical. Its "aerospace DNA" ensures that every connection can withstand extreme pressure, thermal expansion, and high-frequency vibration without compromise.
High-Performance Automotive & Motorsport
In the automotive sector, AN fittings are indispensable for high-stakes performance builds. They are the primary choice for:
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Fuel Delivery Systems: Specifically AN -6 and AN -8 lines, which provide the high flow rates required for EFI (Electronic Fuel Injection) and are compatible with corrosive ethanol-blended fuels (E85).
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Turbocharged Systems: Reliable oil feed and drain lines that must handle high temperatures near the exhaust manifold.
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Cooling & Lubrication: Custom oil cooler setups and high-pressure radiator bypasses.
Aerospace & Defense
Staying true to their SAE AS7112 roots, AN fittings remain a staple in light aircraft and UAV (Unmanned Aerial Vehicle) manufacturing. Their lightweight nature and "fail-safe" metal-to-metal sealing make them ideal for hydraulic flight controls and fuel management.
Marine & Industrial Engineering
Beyond land and air, AN fittings are utilized in:
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Marine Environments: Stainless steel AN fittings are used for their superior resistance to saltwater corrosion in offshore racing boats.
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Industrial Automation: Specialized gas and fluid transfer lines in manufacturing gear where modularity and frequent maintenance (easy "swap-outs") are required.
Why Engineers Choose AN Over Standard Hardware
While standard industrial fittings may be more budget-friendly, AN fittings are selected when failure is not an option. The modularity of the dash-size system allows for rapid prototyping and maintenance, ensuring that high-value systems remain leak-free and operational under the most grueling conditions.
1. What is an AN Fitting? (Technical Definition)
AN (Army-Navy) fittings are a specific type of high-performance fluid connection standard designed to provide a secure, leak-proof seal in demanding environments. Originally developed for the U.S. Military (Aerospace) during World War II, these fittings are now the global benchmark for automotive racing, aviation, and marine hydraulic systems.
The 37° Flare Sealing Principle
The core reliability of an AN fitting lies in its 37-degree flare design. Unlike standard NPT threads that rely on thread deformation, AN fittings create a precise metal-to-metal seal between the flared tubing and the fitting seat. This mechanical seal ensures maximum integrity under high-pressure and high-vibration conditions.
Understanding "Dash" Sizes (-3, -6, -10)
AN fitting sizes are identified by "dash numbers," which represent the Outer Diameter (O.D.) of the tubing in increments of 1/16th of an inch. This standardized system simplifies component matching:
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AN -3: 3/16" O.D.
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AN -4: 4/16" (or 1/4") O.D.
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AN -6: 6/16" (or 3/8") O.D.
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AN -8: 8/16" (or 1/2") O.D.
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AN -10: 10/16" (or 5/8") O.D.
Industry Standards Compliance
Modern AN fittings are governed by rigorous engineering standards, primarily SAE J514 and MIL-F-5509. While the nomenclature may seem complex to newcomers, mastering this system is essential for ensuring the safety and performance of high-precision fluid dynamics.
Conclusion
Wrapping this up, the AN fitting size chart is more than just a list of numbers—it’s your key to mastering a system that’s been trusted for decades. Whether you’re sorting out AN fitting sizes like -4 or -16 or digging into the AN fitting dimensions for a perfect match, it’s all about precision and reliability. These fittings, born from military specs, have evolved into a must-have for anyone serious about performance or safety.
The materials—aluminum, stainless steel, brass—give you options to fit your needs, whether you’re chasing lightweight speed or rugged longevity. And the applications of AN fittings? They’re as broad as your imagination, from screaming race cars to high-flying jets.
Next time you’re staring down a project, grab that AN fitting chart, double-check your AN thread size chart, and pick the right tool for the job. It’s not just about getting it done—it’s about getting it done right.
What does the "AN" in AN fitting stand for, and why is it standardized?
AN stands for Army-Navy. It was originally designed for the US military during WWII to ensure interchangeability in fluid systems. Today, it remains the global standard for high-performance 37° flare connections (SAE J514).
How do I convert AN dash sizes to actual outer diameter (O.D.) measurements?
The dash size refers to the O.D. in 1/16" increments. For example, an AN -8 fitting equals 8/16", or 1/2 inch. This is a critical rule for selecting the correct hose and hardline compatibility.
Why should I choose AN 37° Flare over NPT for high-vibration environments?
Unlike NPT which relies on thread deformation to seal, AN fittings use a metal-to-metal flare surface. This creates a superior, reusable mechanical seal that resists vibration and high pressure, making it ideal for automotive and aerospace racing.
How to identify the difference between AN (JIC) and SAE 45-degree flare fittings?
Visually they look similar, but the flare angle is the key: AN/JIC is 37 degrees, while SAE is 45 degrees. Using them together will cause leaks. Always use a protractor or a dedicated gauge to verify the seat angle.
What are the maximum pressure ratings for aluminum vs. stainless steel AN fittings?
Aluminum AN fittings are typically rated up to 1500-2000 PSI depending on size, whereas stainless steel versions can handle up to 5000+ PSI. Always consult the specific alloy grade (e.g., 6061-T6 Aluminum) for safety factors.