When working with hydraulic systems, fuel lines, or high-pressure applications, banjo fittings are often the unsung heroes. But have you ever wondered, what is the piece that banjo fitting threads onto? The answer lies in the complementary components that make up the banjo fitting system.
Whether you’re dealing with a banjo fitting nut, a 10mm banjo fitting 45-degree elbow, or other hydraulic connections, understanding how they work together is crucial to the system’s efficiency and reliability.
In this article, we’ll explore the essential parts of banjo fittings and provide in-depth guidance on how to use and select them for your specific needs.

What is a Banjo Fitting?
A banjo fitting is a versatile and widely used connector that joins two parts of a hydraulic system, typically where there is a need for fluid transfer at a right angle. This fitting features a banjo bolt, which goes through a hollow, cylindrical fitting (the “banjo” part), allowing fluid to flow through. These types of fittings are commonly used in cars, motorcycles, and industrial applications.
The banjo fitting has a distinct advantage because it allows for a high-pressure connection while occupying a minimal amount of space. They are often used in systems that require high flow rates or in tight spaces where conventional fittings may not fit.
What is the Piece That Banjo Fitting Threads Onto?
The piece that a banjo fitting threads onto is typically a banjo bolt or a banjo fitting nut. The banjo fitting nut is used to secure the fitting in place, ensuring that the connection is tight and leak-free. This nut threads onto the banjo bolt or onto a threaded connection within the hydraulic system.
The banjo fitting nut is an essential part of the assembly, as it keeps the fitting secure while providing the proper compression to prevent leaks. The banjo bolt, which is inserted through the fitting’s hole, ensures that the two parts stay firmly connected, preventing fluid from escaping.
The Role of Banjo Fitting Nut

A banjo fitting nut is specifically designed to provide pressure and create a tight seal between the banjo fitting and the system it’s attached to. These nuts are typically made from high-strength materials such as steel or aluminum to withstand the pressure in hydraulic systems.
The nuts come in various sizes, and the most common sizes for hydraulic systems include 10mm banjo fitting nuts, which are frequently used in automotive and industrial applications.
Banjo fitting nuts are available in different designs, including banjo fitting nuts with a flange, which provide additional sealing and support, and flat-faced nuts, which ensure better fluid control and leakage prevention.
The correct type of nut should always be chosen based on the specifications of your system, as selecting the wrong one can cause fitting failures or leaks.
Classification of Banjo Fittings Based on Size and Angle
Banjo fittings are categorized based on the outer diameter (OD) of the tubing or hose they connect and the angle at which they redirect fluid flow. This classification helps users choose the appropriate fitting for specific applications, ensuring optimal performance and safety. Below is a detailed exploration of various types of banjo fittings under these two categories, with an emphasis on their features and common application scenarios.
Classification by Outer Diameter (OD)
- 6mm Banjo Fitting
- Features: These fittings are designed for smaller hydraulic lines or oil tubes, providing a compact solution that minimizes weight and space requirements.
- Common Applications: They are ideal for use in motorcycles, small agricultural equipment, and other vehicles where space constraints are critical. Additionally, they are often found in precision machinery like CNC machines due to their minimal footprint.
- 8mm Banjo Fitting
- Features: Offering a balance between strength and flexibility, 8mm banjo fittings can handle moderate pressures and flows, making them versatile for a wide range of uses.
- Common Applications: Commonly used in automotive brake systems, suspension components, and industrial hydraulic circuits that don’t require extremely high pressure ratings.
- 10mm Banjo Fitting
- Features: With increased capacity compared to smaller sizes, 10mm banjo fittings can accommodate higher flow rates and pressures, while still maintaining a relatively slim profile.
- Common Applications: Widely employed in passenger cars, trucks, tractors, and light construction equipment. They’re also popular in manufacturing plants for conveyor systems and robotic arms.
- 12mm Banjo Fitting
- Features: Built for handling larger volumes of fluid at higher pressures, these fittings provide robust solutions for heavy-duty tasks.
- Common Applications: Found in larger vehicles such as buses, trucks, and agricultural machinery, as well as in industrial settings like injection molding machines and hydraulic presses.
- 16mm Banjo Fitting
- Features: Designed for maximum throughput, these fittings are engineered to withstand very high pressures and significant fluid volumes.
- Common Applications: Essential in heavy construction machinery like excavators and bulldozers, as well as in large-scale industrial processes involving substantial hydraulic power.

Classification by Angle
- Straight-through Banjo Fitting
- Features: These fittings allow fluid to pass through without any change in direction, reducing turbulence and potential wear on the system.
- Common Applications: Used in straight-line configurations where minimizing friction loss and maintaining laminar flow are important. They are frequently seen in long runs of piping or when connecting components aligned in one axis.
- 45 Degree Elbow Banjo Fitting
- Features: Featuring a gentle bend, this type of fitting redirects fluid flow at a 45-degree angle, allowing for more flexible pipe routing within confined spaces.
- Common Applications: Ideal for situations where space limitations prevent using longer straight sections of pipe. Often utilized in automotive and industrial applications where compact design is necessary.
- 90 Degree Elbow Banjo Fitting
- Features: Providing a sharp turn, these fittings reroute fluid flow at a right angle, which can be useful for changing directions abruptly in plumbing layouts.
- Common Applications: Common in applications where space-saving designs are required or when creating perpendicular connections between components. Frequently used in tight corners or when transitioning from horizontal to vertical pipes.
- Tee Banjo Fitting
- Features: This type of fitting branches off into two additional ports, enabling the distribution of fluid into multiple paths from a single source.
- Common Applications: Utilized in systems that require splitting fluid flow, such as dual-circuit braking systems or multi-output hydraulic actuators. Also helpful for adding monitoring points or auxiliary functions.

Specialized Types: 10mm Banjo Fitting 45 Degree Elbow
The 10mm banjo fitting 45-degree elbow is a commonly used fitting that offers a right-angle connection between the hydraulic or fluid system components. The 45-degree angle helps to maintain the flow of fluid without creating sharp turns, which could cause wear or turbulent flow in the system.
When attaching a banjo fitting to a 10mm banjo fitting 45-degree elbow, the fitting must be aligned correctly to prevent misalignment that could lead to leakage. These elbows are designed to work in both high and low-pressure systems, providing the versatility needed for fluid transfer applications in a variety of industries, from automotive to heavy machinery.

How Do Banjo Fittings Work Together?
The assembly of banjo fittings involves several components that work seamlessly to create a secure connection. Here’s how these pieces fit together:
- Banjo Bolt – This is the central piece that holds the banjo fitting in place and is threaded onto a banjo fitting nut.
- Banjo Fitting Nut – The nut holds the fitting securely in place and ensures that the banjo bolt is tightly threaded onto the hydraulic system.
- Banjo Fitting – The actual connector that allows fluid to flow through. This part has a hollow center for the fluid to pass through and a flat, circular shape for secure mounting.
- Elbows & Other Connectors – Depending on the application, banjo fittings can be attached to elbows (like the 10mm banjo fitting 45-degree elbow) or other types of connectors, facilitating fluid flow at various angles.

Choosing the Right Banjo Fitting for Your Application
Selecting the right banjo fitting depends on several factors, including the type of system, the required fluid flow, and the pressure ratings. Some of the important considerations include:
- Thread Size: Banjo fittings come in different thread sizes, with 10mm banjo fitting being one of the most common. Ensure that the thread size matches the system specifications to avoid compatibility issues.
- Angle: The angle of the fitting plays a key role in determining how the fluid flows through the system. The 45-degree elbow is popular for its ability to redirect fluid at an angle without causing significant resistance.
- Material: Most banjo fittings are made of materials such as steel, brass, or aluminum. Stainless steel is particularly durable for high-pressure and high-temperature applications.
- Seal Type: Some banjo fittings come with additional seals or washers to prevent leaks, so be sure to select the right seal type for your specific needs.
How to Install a Banjo Fitting?
Installing a banjo fitting requires a few simple steps, but it’s essential to ensure that all components are properly aligned and securely tightened. Here’s a step-by-step guide to installing a banjo fitting:
- Prepare the Components: Gather all necessary parts – the banjo fitting, banjo bolt, banjo fitting nut, and any washers or seals.
- Position the Fitting: Place the banjo fitting onto the hydraulic line or component that you are connecting. Align the fitting so that it sits flush against the connection surface.
- Insert the Banjo Bolt: Slide the banjo bolt through the fitting’s hollow section. Ensure that the bolt is properly aligned to allow fluid flow.
- Tighten the Nut: Screw the banjo fitting nut onto the banjo bolt and tighten it securely. Use a torque wrench to ensure proper tension, but avoid overtightening, which could damage the threads or fittings.
- Check for Leaks: After installation, check the fitting for any potential leaks. Tighten the connection as necessary, but be sure not to strip the threads or compromise the fitting.
Conclusion
Understanding what is the piece that banjo fitting threads onto opens up a world of possibilities for maintaining and improving hydraulic systems.
From the anatomy of a standard banjo fitting to specialized variants like the 10mm banjo fitting 45-degree elbow, and the crucial role of the banjo fitting nut, this guide aims to equip you with the knowledge necessary for effective usage.
By following the advice provided here, you can ensure that your machinery remains well-maintained and operational for years to come.
FAQs
What materials are banjo fittings typically made from?
Banjo fittings are usually manufactured from durable metals like brass, steel, aluminum, and stainless steel. The choice of material depends on the application, with considerations given to corrosion resistance, strength, and weight. Stainless steel is often preferred for its longevity and ability to withstand harsh environments.
Can I use a 10mm banjo fitting with a larger system?
Yes, 10mm banjo fittings are versatile, but you must ensure that the system is compatible with that size and that you use the correct adapter for larger fittings.
How do I know if a banjo fitting is compatible with my system?
Compatibility largely hinges on matching the thread specifications of the banjo fitting to those of the piece it will thread onto. Consult the system’s documentation for guidance on required thread sizes and types. Additionally, consider factors such as pressure ratings and temperature ranges to ensure the fitting can handle the operating conditions.
Can I reuse a banjo fitting once it has been removed?
In theory, a banjo fitting can be reused as long as it shows no signs of damage or excessive wear. However, it’s wise to replace any O-rings or seals when reusing a fitting to maintain a proper seal. Always inspect the threads for cross-threading or deformation before reinstalling.
What should I do if a banjo fitting starts leaking?
If you encounter a leak, first check the O-ring for damage or displacement. Replacing the O-ring is often enough to stop the leak. If the issue persists, inspect the threads for cleanliness and alignment. Tighten the banjo fitting nut according to the manufacturer’s torque specifications. In severe cases, replacing the entire fitting may be necessary.
What tools do I need to install a banjo fitting?
Basic installation requires a wrench or socket set to tighten the banjo fitting nut. An adjustable wrench can be useful for fittings with non-standard sizes. For more precise control, a torque wrench ensures that the fitting is tightened to the specified limit without over-tightening. Anti-seize compound may also be needed for certain applications.