What Sizes Do Reusable Hydraulic Hose Fittings Come In?


Have you ever wondered how to ensure your hydraulic system maintains its peak performance without frequent and costly replacements? One efficient solution lies in choosing the right reusable hydraulic fittings. This guide will walk you through the different sizes available, how to measure them accurately, and the steps to select and install the correct fitting for your hydraulic needs.

What sizes of reusable hydraulic fittings are available?

Reusable hydraulic hose fittings come in a variety of sizes, typically measured by the inner diameter of the hose they are intended to connect. Common sizes for these fittings include 1/4″, 1/2″, 3/8″, and up to 2 inches in diameter. These sizes are often denoted using a “dash size” system, where the size is represented as a negative number that corresponds to the inner diameter of the hose in sixteenths of an inch. For instance, a fitting that fits a hose with a 1/2 inch diameter is labeled as -8 because 1/2 inch equals 8/16ths of an inch.


















































































Example. For more detailed parameters, feel free to contact Topa!

Common International Reusable Fitting Sizes

Reusable hose fittings are designed to provide a durable and reliable connection in hydraulic systems, accommodating a range of sizes and pressure requirements. Here’s a more detailed overview of the size ranges and corresponding pressure ratings for these fittings:

1/4 inch (6 mm): Often used in smaller applications where space is limited and less fluid transfer is required.

3/8 inch (10 mm): Suitable for medium flow rates in automotive or construction equipment.

1/2 inch (12 mm): A versatile size used widely across various applications for a balance of flow and pressure.

3/4 inch (19 mm): Ideal for higher flow requirements in industrial hydraulic systems.

1 inch (25 mm) and up to 2 inches (50 mm): Used in large machinery and heavy equipment where high flow rates are necessary.

How to Measure Reusable Fittings Correctly

Accurate measurement of reusable hydraulic fittings is essential for ensuring that they fit properly within your hydraulic system, helping to prevent leaks and maintain system integrity. Below is a detailed guide on how to measure these fittings accurately using the right tools.

Tools Needed

To get precise measurements, ensure you have the following tools:

Calipers: Crucial for measuring both the outer and inner diameters of the fittings accurately. Calipers provide precise measurements that are essential for ensuring the fitting matches the hose or connection point properly.

Rulers: These are useful for measuring the length of the fittings. A standard metal ruler can provide the necessary accuracy for length measurement.

Thread Gauges: Essential for identifying the thread size and type, such as NPT (National Pipe Thread) or BSPP (British Standard Pipe Parallel). This tool helps ensure that the fitting will correctly thread into the hose or component without causing damage or leaks.

Measuring Diameter

reusable hydraulic hose fittings measure diameter

Outer Diameter:

Place the caliper around the largest part of the fitting. It is important to ensure that the caliper is perpendicular to the fitting to avoid skewed measurements. This measurement is crucial as it must match the size of the mating component or hose for a proper connection.

Inner Diameter:

Adjust the caliper to measure the inside opening of the fitting. This diameter is key to determining the flow capacity of the system and must match the inner diameter of the hose to ensure a tight and secure seal.

Measuring Length

Align the ruler along the length of the fitting from one end to the other, ensuring it’s straight to avoid any measurement errors. This measurement is important to ensure that the fitting will physically fit into the hydraulic system’s layout without requiring modifications.

Identifying Thread Size

Select the Correct Gauge: Choose a thread gauge that corresponds to the suspected thread standard of the fitting, such as NPT (National Pipe Thread), BSPP (British Standard Pipe Parallel), or Metric.

Measure the Thread: Insert the gauge into the threads of the fitting until it fits snugly without forcing it. This helps to accurately determine the thread type and size, ensuring that the fitting will thread correctly with other components of the system, preventing leaks and mechanical failures.

reusable hydraulic hose fittings measure length

Important Tips

Ensure Cleanliness: Before measuring, ensure that both the fitting and tools are clean. Debris can affect the accuracy of your measurements.

Handle Tools with Care: Calipers and thread gauges are precision tools that must be handled with care to maintain their accuracy.

Record Measurements: Always write down your measurements immediately to avoid confusion and ensure that you select the correct fittings based on your recorded data.

How to Select the Most Suitable Size

Selecting the most suitable size of reusable hydraulic hose couplings is essential for maintaining the efficiency and reliability of your hydraulic system. Here are some detailed factors to consider when choosing the right size for your reusable couplings:

Factors to Consider

Pressure Requirements

Importance: The pressure requirements of your hydraulic system are critical in determining the appropriate fitting size. High-pressure systems require robust fittings that can handle the stress without failing.

Guidance: Larger diameter fittings generally have a lower pressure rating, whereas smaller diameter fittings can handle higher pressures. Ensure that the fitting’s pressure rating meets or exceeds the system’s maximum operating pressure.

Hose Diameter

Importance: The diameter of the hose directly influences the size of the fitting. A mismatch in hose and fitting sizes can lead to leaks, reduced flow, and potential system failures.

Guidance: Measure the internal diameter of your hose accurately and select a fitting that matches this measurement to ensure a tight and secure connection.

Fluid Type

Importance: The type of fluid being transported can affect the material choice for your fittings. Some fluids can corrode or degrade certain materials, leading to leaks and system contamination.

Guidance: Check the chemical compatibility of the fitting material with the fluid type. Materials like stainless steel are generally resistant to a wide range of chemicals, whereas others like brass may be suitable for less corrosive fluids.

Additional Considerations

Compatibility with Existing System

Ensure that the fittings are compatible with the other components of your hydraulic system, such as valves, pumps, and other connectors. This includes thread type, size, and sealing method.

Environmental Factors

Consider environmental factors such as temperature and external conditions. Extreme temperatures can affect the durability and performance of fittings, while external conditions like dust and moisture can lead to premature wear and failure.

Ease of Installation

Reusable fittings are designed for easy installation and removal. Consider fittings that allow for simple assembly and disassembly without the need for specialized tools, especially in applications where adjustments and maintenance are frequently required.

How to Install Reusable Fittings and Corresponding Hoses


Cleanliness: Begin by ensuring that both the hose and the fittings are completely clean and free of any debris or contaminants. Dirt or particles can cause leaks or blockages once the system is operational.

Inspection: Check the hose and fittings for any signs of damage such as cracks, cuts, or worn threads. Damaged components should be replaced to avoid failures.

Compatibility Check: Verify that the hose and fittings are compatible in terms of size, type, and material. This includes checking the type of thread and the diameter of the hose and fitting.

Installation Steps

Proper installation of reusable hydraulic hose fittings is crucial for the efficient and safe operation of hydraulic systems. Here’s a detailed expansion of the installation steps to ensure a secure and proper fit:


Align the Fitting:

Alignment Check: Before inserting, align the fitting with the end of the hose. It’s crucial to ensure that the fitting is straight to prevent any cross-threading, which can damage both the hose and the fitting.

Lubrication: If recommended by the manufacturer, apply a small amount of hydraulic fluid or appropriate lubricant on the threads of the fitting to facilitate smoother insertion and prevent thread damage.

Insert the Fitting:

Gentle Insertion: Carefully insert the fitting into the hose. Avoid any forceful pushing or twisting that can cause damage. The fitting should slide in with relative ease if aligned correctly.

Thread Engagement: Begin threading by hand to ensure that the threads are correctly aligned. If resistance is felt, back off and realign to avoid cross-threading.

Snug Fit: Continue to insert the fitting until it fits snugly within the hose. Some fittings might require slight twisting to fully engage the threads, depending on their design.


Topa Install and Tighten JIC Hydraulic Fittings

Use Proper Tools:

Tool Selection: Select the appropriate tools for tightening the fitting. Common tools include wrenches or pliers. The tool must match the size of the fitting to ensure a good grip without slipping or damaging the fitting.

Non-Marring Tools: To prevent damage to the finish and integrity of the fitting, consider using non-marring tools that provide adequate grip without scratching or deforming the fitting.

Tighten Securely:

Hand Tighten First: Initially, tighten the fitting by hand to ensure that it is threaded correctly. This reduces the risk of cross-threading with tools.

Final Tightening: Use the selected tool to tighten the fitting to the manufacturer’s specified torque. This is crucial to ensure a leak-free seal and to prevent over-tightening, which can damage the threads or deform the hose.

Torque Specifications: If available, use a torque wrench to apply the exact amount of torque recommended by the fitting manufacturer. This ensures optimal tightness without the risk of over-tightening.

Final Checks

Leak Testing: Once the fitting is installed, conduct a pressure test to check for leaks. This can be done by applying the system’s working pressure and inspecting the fitting for any signs of leakage.

Visual Inspection: Perform a visual inspection to ensure there are no signs of misalignment, kinking of the hose, or stress at the connection points.

System Integration Check: Ensure that the hose and fittings are correctly oriented and do not interfere with other system components or create points of excessive wear.


Selecting and installing the correct size of reusable hydraulic hose fittings is not merely a technical necessity but a cornerstone of system safety and efficiency. By understanding the standard sizes available, adhering to ISO standards, and following proper measurement and installation techniques, one can ensure optimal system performance and longevity.


What is a reusable hydraulic fitting?

A reusable hydraulic fitting is designed to be assembled or disassembled without requiring crimping. These fittings are used to connect sections of hydraulic hoses and can be reused, offering flexibility and cost savings for hydraulic system maintenance and repair.

What does the dash size of a hydraulic fitting mean?

The dash size is a numerical indicator that specifies the size of a hydraulic fitting in sixteenths of an inch. For example, a -8 dash size means the fitting is designed for a hose with an inner diameter of 1/2 inch (8/16).

How do I know if a hydraulic fitting is compatible with my hydraulic fluid?

Compatibility between hydraulic fittings and the hydraulic fluid is crucial to avoid material degradation. Always check the material of the hydraulic fitting (e.g., stainless steel, brass) against the type of hydraulic fluid used, as some materials resist certain chemicals better than others.

How do I measure the diameter of a hydraulic fitting?

To measure the diameter of a hydraulic fitting, use calipers to measure the outer diameter of the male part or the inner diameter of the female part. It’s important to ensure accuracy to avoid mismatches.

How are hydraulic fitting sizes determined?

Hydraulic fitting sizes are typically determined by the inner diameter of the hose they are meant to connect. The size is often indicated using a “dash size,” which is a number that represents the inner diameter in sixteenths of an inch.

What are the common types of threads used in hydraulic fittings?

Common thread types used in hydraulic fittings include NPT (National Pipe Tapered), BSP (British Standard Pipe), and Metric. The type of thread affects compatibility and sealing effectiveness between fittings and hoses.

Can the same hydraulic fitting size be used for different hose types?

Not necessarily. While the fitting size might fit physically, different hose types may have different pressure ratings and structural compositions. It’s important to check both the size and type specifications to ensure proper fit and function.

What tools are needed to install a reusable hydraulic fitting?

Installing a reusable hydraulic fitting typically requires wrenches or pliers to tighten the fitting securely. It’s important to use tools that fit well and do not damage the fitting during installation. Optionally, a torque wrench can be used to apply the precise amount of torque as specified by the fitting manufacturer.