How to Measure ORFS Fittings


ORFS (O-Ring Face Seal) fittings are a vital component in hydraulic systems, known for their exceptional sealing capabilities and reliability in high-pressure applications. These fittings play a critical role in preventing leaks, ensuring system efficiency, and maintaining the overall integrity of hydraulic systems. Accurate measurement of ORFS fittings is essential to ensure proper fitment and compatibility, which directly impacts the performance and longevity of the equipment. This comprehensive guide will walk you through the precise process of measuring ORFS fittings, providing you with the knowledge and tools needed to achieve accurate and reliable measurements.

Understanding ORFS Fittings

ORFS hydraulic fittings are meticulously engineered with a unique design that includes a flat sealing surface and an O-ring integrated into the face of the fitting. This innovative design ensures a secure and leak-proof connection when the fitting is tightened against another flat surface, creating a highly reliable seal that can withstand significant pressure. This sealing mechanism is particularly effective in preventing hydraulic fluid leaks, which is crucial for maintaining the efficiency and safety of hydraulic systems.

ORFS O-ring


ORFS fittings are typically made from robust materials to ensure durability and performance in demanding environments. Common materials include:

Stainless Steel: Known for its corrosion resistance and strength, making it ideal for applications in harsh environments or where hygiene is critical.

Carbon Steel: Offers a good balance of strength, wear resistance, and cost-effectiveness, making it suitable for a wide range of applications.


ORFS fittings are available in various sizes to accommodate different system requirements and ensure a proper fit for a wide range of applications. The availability of multiple sizes ensures that these fittings can be used in diverse hydraulic systems, from small-scale operations to large industrial applications.

Key Features

Flat Face Design with an O-Ring Seal:

The flat face of the fitting, combined with an O-ring, ensures a tight seal that prevents leaks even under high pressure. This design feature is crucial for maintaining system integrity and performance.

High Resistance to Leaks and Pressure:

The O-ring face seal provides a robust barrier against hydraulic fluid leaks, enhancing the reliability of the hydraulic system. This high resistance to pressure and leaks makes ORFS fittings ideal for high-pressure applications.

How to Measure Hydraulic ORFS Fittings

Accurate measurement of ORFS (O-Ring Face Seal) hydraulic fittings is essential for ensuring compatibility and maintaining the integrity of hydraulic systems. The following step-by-step guide will help you measure ORFS fittings with precision, ensuring that your hydraulic systems function efficiently and reliably.

Identify the Fitting Type

Visual Inspection:

Initial Check: Begin with a visual inspection to confirm the fitting is an ORFS type. Look for the characteristic flat face and the O-ring groove. These features are distinct and help in identifying ORFS fittings.

Profile Comparison: Compare the fitting with standard ORFS profiles. This step is crucial as it helps distinguish ORFS fittings from other common types such as JIC (Joint Industry Council) or NPT (National Pipe Thread). ORFS fittings have a unique flat sealing surface designed to accommodate an O-ring, which sets them apart from other fittings with conical or tapered threads.

Measure the Thread Size

Using a Thread Gauge:

Thread Gauge Selection: Select a thread gauge that matches the suspected size of the fitting. Having a variety of gauges on hand can help in finding the correct match quickly.

Application: Place the gauge onto the threads of the fitting to determine the thread pitch and diameter.

Thread Pitch: Measure the distance between threads using the thread gauge. This is typically expressed in threads per inch (TPI) or millimeters per thread for metric fittings.

Thread Diameter: Measure the diameter across the widest part of the threads. This diameter is critical for ensuring the fitting will mate correctly with the corresponding component.


Cleaning: Clean the fitting threads to remove any debris that might interfere with accurate measurement. Use a brush or compressed air to ensure the threads are free from contaminants.

Gauge Insertion: Insert the thread gauge into the fitting’s threads.

Matching Threads: Match the threads with the correct gauge size. The gauge should fit snugly without forcing.

Recording Measurements: Record the thread diameter and pitch accurately for future reference and to ensure proper fitting selection.

Measure ORFS Fittings hex

Measure the Tube or Hose Size

Using Calipers:

Calipers are used to measure both the outside diameter (OD) and inside diameter (ID) of the tube or hose connected to the fitting. Accurate measurement of these dimensions ensures a proper fit and effective sealing.


Calibration: Ensure the calipers are calibrated and in good condition. Properly calibrated calipers are crucial for obtaining accurate measurements.

Positioning: Place the calipers perpendicular to the tube or hose to avoid skewed measurements. Misalignment can lead to incorrect readings.

Outside Diameter (OD): Measure the OD by placing the calipers around the widest part of the tube or hose. Ensure the calipers are snug but not compressing the material.

Inside Diameter (ID): Measure the ID by placing the calipers inside the tube or hose opening. The tips of the calipers should touch the inner walls without applying excessive force.

Recording Measurements: Record both the outside and inside diameters. These dimensions are critical for selecting the correct fitting size and ensuring a secure connection.

Measure the O-ring groove

Using an O-Ring Groove Gauge:

Groove Gauge: An O-ring groove gauge is specifically designed to measure the dimensions of the groove where the O-ring sits. Accurate measurement of the groove ensures the O-ring fits properly and provides an effective seal.


Gauge Selection: Select the appropriate O-ring groove gauge. Ensure the gauge matches the expected size of the groove.

Insertion: Insert the gauge into the groove to measure its depth and width. The gauge should fit snugly within the groove to provide accurate measurements.

Snug Fit: Ensure the gauge fits snugly into the groove to get accurate measurements. The fit should be neither too tight nor too loose.

Recording Measurements: Record the depth and width of the groove. These measurements are essential for selecting the correct O-ring size, which is critical for achieving a reliable seal.

Verify the Face Seal


Damage Check: Inspect the flat sealing surface for any damage or irregularities. A smooth, undamaged surface is essential for creating an effective seal.

Surface Condition: Ensure the sealing surface is free from scratches, dents, or other defects that could compromise the seal.

Using Calipers:

Use calipers to measure the diameter of the sealing face. This measurement helps in confirming the fitting’s compatibility with mating components.


Calibration: Ensure the calipers are calibrated. Accurate calipers are necessary for precise measurement.

Measuring Diameter: Measure the diameter of the flat sealing face.

Inspecting Surface: Inspect the surface for scratches, dents, or other damage. Any defects can affect the sealing ability and lead to leaks.

Ensuring Smoothness: Ensure the surface is smooth and free from defects that could compromise the seal.

Recording Measurements: Record the diameter of the face seal. This dimension is critical for ensuring the fitting will provide a leak-proof connection.

Common Measurement Challenges and Solutions

Misidentification of Fittings


One of the most common challenges when measuring ORFS fittings is the misidentification of the fitting type. ORFS fittings can sometimes be confused with other types of fittings, such as JIC or NPT, due to their similar appearance.


To avoid misidentification, it is essential to cross-reference the fittings with standard ORFS profiles. Utilize manufacturer catalogs and detailed specifications to confirm the fitting types accurately. This ensures that you are working with the correct fitting and can proceed with the appropriate measurement steps.

Difficulty Measuring Worn or Damaged Fittings


Measuring fittings that are worn or damaged poses a significant challenge. Wear and tear can alter the dimensions of the fittings, making it difficult to obtain accurate measurements. Damaged threads or grooves can further complicate the process, leading to potential errors in measurement.


For worn fittings, it is advisable to measure multiple points and average the results to get a more accurate representation of the original dimensions. Using a magnifying glass can help improve the visibility of damaged threads or grooves, allowing for a more precise measurement. If the damage is extensive, consider consulting with experts or using specialized measurement tools designed for assessing worn components.

Overcoming Challenges


Staying updated with the latest measurement tools and techniques is crucial for overcoming the challenges associated with measuring ORFS fittings. Outdated tools or methods can lead to inaccurate measurements and potential system failures.


Regularly update your measurement tools and techniques to ensure accuracy. Seek advice from industry experts or refer to updated industry standards for complex measurements. Continuous learning and adaptation to new measurement practices can significantly improve accuracy and reliability in measuring ORFS fittings. Investing in high-quality measurement tools and keeping them well-maintained also plays a critical role in overcoming these challenges.

How to Select the Right ORFS Hydraulic Fitting

Selecting the right ORFS (O-Ring Face Seal) hydraulic fitting is crucial for ensuring the efficiency, safety, and longevity of your hydraulic system. The following guide outlines key considerations and steps to help you choose the most appropriate ORFS fitting for your application.

Understand Your Application Requirements

Pressure and Temperature Ratings:

Determine the maximum operating pressure and temperature of your hydraulic system. ORFS fittings are known for their high-pressure capabilities, but it’s essential to select a fitting that can handle your specific requirements.

Fluid Compatibility:

Ensure the material of the ORFS fitting is compatible with the hydraulic fluid used in your system. Common materials include stainless steel, carbon steel, and brass, each offering different levels of resistance to various fluids and environmental conditions.

Environmental Conditions:

Consider the environmental conditions where the fittings will be used. Factors such as exposure to chemicals, humidity, and temperature variations can influence the choice of material and coating of the fittings.

Determine the Correct Size

Fitting Dimensions:

Measure the dimensions of the existing fittings or the components they will connect to, including the outside diameter (OD) and inside diameter (ID) of tubes or hoses, as well as thread sizes. Accurate measurements are critical for ensuring a proper fit.

Thread Type and Size:

Identify the thread type and size required for your application. Use a thread gauge to measure the thread pitch and diameter, and refer to industry standards to ensure compatibility.

Choose the Appropriate Material

ORFS connection

Select a fitting material that matches your application’s needs.

Stainless Steel: Ideal for corrosive environments and applications requiring high durability.

Carbon Steel: Offers a good balance of strength and cost-effectiveness, suitable for a wide range of applications.

Brass: Provides excellent corrosion resistance and is suitable for use with a variety of fluids, often used in applications requiring frequent adjustments.

Consider the Seal Type

O-Ring Material:

Choose an O-ring material compatible with your hydraulic fluid and operating conditions. Common O-ring materials include:

Nitrile (Buna-N): Good for general-purpose use with petroleum-based fluids.

Viton: Excellent chemical resistance and high-temperature performance.

EPDM: Suitable for brake fluids and phosphate ester-based fluids.

Face Seal:

Ensure the flat sealing surface of the fitting is smooth and free from defects. The integrity of the face seal is crucial for preventing leaks and maintaining system pressure.

Evaluate Manufacturer Specifications and Standards

Manufacturer Guidelines:

Refer to manufacturer catalogs and specifications to ensure the fittings meet the required standards and performance criteria for your application. Look for fittings that comply with industry standards such as ISO, SAE, and DIN.

Quality and Certification:

Choose fittings from reputable manufacturers with a proven track record of quality and reliability. Check for certifications and quality assurances that indicate the fittings meet rigorous testing and performance standards.

Assess Installation and Maintenance Needs

Ease of Installation:

Consider fittings that are easy to install and do not require special tools or extensive training. Proper installation is crucial for ensuring the longevity and reliability of the fittings.

Maintenance Requirements:

Select fittings that are easy to maintain and inspect. Regular maintenance and inspection are essential for preventing leaks and ensuring the system operates efficiently.


Accurate measurement of ORFS fittings is critical for maintaining the integrity and efficiency of hydraulic systems. Proper measurement ensures that fittings are compatible and correctly matched, which is essential for preventing leaks, ensuring optimal performance, and avoiding costly system failures. By meticulously following the steps outlined in this guide—identifying the fitting type, measuring thread size, assessing tube or hose dimensions, checking the O-ring groove, and verifying the face seal—you can achieve precise measurements.


What should I do if I can't identify the fitting type?

If you’re unable to identify the fitting type, consult manufacturer catalogs or online resources for reference images and specifications. Alternatively, you can contact the manufacturer or a hydraulic fittings specialist for assistance.

What if the thread size I measure doesn’t match standard sizes?

If the thread size doesn’t match standard sizes, recheck your measurements for accuracy. If the discrepancy persists, you may be dealing with a custom or non-standard fitting. Consult with the manufacturer for further guidance.

What tools do I need to measure ORFS fittings?

Essential tools for measuring ORFS fittings include calipers, thread gauges, and O-ring groove gauges. Ensuring these tools are in good condition and properly calibrated is crucial for accurate measurements.

How do I measure fittings that are worn or damaged?

For worn or damaged fittings, measure multiple points around the fitting and average the results to get a more accurate dimension. Use magnification tools to better see and measure worn threads or grooves.

How can I ensure my measurements are accurate?

To ensure accurate measurements, use properly calibrated tools, clean the fitting thoroughly before measuring, and take multiple measurements to confirm consistency. Double-check your readings and consult with industry standards.

How often should I calibrate my measurement tools?

Measurement tools should be calibrated regularly based on usage frequency. For high-precision tasks or frequent use, monthly calibration may be necessary. At a minimum, calibrate tools every six months to ensure accuracy.

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