Why Choose Our CF Fittings？
- Mazak CNC machining systems from Japan, stable precision and consistent knife-edge geometry.
- 22 quality inspection processes, covering raw material verification, precision control, surface treatment, etc.
- Certified in ISO quality management systems, meeting 3A, SMS, DIN standards.
- 2,000＋ standard specification, support quick delivery of common CF sizes and custom configurations.
- Provide complete traceability and OEM customization support.
OMSS — Your Reliable CF Fittings Manufacturer
OMSS has been CF Fitting manufacturing for over 15 years, and our products are exported to many countries and regions, such as North America, Europe, the Middle East, and more.
We offer various types of CF Fittings, including standard models such
as CF fixed fittings, CF rotatable fittings, and CF weld neck fittings, while also supporting customize designs based on your vacuum system structure.
OMSS supplies sanitary CF fittings with material types of 304, 304L, and 316L, which provide a clean surface and are suitable for high vacuum and high-purity gas delivery systems. If you have any needs, contact us, and we will provide support with solutions.
Our Products
Precision-made using high-precision machining techniques, ensuring precise knife-edge geometry.
Provided with a rotatable flange structure, ensuring easier alignment of the bolts during installation.
Designed for welding with vacuum pipelines, ensuring a strong structural connection while keeping the components stable.
Designed for compact vacuum components, ensuring easy installation through threaded connection without the need for welding.
Used to seal unused vacuum ports, manufactured with high surface finish.
Used to change the connection direction of vacuum pipelines, helping optimize vacuum system layout.
Used in the connection of CF flanges of different sizes, providing a smooth transition between the sizes.
Comprises a bellows-type structure that absorbs thermal and mechanical vibration, reducing stress.
Supports the connection of vacuum lines in different directions, allowing the distribution of pipelines in a single node.
Features of CF Fittings
Suitable for baking in a high-temperature baking environment, normally able to withstand temperatures over 450°C.
Due to the flange knife edge structure pressing on the annealed oxygen-free copper gaskets, a plastic deformation is achieved, providing a metal-to-metal seal.
With low leak rates, it is particularly suitable for high vacuum and ultra-high vacuum applications.
Made of high-strength stainless steel, with types ranging from 304, 304L, and 316L, providing high corrosion and mechanical strength.
Achieving Ultra-High Vacuum Range
Our CF Fittings are designed to meet the ultra-high vacuum requirement. The CF Fittings are capable of achieving a vacuum range of up to 10⁻¹² mbar with the help of the knife-edge metal sealing structure, which ensures a metal-to-metal seal with low leak rates. CF Fittings are used in semiconductor equipment, vacuum coating equipment, and scientific research-grade ultra-high vacuum applications.
Copper Gasket Sealing
The sealing mechanism employed by CF Fittings consists of annealed, oxygen-free copper gaskets. During the fitting, compression of the copper gasket by the knife edge results in plastic deformation, which fills all surface irregularities. This sealing mechanism is not only reliable but also easy to maintain. In addition, replacement of the copper gasket is all that is required after multiple assembly and disassembly cycles to maintain stable sealing, thereby making it easier to upgrade systems.
High-Precision Knife Edge
The sealing capability of the CF Fittings is significantly dependent upon the precision level of the knife edge design. Our products are precision-made using Mazak CNC machining equipment from Japan. The critical dimension tolerances of our fittings are tightly controlled within ±0.01mm.
The uniformity of the knife edge design ensures a uniform compression into the surface of the annealed oxygen-free copper gasket material when being installed. The stable machining precision level minimizes the possibility of uneven sealing, micro-leakage, etc.
Applications of CF Fittings
In the semiconductor manufacturing process, CF Fittings are used in the connection of pipelines in vacuum chambers, etching machines, and thin film deposition machines. The metal structure of the CF Fitting meets the demand of the high vacuum and ultra-high vacuum environments.
In the application of the vacuum pipeline connection with the experimental devices in the particle accelerators, synchrotron radiation, and other ultra-high vacuum devices, CF Fittings are used due to the reliability of the sealing requirement in the scientific research systems.
In vacuum coating systems, PVD, and CVD, CF Fittings are often used to connect the chambers with the pipelines. The reliable method of sealing is useful in keeping the vacuum stable, hence ensuring the stability of the coating process.
In the aerospace and high-tech industry, vacuum systems often require the use of CF Fittings for the sealing of equipment. This is useful in ensuring the stability of the equipment, hence satisfying the needs of the industry.
- Certificate of Compliance
Customer Reviews
We purchased sanitary tri clamp fittings and stainless steel ferrules from OMSS for our beverage processing system. The dimensions were accurate, the polishing was clean, and the fittings connected smoothly with our existing pipes without additional adjustment. The consistent quality helped us improve installation efficiency.
EmilyOMSS supported our custom stainless steel fitting project from drawing confirmation to final production. Their engineers provided useful suggestions on material selection and processing details. The finished components matched our requirements well and performed reliably in our food equipment applications.
JohnOMSS has become one of our trusted stainless steel component suppliers. We appreciate their fast communication, clear order updates, and careful packaging. Even for customized parts with different specifications, they maintain good consistency between samples and mass production.
Sarah
CF fittings utilize the knife-edge metal sealing mechanism and provide ultra-high vacuum conditions. On the other hand, KF fittings utilize elastomer O-ring seals and provide high vacuum conditions. KF fittings cannot provide conditions for high-temperature applications or long-term ultra-high vacuum conditions. When the system requires ultra-low leak rates, bakeability, semiconductor-grade vacuum applications, and research-grade vacuum applications, you must use CF flanges.
CF fitting parts are reusable if the knife edge of the fitting is in good condition. However, copper gaskets are consumable parts. When the system is disassembled, the copper gasket must be replaced with a new annealed copper gasket. If the copper gaskets are reused, the sealing performance of the system will be significantly degraded. The bolts and nuts of the CF fitting are reusable if they are not deformed. The status of the bolts and nuts must be regularly inspected.
The standard sizes of CF fittings include CF16, CF35, CF63, CF100, CF150, and so on. The numbers of the specifications refer to the outer diameter of the flange of the small flange itself.
CF16 is mostly used for small-diameter vacuum equipment or analytical equipment, whereas CF35 is used for small vacuum chambers in laboratories, and CF63 is used in semiconductor equipment and main channels of medium-sized vacuum chambers.
The bolt torque should be determined according to the flange size. For example, the recommended torque for the installation of a CF35 flange is about 15–20 Nm, and for a CF63 flange, it is about 30–35 Nm.
The reasons for seal failure include uneven torque, gasket reuse, and impurities on the fitting surface, so you should ensure the cleanliness of the fitting surface before installation.
CF fittings are available for high-purity gas and ultra-high vacuum systems, and they will not cause any contamination issues.
The metal sealing structure of the CF flange does not contain any rubber or polymer materials, so you will not encounter any issues such as those related to elastomer outgassing and gas permeation, and if you choose the 316L stainless steel or electropolished material, the outgassing rates will be lower.
The knife edge is the key component for achieving sealing capability for the CF fitting. In cases where there is apparent flattening, chipping, or scratches on the knife edge, it will be impossible for it to compress into the copper gasket for sealing. In such instances, it is recommended that it should be discarded.
In cases where minor marks do not have a major impact on the sharpness of the knife edge, it is possible to determine whether it should be discarded by means of microscopic examination. In UHV systems, it is recommended that once damage is apparent on the knife edge, it should be replaced.
The advantages of CF fittings are the metal sealing structure, which has a low leak rate and a high vacuum level, and is also capable of withstanding high temperatures in baking processes.
ISO fittings, on the other hand, are based on O-ring seals, which are easy to install but have low vacuum levels. CF fittings are used in UHV and R&D applications, while ISO fittings are used in medium or high vacuum, large diameter, and quick connection applications. CF fittings are also robust in structure, but the time taken in the installation process is longer, and the cost is also higher.
The thickness and annealing state of the copper gaskets will affect the overall sealing performance. Standard annealed oxygen-free copper gaskets are capable of plastic deformation and are in a stable state when compressed by the knife edge.
If the gasket is too hard or does not meet the standard thickness, it will affect the overall leak rate control.
What Is CF Fitting ?
CF fitting, also known as Conflat fitting, is a metallic connector used for high vacuum and ultra-high vacuum systems. The main application of the CF fitting is to connect various vacuum chamber components, pipelines, valves, etc. The components of the CF fitting include the CF flanges, bolt assembly, and annealed copper gaskets.
The main difference between the CF fitting and the conventional vacuum connectors is that the CF fitting uses the metal-to-metal connection method, whereas the conventional connectors make use of the rubber-sealed connection method. The stable connection is achieved by pressing the knife edge of the flange into the annealed copper gasket, resulting in low leak rates and the ability to withstand high-temperature baking procedures.
How to Choose the Right CF Fittings？
Clarify Vacuum Level
To choose the appropriate CF fittings, it is necessary to clarify the level of vacuum needed by the system. In the case of a general high vacuum system, it is possible to use the standard configurations of the CF fittings to fulfill the requirements of the system. In the case of ultra-high vacuum systems, it is necessary to use a higher level of precision, such as precision machine surfaces, stable metal structures, etc.
As a result, it is necessary to choose the appropriate specification of the CF fittings when designing a vacuum system, depending on the actual requirements of the system, such as HV or UHV.
Consider Pipe Diameter and Flow Rate
The size of the CF fittings has to correspond to the diameter of the vacuum pipeline and the conductance needs of the system. Generally, the higher the diameter of the pipeline, the higher the capacity of the gas to conduct, and this could lead to a reduction in the time taken to evacuate the system.
In the system design phase, it is necessary to integrate the concepts used in the calculation of the basic system conductance in order to reasonably determine different specifications, e.g., CF16, CF35, and CF63, in order to allow the system to effectively utilize the pumping speed of the vacuum pumps and avoid limitations in the system’s pumping speed due to the diameter of the pipeline.
Select According to Material (304 / 304L / 316L)
The materials used for CF fittings include 304, 304L, and 316L stainless steel. Different materials should be used depending on the application environment. 304 stainless steel has good mechanical properties and resistance to corrosion, which makes it suitable for normal vacuum systems.
304L stainless steel is used for applications that require stability, especially for welding applications, since it has low carbon content, which reduces carbon precipitation. 316L stainless steel has excellent resistance to corrosion, which makes it suitable for applications where higher cleanliness is required, especially for corrosive gases.
Bolt and Gasket Selection
The sealing of CF flittings is affected, apart from the flanges, by the selection of bolts and copper gaskets. Therefore, you should ensure that you select annealed oxygen-free copper gaskets of standard dimensions, so their thickness is compatible with the flanges.
Bolts should be tightened evenly, as recommended, to ensure the knife edge is pressed into the copper gasket, thus creating a metal seal and ensuring proper sealing by preventing uneven distribution of stress.
Installation Precautions and Common Leakage Issues of CF Fittings
Installation Steps
- Cleanliness Requirements：Before installing the CF components, the cleanliness of the sealing surfaces of the flanges, knife edges, and copper gaskets should be ensured. The presence of dust, oil, and even small particles may affect the knife edge and copper gasket interface. The cleanliness of the sealing surfaces of the flanges may be ensured by using lint-free wipes and anhydrous alcohol.
- Gasket Positioning：The copper gasket should be properly positioned between the two CF flanges and should be centered. The knife edge should be pressed into the copper gasket to ensure plastic deformation. However, if the positioning of the copper gasket is inaccurate, the sealing stress distribution may be affected, thereby affecting the sealing performance of the components.
- Diagonal Uniform Tightening：When tightening the bolts, the tightening should be done in a diagonal manner, tightening the bolts step by step. However, if one bolt is fully tightened, the flange may tilt, affecting the uniformity of the knife edge and copper gasket interface.
Common Leakage Causes
- Gasket Reuse：The copper gasket will suffer plastic deformation when compressed by the knife edge for sealing. After being compressed, the copper gasket’s structure will change permanently. Therefore, if you want to ensure a good seal, you should replace the copper gasket with a new one when you assemble the flange.
- Uneven Torque：Uneven torque may cause uneven force distribution on the flange’s sealing surfaces, resulting in insufficient compression of some areas and creating micro-leakage channels. Therefore, it is recommended to perform uniform tightening with a gradual torque value.
- Flange Knife-Edge Damage：The sealing of the CF flange is realized by a knife edge structure, and the knife edge is precision-made for the copper gasket. Therefore, if the knife edge is damaged, such as having scratches or deformation, it will lose its ability to compress the copper gasket for sealing.
