Features

• Compatible with ISO 2861 Clamped-Type Quick-Release Couplings
• Vacuum-Facing Parts Cleaned Ultrasonically
• To Request Other KF Flange Nominal Diameters, Please Contact Tech Support

KF flanges are ISO-standardized vacuum fittings that provide a vacuum seal by compressing a rubber O-ring between two mating surfaces. Also referred to as NW, QF, or DN flanges, KF flanges are ideal for quickly assembling vacuum systems thanks to their ease of use, maintenance, and reusability.

Thorlabs offers fittings to adapt KF25-flanged components to pipes with outer diameters of 0.250", 0.375", or 0.500" via a compression fitting. Thread adapters are also available to mate British Standard Pipe Parallel (BSPP) or double ferrule compression fittings to KF16 vacuum components. Our Ultra-High-Vacuum-Compatible Fiber Feedthrough KF40 Flanges allow for optical coupling into ultra-high-vacuum (UHV) systems down to 10^-8 Torr using SMA905-terminated fiber patch cables and mating sleeves. These adapters and fiber feedthroughs can be mated to a vacuum system using wing nut clamps and O-ring carriers. Our wing nut clamps and O-ring carriers, as well as our blank caps are available in KF16, KF25, and KF40 sizing. Key dimensions of these KF flanges can be found by visiting the KF Flange Sizes tab. Our in-house machine shop allows us to modify or customize components with any standard KF flange. To submit a request, please contact Tech Support.

For best performance, a very thin coating of vacuum grease should be applied to any O-ring used in a KF system. This should be done by hand while wearing gloves, leaving just enough grease to cause the O-ring to shine. The O-ring and its mating surfaces should be visually inspected before installation to ensure there is no debris which may prevent proper contact and cause a leak. O-rings should be regularly inspected to spot dry rot, cracking, tearing, or accumulation of debris from normal operation. Replace any O-ring suspected of causing a leak.

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Thorlabs KF40 Flange Measurements

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Thorlabs KF25 Flange Measurements

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Thorlabs KF16 Flange Measurements

KF Flange Sizes

KF flanges are defined by ISO 2861 Clamped-Type Quick-Release Couplings. This specification details the dimensions and tolerances for the five standard KF flange sizes: 10 mm, 16 mm, 25 mm, 40 mm, and 50 mm. These sizes are the nominal bore size of the flanged pipe. The name "KF" derives from the German phrase "Klein Flansche," literally translating to "small flange"; this name was used around the time of the flange's adoption by ISO and DIN, as flanges for pipes larger than 50 mm are more appropriately handled by flanges that deform metal gaskets to create a seal, like CF flanges.

Thorlabs offers from stock 16 mm, 25 mm, and 40 mm KF components and accessories. The dimensions of our flanges are shown in the diagrams to the right. Our in-house machine shop allows us to modify or customize components with any standard KF flange. To submit a request, please contact Tech Support.