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All-Metal Sealing for Aluminum Vacuum

The Atlas CF™ Flange—the aluminum flange with a stainless steel knife-edge seal—makes high and ultra high aluminum vacuum systems a reality.  This allows vacuum engineers and designers to fully utilize the exceptional vacuum properties of aluminum.

We’ve combined the time-tested reliability of the stainless steel ConFlat® (CF) knife edge with an aluminum flange body for standard all-metal sealing and weld-up to an aluminum chamber.

The Atlas CF™ Flange is fully compatible with the industry standard ConFlat® flange interface. Employing CERN’s innovative 20° back-bevel (90° included angle) knife-edge design, the Atlas CF™ Flange provides a longer service life than conventional CF flanges.

Atlas CF™ Flanges are suitable for service in vacuum levels to 1 x 10-13 plus Torr and 250°C bake-out temperatures. Our bimetallic flanges can be easily welded to aluminum vacuum vessels and are the key to successful integration of aluminum UHV technology in your application.

Used in prominent high (HV), ultrahigh (UHV) and extreme high vacuum (XHV) applications around the world, they find extensive use with semiconductor fabrication OEMs where superior heat conduction, chemical resistance, manufacturing ease, and the lower cost of aluminum vacuum systems translate into measurable productivity and cost-of-ownership advantages.

Non-Magnetic Atlas CF™ Flanges: Atlas manufactures a large number of aluminum vacuum chambers and flanges for low-magnetic permeability applications. In addition to our standard bimetal flanges with a 316L knife edge, we also offer these flanges made with 316LN. 316LN has a significantly lower magnetic permeability than standard stainless steel. For applications requiring even lower permeability, we manufacture Atlas CF Flanges with a titanium knife edge and face. The titanium-faced Atlas CF flanges offer a non-magnetic, metal-seal flange with the favorable economic and vacuum advantages of an aluminum chamber.

Typical non-magnetic uses are UHV synchrotron, particle physics, and various industrial applications where high magnetic permeability is detrimental to beam quality or experimental results. Such applications include non-magnetic beam tubes, wigglers, undulators, free electron lasers, drift tubes, and spectrometers.

Low Z, Low Nuclear Activation Atlas CF Flanges: In neutron applications, such as the production of radioisotopes for medical imaging, aluminum vessels fitted with our flanges replace all-stainless steel UHV systems. Residual, neutron-induced radiation in aluminum has a half-life orders of magnitude shorter than that of stainless steel (which contains cobalt and chrome).

Our flanges enable aluminum UHV systems to be used in cyclotrons and nuclear reactors. For such applications, Atlas offers bimetal flanges with a reduced-thickness stainless steel face or a titanium face.

Light/Low Weight Atlas CF Flanges: For weight-sensitive applications such as aerospace or portable systems, Atlas offers custom flanges with a reduced cross section. Using these models, engineers can significantly reduce overall weight. Depending on size, these custom flanges have a cross section that is 20% to 40% thinner than standard flanges.

ConFlat® is a trademark of the Varian Corporation.

  • Patented UHV aluminum-to-stainless explosion welding technology (EXW) that is only available from Atlas.
  • UHV Rated to 1 x 10-13 Torr.
  • 1/3 the weight of stainless flanges.
  • 90° included angle long-life knife edge design, developed at CERN.
  • 100% Compatible with the industry standard Conflat ® interface.
  • Standard and reduced stainless steel models available.
  • Cryogenic, non-magnetic, rectangular and other specialty flange solutions also available.


  • UHV Rated to 1×10 -13+ Torr
  • 90° included angle, long-life knife-edge design, developed at CERN.
  • 100% Compatible with the industry standard ConFlat® interface.
  • Standard Flange sizes 1.33 –16.5”


  • Body/Weld Interface: Aluminum 6061-T6
  • Sealing Knife-Edge Face: Stainless Steel 316L
  • Rotatable Collar/Receiver: Aluminum 6061-T6, 304 Stainless Steel Optional


  • Vacuum Leak Tested: < 1 x 10-9 cc/sec of He


  • Peak Temperature: 300°C (during weld-up)
  • Operational Temperature: -200°C to 250°C

Mechanical—Explosion Bonded Interface

  • Tensile: 15,00psi (103MPa)
  • Shear: 10,000psi (69MPa)

Diagrams & Variations

Choose Size

Click images above for larger version.

Rotation Bore Bolt Holes Part # Hardware Files Actions
Rotatable 0.75" M6 mm Tap CFBI-0212-23 Show
Rotatable Blank M6 mm Tap CFBI-0212-26 Show
Rotatable 0.75" 1/4-28 US Tap CFBI-0212-13 Show
Rotatable Blank 1/4-28 US Tap CFBI-0212-16 Show
Rotatable 0.75" 0.265 Clearance CFBI-0212-03 Show
Rotatable Blank 0.265 Clearance CFBI-0212-06 Show
Non-Rotatable 0.75" M6 mm Tap CFBI-0212-22 Show
Non-Rotatable Blank M6 mm Tap CFBI-0212-25 Show
Non-Rotatable 0.75" 1/4-28 US Tap CFBI-0212-12 Show
Non-Rotatable Blank 1/4-28 US Tap CFBI-0212-15 Show
Non-Rotatable 0.75" 0.265 Clearance CFBI-0212-02 Show
Non-Rotatable Blank 0.265 Clearance CFBI-0212-05 Show
Rotation Bore Bolt Holes Part # Hardware Files Actions
Non-Rotatable Blank 0.265 Clearance CFBI-0212-04 Show
Non-Rotatable 0.75" 0.265 Clearance CFBI-0212-01 Show
Non-Rotatable 0.75" 1/4-28 US Tap CFBI-0212-11 Show
Non-Rotatable Blank 1/4-28 US Tap CFBI-0212-14 Show
Non-Rotatable 0.75" M6 mm Tap CFBI-0212-21 Show
Non-Rotatable Blank M6 mm Tap CFBI-0212-24 Show
Rotation Bore Bolt Holes Part # Hardware Files Actions
Non-Rotatable 0.75" M6 mm Tap CFBI-0212-27 Show
Non-Rotatable 0.75" 1/4-28 US Tap CFBI-0212-17 Show
Non-Rotatable 0.75" 0.265 Clearance CFBI-0212-07 Show

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