{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "conflat-cf-flanges",
 "name": "ConFlat (CF) knife-edge vacuum flanges to ISO 3669: flange OD, bolt circle, hole count and diameter, thickness, tapped thread, 1.33 to 8 in + bolt-pattern templates",
 "kind": "standard",
 "category": "Hardware",
 "group": "Vacuum flanges",
 "year": null,
 "question": "What are the OD, bolt circle and number of bolts of a CF 2.75 in (DN40CF) ConFlat flange?",
 "tags": [
  "conflat",
  "cf flange",
  "knife edge",
  "uhv",
  "vacuum flange",
  "iso 3669",
  "dn40cf",
  "bolt circle",
  "vacuum",
  "tool"
 ],
 "aliases": [
  "cf flange dimensions",
  "conflat flange bolt circle",
  "cf 2.75 flange od",
  "dn40cf dimensions",
  "cf 4.5 flange bolt pattern",
  "cf 6 inch flange",
  "conflat flange size chart",
  "cf35 flange",
  "cf63 bolt circle",
  "cf100 flange",
  "cf16 flange 1.33",
  "uhv flange bolt pattern",
  "ISO 3669 cf flange"
 ],
 "overall_mm": {
  "length": 203,
  "width": 203,
  "height": 6
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/conflat-cf-flanges/",
 "sheet_txt": "https://xemstudio.com/objects/conflat-cf-flanges/sheet.txt",
 "sheet": {
  "basis": "Neyco's CF flange catalogue table (fixed blank flanges), cross-checked against Kurt J. Lesker's catalogue and two Vacgen listings, read in this session; numbers and bolt-pattern templates only",
  "overall_mm": {
   "length": 203,
   "width": 203,
   "height": 6
  },
  "notes": [
   "A ConFlat (CF) flange is the all-metal UHV flange: a knife edge on each face bites into a copper gasket. North American sizes are named by the flange OD in inches (1.33, 2.75, 4.5, 6, 8 in); European sizes by the nominal tube ID in mm (DN16CF, DN40CF, DN63CF, DN100CF, DN160CF). The standard is ISO 3669 (the 2020 edition is marked withdrawn, revised as ISO 3669:2026; its summary prints a knife edge height 0.65 ± 0.05 mm; no other numbers of it were readable).",
   "Table: Neyco page F8, 'fixed blank flange' P/N F16, F35, F63, F100, F150; mm. The OD is the column printed D1, the bolt circle PCD, the hole diameter BH and the thickness the column printed A; the extracted text does not define these letters, so they are matched by value to the other sources below. DN as printed by Neyco: 16, 35, 63, 100, 150; 2.75 in is also sold as DN40CF and 8 in as DN160CF.",
   "Cross-checks: Lesker's catalogue (extracted text, third data column unlabelled) gives 6 holes, hole 0.172 in, tapped 8-32, bolt circle 1.062 in (26.9 mm) for 1-1/3 in; 6, 0.265 in (6.73 mm), 1/4-28, 2.312 in (58.7 mm) for 2-3/4 in; 8, 0.332 in (8.4 mm), 5/16-24, 3.628 in (92.2 mm) for 4-1/2 in; and rows for 2-1/8 in (4 holes, 1.625 in) and 3-3/8 in (8 holes, 2.850 in) that Neyco does not list. Lesker's 6 and 8 in rows were not in the text read. Bolt circles agree within rounding (Neyco 27 / 58 / 92 against Lesker 26.9 / 58.7 / 92.2 mm and Vacgen 27 / 58.7 / 181).",
   "Disagreements, shown not resolved: hole 6.7 (Neyco), 6.73 (Lesker) and 6.8 (Vacgen 70 mm) on the 2.75 in flange; 8.3 (Neyco) against 8.4 mm (Lesker) on the 4.5 in; thickness 12.7 (Neyco A) against 13 (Vacgen B) on 2.75 in, and 22.3 against 22 on 8 in; Vacgen's 34 mm listing prints the tapped thread as M6, Neyco M4 and Lesker 8-32 (M4). The Vacgen 203 mm listing also prints a Ø8.4 mm hole against Neyco 8.3.",
   "Vacgen's listings add: 70 mm flange: land thickness 4.8, bolt circle 58.7; 203 mm flange: land thickness 9.5. These are a maker's own dimensions for those parts, not standard values. Knife-edge diameter, groove diameter and gasket sizes were not read from any source and are not given.",
   "Files: CF bolt-pattern templates, one per size, drawn with Neyco's OD, bolt circle, hole count and hole diameter. 6 mm thickness (the catalogue flange thickness is in the table), the central aperture (half the bolt circle) and the first hole position (on +X) are Xem choices; the knife edge, bore and tube are not modelled. Hole position relative to the axis (straddling or on it) is not given by the sources.",
   "Small flanges are on iso-kf-flanges-nw10-nw50 and large ISO flanges on iso-k-iso-f-flanges-dn63-dn630. McMaster-Carr's vacuum-fittings category is linked for per-part STEP."
  ],
  "table": {
   "columns": [
    "size (OD)",
    "DN (Neyco)",
    "flange OD (mm)",
    "bolt circle (mm)",
    "holes",
    "hole Ø (mm)",
    "tapped thread",
    "thickness A (mm)"
   ],
   "rows": [
    [
     "CF 1.33 in",
     "16",
     34,
     27,
     6,
     4.3,
     "M4",
     "7.6"
    ],
    [
     "CF 2.75 in",
     "35 (also DN40)",
     70,
     58,
     6,
     6.7,
     "M6",
     "12.7"
    ],
    [
     "CF 4.50 in",
     "63",
     114,
     92,
     8,
     8.3,
     "M8",
     "17.4"
    ],
    [
     "CF 6.00 in",
     "100",
     152,
     130,
     16,
     8.3,
     "M8",
     "19.9"
    ],
    [
     "CF 8.00 in",
     "150 (also DN160)",
     203,
     181,
     20,
     8.3,
     "M8",
     "22.3"
    ],
    [
     "Lesker 1-1/3 in",
     "—",
     "—",
     "1.062 in (26.9 mm)",
     "6",
     "0.172 in (4.3 mm)",
     "8-32 (M4)",
     "—"
    ],
    [
     "Lesker 2-3/4 in",
     "—",
     "—",
     "2.312 in (58.7 mm)",
     "6",
     "0.265 in (6.73 mm)",
     "1/4-28 (M6)",
     "—"
    ],
    [
     "Lesker 4-1/2 in",
     "—",
     "—",
     "3.628 in (92.2 mm)",
     "8",
     "0.332 in (8.4 mm)",
     "5/16-24 (M8)",
     "—"
    ],
    [
     "Lesker 2-1/8 in (not in the Neyco table)",
     "—",
     "—",
     "1.625 in",
     "4",
     "0.265 in",
     "1/4-28",
     "—"
    ],
    [
     "Lesker 3-3/8 in (not in the Neyco table)",
     "—",
     "—",
     "2.850 in",
     "8",
     "0.332 in",
     "5/16-24",
     "—"
    ]
   ]
  }
 },
 "sheet_text": "ConFlat (CF) knife-edge vacuum flanges to ISO 3669: flange OD, bolt circle, hole count and diameter, thickness, tapped thread, 1.33 to 8 in + bolt-pattern templates — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/conflat-cf-flanges/  (sheet CC BY 4.0)\nBasis: Neyco's CF flange catalogue table (fixed blank flanges), cross-checked against Kurt J. Lesker's catalogue and two Vacgen listings, read in this session; numbers and bolt-pattern templates only\nCatalog version: 2026-10-20\n\nOverall (mm): length 203.0, width 203.0, height 6.0\n- A ConFlat (CF) flange is the all-metal UHV flange: a knife edge on each face bites into a copper gasket. North American sizes are named by the flange OD in inches (1.33, 2.75, 4.5, 6, 8 in); European sizes by the nominal tube ID in mm (DN16CF, DN40CF, DN63CF, DN100CF, DN160CF). The standard is ISO 3669 (the 2020 edition is marked withdrawn, revised as ISO 3669:2026; its summary prints a knife edge height 0.65 ± 0.05 mm; no other numbers of it were readable).\n- Table: Neyco page F8, 'fixed blank flange' P/N F16, F35, F63, F100, F150; mm. The OD is the column printed D1, the bolt circle PCD, the hole diameter BH and the thickness the column printed A; the extracted text does not define these letters, so they are matched by value to the other sources below. DN as printed by Neyco: 16, 35, 63, 100, 150; 2.75 in is also sold as DN40CF and 8 in as DN160CF.\n- Cross-checks: Lesker's catalogue (extracted text, third data column unlabelled) gives 6 holes, hole 0.172 in, tapped 8-32, bolt circle 1.062 in (26.9 mm) for 1-1/3 in; 6, 0.265 in (6.73 mm), 1/4-28, 2.312 in (58.7 mm) for 2-3/4 in; 8, 0.332 in (8.4 mm), 5/16-24, 3.628 in (92.2 mm) for 4-1/2 in; and rows for 2-1/8 in (4 holes, 1.625 in) and 3-3/8 in (8 holes, 2.850 in) that Neyco does not list. Lesker's 6 and 8 in rows were not in the text read. Bolt circles agree within rounding (Neyco 27 / 58 / 92 against Lesker 26.9 / 58.7 / 92.2 mm and Vacgen 27 / 58.7 / 181).\n- Disagreements, shown not resolved: hole 6.7 (Neyco), 6.73 (Lesker) and 6.8 (Vacgen 70 mm) on the 2.75 in flange; 8.3 (Neyco) against 8.4 mm (Lesker) on the 4.5 in; thickness 12.7 (Neyco A) against 13 (Vacgen B) on 2.75 in, and 22.3 against 22 on 8 in; Vacgen's 34 mm listing prints the tapped thread as M6, Neyco M4 and Lesker 8-32 (M4). The Vacgen 203 mm listing also prints a Ø8.4 mm hole against Neyco 8.3.\n- Vacgen's listings add: 70 mm flange: land thickness 4.8, bolt circle 58.7; 203 mm flange: land thickness 9.5. These are a maker's own dimensions for those parts, not standard values. Knife-edge diameter, groove diameter and gasket sizes were not read from any source and are not given.\n- Files: CF bolt-pattern templates, one per size, drawn with Neyco's OD, bolt circle, hole count and hole diameter. 6 mm thickness (the catalogue flange thickness is in the table), the central aperture (half the bolt circle) and the first hole position (on +X) are Xem choices; the knife edge, bore and tube are not modelled. Hole position relative to the axis (straddling or on it) is not given by the sources.\n- Small flanges are on iso-kf-flanges-nw10-nw50 and large ISO flanges on iso-k-iso-f-flanges-dn63-dn630. McMaster-Carr's vacuum-fittings category is linked for per-part STEP.\n\nsize (OD)  DN (Neyco)  flange OD (mm)  bolt circle (mm)  holes  hole Ø (mm)  tapped thread  thickness A (mm)\nCF 1.33 in  16  34  27  6  4.3  M4  7.6\nCF 2.75 in  35 (also DN40)  70  58  6  6.7  M6  12.7\nCF 4.50 in  63  114  92  8  8.3  M8  17.4\nCF 6.00 in  100  152  130  16  8.3  M8  19.9\nCF 8.00 in  150 (also DN160)  203  181  20  8.3  M8  22.3\nLesker 1-1/3 in  —  —  1.062 in (26.9 mm)  6  0.172 in (4.3 mm)  8-32 (M4)  —\nLesker 2-3/4 in  —  —  2.312 in (58.7 mm)  6  0.265 in (6.73 mm)  1/4-28 (M6)  —\nLesker 4-1/2 in  —  —  3.628 in (92.2 mm)  8  0.332 in (8.4 mm)  5/16-24 (M8)  —\nLesker 2-1/8 in (not in the Neyco table)  —  —  1.625 in  4  0.265 in  1/4-28  —\nLesker 3-3/8 in (not in the Neyco table)  —  —  2.850 in  8  0.332 in  5/16-24  —\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Neyco (CF flange catalogue, page F8): Fixed blank CF flanges F16 to F272: DN, A, D1, GR, PCD, BH, bolt holes count, tapped thread; letters not defined in the extracted text — web — Maker catalogue; numbers only — https://www.neyco.fr/uploads/media/category/0001/03/Vacuum-F-Brides-CF.pdf\n- Kurt J. Lesker (catalogue, extracted text): Flanges, fittings and components: CF fixed flange standard dimensions (bolts, hole diameter, tapped thread, bolt circle); size lists for KF 1-4 and ISO 1-5 — web — Maker catalogue copy; numbers only. Column letters were not labelled in the extracted text — https://www.acomee.com.mx/catalogos/catalogosk/KURT-J-LESKER FLANGES, FITTINGS AND COMPONENTS.pdf\n- Vacgen (CFR34-6 listing): 304L rotatable bored CF flange 34 mm OD (DN16): flange thickness B 7.6, bolt circle F 27, 6 holes of 4.3 mm, tapped thread printed M6 — web — Maker listing; numbers only — https://vacgen.com/34mm-od-6mm-id-304l-rotable-bored-cf-flange\n- Vacgen (CF70-41 listing): 304L fixed bored CF flange 70 mm OD: clear bore A 40, flange thickness B 13, land C 4.8, counter bore D 41.3, bolt circle F 58.7, clear holes 6.8 mm, 6 holes, tapped M6 — web — Maker listing; numbers only — https://vacgen.com/70mm-od-41mm-id-304l-fixed-bored-cf-flange\n- Vacgen (CF203 listing): 316LN fixed bored CF flange 203 mm OD: OD 203, flange thickness B 22, land C 9.5, bolt circle F 181, 20 holes of 8.4 mm, tapped M8 — web — Maker listing; numbers only — https://vacgen.com/203mm-od-153mm-id-316ln-2d-fixed-bored-cf-flange\n- ISO (iTeh catalogue): ISO 3669:2020 Vacuum technology - Dimensions of knife-edge flanges (withdrawn, revised as ISO 3669:2026); knife edge height 0.65 ± 0.05 mm — web — Publisher's page; dimensions are facts — https://standards.iteh.ai/catalog/standards/iso/02727f16-c080-4811-8a11-c40453bd9e38/iso-3669-2020\n- McMaster-Carr: Vacuum fittings (KF / ISO flanges) (free STEP/IGES per part, for your own design use; no redistribution) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution [verify license at link] — https://www.mcmaster.com/products/vacuum-fittings/\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=conflat-cf-flanges\n",
 "sources": [
  {
   "publisher": "Neyco (CF flange catalogue, page F8)",
   "title": "Fixed blank CF flanges F16 to F272: DN, A, D1, GR, PCD, BH, bolt holes count, tapped thread; letters not defined in the extracted text",
   "url": "https://www.neyco.fr/uploads/media/category/0001/03/Vacuum-F-Brides-CF.pdf",
   "formats": [
    "web"
   ],
   "license": "Maker catalogue; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Kurt J. Lesker (catalogue, extracted text)",
   "title": "Flanges, fittings and components: CF fixed flange standard dimensions (bolts, hole diameter, tapped thread, bolt circle); size lists for KF 1-4 and ISO 1-5",
   "url": "https://www.acomee.com.mx/catalogos/catalogosk/KURT-J-LESKER FLANGES, FITTINGS AND COMPONENTS.pdf",
   "formats": [
    "web"
   ],
   "license": "Maker catalogue copy; numbers only. Column letters were not labelled in the extracted text",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Vacgen (CFR34-6 listing)",
   "title": "304L rotatable bored CF flange 34 mm OD (DN16): flange thickness B 7.6, bolt circle F 27, 6 holes of 4.3 mm, tapped thread printed M6",
   "url": "https://vacgen.com/34mm-od-6mm-id-304l-rotable-bored-cf-flange",
   "formats": [
    "web"
   ],
   "license": "Maker listing; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Vacgen (CF70-41 listing)",
   "title": "304L fixed bored CF flange 70 mm OD: clear bore A 40, flange thickness B 13, land C 4.8, counter bore D 41.3, bolt circle F 58.7, clear holes 6.8 mm, 6 holes, tapped M6",
   "url": "https://vacgen.com/70mm-od-41mm-id-304l-fixed-bored-cf-flange",
   "formats": [
    "web"
   ],
   "license": "Maker listing; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Vacgen (CF203 listing)",
   "title": "316LN fixed bored CF flange 203 mm OD: OD 203, flange thickness B 22, land C 9.5, bolt circle F 181, 20 holes of 8.4 mm, tapped M8",
   "url": "https://vacgen.com/203mm-od-153mm-id-316ln-2d-fixed-bored-cf-flange",
   "formats": [
    "web"
   ],
   "license": "Maker listing; numbers only",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "ISO (iTeh catalogue)",
   "title": "ISO 3669:2020 Vacuum technology - Dimensions of knife-edge flanges (withdrawn, revised as ISO 3669:2026); knife edge height 0.65 ± 0.05 mm",
   "url": "https://standards.iteh.ai/catalog/standards/iso/02727f16-c080-4811-8a11-c40453bd9e38/iso-3669-2020",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Vacuum fittings (KF / ISO flanges) (free STEP/IGES per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/products/vacuum-fittings/",
   "formats": [
    "STEP",
    "IGES",
    "PDF"
   ],
   "license": "McMaster-Carr site terms: personal design use, no redistribution",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "iso-kf-flanges-nw10-nw50",
  "iso-k-iso-f-flanges-dn63-dn630",
  "asme-b16-5-class-150-flanges",
  "asme-b16-5-flange-bolt-patterns",
  "socket-head-cap-screws-metric",
  "tri-clamp-ferrule"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no tolerance added)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no tolerance added. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn. Typical accuracy by process and ISO 286 fits: https://xemstudio.com/tolerances/",
 "mating": [
  {
   "feature": "CF bolt holes",
   "exact": "1.33 in: 6 × Ø4.3 on Ø27; 2.75 in: 6 × Ø6.7 on Ø58 (Lesker 58.7); 4.5 in: 8 × Ø8.3 on Ø92; 6 in: 16 × Ø8.3 on Ø130; 8 in: 20 × Ø8.3 on Ø181 (Neyco; sources differ by 0.1 mm on some holes)",
   "mates": "bolts through the mating CF flange's identical pattern, or its tapped holes M4 / M6 / M8 (Neyco) or 8-32 / 1/4-28 / 5/16-24 (Lesker)",
   "fit": "slide",
   "files": "cf-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. ISO 286 equivalent: H7/p6 (locational interference) or tighter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. ISO 286 equivalent: H7/g6 or H7/h6.",
  "run": "turns or slides in use: pin in a link, rod through a guide. ISO 286 equivalent: H8/f7 (close running).",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. ISO 286 equivalent: H9/d9 (free running) or looser.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "What is the bolt circle of a 2.75 in ConFlat flange?",
   "a": "58.7 mm (2.312 in) in Lesker and Vacgen, 58 mm rounded in Neyco; 6 holes of about 6.7 mm, flange OD 70 mm (DN40CF)."
  },
  {
   "q": "How many bolts does a CF 6 in flange have?",
   "a": "16 holes of Ø8.3 on a 130 mm bolt circle (Neyco, flange OD 152 mm)."
  },
  {
   "q": "How many bolts does a 4.5 in CF flange have?",
   "a": "8 on a 92 mm (3.628 in) bolt circle; hole 8.3 (Neyco) or 8.4 mm (Lesker)."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/conflat-cf-flanges/index.md"
}