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ISO-KF (NW, QF) small flanges to ISO 2861: flange OD, bore, O-ring and centering ring, KF10 to KF50

What is the outside diameter of a KF10, KF16, KF25, KF40 and KF50 vacuum flange, and what centering ring fits? · Standard part · basis: ISO 2861:2013 sample pages (d1, d2, d3, O-ring), a reseller table of external and internal diameter, and ANCORP's centering ring table, read in this session; numbers only

Also called: kf16 dimensions, kf25 flange od, kf40 flange dimensions, nw25 flange, nw40 flange od 55, iso kf flange size chart, kf flange sizes, kf vs nw flange, kf50 centering ring, quick flange dimensions, iso 2861 flange, kf10 outside diameter

Exact dimensions. Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part. Mating features

sizes: 5 in table

Notes

KF (also NW, QF or the Pneurop quick flange) is the small quick-release vacuum flange: two flanges with a chamfered back are held by a hinged or wing-nut clamp over a centering ring with an O-ring. The standard is ISO 2861; sizes are named by the nominal bore in mm. Values in mm unless stated.
Standard (ISO 2861 sample pages, nominal bores 10 / 16 / 25 / 40 / 50): d3 (outside diameter of the coupling, flange) is 30, 30, 40, 55, 75; d1 max (outside diameter of the connecting pipe) 14, 20, 28, 44.5, 61; d2 (diameter of the O-ring carrier retainer) 12.2, 17.2, 26.2, 41.2, 52.2; O-ring D 15, 18, 28, 42 (or a 5.33 mm section ring of 40.65 mm for 40) and 55 (or 53.3 mm for 50). The sample's decimals use commas and the tolerance signs were garbled, so tolerances are not given. The sample prints no chamfer angle, rim thickness or tube length, so no flange body is drawn.
The reseller table prints 'internal diameter' 14, 20, 28, 45, 57 mm (metric) or 12.7, 19.05, 25.4, 38.1, 50.8 mm (imperial tube sizes). These disagree with ISO d1 max for KF40 and KF50 (44.5 / 61), because the sources use different definitions: do not substitute one for the other.
Centering ring (ANCORP catalogue, inches): dimension A is 0.39, 0.63, 0.98, 1.53, 1.97 in for KF10 to KF50 and B 0.21 in; the catalogue does not define A and B in text, so they are given as printed. Its tubing OD cross-reference is 0.50, 0.75, 1.00, 1.50, 2.00 in (inch tube sizes).
MKS lists blank KF-10 to KF-50 flanges with a 0.20 in (5 mm) thickness; this is a catalogue thickness for those parts, not a standard value. The flange body is therefore not drawn: the sources read give no rim thickness, chamfer angle or clamp seat.
McMaster-Carr's vacuum-fittings category is linked for per-part STEP; the flange types are in ISO 2861, available from ISO.

ISO-KF (NW, QF) small flanges to ISO 2861: flange OD, bore, O-ring… size chart

flange	d3 flange OD (mm, ISO 2861)	d1 max (mm, ISO 2861)	d2 (mm, ISO 2861)	O-ring D (mm, ISO 2861)	'internal diameter' metric / imperial (mm, reseller)	tubing OD (in, ANCORP)	centering ring A × B (in, ANCORP)
KF10 (NW10, DN10KF, QF10)	30	14	12.2	15	14 / 12.7 (1/2 in)	0.50	0.39 (A) × 0.21 (B)
KF16 (NW16, DN16KF, QF16)	30	20	17.2	18	20 / 19.05 (3/4 in)	0.75	0.63 (A) × 0.21 (B)
KF25 (NW25, DN25KF, QF25)	40	28	26.2	28	28 / 25.4 (1 in)	1.00	0.98 (A) × 0.21 (B)
KF40 (NW40, DN40KF, QF40)	55	44.5	41.2	42 (or 40.65 with 5.33 section)	45 / 38.1 (1-1/2 in)	1.50	1.53 (A) × 0.21 (B)
KF50 (NW50, DN50KF, QF50)	75	61	52.2	55 (or 53.3 with 5.33 section)	57 / 50.8 (2 in)	2.00	1.97 (A) × 0.21 (B)

Mating features

Drawn at the exact size. Open press, slide, run and socket features by your process's clearance (tolerances by process); leave designed gaps and clamp fits as drawn.

feature	exact	mates with	fit	files
flange OD	Ø30 (KF10, KF16), Ø40 (KF25), Ø55 (KF40), Ø75 (KF50) (ISO 2861 d3)	hinged or wing-nut KF clamp that grips the flange back	clamp	all
centering ring (A)	0.39, 0.63, 0.98, 1.53, 1.97 in for KF10, 16, 25, 40, 50 (ANCORP, dimension A as printed)	seats between two KF flanges with its O-ring (ISO 2861 O-ring D 15, 18, 28, 42, 55 mm)	slide	all

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

ISO (iTeh preview)	ISO 2861:2013 Vacuum technology - Quick-release couplings - Dimensions (sample pages): nominal bores 10, 16, 25, 40, 50; d1 max, d2, d3, O-ring D, O-ring carrier d1, d5, d6	web	Standard preview; numbers only
ProSciTech (support article)	Vacuum flange types and sizes: NW/KF10 to NW/KF50 external diameter and internal diameter (metric and imperial)	web	Reseller article; numbers only
ANCORP (catalogue)	ISO quick flange (QF/KF) and large flange (LF) centering rings: ID cross-reference, A and B dimensions in inches (stainless and aluminium centering ring assemblies)	web	Maker catalogue; numbers only
MKS	ISO-KF blank flanges with bore: tube OD, bore, thickness 0.20 in (5 mm) for KF-10 to KF-50	web	Maker listing; numbers only
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
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

Xem scan

File coming

No downloadable true-size file yet: the published figures do not fix the whole shape, and Xem never guesses a number. A measured scan is planned; request it and it moves up.

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Plain text: sheet.txt · JSON: /api/geometry?object=iso-kf-flanges-nw10-nw50

Schematic, not to scale.