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O-ring sizes for KF vacuum flanges

KF system (also known as: Klein Flange, ISO-KF, DN, NW, QF, and other names) is used for low to medium vacuum. DIN 28043 or Pneurop 6606 ISO 2961 Ref: ISO 2861:2013 Vacuum technology – Dimensions of clamped-type quick-release couplings

This is not the same as ISO-K, which is for larger flanges (63 to 250mm diameter) uses multiple claws or clamps to compress the o-ring. ISO-K is defined by ISO 1609/3669, and also DIN 28 404 . Also known as ISO-LF

Also is not CF, aka Conflat or ISO-F

KF nominal size I.D. (mm:inch) Section (mm:inch) BS 1806
10 15.24 : 0.60 5.334 : 0.210 312
test test multiline
16 18.288 : 0.72 5.334 : 0.210 314~
25 27.94 : 1.10 5.334 : 0.210 320
40 40.64 : 1.60 5.334 : 0.210 326
50 53.34 : 2.10 5.334 : 0.210 330

ISO-K flanges:

DN ID section
63 76 5.3
80 88 5.3
100 107 5.3
160 158 5.3
200 209 5.3
250 253 5.3
320 330 7

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