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Cast Iron Flanges - ASME/ANSI Class 250

ASME/ANSI B16.1 Cast Iron Pipe Flanges and Flanged Fittings - Class 250 Flanges - outside and inside diameters, bolt circles, numbers and diameters of bolts.

ASME/ANSI B16.1 - 1998 - Cast Iron Pipe Flanges and Flanged Fittings - Class 250 Flanges - outside and inside diameters, bolt circles, numbers and diameters of bolts:

Cast Iron Flanges - ASME/ANSI 250 lb
Pipe Size
(inches)
Outside Diameter
(inches)
Number of Bolt HolesBolt Hole Diameter
(inches)
Bolt Circle
(inches)
1 4-7/8 4 3/4 3-1/2
1-1/4 5-1/4 4 3/4 3-7/8
1-1/2 6-1/8 4 7/8 4-1/2
2 6-1/2 8 3/4 5
2-1/2 7-1/2 8 7/8 5-7/8
3 8-1/4 8 7/8 6-5/8
3-1/2 9 8 7/8 7-1/4
4 10 8 7/8 7-7/8
5 11 8 7/8 9-1/4
6 12-1/2 12 7/8 10-5/8
8 15 12 1 13
10 17-1/2 16 1-1/8 15-1/4
12 20-1/2 16 1-1/4 17-3/4
14 23 20 1-1/4 20-1/4
16 25-1/2 20 1-3/8 22-1/2
18 28 24 1-3/8 24-3/4
20 30-1/2 24 1-3/8 27
24 36 24 1-5/8 32
30 43 28 2 39-1/4
36 50 32 2-1/4 46
42 57 36 2-1/4 52-3/4
48 65 40 2-1/4 60-3/4
  • 1 inch = 25.4 mm
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