Welding Neck Flanges Tolerance

Tolerances for Welding Neck Flanges
Outside Diameter
24" and smaller 
± 1.6 mm.
26" and larger
± 3.2 mm.
Inside Diameter
10" and smaller
± 0.8 mm.
12" a 18"
± 1.6 mm.
20" and larger
+ 3.2 mm. - 1.6 mm.
Diameter of
Contact  Face
Raised face 1.6 mm.
± 0.8 mm.
Raised face 6.35 mm.
± 0.5 mm.
Tongue and Groove 
± 0.5 mm.
Male and Female
± 0.5 mm.
Diameter of Hub at the point of Welding 
5" and smaller
+ 2.4 mm. - 0.8 mm.
6" and larger
+ 4 mm. - 0.8 mm.
Diameter of Hub at Base 
Diameter at base 24" = 609.6 mm and smaller.
± 1.6 mm.
Diameter at base larger than 24" = 609.6 mm.
± 3.2 mm.
Drilling 
Bolt Circle
±1.6 mm.
Bolt hole spacing
± 0.8 mm.
Excentricity of Bolt-circle facing with respect to bore 
≤ 2.1/2" 0.8 mm.   
≥ 3" 1.6 mm.
Width of Land 
For all Sizes
± 0.8 mm.
Angle of Bevel 
For all Sizes
± 2º30'
Overall Height 
10" and smaller
± 1.6 mm.
12" and larger
± 3.2 mm.
Thickness 
18" and smaller
+ 3.2 mm. - 0 mm.
20" and larger
+ 4.8 mm. - 0 mm.

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