According to the national standard of the People's Republic of China GB-17395-1988 1 Allowable outer diameter deviation Table 1 Standardized outer diameter allowable deviation Deviation level Standardized outer diameter allowable deviation D1 ±1.5%, minimum ±0.75 mm D2 ±1.0%. Minimum ±0.50 mm D3 ±0.75%. Minimum ±0.30 mm D4 ± 0.50%. Minimum ±0.10 mm Table 5 Non-standardized outer diameter allowable deviation Deviation level Non-standardized outer diameter allowable deviation, % ND1 +1.25 -1.50 ND2 ±1.25 ND3 +1.25 -1.O ND4 ±0.8 2. The absolute tolerances of the outer diameter allowable deviations of special-purpose steel tubes and cold-rolled (pull-out) steel tubes can be used. 2.1 Wall thickness tolerances Wall thickness tolerances are divided into standard and non-standard. The standardized wall thickness tolerances should be prioritized (see Table 6). Table 6 Wall thickness tolerance deviation level Wall thickness tolerance S/D 0.1< S/DO. 05 0.025 S/D ≤ 0.025 S1 ±15%, minimum ±0.6 mm S2 A ±12.5%, minimum ±0.4 mm B + positive deviation depends on weight requirement -12.5 S3 A ±10%, minimum ±0.2mm B ±10% ±12.5% ​​±15% Minimum ±0.4mm C + positive deviation depends on weight requirement -10% S4 A ±7.5%, minimum ±0.15 mm B 7.5% ± 10% ± 12.5% ​​± 15% Minimum ± 0.2 mm S5 ±5%, minimum ±0.10 mm Note: S is the nominal wall thickness of the pipe and D is the nominal outside diameter of the pipe.
