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justification for rejection of steel tube (Where light tubes approach the low limit of outside diameter, some 'black' threads (perfect at the root and imperfect at the crest) are to be expected beyond the gauge plane, but such 'black' threads shall not be regarded as justification for the rejection of the tubes. 薄壁管的外径接近下限值时,会有一些超过基准面的"黑皮"螺纹(根部完整,顶尖不完整),但这些"黑皮"螺纹不能作为钢管判废的依据。) |