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简介--[b]一、严格地说,UN、UNR、UNC、UNF、UNS以及UNEF是螺纹系列的规定代号,而不是某些英文词组的缩写:
统一螺纹:Unified Screw Threads( 由英国(United Kingdom)、加拿大(Canada)和美国(United States)於948年共同制定;
UN:外螺纹设计牙型根部可平可圆(A flat root contour is specified ,but it is necessary to provide for some threading tool crest wear, hence a rounded root contour cleared beyond the 0.25p flat width of the Basic Profile is optional.)
UNR:外螺纹设计牙型根部必须为圆弧(In order to reduce the rate of threading tool crest wear and to improve fatigue strength of a flat root thread, the Design Profile of the UNR thread has a non-reversing continuous curved root tangent to the thread flanks at a depth of 0.625 H.)
UNC:粗牙系列(Coarse-Thread Series);
UNF:细牙系列(Fine-Thread Series);
UNEF:超细牙系列(Extra-Fine-Thread Series);
UNS:特殊螺距系列(Selected Combinations和 Other Threads of Special Diameters, Pitches, and Lengths of Engagement);
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