英制螺纹标注说明

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英制螺纹标注说明
-、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-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)；