Screw: In machine construction, a usually circular cylindrical member with a continuous spiral rib or thread, used either as a fastener or as a force and motion modifier.
螺纹件： 机器结构中带连续螺旋肋的圆柱形件，用作紧固件或力和运动变换装置。
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Usually there are 12 categories which are bolt , stud, screw, nut , self tapping screw, wood screw, gasket, retainer ring, pin, composite member, bolting, and soldering lamp.