推荐回答（5个）
区分半牙和全牙螺栓的最简单的方法是直接拿螺栓看，螺纹布满整个螺杆的就是全牙，螺纹只分布在螺栓头部的就是半牙。另外，GB/T5780、GB/T5782为半牙(4.8级），GB/T5781、GB/T5783为全牙（8.8级）
ISO的不清楚，国标的是这样的
以普通C级六角螺栓来说GB/T5780就是半螺纹的，而 GB/T5781是全螺纹的
M20大概参数，六角最大的尖角距离30，厚度12.5，螺杆长度80-200，有效螺纹分三种46；52；65
4.8级半牙外六角 ISO 4016 GB 5780 DIN 601
4.8级全牙外六角 ISO 4018 GB 5781 DIN 558
8.8级及以上半牙外六角 ISO 4014 GB 5782 DIN 931
8.8级及以上全牙外六角 ISO 4017 GB 5783 DIN 933
其中4.8级螺栓，DIN标准以取消，目前德国4.8级螺栓已取消
国标的是这样的
以普通C级六角螺栓来说GB/T5780就是半螺纹的，而 GB/T5781是全螺纹
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