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国内外,压下螺丝头部的形状主要有凸球面、凹球面和平面三种;通常都是将头部与螺丝本体制成一个整体件;与压下螺丝头部直接接触的是安全臼或球面铜垫。
Domestic and international, the shape of the head screw down the main convex spherical, concave spherical and three kinds of plane; usually the head and the screw body made of a single piece; with the screw head is in direct contact with safety mortar or Spherical copper pad.