Bolt circle diameter and pitch between bolt holes.

螺栓圆周直径及螺栓孔间距。

Pitch Diameter (D) is the diameter of the pitch circle.

节圆直径（D）： 节圆直径是节圆所在圆的直径。

The maximum inscribed circle diameter on the steel bar pitch of the grating .

钢格板开敞通孔的最大内接圆直径。