The invention relates to a main axle structure of polygonal tail support, which is formed by upper frame, lower frame, main axle moving driving screw, and nut, wherein the main axle is a octahedron; the tail support frame is connected by upper and lower frames to form a main axle with an octahedron inner hole at the middle that matches the main axle; the lower two track surfaces of main axle via the track connects two track surfaces of lower frame; the upper two track surfaces of main axle are sliding connected to the two track surfaces of upper frame. The invention has simple adjustment, and confirmed accuracy of main axle. |