The existing circular tube needs to drill three holes in its wall along the radial direction of the circular tube, and the included angle between every two adjacent holes is required to be equal. Originally, there was no special mold, so we had to draw a line on the circular tube to locate the punching position of three holes, and then punch three holes on the circular tube in turn. Using line drawing to locate the punching position is easy to make the position of the three holes inaccurate, which will greatly reduce the production efficiency. Just fix it.