Generally speaking, the expansion screw consists of a screw and an expansion tube and other components, the screw tail is conical, and the inner diameter of the cone is greater than the inner diameter of the expansion tube.

When the nut is tightened, the screw moves outward, the cone part moves through the axial movement of the thread, and then forms a large positive pressure on the outer surface of the expansion tube, and the Angle of the cone is small, so that the friction self-locking is formed between the wall, the expansion tube and the cone, and then achieves the fixing effect.

Expansion screws are generally used for securing materials such as guardrail, awning, air conditioning, etc., on cement and bricks. In the case of good environment, expansion screws can be used for decades, like the expansion screws on ordinary air conditioners, the expansion screws on ordinary water heaters, and the expansion screws on home decoration ceilings, all of which need not be replaced for decades.