When the expansion screw is fixed, the trapezoid angle is used to exert the huge friction force on the expansion screw until it has the desired effect. We usually use expansion screw can be divided into two kinds, one is plastic, the other is iron. When it is used, it is mostly through the standard of expansion screw to get the corresponding hole, then the expansion screw can be used. So long as the expansion screw is opened, it has a very good fixing effect.

The expansion screw is threaded on one side tapered on the other. Generally, there is a layer of iron sheet around the group of expansion screws, some products of this layer are steel pipes. There are half incisions on the iron sheet cylinder, which are applied to the holes on the wall. If the cylinder of iron sheet expands, the tightening effect can be achieved very well.

Most of the expansion type screws are used on the protective fence, air conditioner other materials with bricks cement. The expansion screw is composed of screw, expansion tube other parts. At the bottom of the screw has a cone shape, the diameter of the cone is larger than the inner diameter of the expansion tube. When tightening the nut, the screw will move outward use the screw thread to move. Even when the force is large, it can achieve good tightening effect.