Expansion screws are generally referred to as metal expansion screws. Its fixing principle: the fixing of expansion screws is to use the wedge-shaped slope to promote expansion and generate frictional binding force to achieve a fixed effect.
The screw has a thread on one end and a taper on the other end. The outer shell is an iron sheet, an iron sheet cylinder, half of which has several cuts. Put them together into the holes made in the wall, and then lock the nut. The nut pulls the screw outward, and the taper is pulled into the iron sheet cylinder. The iron sheet cylinder is expanded. Open, so it is tightly fixed on the wall, generally used to fasten protective fences, awnings, air conditioners, etc. on cement, bricks and other materials.
Disadvantages: The fixation is not very reliable. If the load has a large vibration, it may loosen, so it is not recommended to install ceiling fans.