Generally speaking, the expansion screw is a metal expansion screw. The fixation principle of the expansion screw is that the wedge Angle is used to promote the expansion to produce friction binding force and achieve the fixation effect. The screw is threaded at one end and tapered at the other. Bread outside a tin (have a plenty of steel tube), iron cylinder (steel tube) half number of incision, put them together into a good hole in the wall, then lock nut and the screw nut to pull, pull taper into the tin drum, tin drum is open, so firmly fixed on the wall, and is generally used in fence, rain loose, air conditioning, etc on the materials such as cement, brick of fastening. However, its fixation is not very reliable, if the load has a large vibration, may occur loose, so it is not recommended for the installation of ceiling fans. Ii. Scope of use Expansion screw as a result of drilling small, pull big, after using the exposure is flat, if need not be dismantled at will, keep metope level off the advantage is remarkable, widely used in various decoration occasions ☆ tighten air conditioning, water heater, range hood, etc ☆ fixed frameless balcony Windows, security doors and Windows, kitchen, bathroom components ☆ fixed ceiling screw (combined with casing and cone cap) ☆ other need fixed occasions