The fixing principle of steel drop in anchor : The fixing of expansion bolts is to use the slope of the shape to promote the expansion of friction and gripping force to achieve the fixing effect. The screw is threaded at one end and conical at the other. There is a steel skin on the outside, and there are some cuts in the half of the iron cylinder. Insert them together into the holes made in the wall, and then lock the nut. The nut pulls the screw outward and pulls the vertebra into the steel cylinder. The tube is expanded, so it is tightly fixed to the wall, and is generally used for the fastening of protective fences, rain canopies, air conditioners, etc. on cement, bricks and other materials. However, its fixation is not very reliable. If the load has large vibration, it may loosen, so it is not recommended for installing ceiling fans. The principle of the expansion bolt is to drive the expansion bolt into the hole on the ground or wall, and then tighten the nut on the expansion bolt with a wrench. The bolt goes out, but the outer metal sleeve does not move, so the big head under the bolt The metal sleeve expands so that it fills the entire hole. At this time, the expansion bolt cannot be pulled out.