M12 expansion screws, hammer drill bit number
Outside the bread (some tin pipe), iron cylinder (steel tube) has several half incision, put them together into the wall lay the hole, then the lock nut, the nut screw pull, pull cylinder taper iron, iron cylinder is open up, so tightly fixed on the wall, generally used for protection bar, awning, air conditioning and other fastening in the cement, bricks and other materials. But its fixed is not very reliable, if the load has a larger vibration, may occur loose, so installation of ceiling fans and other tools are not suitable for use.
Expansion screw generally refers to the metal expansion screws, expansion screws fixed, but the use of wedge slope to promote expansion, friction, grip force, to achieve fixed effect. One end of the screw is threaded, and the other has taper.
Use 16 bit. The diameter of the outer diameter of the expansion screw is wider than that of the bolt 4mm.
