Thread Forming Self Tapping Screws- system evolved directly from the metal screws, thread forming Self Tapping Screws used to be pre-drilled, and then drive the screw into the hole, force out with the female thread, the original position in the female thread The materials will be relegated to the male, between what we called the thread forming Self Tapping Screws. only apply to plastic materials and has a thin, it is also developed the other kind of Thread Cutting Self Tapping Screws. (Thread Cutting Self Tapping Screws) -at the end of screws the cutting out of one or more channel mouth, so that in pre-drilling screw, the use of screw tail and teeth similar to tap the Ministry of the way to cutting out with the female thread. It can be used in thick, relatively hard or fragile materials such difficult shape.