Generally, it refers to the wood screws with sharp head, coarse teeth and hard texture, as well as aluminum alloy and plastic. A special self tapping screw for tapping metal holes is called a tap.
Self tapping screw is used for non-metallic or soft metal, without bottom hole and tapping; self tapping screw is pointed, so as to "self tapping"; ordinary screws are flat head, with the same thickness.
Self tapping screw is to say: the hole drilled is the hole without tapping teeth, and the screw used is different from the general one. The head is pointed, and the pitch is relatively large, which is similar to the non chip tapping. It can be screwed in directly without tapping teeth. This method is usually used for metal and plastic.
It can tap, drill, squeeze and press the solidified body out of the corresponding thread on the consolidated material by its own thread, so as to make it closely cooperate with each other.