Screw, has head preformed of square pattern cavity, where pattern cavity comprises four rectilinear walls in part of head to form pattern cavity with side, and length of side is less than diameter of hole to be drilled

摘要

The screw (V) has a head (200) that is preformed of a square pattern cavity to drive the head through an end of a drill (300), where the drill drills a hole (T) of a thole pin (C). The pattern cavity comprises four rectilinear walls in an emerging upper part of the head to form the pattern cavity with a side, where length of the side is less than diameter of the hole to be drilled. The pattern cavity accommodates a triangular pattern cavity at an end of a triangular drill with three lips. The screw is made of high resistant materials such as tempered steel.