A perfected screw, for little consistent materials. (Machine-translation by Google Translate, not legally binding)

摘要

An improved screw, for inconsistent materials, characterized by comprising a thread whose tip angle of the generating triangle is less than 40 degrees, and extends to the bottom in contact with the head of the screw or leaving a stroke under the head, without thread to meet other needs, resulting in a reduced penetration torque and a large contact surface with the material and having a thin surface layer that extends to the entire thread of the screw and has characteristics of decrease in friction between the thread and the material of the screw. (Machine-translation by Google Translate, not legally binding)