What are the structural elements of self-tapping screws?

Update:26-07-2018
Summary:

The self-tapping screws are composed of the head, the r […]

The self-tapping screws are composed of the head, the rod and the end of the rod from beginning to end. Each self-tapping screw has four major components: head shape, wrenching, thread type, and end pattern. Head shape - the shape of the head is varied. Round head (semicircular head), oblate head, round head flange (with pad), flat head flange (with pad), pan head, pan head flange (with pad), countersunk head, semi-recessed head, Cylindrical head, spherical cylindrical head, horn head, hex head, hex flange head, hexagonal flange (with pad), etc. Twisting method - the wrenching method is varied. External wrench: hexagonal, hexagonal flange face, hexagonal flange, hexagonal flower shape, etc.; internal wrench: slot, cross recess H (Phillips), cross slot Z (Pozidriv), cross slot F (Frearson) , Scrulox, composite groove, internal spline, hexagonal flower (plum), inner triangle, inner hexagon, inner 12 angle, clutch groove, six-blade groove, high torque cross groove and so on. Thread type - a wide variety of threads. Self-tapping threads (wide thread), machine threads, drywall nail threads, fiberboard nail threads, and other special threads. In addition, the thread can be divided into single lead (single head), double lead (double head), multi-lead (multi-head) and high and low double-head thread. The end type - the end type mainly has a saw end and a flat end. However, depending on the function of use, grooves, grooves, slits or portions similar to the shape of the drill can be machined. In some standards, the same is the saw end or the flat end, and there are different forms. As can be seen from the above description, there are various changes in the shape of the head of the self-tapping screw, the way of screwing, the type of thread and the type of end of the rod. They can be combined with each other to release many different products that belong to the category of self-tapping screws.