Self tapping screw-self-drilling screw
Each self tapping screw is composed of head, rod and rod end. Each self tapping screw consists of four elements: head shape, tightening method, thread type and end form.
1. Head shape
The head shapes are various. There are round head (semi round head), flat round head, round head flange (with PAD), flat round head flange (with PAD), pan head, pan head flange (with PAD), countersunk head, semi countersunk head, cylindrical head, spherical cylindrical head, horn head, hexagonal head, hexagonal flange head, hexagonal flange (with PAD) head, etc.
2. Screwing method
The screwing method refers to the method of twisting the screw head when installing and tightening the screw. The basic methods include external screwing and internal screwing. Generally speaking, the allowable torque of external wrenching is larger than that of any form of internal wrenching (internal groove). External wrench: Hexagon, hexagon flange face, hexagon flange, hexagon flower shape, etc; Internal wrenching: slotted groove, cross groove H-type, cross groove Z-type, cross groove F-type, square groove, composite groove, internal spline, hexagonal flower shaped, triangular, hexagonal, 12 angle, clutch groove, six blade groove, high torque cross groove, etc.
3. Thread type
There are many kinds of threads, including self tapping thread (wide thread), machine thread (ordinary thread), drywall screw thread, fiberboard screw thread, and other special threads. In addition, threads can be divided into single lead (single head), double lead (double head), multi lead (multi head) and high and low tooth double head threads.
4. End form
The end forms mainly include cone end and flat end. However, according to the needs of use, grooves, notches or parts similar to the shape of drill bits with cutting function can be processed at the screw in part at the end. In some standards, the same conical end or flat end also has different forms, such as round head end.