What are the classification of self-tapping screws?

1. Ordinary self-tapping screws
The thread is "self-tapping thread", also known as "wide thread". The surface is mostly electroplated.
2. Self-cutting self-tapping screws
The Chinese standard is called "self-tapping screw scraping end", the thread is self-tapping thread or machine thread, and the cross groove is also "H" type. There are several types of self-cutting self-tapping screws: cross recessed pan head self-cutting self-tapping screws, and cross recessed countersunk head self-cutting self-tapping screws. Cross recessed countersunk head self-cutting self-tapping screws, hexagon head self-cutting self-tapping screws.
3. Self-drilling self-tapping screws
Threads for self-drilling self-tapping screws are self-tapping threads in Chinese, German and international standards.
4. Self-extruded self-tapping screws
The thread of self-extruded self-tapping screws is generally machine thread, and self-tapping threads are rarely used. The cross section of the self-extruded self-tapping screw is triangular. So it is also called triangle thread screw.
5. Combination self-tapping screws
Common white tapping screws, self-cutting white tapping screws, self-drilling self-tapping screws, etc. combined with flat washers and elastic washers (including spring washers and elastic lock washers) are self-tapping screws.