What are the classifications of self-tapping screws?

Thread-forming self-tapping screws: directly developed from metal screws, thread-forming self-tapping screws must be pre-drilled when used, and then screw the screw into the hole, and forcefully extrude to fit the female thread, and the original material in the female thread position Will be squeezed between the male threads, this is called thread forming self-tapping screw. It can only be applied to thin and plastic materials, so it has been developed.
Thread cutting self-tapping screws: cut one or more cutting holes at the end of the thread, so that when screwing into the pre-drilled hole, the tail and teeth of the screw are used to cut the matching female thread in a manner similar to a screw tap. It can be used on thick plates, hard or fragile materials that are not easy to shape.
Thread rolling into self-tapping screws: Triangular tooth self-tapping screws are developed based on the principle of forming screw taps. The thread rolling into self-tapping screws has a specially designed thread and end so that the screw can roll into a fit under intermittent pressure. The female thread. At the same time, the material around the hole can more easily fill the space between the thread and the bottom of the self-tapping screw. Because its friction force is smaller than that of the thread-forming self-tapping screw, it can be used on thicker materials. The required torque is better controlled, and the strength is higher after combination. The engineering standard definition of thread rolling into self-tapping screws is higher and more clear in the definition of material, heat treatment, and strength than forming or cutting self-tapping screws, making thread rolling The self-tapping screw becomes a real fastener for construction.
Self-drilling self-tapping screws: In all the processes of assembling self-tapping screws, the most costly preparation is the preparation of pre-drilling. The use of self-tapping screws must be drilled first. And the hole diameter must be limited. No pre-drilling is required. Some aspects can save costs. This is a self-drilling self-tapping screw that integrates drilling, tapping, and tightening in one operation. The surface hardness and core hardness of the self-tapping screw are a bit higher than that of the general self-tapping screw. This is because the self-drilling screw There is one more drilling operation. In addition, the self-drilling screw still needs a penetration test to test that the screw can drill and tap the thread within the specified time.

Pan Framing Head Phillips Self-Tapping Screw