The main categories of screws include ordinary screws, self-tapping screws and expansion screws.

1. Ordinary screws

Screw is a tool that uses the physical and mathematical principles of the object's inclined plane circular rotation and friction to gradually tighten the device. Screw is a common term for fasteners and a daily spoken language. Screws are indispensable industrial necessities in daily life: extremely small screws used in cameras, glasses, clocks, electronics, etc.

2. Self-tapping screws

Generally refer to wood screws with pointed tips, coarse teeth, and hard texture, as well as aluminum alloy and plastic screws. A special self-tapping screw used for threading metal holes is called a tap.

3. Expansion screws

Expansion screws are generally referred to as metal expansion screws. The fixation of expansion screws uses wedge-shaped inclination to promote expansion and produce frictional gripping force to achieve a fixing effect. The screw has threads on one end and a taper on the other.

Extended information:

Anti-corrosion technology of screws:

Stainless steel screws are made of metal, and there are four main ways to prevent metal corrosion, namely the material itself properties, the environment in which they are used, the interface between materials and the environment, and the design of improved metal structures. If a complete corrosion-resistant alloy is used to make stainless steel screws, unless there are special needs, it is not practical from an economic point of view, or the screws will be It may not be feasible in practice to completely isolate the surface from corrosive environmental factors, and it may be very difficult.

Improving the design of metal structures can improve the impact of special circumstances in some cases, but the design of most stainless steel screws cannot be fully modified, and their protective effect is not permanent, so this method cannot basically solve it. The problem is that only corrosion protection on the interface, that is, surface anti-corrosion treatment, is the most widely used method.

The surface anti-corrosion treatment of stainless steel screws refers to the use of various methods to apply a protective layer on the metal surface. Its function is to isolate the metal from the corrosive environment to inhibit the occurrence of the corrosion process or reduce the corrosive medium. Contact with the metal surface to prevent or reduce corrosion.

Baidu Encyclopedia-Screws