Fasteners generally need to undergo surface treatment. […]
Fasteners generally need to undergo surface treatment. There are many types of surface treatments for standard parts. The commonly used ones are electroplating, oxidation, phosphating, and non-electrolytic zinc coating treatment. However, electroplated fasteners account for a large proportion in the actual use of fasteners. It is especially widely used in industries and fields such as automobiles, tractors, home appliances, instrumentation, aerospace, and communications.
However, for threaded screws, it is not only required to have a certain anti-corrosion ability in use, but also to ensure the interchangeability of the threads, which can also be referred to as screwability here. In order to meet the dual use functions of "anti-corrosion" and "interchangeability" required by threaded fasteners at the same time, it is often necessary to develop a special plating layer size.
There are many types of screw head types and groove types, which are generally different according to appearance and tamper resistance, or other requirements. This is relatively intuitive. The shape of the screw tail is more complicated. However, the more common ones we use are flat tail, pointed tail, grooved, triangular, cone and so on. These shapes have several functions: positioning, tin transfer, self-tapping, self-locking and other functions. Different tail requirements can be selected according to the function.
There are three types of screw pitch: machine teeth, plastic screws, wood screws or wall screws. The screw pitch is mainly related to the density of the material to be locked. The higher the material density, the smaller the pitch. Coarse teeth in machine teeth refer to standard screws used in ordinary occasions; fine teeth can have different pitches according to different requirements, and they also refer to non-standard screws used in special occasions. The pitch of the plastic screws can also be different. For example, the pitch of soft materials such as PP and PE can be increased, so that it is not easy to slip; while the denser materials such as POM and PC can use screws with a smaller pitch.
Self-tapping screws are divided into two categories: plastic and hardware. Plastics generally use self-tapping, except for some special requirements. However, it should be noted that different plastics use screws with different pitches and tail shapes, especially in some heat and stress conditions. Hardware self-tapping generally uses triangular screws, the pitch is the same as machine screws, triangular screws have the characteristics of self-locking and self-tapping, but generally can not be repeatedly disassembled.
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