Use of bolt and its manufacturing process

What are the purposes of nuts and bolts?

Due to the rapid industrialization of industrialization and the introduction of capital-intensive technology, nuts and bolts, as industrial fasteners, are widely used in manufacturing, connecting various machines and structures and installed on various types of mechanical equipment.

Nuts are used as fasteners, which consist of threaded holes and are used together with matching bolts to fasten multiple parts together. Although this bolt is described as a threaded fastener, it includes an external thread and needs an internal thread, just like a nut. Nuts and bolts complement each other and have different uses. They are used to make finished products and furniture, which is necessary to make the final products that can be used for consumption.

 

In the screw, nut and bolt manufacturing industry, the metal fastening products produced by operators can be divided into precision fastening products, which can be customized for specific projects or customers. General fasteners are made of metal bolts, nuts, screws, rivets and washers according to industry standards and designed for a wider market.

 

Bolt production process

Bolts can have many different sizes and shapes, corresponding to different specifications, but the production process is roughly the same. First, the steel wire is cold forged into the correct shape, then heat treated to increase strength, and surface treated to improve durability, and then packaged and transported. However, for more accurate and complicated bolt design, other process steps will be added to the production process. Depending on where the fasteners are used, there are many different process matching options to produce the correct bolts.

 

The manufacture of bolts begins with cold forging. Firstly, the large steel wire is unfolded and cut into specified lengths to meet the requirements of international ISO898-1. Use special tools to process the cold forged wire into the correct shape. In the main process, steel is formed at room temperature, and then a series of dies are made by high pressure. The tolerance requirement may be only one hundredth of a millimeter. Accuracy meets the requirements. The cold forging process ensures the fast production speed, large batch and high uniformity of bolts.For more complicated bolt design, it cannot be formed by cold forging alone, and additional turning or drilling process may be needed. Turning is to cut steel while rotating bolts at high speed to obtain the required shape and design. Drilling can be used to drill holes in bolts. During this stage, some bolts may also be connected with washers.

 

Heat treatment is a standard process for all bolts, including exposing the bolts to extreme temperatures to harden the steel. Thread processing is usually carried out before heat treatment, and rolling or cutting is carried out when the steel is soft. The working principle of rolling is very similar to that of cold forging. Bolts need to be formed by dies and steel needs to be molded into threads. Cutting involves cutting and removing steel to form threads. Because heat treatment changes the characteristics of steel and makes it harder, it is easier and more cost-effective to pre-thread. However, the thread after heat treatment will mean better fatigue performance. For long bolts whose length exceeds ten times the diameter of the bolt, heat treatment can restore the steel to the original round shape of the steel wire. Therefore, straightening process is often needed.

 

The choice of surface treatment depends on the application of bolts and the requirements of customers. Generally speaking, the main problem of fasteners is corrosion resistance, so electrolytic galvanized coating is a common solution. This is a process of soaking the bolt in a liquid containing zinc and applying current to make zinc form a coating on the bolt. However, electrolytic treatment does increase the risk of hydrogen embrittlement. Another option is zinc sheet, which has higher corrosion resistance.

 

The above are the process steps of bolts, and the next step is quality control to ensure that the quality of each bolt has been tested and that the quality of each bolt product is good.