If you check around, almost every small and big object is held together using bolts and nuts. From doors to windows, pumps to speed reducers, bridges to missiles, however small or gigantic, require fasteners to keep different parts together.

While bolts and nuts are some of the basic engineering components, their production has advanced and relies on high-tech processes with different steps. This post demonstrates how raw steel, call it a steel wire rod, is transformed into the bolts and nuts that we know of today.

There are three main methods used in making nuts and bolts; cold forming, hot forming and machining.

Cold Forming (Cold Extrusion)

Cold forming is the most preferred method of designing fasteners today. In cold forming, the fastener is made in a multistage process through pressure forging, cold extrusion, and reducing. Manufacturers opt for cold forming, especially when dealing with large quantities of fasteners because of economies of scale.

The forming machine is selected depending on the size of the fastener. Furthermore, the decisive quality of fasteners depends on the choice of the input material. In most cases, the wire is phosphate treated to make the forming process easy and reduce tool wearing.

The nuts and bolts designer tries to harmonize the advantages and disadvantages of the selected material for quality assurance. For example, if additional strength is required, it is necessary to subject the parts to heat treatment. Stronger nuts are required for projects and equipment that handle a lot of weight, such as material handling, bridges, and mining facilities. Here is a demonstration of how a head screw is made using cold forming:
 

Advantages

• Promotes optimal use of materials.
• High output.
• Impressive dimensional accuracy.
• You can enhance the strength of the fastener using strain hardening.

Hot Forming

This method of creating bolts and nuts is preferred when targeting fasteners with very large diameters, approximately M27, and longer pieces starting from about 300 mm. In addition, it is recommended for producing fasteners that cannot be made using cold forming method because of low volume, size, and/or cost.

To produce fasteners using hot forming, the input material is heated either wholly or partially to reach the preferred forging temperature. The heating makes it possible to realize even the most complicated geometrics. So, if you are looking for fasteners to use in heavy equipment, such as industrial conveyor belt systems and farm equipment, the types designed through hot forming might be a better option.

Note: Strain hardening is not done during hot forming.

Advantages

• Makes it possible to create fasteners with complicated geometries.
• Good for making thicker and longer nuts.
• Low production runs.

Machining

The last method of creating nuts and bolts is machining, which mainly involves turning. It is also recommended for fasteners that cannot be produced through cold forming. However, the process is expensive and takes long to create nuts and bolts. The method is considered wasteful because the chamfer of the input material is destroyed.

During turning, the contours of the fasteners are cut on the rod. The diameter of the input material (steel wires) depends on the targeted diameters of the fastener.

Quality Control in Nuts and Bolts Making

The National Screw Thread Commission was created in 1928 to enhance the quality and interoperability of nuts and bolts. The main standards that are given a lot of weight are the thread per inch, the shape of the head, and designated pitch. When designing bolts, manufacturers also follow the International Standards Organization (ISO), which provides additional guidelines for quality assurance.

Conclusion

Bolts and fasteners are crucial in life – it is almost impossible to imagine life without them. As we have demonstrated, they are designed using steel wires or rods to meet international standards for quality. Because they come in various sizes, make sure to select the right option based on your application and purchase from a trusted supplier.