**2. Function of bolt and nut**

When asked about the function of bolt and nut, almost everyone says that it is designed for assembly which is true. However, there is one more function which may be much more important than "assembly." Another function we must understand more is that it was designed for disassembly anytime when necessary, too. It means that the assembly should stay assembled no matter how long it is, but at the same time, it

should be able to be disassembled by tool anytime. Does this sound logical to meet both requirements at the same time to you? In reality, design engineers have spent a lot of time to design mechanical fasteners that can achieve those two functions. Consequently, various mechanical fasteners have been introduced, and they will be reviewed more in detail on each fastener in this article.

In order for fasteners to do their job ideally, they should resist to external vibrations, shock, and impact, withstand shock and impact, tolerate differences in thermal expansions, protect against corrosion, and provide a consistent torque control during assembly.
