How does thread rolling improve the strength of threads?

Thread rolling improves the strength of threads by compressing the metal structure. This process involves deforming the material through plastic deformation rather than removing any material. When the threads are rolled, the high pressure applied to the metal enhances the grain structure in the area of the threads, which aligns and compresses the material fibers. This alignment and compression increase the tensile strength of the threads, making them less likely to fail under stress compared to cut threads, which can introduce weaknesses due to cutting and stress concentration.

Using heat or chemicals, as suggested by some other options, does not apply to the thread rolling process. Instead, thread rolling primarily relies on mechanical deformation to enhance the material properties, which makes it a superior method for producing strong and durable threads in fasteners.