Thread Rolling Process

With thread rolling hardened dies are used, which press onto the material causing it to plastically deform to the die's mirror image.
Thread rolling is the process used for making external threads. It is a important process in tooling and presswork manufacturing. A die, which is a hardened tool with the thread profile, is pressed on to a rotating workpiece. As the force is gradually increased, the thread profile is transferred to the workpiece. This process produces screws with greater strength than machined threads due to the cold working, as well as better material yield.

Because thread rolling is a cold forming process, it's done on room temperature blanks. Rotating hardened steel dies are pressed against the surface of cylindrical blank.The cold forming gives thread a higher fatigue strength. During the threading process, the surface layer of the raw material is put into compressive stress. There are no sharp corners in the root or tool marks on the flanks to cause stress risers. Thread rolling tools can be used on a wide variety of standard and special machine tools: