Abstract: A method of forming on a workpiece a resilient thread, having a closed helical cavity inside the thread, includes plastic deformation of the walls of a preformed helical groove whose depth exceeds the depth of the roots of the thread to be obtained. The volume of the workpiece material, expelled in forming the helical groove, correspondsto the volume of the closed helical cavity inside the thread being obtained.A thread-forming tool for carrying out the method comprises a shank and an operating piece which consists of a groove-forming portion and a thread-forming portion arranged in series along one axis and having the same pitch of projections of their thread. The groove-forming portion and the thread-forming portion are displaced relative to each other in the axial direction at least by half the pitch, the major diameter of the groove-forming portion exceeding the major diameter of the thread-forming portion.