Abstract: A thread-rolling tool having a body provided with thread rollers uniformly disposed along the circumference thereof, the axes of the rollers being in angular position relative to the axis of rotation of the body and at an angle equal to the lead angle of the helical line of the thread being rolled. The body includes groove-forming rollers having a pitch equal to that of the thread rollers and being disposed at an angle relative to the axis of rotation of the body and at an angle relative to the latter. The top portions of the thread of the groove-forming roller being disposed with an axial displacement relative to the top portions of the thread of a preceding thread roller, when viewed in the projection on a plane normal to the axis of rotation of the body 1, the amount of said displacement being:(P/2)-(P.beta./360.degree.)whereP is a pitch of the thread being rolled..beta.

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.

Abstract: A method of making an elastic thread having a closed cavity inside the thread profile comprises plastically deforming the walls of a preformed helical groove by means of a thread-forming tool (2). The helical groove is made at least double-start and having a pitch equal to that of the thread to be formed, one of the starts serving for directing the thread-forming tool (2) which, during the process of plastically deforming the walls of the helical groove, transforms each of the remaining starts into a closed helical cavity (3) disposed inside the thread profile.A thread-forming tool for practicing the above described method comprises threading rollers (7) having a circular thread and uniformly disposed around a circumference in a body (4) provided with a starting portion (5).

Abstract: The tap comprises a groove forming portion (1) with a shank (2) having a thread forming portion (3) such that the thread pitch thereof is equal to that of the groove forming portion (1), the crests of the thread forming portion (3) being axially displaced from those of the groove forming portion (1). The thread forming portion (3) is threadedly positioned behind the groove forming portion (1) for axial movement on the shank (2), the movement thereof being limited by a stop (4) arranged on the shank.