METHOD FOR FORMING EXTERNAL AND INTERNAL THREAD IN CYLINDRICAL BLANK

摘要

PURPOSE:To form an external and an internal thread in a short time, a small power, and a high yield by covering the outside of an inner die having spirallike recesses and projections on its periphery with a cylindrical material and recessing the material into the recesses of the inner die with a pressing roller having a projection. CONSTITUTION:The outside of an inner die 1 having spirallike recesses 3 and projections 4 on its periphery and a flange 5 engaging with a proper driving device (its illustration is omitted) at an end of the die 1 is covered with a cylin drical material 7. A pressing roller 2 having a forming projection 6 extended to the entire periphery of the roller 2 is set rotatably and movable in parallel to the axial line of the die 1. The roller 2 pushes the periphery of the material 7 and rotates and moves with the projection 6 pressing parts of the material 7 corresponding to the recesses 3 of the die 1. Thus, the periphery of the mate rial 7 is spirally recessed to form an external and an internal thread.