PRODUCTION OF PLUNGER FOR VALVE LASH ADJUSTER

摘要

PURPOSE:To eliminate the need for a stage for cutting a relief groove by drawing the open end of a bottomed cylindrical blank material having a tapered shoulder part to form a seat surface consisting of a semispherical surface having a large diameter and forming the part adjacent to the seat surface to an undercut shape. CONSTITUTION:Oil holes 2, 3 are formed to the bottom and circumferential wall of a bottomed cylindrical blank material 1 and an open end 4 is cut even. The end 4 is drawn for a specified length to form a stepped shape having a tapered shoulder part 5. The part near the shoulder thereof is grasped by split dies 11 and an upper die 10 is brought down to draw the open end 4 to a seat surface 6 consisting of the semispherical surface having the diameter larger than the diameter of a drawn part 7 according to the shape of a recessed spherical surface 10a and to form the part adjacent to the surface 6 to an undercut shaped part 8 of the spherical shape having the diameter smaller than the diameter of the surface 6 according to the shape of the inside circumferential top edge of the dies 11. The compressive deformation of the blank material is thus prevented as far as possible and the need for machining the inside circumferential surface at the open end is eliminated.