| 摘要 |
PROBLEM TO BE SOLVED: To reduce a bending stress acting on the punch while inhibiting a material flow of the nut material to the axial end face in forming a ball circulation groove in an inner circumferential face in an axial end of a nut material by a forging processing method using a punch. SOLUTION: The method includes: detaining a top end face of a nut material 1 through coil springs (an elastic mechanism) 91 with a press member 4 and an upper member 8; and pressing a cam driver 6 in under the state of detaining a lower end face of the nut material 1 with a lower form 3. By this process, a punch 7 is moved radially outward of the nut material 1 such that a protrusion 71 of the punch 7 is plunged into an inner circumferential face 11 of the nut material 1, and the nut material 1 is plasticity deformed while a material flow to the axial end face of inhibited wit. The ball circulation groove 15 is then formed in an axially upper end portion of the inner circumferential face 11. COPYRIGHT: (C)2012,JPO&INPIT |
