| 摘要 |
PROBLEM TO BE SOLVED: To provide a thread mandrel of a ball screw having higher accuracy and being inexpensive, which is not affected by shear droop of an end caused by rolling, and does not require machining to remove the shear droop, and its manufacturing method. SOLUTION: In the manufacturing method of the thread mandrel of the ball screw, a round bar material 1 is interposed between roll dies 2a, 2b on which helical convex threads 3a, 3b are formed, and the mandrel is rolled through thread grooves that continues helically on an outer peripheral face of that rolling portion 1a, wherein parallel portions 4a, 4b in which outside diameters of the convex threads 3a, 3b and outside diameters of helical flat portions 8a, 8b of which diameters are smaller than the above are constantly formed on surfaces of the roll dies 2a, 2b in a predetermined range of length, and bevel leads 5a, 5b and relief parts 6a, 6b having angles of inclinationθ1,θ2 are formed at both sides of the parallel portions 4a, 4b. A small diametrical stepped portion 1b is formed in advance at an end of the round bar material 1, and an outside diameter of the small diametrical stepped portion 1b is set to be smaller than a distance between the convex threads 3a, 3b obtained when the roll dies 2a, 2b most approach. COPYRIGHT: (C)2005,JPO&NCIPI
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