| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a manufacturing method of a crank shaft which can easily form penetration holes having a variety of shapes at the crank shaft, and the crank shaft efficiently achieving weight reduction.SOLUTION: A manufacturing method of a multi-cylinder crank shaft 10 provides a preliminary molded product of the crank shaft 10 having crank pin parts 61, 64 and weight parts 52, 53 which are aligned on a linear line L1 parallel with an axial core a of the crank shaft 10, and forms penetration holes 20a to 20d at the crank pin parts 61, 64 and the weight parts 52, 53 by making punches penetrate all the crank pin parts 61, 64 and the weight parts 52, 53 which are aligned on the linear line L1 by relatively moving the punches to the preliminary molded product in the axial direction.</p> |
