| 摘要 |
A method for manufacturing according to the present invention includes a step of obtaining a bent workpiece 13 with prepared apertures 21 and 21 , wherein the bent work piece 13 includes a pair of side walls 20 and 20 disposed in parallel with each other and connecting walls 30 and 40 for connecting the side walls 20 and 20 , the pair of side walls 20 an d 20 each having a prepared aperture 21 , and a step of forming a roller supporting shaft fixing aperture 25 by inserting a sizing punch 60 into the prepared aperture 21 , wherein the sizing punch 60 has a tapered push enlarging portion 61 at a tip end portion, a basal end side of the push enlarging portion being larger than the prepared aperture 21 in diameter, and a tip end side of the push enlarging portion 61 being smaller than the prepared aperture 21 in diameter, whereby the push enlarging portion 61 causes plastic flow of an inner peripheral portion of the prepared aperture to finish the inner peripheral surface of the prepared aperture to thereby obtain a roller supporting shaft fixing aperture 25 . By this structure, sufficient shaft holding ability can be given to the roller supporting shaft fixing aperture, and a rocker arm can be manufactured at low costs.
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