PROCESS FOR MANUFACTURING RACEWAY RING MEMBER AS CONSTITUENT OF ROLLER BEARING UNIT FOR WHEEL SUPPORT

摘要

This invention provided a manufacturing method to process a small-diameter step section 18 on an inside end section of a hub body 13a that comprises an outward facing flange 15 and a positioning cylinder 16 stably and with high precision. In this invention, an intermediate material 40 is pressed between a lower punch 36 and an upper punch 46 with an outer peripheral surface of the intermediate material 40 being held by a lower die 37 and an upper die 43, and then a part of the intermediate material 40 is pressed into the lower punch 36 such that the small-diameter step section 18 is formed by cold plastic working.