A bolt-holework process for forming bolt holes in a flange of a hub unit bearing

摘要

The invention has an object to provide a bolt-hole work process for forming bolt holes in a flange of a hub unit bearing. Cores 1w are formed at multiple places circumferential of a flange 1f of an outer race 1 of the hub unit bearing. The cores 1w are punched by a punching press 11, 12, 13 and then are directly serrated by a serration punching press 31, 32, 33 for forming serrated holes 1p. Alternatively, the cores are formed with chamfers 1h, k, i at their respective opposite circumferential edges and then are serrated by the serration punching press utilising a female die with die holes and serrating punches so as to be formed with serrated holes therein.