Importance

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Abstract

When the column-shaped raw material 10 is subjected to an upsetting process, a simultaneous forward-backward extrusion process, a punching process, a rolling process and a finishing process in order, to obtain an outer ring 3 that constitutes a back-to back double-row angular ball bearing 3, in the simultaneous forward-backward extrusion process, using a floating die 31 having a bottom plate section 35 with a circular convex section 34 and a punch 33 having a punch side convex section 37 provided on an distal end thereof, the section closer to the center in the radial direction of the first intermediate material 11a is compressed in the axial direction, causing the metal material of the first intermediate material 11a to move outward in the radial direction and move approximately uniformly in both extrusion (forward and backward) direction of the punch 33, whereby the middle metal material 29 having a high degree of cleanliness of the column-shaped raw material 10 is exposed over the entire portion that will become the double-row outer-ring raceways 2.

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First Claim