Patent ID: 7707724

Claim:
A manufacturing method for a drive wheel rolling bearing unit comprising an outer ring, a hub, an inner ring, and a plurality of rolling elements, the outer ring having a first flange for securely connecting a suspension system to an outer peripheral surface, and double-row outer ring raceways on an inner peripheral surface, the hub having a spline hole in the center, a second flange for supporting and fixing a drive wheel, on an axial outside end side of an outer peripheral surface, a first inner ring raceway on an axial middle portion of the outer peripheral surface, and a fitting cylindrical surface portion on an axial inside end side of the outer peripheral surface, the inner ring having a second inner ring raceway on an outer peripheral surface and being externally secured tightly to the fitting cylindrical surface portion, and the plurality of rolling elements being rotatably provided respectively between the double row outer ring raceways and the first and second inner ring raceways, the manufacturing method comprising the steps of: holding the fitting cylindrical surface portion by a holding device, and contracting an inner diameter of a portion of the holding device which holds the fitting cylindrical surface portion more than an outer diameter of the fitting cylindrical surface portion in a free state, so that the inner peripheral surface of the axial inside end of an original hole of the hub is elastically deformed radially inwards, broaching the inner peripheral surface of the original hole with a cutting device comprising a broach in the condition where the inner peripheral surface of the axial inside end of the original hole is elastically deformed radially inwards so as to form a female spline portion on the original hole with compensation for the deformation caused by externally securing tightly the inner ring to the fitting cylindrical surface portion, thereby forming the spline hole, expanding the inner diameter of the portion of the holding device more than the outer diameter of the fitting cylindrical surface portion, so that the elastic deformation is released, and externally securing tightly the inner ring to the fitting cylindrical surface portion to ensure that the inner peripheral surface of the axial inside end of the spline hole is not protruded radially inward beyond the other portion of the spline hole.