Patent ID: 7052402

Claim:
A shaft including a shank comprising: a large diameter portion; a splined portion engaged with a fitting member, said splined portion including a plurality of splines and a plurality of grooves which diametrically converge at a position spaced from the large diameter portion in the axial direction of the shaft; a tapered portion which stops the fitting member and which is located adjacent the large diameter portion, wherein the tapered portion which stops the fitting member includes a curved transitional portion contiguous therewith and reduces the diameter of the shank in the space between the splined portion and the large diameter portion to a minimum diameter at the transitional portion which is greater than that of the splined portion at the position where the plurality of splines and the plurality of grooves diametrically converge; and a further portion in the space between the splined portion and the tapered portion, wherein the further portion includes a curved portion reducing the diameter of the shank from that of the minimum diameter of the transitional portion of the tapered portion which stops the fitting member to that of the splined portion at the position where the plurality of splines and the plurality of grooves diametrically converge.