Patent ID: 8262498

Claim:
A golf club shaft assembly for attaching to a club head, the assembly comprising: a shaft having a lower end portion; and a sleeve mounted on the lower end portion of the shaft and configured to be inserted into a hosel opening of the club head, the sleeve having an upper portion defining an upper opening that receives the lower end portion of the shaft and a lower portion having a plurality of longitudinally extending, angularly spaced external splines located below the shaft and adapted to mate with complimentary splines in the hosel opening, the lower portion defining a longitudinally extending, internally threaded opening adapted to receive a screw having a nominal diameter of about 4 mm for securing the shaft assembly to the club head when the sleeve is inserted in the hosel opening, wherein each spline has two radially extending sidewalls that diverge from each other moving in a direction from the base of the spline to its outer surface, and each spline has a mid-span width to height ratio of about 1 to about 22, and a mid-span width to average diameter ratio of about 0.1 to about 0.5; and wherein the upper portion of the sleeve has an upper flange surface that is adapted to engage a hosel of the club head when the sleeve is inserted into the hosel opening, and the sleeve and the shaft have a combined axial stiffness from the upper flange surface to a lower end of the sleeve of about 1.86×10 8 N/m or less.