Patent ID: 6990865

Claim:
A method of determining straightness of a golf club shaft, said shaft having a handle end and having a tip end for mating to a club head, said method comprising: immobilizing said handle end of said golf club shaft and defining a longitudinal axis passing through said handle end and extending perpendicularly with respect to a plane perpendicular to said handle end; determining a spring constant of said golf club shaft in a transverse bending mode; and for each of a plurality of angles about said longitudinal axis: displacing said tip end of said shaft transversely to, and by a predetermined distance from, said longitudinal axis, measuring a restoring force during said displacing, determining a difference between said measured restoring force during said displacing and an expected restoring force based on said predetermined distance and said spring constant, and deriving from said difference and said spring constant a deviation of said tip end from said longitudinal axis at said angle.