Golf shaft and manufacturing method for same

Abstract

Provided is a golf shaft capable of realizing a sufficient low trajectory and low spin. The golf shaft has a rigidity distribution in which rigidity is gradually increased from a tip end section to a butt end section, and, in the rigidity distribution, has an intermediate point at which inclination is changed in an intermediate section between the tip end section and the butt end section, a difference in rigidity between the tip end section and the intermediate point is 3.00 kgf·m2-5.00 kgf·m2, and a difference in rigidity between the intermediate point and the butt end section is 2.00 kgf·m2or less.

1 . A golf shaft comprising:
 a tip end section, a butt end section and an intermediate section spanning between the tip end section and the butt end section so as to have a rigidity distribution in which rigidity gradually increases from the tip end section to the butt end section, wherein   the rigidity distribution has an intermediate point at which inclination is changed in the intermediate section, a difference in rigidity between the tip end section and the intermediate point is 3.00 kgf·m 2 -5.00 kgf·m 2 , and a difference in rigidity between the intermediate point and the butt end section is 2.00 kgf·m 2 or less.   
     
     
         2 . The golf shaft according to  claim 1 , wherein
 the intermediate point is located in a range having a distance from a tip end being 40%-60% of an entire length.   
     
     
         3 . The golf shaft according to  claim 1 , wherein
 a stepped shape is exhibited between the tip end section and the butt end section so that an outer diameter is gradually increased, and   in the stepped shape, a difference in outer diameter between adjacent steps from the intermediate point to the butt end section is smaller than a difference in outer diameter between adjacent steps from the tip end section to the intermediate point.   
     
     
         4 . A manufacturing method of a golf shaft having a rigidity distribution in which rigidity gradually increases from a tip end section to a butt end section, comprising:
 extending a length of the butt end section in an axial direction by one or more adjustment steps with respect to a basic shape, and eliminating the adjustment steps corresponding to an amount of the extending of the length of the butt end section with respect to the basic shape, the basic shape in which an intermediate section between the tip end section and the butt end section has a main body, a plurality of adjustment steps having different outer diameters located on a tip end side relative to the main body, and a straight portion having a constant outer diameter and located on the tip end side relative to the adjustment steps.   
     
     
         5 . The manufacturing method for a golf shaft according to  claim 4 , wherein
 an outer diameter of the straight portion is made equivalent to a largest outer diameter in the eliminated adjustment steps.