Golf club shafts

A method of making a tubular blank from which a golf club shaft is produced comprising the steps of;

• forming a tube having a constant cross-sectional configuration along its length, positioning a plug mandrel inside the tube, the plug mandrel having alternating parallel longitudinally extending lands and grooves on an outside surface thereof, drawing the tube over the plug mandrel to metallurgically form rifling on the inside surface of the tube in the form of a plurality of alternating longitudinally extending parallel lands and grooves corresponding to the lands and grooves on the plug mandrel, cutting the tube into desired lengths, and swaging each length of tube to form tip and butt sections and an interconnecting tapered section, the lands and grooves of said butt section being parallel to each other, and the lands and grooves of said tip section being parallel to each other, and said tip section having a diameter smaller than the diameter of the butt section.

A method of producing a frequency matched set of golf club shafts from a plurality of oversized tubular blanks, each shaft in the set having a stiffness distribution directly related to the stiffness distribution of the other shafts in the set such that each successive shorter shaft has an increased stiffness along a predetermined gradient, each blank having a tip end section and a butt end section and an intermediate tapered section, the method comprising the steps of;

• selecting a plurality of oversized blanks equal in number to the number of shafts in the set, each blank having substantially the same natural frequency and length, each blank having metallurgically formed rifling to define a plurality of alternating longitudinally extending parallel lands and grooves on an interior surface of said tip section and of said butt section, removing a predetermined portion of length from the rifled tip end section of each blank and a constant additional length differential of tip end removal between said successive blanks of the plurality of said blanks to produce a set of golf club shafts with said constant length differential of overall length between successive shafts of the set.

A method of producing a set of matched golf club shafts, comprising the steps of:

• forming a plurality of metal tubes and cutting each said tube to a predetermined length, forming rifling on the interior surface of said metal tube extending throughout the length thereof, working said metal tubes to form a butt section having a given outer diameter and a plurality of alternating, longitudinally extending, parallel lands and grooves on the interior surface, a tip section having a given outer diameter smaller than said butt section diameter and having a plurality of alternating, longitudinally extending, parallel lands and grooves on the interior surface, and a tapered section joining said butt section and said tip section, to form a plurality of blanks;
• determining the stiffness of said blanks by measuring the natural frequency thereof and selecting a set of blanks having matched natural frequencies;
• forming successive blanks in said set by removing an amount from the tip section of each blank of a set of blanks, the removed amount increasing for each said successive blank by a constant increment such that said resulting set of shafts includes members varying in length by said constant increment so that said set of said successive length shafts represents a set of golf club shafts having matched frequencies along a predetermined gradient.

A set of frequency matched shafts, comprising;

• a plurality of shafts varying in successive lengths by a constant increment and each comprising a butt section having a continuous exterior surface of a given outer diameter and having a plurality of alternating, longitudinally extending, parallel lands and grooves on an interior surface, a tip section having a continuous exterior surface of a given outer diameter smaller than said butt section diameter and having a plurality of alternating, longitudinally extending, parallel lands and grooves on an interior surface, and a tapered section joining said tip section and said butt section, the butt section of each shaft of said set being a constant length, the tip section of each shaft varying in length successively from the prior length shaft in said set by said constant increment.

A golf club shaft, comprising:

• a tubular blank having a continuous cylindrical exterior surface, and an interior surface, a butt section having a given outer diameter, a tip section having a given outer diameter smaller than the outer diameter of the butt section, a tapered section interconnecting the butt and tip sections, and metallurgically formed rifling comprising lands and grooves on the interior surface of the blank extending throughout the entirety of said butt, tip and tapered sections, said lands and grooves in said butt section being parallel to each other, and said lands and grooves in said tip section being parallel to each other.