Golf Club Shaft Assemblies With Partially Bonded and Unbonded Permanent Inserts

Abstract

A golf club shaft assembly including a golf club shaft and a permanent shaft insert that is partially bonded, or is unbounded, to the golf club shaft.

Description

BACKGROUND OF THE INVENTIONS

1. Field of the Inventions

The present inventions relate generally to golf clubs.

2. Description of the Related Art

Fiber reinforced resin shafts are commonly used in golf club drivers and irons. Such shafts, which are typically hollow and consist of a shaft wall formed around a tapered mandrel, may be produced with varying stiffness and bending profiles. As a result, golfers are able to choose shafts that are appropriate for their particular swing. If a shaft is too stiff for the golfer, then the shaft will not deflect sufficiently to generate a “kick” behind the golf ball. Conversely, if the shaft is not stiff enough, then the shaft will either lead or lag excessively, thereby causing the ball to leave the club head at a launch angle that is higher or lower than intended.

Another issue involves the stability of the shaft region that is near the club head. Upon impacting the golf ball, this region vibrates violently as does, to a lesser extent, other portions of the shaft. Some shafts may even bend into an S-shape at the center-of-percussion. One proposed method of stabilizing golf club shafts involves adding additional layers of material to the shaft in the tip section during the shaft manufacturing process in an attempt to reduce or eliminate impact vibrations and deformation.

The present inventor has determined that conventional methods of increasing shaft stability are susceptible to improvement. For example, additional layers of material do not substantially decrease the impact vibrations and shaft deformation. The additional layers of material do, on the other hand, substantially increase longitudinal and torsional stiffness of the shaft. The increased longitudinal and torsional stiffness alters the playing characteristics of the shaft, and can render the shaft too unforgiving for many golfers. The present inventor has also determined that one reason for both of these shortcomings relates to the fact that additional layers of material become an integral part of the associated shaft over their entire length.

SUMMARY

A golf club shaft assembly in accordance with one embodiment of a present invention includes a golf club shaft and a shaft insert. The shaft insert is permanently secured within the golf club shaft, and the shaft insert is either not bonded to the golf club shaft or is bonded to the golf club shaft over less than the entire length of shaft insert.

A golf club shaft assembly in accordance with one embodiment of a present invention includes a golf club shaft and a shaft insert. The shaft insert is permanently secured within the golf club shaft such that the tip end and/or the butt end of the shaft insert is longitudinally and/or rotationally movable relative to the adjacent portion of the golf club shaft inner surface.

There are a variety of advantages associated with such golf club shaft assemblies. For example, the insert will, over its entire length, contribute to the reduction of impact vibrations and deformation, but will do so without substantially increasing the longitudinal and/or torsional stiffness of the shaft because the shaft can move relative to a substantial portion (or all) of the insert as the shaft bends and twists.

The above described and many other features of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description of embodiments of the inventions will be made with reference to the accompanying drawings.

FIG. 1 is a side view of a golf club in accordance with one embodiment of a present invention.

FIG. 2 is a cutaway view of a portion of the golf club illustrated in FIG. 1.

FIG. 3A is section view taken along line 3A-3A in FIG. 2.

FIG. 3B is section view taken along line 3B-3B in FIG. 2.

FIG. 3C is section view taken along line 3C-3C in FIG. 2.

FIG. 4 is a partial section view of a portion of the golf club shaft assembly illustrated in FIG. 2.

FIG. 5 is a partial section view of a portion of a golf club shaft assembly in accordance with one embodiment of a present invention.

FIG. 6 is a partial section view of a portion of a golf club shaft assembly in accordance with one embodiment of a present invention.

FIG. 7 is a partial section view of a portion of a golf club shaft assembly in accordance with one embodiment of a present invention.

FIG. 8 is a partial section view of a portion of a golf club shaft assembly in accordance with one embodiment of a present invention.

FIG. 9 is a partial section view showing a step in an exemplary process for manufacturing the golf club shaft assembly illustrated in FIGS. 1-4.

FIG. 10 is a partial section view showing a step in another process for manufacturing a golf club shaft assembly.

FIG. 11 is a partial section view of a portion of a golf club shaft assembly in accordance with one embodiment of a present invention.

FIG. 12 is a section view of a portion of the golf club shaft assembly illustrated in FIG. 11.

FIG. 13 is a side view of a plug coated with adhesive in accordance with one embodiment of a present invention.

FIG. 14 is a side view of the plug illustrated in FIG. 13 with a portion not coated with adhesive.

FIG. 15 is a partial section view of a portion of a golf club shaft assembly in accordance with one embodiment of a present invention.

FIG. 16 is a section view of a portion of the golf club shaft assembly illustrated in FIG. 15.

FIG. 17 is a partial section view of a portion of a golf club in accordance with one embodiment of a present invention.

DETAILED DESCRIPTION

The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions. Additionally, although the present inventions are described in the context of fiber reinforced resin composite golf club shafts because the inventions are particularly well suited to such shafts, the inventions are not so limited and are applicable to a wide variety of golf club shafts, including those currently available and those yet to be developed.

The exemplary golf club 10 illustrated in FIGS. 1-3C includes a shaft 100 has tip section 102, a grip section 104, and a main section 106 between the tip section and the grip section. The tip end of the shaft 100 is identified by reference numeral 108 and the butt end is identified by reference numeral 110. Although the present inventions are not so limited, the exemplary shaft 100 is a tapered fiber reinforced resin composite shaft. To that end, the shaft 100 is defined by a wall 112 that is circular in cross-section, from the tip end 108 to the butt end 110, and has an inner surface 114. Other suitable shafts include, but are not limited to, shafts with other shapes (e.g., shafts that include parallel tip or grip sections) and shafts formed from other materials (e.g., steel and lightweight metal such as titanium, aluminum and alloys). The exemplary shaft 100 also has a center-of-percussion COP and a flex point FP.

A grip 116 covers the shaft grip section 104 and an end cap 118 covers the butt end 110. The illustrated grip 116 and end cap 118 arrangement may, in other implementations, be replaced by a continuous, integrally formed grip that covers both the shaft grip section 104 and butt end 110.

A club head 200 is carried on the tip section 102 of the shaft 100. Although the present inventions are not limited to any particular golf club configurations, the exemplary golf club 10 is a “driver” and the club head 200 is a driver type club head. The present inventions are, however, equally applicable to any and all golf clubs including, but not limited to, all “woods,” “irons,” “wedges” and “putters.”

A shaft insert (or “insert”), which is generally represented by reference numeral 300 (or 300a in FIG. 17), may be permanently secured to the shaft 100 to form a shaft assembly 12. As discussed in greater detail below, the insert 300 is permanently secured to the shaft 100 in such a manner that less than all of the insert, or no portion of the insert at all, is itself bonded to the shaft. Put another way, the insert 300 is permanently partially secured to the shaft 100. The insert 300 will, over its entire length, contribute to the reduction of impact vibrations and deformation, but will do without substantially increasing the longitudinal and/or torsional stiffness of the shaft. The substantial increase in longitudinal and/or torsional shaft stiffness is avoided, in those portions of the insert 300 that are not bonded to the shaft, because the shaft 100 can move relative to the insert as the shaft bends and twists.

It should be noted that, as used herein, a portion of one structure is “bonded” to a portion of another structure if the two portions abut (or face) one another and there is some instrumentality (e.g., a layer of adhesive) that fixedly secures the abutting portions. Other portions of the same two structures may abut one another, but are not “bonded” to one another, if there is no adhesive (or other securing instrumentality) therebetween, despite the fact that they may remain adjacent to one another as a result of the bond between other portions of the structures. Such portions are referred to herein as “non-bonded” structure. This aspect of the present invention is discussed in greater detail below with reference to FIGS. 4-8. It should also be noted that, as used herein, one structure is “permanently” secured to another structure if the structures may not be separated from one another without destruction of one or more the structures and/or destruction of the instrumentality (e.g., an adhesive bond) securing the structures to one another. For example, a lock that is configured to be unlocked as desired so that the associated structures can be separated does not “permanently” secure the structures to one another.

Referring to FIGS. 2-3C, the exemplary insert 300 is a tapered tube that is defined by a wall 302 which is circular in cross-section, from the tip end 304 to the butt end 306, and has an outer surface 308. A relatively small portion of the insert outer surface 308 is bonded to the shaft inner surface 114 with a layer of permanent adhesive 310 that is located between the shaft and insert. The exemplary insert 300 is also sized and shaped such that the insert butt end 306 is within the main section 106 of the shaft 100 and the insert tip end 304 is within or near the tip section 102. In particular, and referring more specifically to FIG. 2, the exemplary insert 300 is sized and shaped such that the insert will be located between the shaft flex point FP (i.e., the point of maximum bending when axial force is applied to the shaft at the tip and butt ends) and the shaft tip end 108 (e.g., six inches from the tip end). Other insert locations may also be employed in those instances where the designer intends to alter the characteristics of the shaft 100. For example, the insert 300 may be positioned such that the insert butt end 306 is above (in the illustrated orientation) the flex point FP or the insert may be associated with the grip section 104 (FIG. 17). The butt end 306 of the insert 300 may be located in the shaft grip section and the tip end 304 of the insert may be located in the shaft tip section.

The perimeter of the insert outer surface 308 and the perimeter of the associated portions of the shaft inner surface 118 are extremely close in shape and dimension in the illustrated implementations. For example, and referring to FIG. 2, the insert 300 will typically have the same taper as the shaft 100 and the insert tip end 304 will have an outer diameter that is substantially the same as the diameter of the shaft inner surface 114 at the point at which the insert tip end is to be located. The insert tip end 304 will, of course, be prevented from moving beyond this point because the inner diameter of the tapered shaft 100 beyond this point will be smaller than the outer diameter of the insert tip end. The outer diameter of the insert 300 may also be substantially the same as the inner diameter of the associated portion of the shaft 100 from the insert tip end 304 to the insert butt end 306. In other implementations, the taper of insert may be slightly different than the taper of the shaft and, as a result, there will be a small gap between the outer surface of the insert and the inner surface of the shaft. Here, the insert may be configured such that the tip end of the insert touches the inner surface of the shaft (in some instances with nothing therebetween) or the butt end of the insert touches the inner surface of the shaft (in some instances with nothing therebetween).

Referring to FIG. 4, and as alluded to above, only a relatively small portion of the insert 300 is bonded to the shaft 100. The length (in the longitudinal direction) of the bonded portion of insert 300, i.e., the length that is bonded to the shaft 100 with the adhesive 310, is represented by reference character L_B and the length of the non-bonded portion of the insert 300, i.e., the length that abuts but is not itself bonded to the shaft 100 with the adhesive 310, is represented by reference character L_NB. Put another way, the length L_B of the bonded portion of the insert 300 is equal to the length of the adhesive layer 310 or other bonding instrumentality. The length of the relatively small bonded portion may range from about 0.5% to about 50% of the length of the insert 300 (i.e., the length L_NB of the non-bonded portion may range from about 50% to about 99.5% of the length of the insert). Other ranges for the length L_B of the relatively small bonded portion may include, but are not limited to about 0.5% to about 25% of the length of the insert 300 (i.e., the length L_NB of the non-bonded portion may range from about 75% to about 99.5% of the length of the insert), about 0.5% to about 10% of the length of the insert (i.e., the length L_NB of the non-bonded portion may range from about 90% to about 99.5% of the length of the insert), and about 0.5% to about 5% of the length of the insert (i.e., the length L_NB of the non-bonded portion may range from about 95% to about 99.5% of the length of the insert). The length of the bonded portion of a 12-inch insert 300 may, therefore, range from about 1/16 inch to 6 inches. For purposes of comparison, the bonded and non-bonded lengths L_B and L_NB in the shaft assembly 12 (FIG. 4) are about 1% and 99%, respectively, of the total length of insert 300 in FIG. 4, while the bonded and non-bonded lengths L_B and L_NB are about 50% each in the shaft assembly 12a (FIG. 5).

In some embodiments (e.g., the embodiments illustrated in FIGS. 1-5), the layer of adhesive 310 (or other bonding instrumentality) begins at or near the insert butt end 306 and extends continuously toward the insert tip end 304, while the non-bonded portion of the insert begins at the tip end of the insert and extends toward the butt end. The present inventions are not, however, limited to continuous bonding. Referring for example to the shaft assembly 12b illustrated in FIG. 6, the adhesive 310 (or other bonding instrumentality) may be provided in two (or more) longitudinally spaced locations. Here, bonded length L_B is the total length spanned by the adhesive (or other bonding instrumentality), including the gaps therebetween, and the non-bonded length L_NB is the remainder of the insert length and extends from the insert tip end 304 to the edge of the adhesive 310.

The present inventions are also not limited to bonds that extend to the insert butt end 306. For example, the adhesive 310 in FIGS. 1-4 may be moved a short distance toward the insert tip end 304. Referring to the exemplary shaft assembly 12c illustrated in FIG. 7, the adhesive 310 (or other bonding instrumentality) may be located at the tip end 304 instead of the butt end 306. Alternatively, the exemplary shaft assembly 12d illustrated in FIG. 8 includes adhesive 310 (or another bonding instrumentality) that is located between the tip end 304 and butt end 306. Here, the non-bonded length L_NB is sum of the non-bonded lengths L_NB1 and L_NB2 on either side of the bond.

Although the present inventions are not limited to any particular permanent adhesive, the exemplary permanent adhesive 310 is epoxy. Other suitable adhesives include, but are not limited to, polyurethane, acrylic, cyanoacrylate adhesives. It should also be noted that instrumentalities other than adhesives may also be used to perform the permanent bonding function. Such bonding instrumentalities include, but are not limited to, ultrasonic welds. Here, the insert and the shaft may be bonded directly to one another, or a thin plastic tube (which melts during the welding process) may be positioned over the butt end of the insert. Other instrumentalities include a thin strip of a polymeric material, such as plastic, nylon, PVC, neoprene, polyurethane and rubber, with a permanent adhesive on both sides. The strip is too thin (e.g., less than 1 mm thick) to act as an effective vibration damper. It should also be noted that the bond need not extend continuously around the circumference of the insert. For example, the layer of adhesive could consist of spaced strips, dots, spirals, or the like.

One exemplary method of permanently bonding a portion of the insert 300 to the shaft with epoxy adhesive is illustrated in FIG. 9. First, a layer of epoxy adhesive 310 is applied to outer surface 308 at or near the butt end 306 through the use of a brush, squeeze or a carrier tape. The epoxy is then cooled to about 15° F. for 15-30 minutes, which freezes the epoxy and eliminate the tackiness of the epoxy. The insert 300 is then placed into the shaft 100 at room temperature and is moved toward the shaft tip end 108 until the outer diameter of the insert is equal to the inner diameter of the shaft along the length of the insert, thereby preventing further movement of the insert toward the shaft tip end. A tool 400, which consists of a weight 402 (e.g., a 20-50 g weight) and a rod 404 attached to the weight, is then inserted into the shaft 100 as shown in FIG. 9. The tool 400 holds the insert 300 down as the epoxy 310 melts (and returns to its emulsified state) and then hardens to form the above-described permanent bond. The rod 404 is then used to remove the weight 402 from the completed shaft assembly 12.

Turning to FIG. 10, another exemplary instrumentality that performs the permanent bonding function is a weld 312 in the exemplary shaft assembly 12e. The weld 312 may be formed by heating respective portions of the shaft 100 and insert 300 along the bonded length L_B with, for example, an ultrasonic welding device WD.

In the embodiments illustrated in FIGS. 1-10, a portion of the insert 300 is bonded to the shaft 100, thereby permanently securing the insert to the shaft. In other embodiments, no portion of the insert 300 is bonded to the shaft 100, yet the insert is nevertheless permanently secured to the shaft. Referring to the exemplary insert assembly 12f illustrated in FIGS. 11-13, another method of permanently securing the insert 300 to the shaft 100 involves the use of a plug 500 that is bonded to the inner surface 114 of the shaft 100. The plug 500, which may be hollow (as shown) or solid, includes a wide portion 502 and a narrow portion 504. The wide portion 502 engages the insert butt end 306 and the narrow portion 504 is located within the insert 300. The plug 500 may be formed from a polymeric material, such as plastic, ABS, PVC, Nylon, acrylic, Delrin, or any other suitable material. The axial length of the wide portion 502 may, in some implementations, be about 1/16 inch to about ½ inch and the narrow portion 504 may be about the same length or less.

During assembly, the insert 300 is placed in the shaft 100 and moved toward the shaft tip end 108 until the outer diameter of the insert is equal to the inner diameter of the shaft, thereby preventing further movement of the insert toward the shaft tip end. Movement of the insert 300 toward the shaft butt end 110 is prevented by the plug 500. To that end, the plug 500 may be coated with a layer of adhesive 310. The adhesive 310 is used to permanently bond the relatively wide portion 502 to the shaft inner surface, and to permanently bond the narrow portion to the insert inner surface 314. The adhesive cooling/warming technique and tool 400 described above may be used here as well. Alternatively, the adhesive 310 may be omitted from the plug narrow portion 504 (FIG. 14). The adhesive 310 may also be omitted completely and a bonding technique, such as ultrasonic welding, may be used to permanently bond the plug to the shaft. In any case, once bonded, the entire length of the insert 300 will be the non-bonded length L_NB.

Referring to FIGS. 15 and 16, the plug 500a in the exemplary shaft assembly 12g is similar to plug 500 and is used to permanently secure the insert 300 to the shaft 100 in the manner described above. Here too, the plug 500a prevents the insert 300 from moving toward the butt end of the shaft 100 and the entire length of the insert will be the non-bonded length L_NB. The plug 500a does not, however, include a narrow portion and a wide portion. The plug 500a, which may be hollow (as shown) or solid, is simply sized to fit into the shaft 100 and abut the butt end 306 of the insert 300 in the manner illustrated in FIG. 16. A layer of adhesive 310 permanently secures the plug 500a to the shaft 100.

As alluded to above, inserts may be configured such that they will be located in portions of the shaft other than that illustrated in FIG. 4. To that end, and as illustrated for example in FIG. 17, the golf club 10a includes a shaft assembly 12h with a shaft 100 and an insert 300a that is identical to insert 300 but for dimensions. The insert 300 is permanently secured to the shaft 100 at a location that includes portions of the grip section 104 and main section 106 for purposes of, for example, adjusting the bending characteristics of the shaft 100.

Turning to the dimensions and materials, the length of the insert 300 will typically range from about 4 inches to about 30 inches and the exemplary insert 300 is about 12 inches in length. The outer diameter may, depending on the length of the insert and the size of the associated golf club shaft, range from about 4 mm to 10 mm at the tip end to about 7 mm to 13 mm at the butt end. The length of the insert 300a will typically range from about 6 inches to about 35 inches and the exemplary insert 300a is about 15 inches in length. The outer diameter of the insert 300a may, depending on the length of the insert and the size of the associated golf club shaft, range from about 5 mm to 11 mm at the tip end to about 8 mm to 14 mm at the butt end.

The insert lengths may also be a function of intended position. For example, the insert 300 may be configured to extend much closer to the shaft tip end 108 and/or to the shaft butt end 110. The insert 300a may be re-configured such that its tip end 304 is in the location illustrated in FIG. 17, while the butt end 306 is either located closer to, or is located further from, the main section 106 (yet still within the grip section 104). The butt end 306 of the insert 300a may also be located within the shaft main section 106. Depending on the intended adjustment to the shaft 100, the insert assembly 300a may be secured within the shaft without the insert 300, both inserts may be secured within the shaft, or the insert 300 may secured within the shaft without the insert 300a.

In those instances where the golf club shaft is not tapered from tip end to butt end, e.g. in those instances where the shaft has a tapered main section and cylindrical tip and/or grip sections, the insert may be shaped accordingly. For example, the insert may be tapered over its entire length and dimensioned so as to reside only in the shaft main section, or the insert may be tapered over the substantial majority of its length and have a short cylindrical section that is coextensive with a small portion of the cylindrical grip section or tip section of the shaft.

Turning to materials, the inserts 300 and 300a may be formed from relatively light weight materials, such as graphite or a polymer. A typical weight is about 15 grams or less. Different portions of the inserts may also be made from different materials if desired. The inserts may be manufactured to the desired lengths or manufactured to set lengths and then cut as necessary. Dimensional marking may be provided to facilitate accurate cuts. Suitable graphite insert manufacturing techniques include sheet-wrapping, filament-winding, and internal bladder molding, among other appropriate techniques. For example, one or more layers of Toray graphite material (e.g. Toray T700, M30, M40J, M46J or M50J) may be sheet-wrapped around a layer of light weight (e.g. about 100 g/m² or less) scrim or a layer of graphite pre-preg. Suitable polymer manufacturing techniques include injection molding. The outer surface of the inserts 300 and 300a may, in some instances, be coated with a coating that improves the fit between the insert and the golf club shaft 100 and reduces noise that may result from the engagement of the insert and the shaft. One example of such a coating is a polyurethane based coating. Additional details concerning inserts is provided in U.S. Pat. Nos. 7,479,069, 7494,423 and 7,500,921.

With respect to wall thickness (i.e. the difference between the inner diameter and the outer diameter), the inserts 300 and 300a may have a constant wall thickness or one that varies. In the illustrated implementations, 0.1 mm to 1.0 mm.

Although the present inventions have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. By way of example, but not limitation, the present inventions include golf clubs (e.g. a shaft and a club head) in combination with the shaft/insert combinations described above and defined by the claims below. The golf clubs may also include a grip and an end cap. It is intended that the scope of the present inventions extend to all such modifications and/or additions.

Claims

1. A golf club shaft assembly, comprising:

a golf club shaft having an inner surface; and

a shaft insert defining a tip end, a butt end and a length that extends from the tip end to the butt end, and having an outer surface that abuts the inner surface of the golf club shaft;

wherein the shaft insert is permanently secured within the golf club shaft; and

wherein the shaft insert is either not bonded to the golf club shaft or is bonded to the golf club shaft over less than the entire the length of the shaft insert.

2. A golf club shaft assembly as claimed in claim 1, wherein the shaft insert comprises a hollow, tubular shaft insert.

3. A golf club shaft assembly as claimed in claim 2, wherein the shaft insert comprises a thin wall and there no structures located inwardly of the thin wall.

4. A golf club shaft assembly as claimed in claim 1, wherein the shaft insert comprises a graphite shaft insert.

5. A golf club shaft assembly as claimed in claim 1, wherein the shaft insert comprises a tapered shaft insert.

6. A golf club shaft assembly as claimed in claim 1, wherein the shaft insert is not bonded to the golf club shaft over at least 90% of the length of the shaft insert, the length being continuous and beginning at the tip end of the insert.

7. A golf club shaft assembly as claimed in claim 1, wherein the outer surface of the shaft insert is permanently bonded to the inner surface of the golf club shaft over no more than 50% of the length of the shaft insert.

8. A golf club shaft assembly as claimed in claim 7, wherein outer surface of the shaft insert is permanently bonded to the inner surface of the golf club shaft over no more than 10% of the length of the shaft insert.

9. A golf club shaft assembly as claimed in claim 7, wherein outer surface of the shaft insert is not permanently bonded to the inner surface of the golf club shaft at the tip end of the shaft insert.

10. A golf club shaft assembly as claimed in claim 7, wherein the outer surface of the shaft insert is permanently bonded to the inner surface of the golf club shaft with adhesive.

11. A golf club shaft assembly as claimed in claim 7, wherein the outer surface of the shaft insert is permanently bonded to the inner surface of the golf club shaft with a weld.

12. A golf club shaft assembly as claimed in claim 7, wherein outer surface of the shaft insert is permanently bonded to the inner surface of the golf club shaft with a bond that extends from a location substantially adjacent to the butt end of the shaft insert towards the tip end of the shaft insert.

13. A golf club shaft assembly as claimed in claim 1, further comprising:

a plug that abuts the shaft insert butt end and is permanently bonded to the inner surface of the golf club shaft.

14. A golf club shaft assembly as claimed in claim 13, wherein the outer surface of the shaft insert is not bonded to the inner surface of the golf club shaft.

15. A golf club shaft assembly as claimed in claim 1, wherein the golf club shaft comprises a fiber reinforced shaft.

16. A golf club shaft assembly as claimed in claim 1, wherein the tip end and/or the butt end of the shaft insert is longitudinally and/or rotationally movable relative to the adjacent portion of the golf club shaft inner surface.

17. A golf club shaft assembly as claimed in claim 1, wherein the tip end and/or the butt end of the shaft insert is in direct contact with the golf club shaft inner surface.

18. A golf club shaft assembly, comprising:

a golf club shaft having an inner surface; and

a hollow, tubular shaft insert, defining a tip end and a butt end, permanently secured within the golf club shaft such that the tip end and/or the butt end of the shaft insert is longitudinally and/or rotationally movable relative to the adjacent portion of the golf club shaft inner surface.

19. A golf club shaft assembly as claimed in claim 18, wherein the shaft insert comprises a graphite shaft insert.

20. A golf club shaft assembly as claimed in claim 18, wherein the shaft insert comprises a tapered shaft insert.

21. A golf club shaft assembly as claimed in claim 18, wherein only one of the tip end and the butt end of the shaft inert is longitudinally and/or rotationally movable relative to the adjacent portion of the golf club shaft inner surface.

22. A golf club shaft assembly as claimed in claim 18, wherein

the shaft insert is permanently bonded to the golf club shaft at the tip end of the insert or at the butt end of the insert; and

the shaft insert is not bonded to the golf club shaft over at least 90% of the length of the shaft insert.

23. A golf club shaft assembly as claimed in claim 22, wherein the shaft inert is permanently bonded to the golf club shaft with adhesive.

24. A golf club shaft assembly as claimed in claim 18, wherein the tip end and/or the butt end of the shaft insert is in direct contact with the golf club shaft inner surface.

25. A golf club shaft assembly as claimed in claim 18, further comprising:

a plug that abuts the shaft insert butt end and is permanently bonded to the inner surface of the golf club shaft.

26. A golf club shaft assembly as claimed in claim 25, wherein the outer surface of the shaft insert is not bonded to the inner surface of the golf club shaft.

27. A golf club shaft assembly as claimed in claim 18, wherein the golf club shaft comprises a fiber reinforced shaft.