the present invention is directed to a quick connection system for connecting the shaft to a club head and for changing the shaft or the club head to optimize the golfer &# 39 ; s strength to the playing conditions . such a system can be utilized or customized for various applications , including , but not limited , to the shaft - club head connection , the insertion of adjustable weights in the club head , and the connection of a sole plate to the club head . the invention can also be used to change the trajectory properties of the golf club , e . g ., by changing the loft angle . several embodiments of the present invention are described below . in some embodiments , the designs offer improved functionality and weight savings . inventive connection system 10 is designed for club fitters to repeatedly change shaft or club head combinations during a fitting session . inventive connection system 10 is designed to give fitting accounts maximum fitting options with a system that is fast and easy to use . referring to fig1 and 2 , connection system 10 releasably connects club head 12 to shaft 14 , such that different shafts 14 can be connected to different club heads 12 . connection system 10 comprises a two - part hosel , i . e ., shaft serrated hosel 16 and driver serrated hosel 18 and internally threaded shaft insert 20 . serrated surface 17 of shaft hosel 16 and serrated surface 19 driver hosel 18 are sized to mate with each other to minimize or prevent relative rotation between shaft hosel 16 and driver hosel 18 . preferably , each serrated surface comprises a plurality of corresponding teeth . connection system 10 further comprises driver sole insert 22 and screw 24 , which are connected to club head 12 on the sole side , as shown . as best shown in fig3 , shaft 14 is at least partially hollow and is sized and dimensioned to receive and retain internally threaded shaft insert 20 therewithin . preferably , shaft insert 20 is securely attached to shaft 14 by means of adhesives , epoxies or similar materials . shaft serrated hosel 16 is sized and dimensioned to fit on the outside of shaft 14 . a predetermined length 26 of shaft 14 is positioned below shaft serrated hosel 16 for insertion into club head 12 . the internal threads of shaft insert 20 are adapted to receive the external threads of fastener 24 , such as screw 24 . as best shown in fig4 , driver serrated hosel 18 has external threads , as shown , and is threaded into the top of bore 28 of club head 12 . adhesives or epoxies can also be used to affix driver serrated hosel 18 to bore 28 . at the bottom of bore 28 , driver sole insert 22 is inserted into bore 28 and affixed therein . preferably , driver sole insert 22 is serrated or threaded on the outside surface to increase the surface area to adhesives or epoxies . the assembled shaft 14 with shaft insert 20 and shaft hosel 16 as shown in fig3 is inserted through driver hosel 18 and into bore 28 . screw 24 is inserted through driver sole insert 22 and is threaded into shaft insert 20 to secure shaft 14 to club head 12 . preferably , distal tip 30 of shaft 14 is spaced apart from the top of driver sole insert 22 and shaft 14 and driver sole insert 22 is separated by gap 32 . gap 32 ensures that screw 24 can fully pull shaft 14 downward toward the sole of club head 12 so that serrated surfaces 17 and 19 fully engage each other to minimize relative rotation between the two hosels 16 and 18 thereby minimizing relative rotation between shaft 14 and club head 12 . in other words , gap 32 ensures that screw 24 does not “ bottom out ” inside threaded shaft insert 20 so that serrated hosels 16 and 18 can fully mate with each other . optionally , bore 28 has ledge 34 shown in fig4 formed integrally thereon , e . g ., through the casting process , to abut driver sole insert 22 to provide additional structural support for driver sole insert 22 and screw 24 . alternatively , driver sole insert 22 can be formed integrally on bore 28 . these alternatives are applicable to all of the embodiments described herein . referring to fig5 , a fully assembled golf club is shown . serrated hosels 16 and 18 form a single hosel and the serrated lines 17 and 19 separating the two hosels are preferably located above the top of club head 12 . the advantage of locating the anti - rotation device , i . e ., shaft serrated hosel 16 and driver serrated hosel 18 , above the club head is that no additional mass is added , thereby preserving the mass properties of the club head and eliminating a protrusion at the shaft / hosel intersection . the anti - rotation device uses a standard hosel to make both the shaft serrated hosel and the driver serrated hosel . this means there is no weight gained or lost from the device , which in turn means no change in moment of inertia or center of gravity . furthermore , serrated lines 17 and 19 add a visual distinction to the golf club and readily identify the golf club as an interchangeable golf club . driver sole insert 22 and shaft threaded insert 20 , as well as hosel insert 16 and / or hosel insert 18 , can be made out of aluminum , stainless steel or titanium . screw 24 can be any threaded screw , and is preferably a torx ™ drive flat head screw and the sole insert 22 is tapered so that the head of screw 24 can be flushed with sole insert 22 , as best shown in fig4 . referring to fig6 and 7 , another embodiment of connection system 10 is shown . in this embodiment , the two - part hosel of the first embodiment is replaced by a keyed anti - rotation device . this keyed anti - rotation device comprises angled cut - out 36 on the distal tip of shaft 14 . shaft 14 is also hollow and has threaded shaft insert 20 inserted therein and conventional hosel 40 disposed thereon . driver sole insert 22 ′ has angled surface 38 sized and dimensioned to match cut - out 36 . in this embodiment , shaft 14 is inserted into driver sole insert 22 ′, and angled cut - out 36 is keyed to angled surface 38 as screw 24 is threaded into shaft insert 20 to minimize or prevent relative rotation between shaft 14 and driver sole insert 22 ′/ club head 12 . an advantage of this embodiment is that an anti - rotation device can be added without adding substantial weight to the club head thereby minimizing the effect on the club &# 39 ; s swing weight . referring to fig8 , another embodiment of connection system 10 is shown . in this embodiment , bore 28 does not extend through club head 12 . club head 12 has hosel 42 , which has at least one and preferably two or more channels 44 . channel 44 has entry leg 46 and locking leg 48 . leg 46 is adapted to receive post 50 on shaft 14 . after post 50 travels through entry leg 46 , it passes transverse leg 47 before being received and held in locking leg 48 . disposed within hosel 42 is spring 52 that exerts an upward force on shaft 14 to hold securely post 50 in locking leg 48 . spring 52 is selected so that it can exert a sufficient force to hold post 50 within channel 44 . preferably , spring 52 has a spring constant from about 5 to about 100 pounds - force / inch . more preferably , the spring constant can be in the range of about 20 to about 75 pounds - force / inch and most preferably about 33 pounds - force / inch . a golfer can conveniently insert shaft 14 into hosel 42 after aligning post 50 to leg 46 . thereafter , shaft 14 is rotated along transverse leg 47 and afterward spring 52 pushes shaft 14 up locking leg 48 . post 50 and channel 44 is also known as a bayonet mount or connection . although channel 44 is illustrated as a “ j - shaped ” channel , it can have any shape , e . g ., “ u ”, “ l ”, “ s ”, “ v ” or “ w ” shape . also , preferably leg 46 is preferably deep so that as post 50 is moved down into hosel 42 , more of shaft 14 overlaps hosel 42 to increase mechanical stability . alternatively , the top of locking leg may have a reduced diameter section to hold post 50 by press - fit or by increased friction . as illustrated in fig8 a , the reduced diameter section can be a triangular section . the reduced diameter section can also be a figure - eight or waist section . in another embodiment , shown in fig8 b , the connection system provides adjustability of an angular attribute of golf club head 12 relative to shaft 14 , such as face angle , loft and lie . similar to previous embodiments , club head 12 includes hosel 42 , but in the present embodiment , hosel 42 has at least two channels 44 so that the shaft may be positioned in at least two discrete orientations relative to head 12 . for example , shaft 14 may be coupled to hosel 42 in a first orientation and in a second orientation in which the shaft is rotated about a longitudinal axis of hosel 42 from the first orientation . channels 44 are spaced circumferentially around hosel 42 and each channel 44 has entry leg 46 and locking leg 48 . shaft 14 includes a distal engagement portion 43 and a proximal portion that extends from the distal portion to a grip end of shaft 14 . in an assembled golf club , engagement portion 43 is at least partially received in hosel 42 and coupled thereto . the engagement portion may comprise a separate sleeve component that is attached to shaft 14 or it may be formed as an integral part of shaft 14 during the manufacture . engagement portion 43 is a generally elongate portion of shaft 14 that is shaped to engage hosel 42 and defines a longitudinal axis a . the engagement portion of shaft 14 defines a longitudinal axis b that is angled relative to axis a by an angular offset θ . by providing at least two discrete orientations of shaft 14 relative to head 12 and angular offset θ , an angular attribute of club head 12 relative to shaft 14 may be altered . preferably , the angular offset θ ranges from about 0 . 5 ° to about 5 . 0 °. at least one post 50 is included on engagement portion 43 . post 50 extends radially outward from an outer surface of engagement portion 43 and is configured to engage channel 44 . preferably , shaft 14 includes the same number of posts 50 as channels 44 . for example , in an embodiment that includes two channels circumferentially spaced about the hosel by 180 ° also , preferably includes two posts circumferentially spaced about the engagement portion by 180 °. in the present embodiment , post 50 is a screw that engages a threaded bore in engagement portion 43 and is therefore movably coupled to engagement portion 43 . in channel 44 , leg 46 is adapted to receive post 50 on shaft 14 . after post 50 travels through entry leg 46 , it passes transverse leg 47 before being received and held in locking leg 48 . disposed within hosel 42 is spring 52 that exerts an upward force on shaft 14 to hold securely post 50 in locking leg 48 . spring 52 is selected so that it can exert a sufficient force to hold post 50 within channel 44 . additionally , the top of locking leg may include a receptacle 49 that receives a portion of post 50 to prevent relative motion between shaft 14 and club head 12 when post 50 is fully engaged in channel 44 . for example , the screw may be configured to lock into receptacle 49 when the screw is tightened , such as by forming receptacle as a countersunk portion of locking leg 48 and engaging it with a countersunk screw head . fig9 illustrates another variation of the embodiment of fig8 , where hosel 42 has two or more channels 44 . channels 44 can have the shapes or configurations of those described in fig8 and 8a . an advantage of this embodiment is that having two or more locking legs 48 prevents twisting at the lower end of the leg and it offers a back up should one of the locking legs 48 fail . referring to fig1 a to 10d , another embodiment of connection system 10 comprises a first rotatable hosel sheath 70 with internal threads and a second threaded , hollow hosel part 72 , which is fixedly attached to club head 74 . preferably , second threaded hosel part 72 is made integral to club head 74 , and hosel sheath 70 and hosel part 72 are sized and dimensioned to threadably attach to each other to connect shaft 14 to club head 74 . connection system 10 further comprises an anti - rotation device , made up of first serrated surface 76 disposed on inner shaft insert 80 and corresponding second serrated surface 78 disposed on second threaded hosel part 72 . to assemble the club , upper end 82 of inner shaft insert 80 is inserted into the threaded end of rotatable hosel sheath 70 , as shown in fig1 c . end 82 is sized and dimensioned to pass through aperture 84 of hosel sheath 70 , but the top portion of serrated surface 76 is retained within hosel sheath 70 . end 82 is then inserted into aperture 86 and finally attached to outer shaft insert 88 . after end 82 of inner shaft insert 80 is fixedly connected to outer shaft insert 88 , there is sufficient clearance for first hosel sheath 70 to be freely rotatable to connect to second hosel part 72 . preferably , the length of end 82 is dimensioned so that once end 82 is fully inserted into aperture 86 , there remains sufficient clearance between outer shaft insert 88 and hosel sheath 70 for hosel sheath 70 to rotate freely . outer shaft insert 88 is then inserted into shaft 14 . alternatively , inner sheath insert 80 is inserted into and attached directly to shaft 14 and outer sheath insert 88 can be omitted . although this embodiment of the present invention is particularly suited to hosel sheath 70 made of metal , hosel sheath 70 can be made of high impact transparent or translucent materials . suitable materials include , but are not limited to , polymethacrylate , cellulose acetate butyrate , polycarbonate ( lexan ®), and glycol modified polyethylene teraphthalate . afterward , as shown in fig1 d , shaft 14 , with decorative ferrule 90 , hosel sheath 70 and both shaft inserts 80 and 88 , is assembled with club head 74 . more specifically , lower end 83 of inner shaft 80 is inserted into second hosel part 72 to allow corresponding threads of hosel sheath 70 and hosel part 72 to mate and connect shaft 14 to club head 74 . end 83 may extend partially or fully into club head 74 . serrated surfaces 76 and 78 also mate to minimize relative rotation between the shaft and the club head . referring to fig1 a to 11d , another embodiment of connection system 10 comprises a rotatable hosel reverse sheath 92 with internal threads and a threaded , hollow shaft insert 94 , which is fixedly attached to shaft 14 . hosel reverse sheath 92 and shaft insert 94 are sized and dimensioned to threadably attach to each other to connect shaft 14 to club head 98 . connection system 10 further comprises an anti - rotation device , made up of first serrated surface 100 disposed on club insert 102 and corresponding second serrated surface 104 disposed on shaft insert 94 . to assemble the club , upper end 96 of shaft insert 94 is inserted into and fixedly connected to shaft 14 for example by adhesive or epoxy , as shown in fig1 c . preferably , the length of end 96 is dimensioned so that there is a sufficient bond between shaft insert 94 and shaft 14 . threads 106 and second serrated surface 104 should remain outside of shaft 14 and next to decorative ferrule 108 . as shown in fig1 d , lower end 110 of club insert 102 is inserted into reverse sheath 92 . end 110 is sized and dimensioned to pass through aperture 112 of reverse sheath 92 , but the bottom portion of serrated surface 100 is retained within rotatable reverse sheath 92 . end 110 is then inserted into hosel 114 and is attached thereto . end 110 may extend partially or fully into club head 98 so long as there is sufficient clearance for reverse sheath 92 to rotate freely . to assemble the club , the assembled version of fig1 c is inserted into the assembled version of fig1 d . serrated surfaces 100 and 104 mate to minimize relative rotation between the shaft and the club head and reverse hosel sheath 92 is rotated so that its internal threads mate with threads 106 of shaft insert 94 to connect club head 98 to shaft 14 . referring to fig1 a to 12e , another embodiment of connection system 10 comprises hollow shaft insert 54 connecting shaft 14 to club head 56 . shaft insert 54 comprises affixing leg 57 and non - affixing leg 58 , which have uneven lengths , as best shown in fig1 b . hosel 55 has receiving area 59 adapted to receive shaft insert 54 . to assemble the club , shaft tip 60 is maintained below decorative ferrule 61 disposed on shaft 14 , as shown in fig1 d . upper end 62 of shaft insert 54 is inserted into shaft tip 60 , and shaft insert 54 is fixedly attached to shaft 14 . afterward , as shown in fig1 e , shaft 14 , with decorative ferrule 61 and shaft insert 54 is assembled with club head 56 . specifically , lower end 63 of shaft insert 54 is inserted into receiving area 59 to connect shaft 14 to club head 56 . more specifically , affixing leg 57 is inserted into aperture 64 and threadably attached to sole nut 65 in bore 66 of club head 56 , while non - affixing leg 58 is mated to receiving area 59 to minimize relative rotation between the shaft and the club head . preferably , non - affixing leg 58 is conical , wedge , or other key shape . referring to fig1 to 12e and 14 a to 15 g , the embodiments of the present invention are illustrated with various single thread fasteners . these fasteners can be right - handed or left - handed and can have single thread or multiple threads . these fasteners need to be sufficiently strong to withstand repeated impacts between the golf club and the balls . an impact can create a force of up to 2 , 000 lbs . and depending on the location of the impact on the hitting face , connection system 10 may experience a torque load of 2 , 000 · x , where x is a distance between the impact location and the neutral axis of the club . for example , a toe impact would produce more torque than a center impact . a heel impact would produce more torque ( reverse direction ) than a center impact . the density of threads and the dimensions of the threads should be designed to withstand the torque produced by toe and heel impacts . fig1 a illustrates the force - flow lines 120 through a set of threaded fasteners used to clamp two members together . ( further detail can be found in fundamentals of machine component design by robert c . juvinall , copyright 1983 , by john wiley & amp ; sons , inc .) direct compressive stress , often called bearing , exists between threaded fastener 122 and corresponding fastener 124 . stress ( a ) is defined as load ( p ) 128 divided by the cross sectional area ( a ) 130 that exists when the load is acting : σ = p / a . in this particular situation , the area used for the p / a stress calculation is projected area 132 that , for each thread , is π ( d 2 − d i 2 )/ 4 , where d 134 is outer diameter of fastener cylinder and d i 136 is inner diameter of fastener 122 contact with nut 124 . the number of threads in contact is t / p , where t is fastener length of engagement 138 and p is fastener thread pitch , typically reported as inches per thread turn . ( in practice , thread pitch is known by its reciprocal of threads per inch .) by substitution , σ =( 4p / π ( d 2 − d i 2 ))· p / t . this equation demonstrates the advantage of more threaded contacts in the present invention , which is the strength of a set of threaded fasteners is proportionately increased by increasing the threaded fastener contacts . preferably , fastener threads per inch is 12 to 36 threads / inch . more preferably , fastener threads per inch is 18 to 30 threads / inch and most preferably 24 threads / inch . increasing fastener contacts could increase the golfer &# 39 ; s fastener tightening and untightening time , which is undesirable to a method for quickly and easily interchanging the shaft , removable weights and other attachments with the club head . typically , threaded fasteners comprise a single helical groove 140 disposed on a cylindrical rod from end thread 142 , however if the helix angle 144 is increased other threads may be cut between the grooves of the first thread , so fasteners can have two 146 or more parallel threads , as shown in fig1 b . ( further detail can be found in fundamentals of machine component design by robert c . juvinall , copyright 1983 , by john wiley & amp ; sons , inc .) a fastener thread is assumed to be single thread , unless otherwise stated . lead is the distance a threaded fastener advances axially in one turn . on a single threaded fastener 140 , the lead 148 and pitch 150 are identical ; on a double thread fastener 146 , the lead 152 is twice the pitch 154 , etc . the end result is that the threaded fastener will advance twice as far in a single turn on a double thread fastener than it would on a single thread fastener , etc ., so double , triple , or more threads are used whenever rapid advance is desired . the advantage of multiple parallel threads is that the thread count of the fastener connection can be increased to strengthen the fastener connection while minimizing the golfer &# 39 ; s time to connect the threaded connectors together . preferably , fasteners will be multiple thread and have the same direction . more preferably , fasteners will be double thread and have the same direction . referring to fig1 b , a thread may be either right - hand 140 or left - hand 146 . almost all threaded fasteners tighten , or move away from the viewer , when rotated clockwise ; a left - hand thread advances when turned counterclockwise . a fastener thread is assumed to be right - hand unless otherwise stated . during use of an assembled golf club , swinging the golf club and hitting the ball tends to tighten or loosen threaded connections , depending on whether the club is right - or left - handed and whether the thread is right - or left - hand . for right - handed golf clubs , left - hand threading would tighten during ball striking ; for left - landed golf clubs , right - hand threading would tighten during ball striking . preferably , fastener threading would be matched to loosening and tightening needs , so that the club can be readily assembled and disassembled before and after use . referring to fig1 a to 14e , another embodiment of connection system 10 comprises a wedge hosel 160 with tapered receiving area 162 , a hollow club head insert 164 that is fixedly attached to club head 166 , and a wedge screw 168 with a first smooth tapered end 170 and a second threaded cylindrical end 172 . tapered receiving area 162 of wedge hosel 160 is adapted to receive tapered head 170 of wedge screw 168 . connection system 10 further comprises an anti - rotation device , made up of first serrated surface 174 disposed on wedge hosel 160 and corresponding second serrated surface 176 disposed on club head insert 164 . additionally , when tapered head 170 is inserted into receiving area 162 , tapered head 170 also minimizes relative rotation between club head 166 and shaft 14 . wedge screw 168 is preferably aligned substantially perpendicular or orthogonal to the shaft . to assemble the club , shaft tip 178 is maintained below decorative ferrule 180 disposed on shaft 14 , as shown in fig1 c . upper end 182 of wedge hosel 160 is sized and dimensioned to fit on the outside of shaft 14 , and wedge hosel 160 is fixedly attached to shaft 14 by means of adhesives , epoxies or similar materials . shaft tip 178 is retained within wedge hosel 160 , as shown in fig1 d . preferably , upper end 182 of wedge hosel 160 is flush with decorative ferrule 180 . club head insert 164 is inserted the top of bore 184 of club head 166 and affixed therein with diametric aperture 186 of club head insert 164 aligned with threaded side aperture 188 of club head 166 . preferably , club head insert 164 is serrated or threaded on its outside surface to increase the surface area to adhesives or epoxies . alternatively , club head insert 164 is made integral to club head 166 . thereafter , shaft 14 and wedge hosel 160 assembly , as shown in fig1 f , is inserted the top of bore 184 of club head 166 . the interaction of serrated surfaces 174 and 176 of wedge hosel 160 and club head insert 164 directs shaft 14 within bore 184 so that tapered receiving area 162 of wedge hosel 160 aligns with side aperture 188 of club head 166 . tapered end 170 of wedge screw 168 is inserted through side aperture 188 of club head 166 into receiving area 162 of wedge hosel 160 and threaded end 172 of wedge screw 168 is releasably fastened into threaded side aperture 188 of club head 166 . wedge 168 may comprise two components : wedge shell 169 and threaded fastener 171 , as shown in fig1 g - j . fastener 171 fits within wedge shell 169 and is rotatably connecting hosel 160 to club head 12 . the two - component wedge is similar to the one - component wedge , except that the threads are located on the inner threaded fastener 171 and wedge shell 169 has substantially smooth outer surface to fit snugly to receiving area 162 . the end of wedge shell 169 can be conical , as shown in fig1 h or tapered , as shown in fig1 i . the conical end has an advantage of self - centering as two component wedge 168 is being inserted into hosel 160 . the tapered end has an advantage of providing an anti - rotation tendency between wedge 168 and hosel 160 . alternatively , wedge housing 169 can have a cylindrical outer shape as shown in fig1 j . in the cylindrical embodiment , all of outer surface 173 is in contact with hosel 160 to provide enhanced contact between these two parts . a cover 175 is optionally provided to keep wedge 168 free of debris . fig1 a to 15d illustrate another embodiment of connection system 10 with a bendable hosel 190 . hosel 190 is designed to bend preferable at section 192 , where the outer diameter of hosel 190 has a substantial change . hosel 190 can be bent about section 192 to change the loft and / or lie angle of the golf club . any bendable hosel with predetermined bends or any hosel with a weakened section can be used . hosel 190 can be bent by automatic / motored or hydraulic bending tools , commonly used in golf pro shops , e . g ., steelclub angle machine sold by mitchell golf equipment co ., and those used to bend pipes in the plumbing art . suitable bendable hosels are disclosed in commonly owned , co - pending u . s . patent application ser . no . 11 / 621 , 754 , filed on jan . 10 , 2007 , which is incorporated herein by reference in its entirety . hosel 190 should be bendable only by equipment made for bending hosels , and not by impact with golf balls . similar to the embodiment in fig1 a - 14f , this connection system also has an anti - rotation device comprising a first serrated surface 194 on the hosel and a corresponding second serrated surface 196 on hollow club head insert 198 . to assemble the golf club , shaft insert 200 with internal threads in first inserted into shaft 14 , and then bendable hosel 190 is attached to the outside of shaft 14 , as shown in fig1 c - 15d . the shaft and hosel assembly is then inserted into club head 202 . a screw 204 is inserted into heel opening 206 of club head 202 and is threaded into shaft insert 200 to retain shaft 14 to club head 202 , similar to the retaining mechanism shown in fig1 - 4 and described above . fig1 a - 16e illustrate a system for retaining screw 204 within club head 202 during the changing of hosel or club head . the connection system shown in fig1 a is similar to that shown in fig1 d , except for hollow screw cap 208 . after screw 204 is inserted into heel opening 206 , as discussed in the preceding paragraph , screw cap is inserted into heel opening 206 and is sized and dimensioned to be positioned at a predetermined distance , l , below the top of screw 204 , as best shown in fig1 b . distance l is preferably greater than the depth of the teeth of serrated surfaces 194 and 196 . when a user wishes to change the hosel or club head , the user would insert a screwdriver to similar tool into heel opening 206 , through hollow screw cap 208 to the top of screw 204 . the user would then unscrew screw 204 to move screw 204 a distance l , or until the top of screw 204 comes into contact with screw cap 208 . at this point , the user can pull shaft 14 upward to disengage first serrated surface 194 of hosel 190 from the corresponding second serrated surface 196 of club head insert 198 . the user then can freely rotate shaft 14 relative to club head 202 to separate shaft 14 from club head 202 . the advantage of using screw cap 208 is that screw 204 is kept within the club head and the chance of misplacing screw 204 is minimized . screw cap 208 , as shown in fig1 c , may have waist 210 , and heel opening 206 may have at least one ledge 212 , as shown in fig1 d , adapted to be received within waist 210 to keep screw cap 208 securely within the club head . alternatively , as shown in fig1 e may have one or more protrusions 214 , as shown in fig1 e , to provide an interference fit between screw cap 208 and the walls of heel opening 206 . in another embodiment , the club head may have an opening 216 formed on its heel as shown in fig1 a . opening 216 is adapted to receive a high impact transparent or translucent cap 218 , which allows the user to view the mechanisms of connection system 10 , as best shown in fig1 b . suitable materials include , but are not limited to , polymethacrylate , cellulose acetate butyrate , polycarbonate ( lexan ®), and glycol modified polyethylene teraphthalate , discussed above . another way to change the lie and / or loft angle of the golf club is illustrated in fig1 a and 18b . here , golf club 10 which includes club head 12 , shaft 14 and hosel parts 16 and 17 , shown above in fig5 , has hosel insert 220 disposed between hosel parts 16 and 17 . hosel insert 220 have serrated surfaces on its top and bottom to match the serrated surfaces of hosel parts 16 and 17 , so that hosel insert 220 would fit flush in between . to change the loft / lie angle of club 10 , first side 222 and second side 224 of hosel insert 220 are different from each other , or top line 226 is not parallel to bottom line 228 , as illustrated by lines 226 ′ and 228 ′. in other words , hosel insert 220 is askew . in one example , if first side 222 is shorter than second side 224 , then and α = 91 ° and β = 90 °, then the shaft angle has been shifted by 1 °. if the shaft coincides with the vertical axis then the shaft would have been shifted toward first side 222 by an amount equal to in this example , if first side 222 and second side 224 are oriented in the toe - heel direction , then hosel insert 220 can change the lie angle . if first side 222 and second side 224 are oriented in the front - rear direction , then hosel insert 220 can change the loft angle . it is noted that hosel insert 220 does not need to have the serrated top and bottom surfaces as shown , so long as these surfaces match the corresponding surfaces on hosel parts 16 and 17 . for example , if the corresponding surfaces of hosel parts 16 and 17 are linear or curvilinear , then the top and bottom surfaces of hosel insert 220 can assume the same shape . furthermore , hosel insert 220 can be positioned above club head 12 , as shown ; however , it can also be located inside the club head . furthermore , one of the hosel parts , can be made integral with club head 12 , as illustrated in fig2 a . the hosel parts are preferably made from low density aluminum so that more mass can be distributed elsewhere to improve inertia and center of gravity properties . fig2 a is similar to fig1 - 5 and is illustrated with similar reference numbers . as shown , hosel part 18 is made integral to club head 12 and matching serrated surfaces 17 and 19 are positioned above club head 12 , similar to the view shown in fig5 . furthermore , hosel insert 220 , shown in fig1 a - b , can be used with this embodiment to change the lie and loft angle without bending the hosel . alternatively , as shown in fig2 b , matching serrated surface 17 and 19 are positioned internal to club head 12 . in this embodiment , serrated surface 19 may be formed directed on club head 12 during the casting process , and hosel part 18 can be omitted . also , threaded shaft insert 20 can be omitted , when hosel insert 16 has threaded internal surface 238 , sized and dimensioned to receive screw 24 to attach hosel 14 to club head 12 , as shown in fig2 c . an advantage of this embodiment , is that it has fewer parts than the embodiments shown in fig2 a and 20b and that instead of the smaller contact surface between shaft insert 20 and hosel 14 , a larger contact surface between hosel 14 and hosel 16 is available to be epoxied together to withstand the impact force between club and golf balls . to minimize the possibility of vibration caused by ball - club impacts , a damper or a pre - load spring can be added , for example between the shaft and the club head or portion thereof as shown in fig2 d . fig2 d is an enlarged portion fig2 c , showing damper / spring 240 . it is noted that damper / spring 240 can be used with any of the embodiments discussed and claimed herein . part 240 can be an elastomeric or viscoelastic member designed to absorb vibration caused by impacts , and can be compressed between the hosel and the club head , as shown . alternatively , part 240 can be one or more spring washers being compressed between the hosel and the club head to absorb the vibration . suitable spring washers include , but are not limited to , belleville or cupped spring washers , star spring washers , wave spring washers , curve spring washers , and locking washers . also , any of the threaded connections described herein , can be reinforced by a threaded helical coil , commercially available as helicoil ™ from many sources , including emhart teknologies . these coils are precision formed screw thread coils made from stainless steel , titanium or other durable metals , that have a diamond shaped cross - section . these coils are inserted into threaded holes , and are adapted to receive threaded fasteners . these coils are designed to be placed snugly between the threaded fasteners and threaded holes , and are designed to spread the load evenly among the threads . typically , these coils are harder than the holes and the fasteners to minimize the possibility of thread tripping . typically , shafts 14 are long and slender and their geometry affects the number of teeth that can be present on serrated surfaces 17 and 19 , as shown generally in fig1 - 2 , as well as the geometry of these teeth . the size of the teeth also needs to be sufficiently robust to withstand the stresses and torque applied to the shaft . the cutting tools have their own limitation as to how small they can cut the serrated teeth . the inventors of the present invention have discovered that in one preferred embodiment three teeth on each hosel insert 16 , 18 can sufficiently perform the anti - rotation function , as shown in fig1 a - c . as shown , hosel part 16 has three thick tapered teeth 230 and hosel part 18 has three corresponding thin tapered teeth 232 . alternatively , thick tapered teeth 230 can be associated with hosel part 18 and vice versa . the slopes of tapered teeth 230 and tapered teeth 232 are substantially the same and are from about 20 ° to about 40 °, preferably from about 25 ° to about 35 °, and more preferably about 30 °. such angle extends the wear of the teeth and allows debris and dirt to escape . teeth 232 can be from about 0 . 07 inch to 0 . 25 inch in height , preferably between about 0 . 09 inch to about 0 . 20 inch in height , and more preferably between about 0 . 10 inch to about 0 . 15 inch in height . in accordance with another aspect of the present invention , the tapered teeth ( or prongs ) on serrated surfaces 17 and 19 , such as teeth 230 and 232 , do not come into contact with the opposing hosel part , so that the tapered teeth or prongs don &# 39 ; t bottom out or come into contact with the opposing hosel part . in other words , a gap 236 shown in fig1 a is present when hosel parts 16 and 18 are assembled . this provides a manufacturing tolerance so that hosel parts 16 and 18 can fit flush together . for example , if no gap 236 is allowed and one of the teeth is slightly longer than the rest , then when assembled this longer tooth prevents the two hosel parts from coming flush together . fig1 d illustrates another example of gap 236 with tapered teeth 230 and 232 having substantially the same size . alternative joining systems may be used to reversibly attach and detach club heads from shafts . these systems can be used for club sets having interchangeable heads as well as clubs having adjustable loft and / or lie angles . in some embodiments , such as shown in fig2 a and 21b , a shaft 310 will interface with a club head 320 using a fastener 330 designed to be received by the end of the shaft 310 . in some embodiments , the club head 320 will comprise a heel opening 323 that allows the fastener 330 to pass through , however a head 360 of the fastener ( see fig2 ) cannot pass through the heel opening . as such , the fastener 330 exerts a force between the club head 320 and the shaft 310 as the fastener 330 is tightened , e . g ., with rotation . while not shown in detail in fig2 a and 21b , it is understood that rotation of the shaft 310 may be limited by the hosel 327 , which may include a serrated surface , e . g ., as described above . the design allows the shaft 310 to be loosened , the shaft 310 rotated with respect to the club head 320 , and then the fastener 330 retightened in order to change the trajectory profile of the club head 320 with respect to the shaft 310 . while not shown in fig2 a , the hosel 327 may have an opening , e . g ., a window , that is designed to indicate a loft or lie angle corresponding to the position of the shaft 310 . while fig2 a and 21b clearly show the fastener 330 mating with the shaft 310 , a user of the club will , in fact need to mate the fastener 330 with the shaft blindly . that is , the user will have to align the fastener 330 axially with the shaft so that the fastener can mate with the appropriate structure in the shaft 310 , e . g ., a threaded hole , in order to secure the shaft 310 without damaging the fastening mechanism , e . g ., cross - threading a screw . optimally , the fastener 330 will also be held in an elevated position even when the club is normally - oriented ( i . e ., the fastener 330 is upside down ), thereby making it easier to mate the shaft 310 , e . g ., by initially hand - threading the shaft 310 onto the fastener 330 . these goals are met with the design shown in fig2 b whereby a fastener 330 having a retaining shoulder 340 is held in place by a retaining structure 350 . with the design shown in fig2 b , the fastener 330 cannot move down away from the heel opening 323 nor can it move substantially from the axis of the shaft 310 . the fastener 330 can rotate freely , however , making it easier to engage the shaft 310 . additionally , because the retaining structure 350 does not interact with the fastener 330 except to hold it in place , the retaining structure 350 will not be damaged with repeated attachment of the club head 320 to the shaft 310 . that is , if the retaining structure 350 interacted with a threaded portion of fastener 330 , it is possible that the retaining structure could be stripped or pulled away from the heel opening 323 with repeated engagement of the fastener 330 . when used to attach a golf club head to a golf club shaft , the inventive design in fig2 b benefits the golfer by making the club head lighter and easier to manufacture , thus reducing costs . prior art designs used align a fastener similar to fastener 330 have required intricate extensions to be cast or stamped into the head 320 to maintain the fastener alignment . such extensions make the head more difficult to manufacture , and result in added weight . using the design of fig2 b , for example , the heel opening 323 can be closer to the bottom of the head , reducing the complexity of placing the heel opening 323 . additionally , the material surrounding the heel opening 323 can be fabricated from thinner materials , further reducing cost and weight . furthermore , the weight that is required to secure the retaining structure 350 is moved lower in the head 320 . in the embodiment shown in fig2 b , it is estimated that the use of the disclosed retaining structure 350 saves between 1 and 2 grams of weight . an embodiment of a fastener 330 having a retaining shoulder is shown in fig2 . the fastener 330 also has a head 360 and a threaded portion 370 . the head 360 has an engagement structure 365 ( fig2 ) configured to receive a tool , such as an allen key or a screwdriver . the tool need not have a particular configuration , as any configuration , such as triangular , square , pentagonal , hexagonal , heptagonal , octagonal , cross , slot , or star shaped , can be used to secure fastener 330 to shaft 310 . the retaining shoulder 340 is shown as a tapered ring that fits on fastener 330 and interacts with retaining structure 350 to keep fastener 330 in the desired position . the retaining shoulder 340 need not be tapered , as it can be semicircular , triangular , or rectangular in cross - section provided that it can interact with the retaining structure 350 to keep the fastener 330 in position . alternatively , retaining shoulder 340 can be a slotted ring or a clip provided that the retaining shoulder can move through the retaining structure 350 . if the retaining shoulder 340 is a separate piece that mates with the fastener 330 , it may be constructed from metal or plastic . in alternative embodiments , the retaining shoulder 340 can be integral with the fastener , e . g ., a bolt having a shaft with a slot cut in it toward the threaded end to interact with the retaining structure 350 . while the fastener is depicted as a screw or a bolt , fastener 330 may alternatively be a hook structure , or a shaft with a structure to interact with a slot , similar to the structure described in fig8 and 9 . fastener 330 may be fabricated from metal , such as steel , aluminum , or titanium , or from a resilient plastic or lightweight composite . fig2 shows a cross - section detailing the interaction between retaining structure 350 and fastener 330 . retaining structure 350 is typically a thin structure protruding from the interior surface of the club head in an upward direction toward the shaft 310 , as shown in fig2 b . the protrusions of retaining structure 350 must be sufficiently resilient to accept the retaining shoulder 340 of the fastener 330 and then return to a position to restrain the fastener 330 via the retaining shoulder 340 as shown in fig2 . in some embodiments , as shown in fig2 , the head 360 of fastener 330 will provide pressure against the club head directly . in other embodiments , the head may provide pressure against a washer or another intermediate structure which provides pressure against the head 320 . the retaining structure 350 may be integrated into the club head , or an independent retaining member may be used to secure the fastener 330 in the correct position . in embodiments wherein the retaining structure 350 is integrated into the club head , the retaining structure 350 will typically be constructed from the material of the club head , e . g ., aluminum , titanium , or composite . in other embodiments , a retaining member , such as depicted in fig2 a , b and 25 a , b , is the retaining structure 350 that holds fastener 330 in the desired position . as shown in fig2 a , a retaining member may comprise a sleeve 400 of lightweight material , having slots to allow the protrusions to expand to receive the retaining shoulder 340 and then return to a shape to hold the retaining shoulder 340 in place . once fastener 330 is secured in sleeve 400 , the sleeve and fastener 330 can be inserted into the heel opening 323 in the heel of the club . the annular protrusions 410 on the sleeve 400 will cause the sleeve 400 to be secure in the heel opening 323 , thereby keeping fastener 330 at the correct height and axially - aligned with the shaft 310 . the sleeve 400 additionally assures that fastener 330 does not fall from the club head when not engaged with the shaft 310 . the sleeve 400 can be made from any suitable lightweight and resilient material such as plastic , composite , or metal . in preferred embodiments , the sleeve 400 is constructed from injection molded plastic . a cross section of the fastener 330 mated with the sleeve 400 is shown in fig2 b . other retaining member structures can be used to retain fastener 330 with club head 320 , as shown in fig2 a and 25b . fig2 a shows a clip 500 suitable to retain fastener 330 via retaining shoulders 340 . in fig2 a , the clip 500 is shown in a relaxed state , i . e ., not interfaced with a fastener 330 . the clip 500 has a plurality of protrusions that allow the clip to expand to receive the retaining shoulder 340 of fastener 330 and then return to a position suitable to restrict motion of retaining shoulder 340 ( see fig2 b ). like the sleeve 400 shown in fig2 a and 24b , the clip 500 is inserted into the heel opening 323 once assembled . a waist 510 causes the clip 500 to be retained , as shown in fig2 b . other suitable clips 500 may be designed to meet the same needs with similar structures . the clip 500 can be made from any suitable lightweight and resilient material such as plastic , composite , or metal . in preferred embodiments , the clip 500 is constructed from injection molded plastic . a cross section of the fastener 330 mated with the clip 500 is shown in fig2 b . the embodiments of the present invention are illustrated with driver - type or iron - type clubs . however , it is understood that any type of golf club , e . g ., hybrid , wedge , or putter , can use one or more of the connection systems 10 disclosed . additionally , connection system 10 can be used with non - golf equipment , such as fishing poles , tennis rackets , squash rackets , racquetball rackets , lacrosse sticks , aiming sights for firearms , hammers , axes , plumbing , etc . while it is apparent that the illustrative embodiments of the invention disclosed herein fulfill the objectives stated above , it is appreciated that numerous modifications and other embodiments may be devised by those skilled in the art . elements from one embodiment can be incorporated into other embodiments . therefore , it will be understood that the appended claims are intended to cover all such modifications and embodiments , which would come within the spirit and scope of the present invention . references and citations to other documents , such as patents , patent applications , patent publications , journals , books , papers , and web contents , have been made throughout this disclosure . all such documents are hereby incorporated herein by reference in their entirety for all purposes . various modifications of the invention and many further embodiments thereof , in addition to those shown and described herein , will become apparent to those skilled in the art from the full contents of this document , including references to the scientific and patent literature cited herein . the subject matter herein contains important information , exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and equivalents thereof .
a releasable connection system for assembling a shaft and a club head , e . g ., a golf club shaft and a golf club head . the connection system provides interchangeability between a shaft and a club head and allows the head to be adjusted with respect to the shaft . the mating structures between the shaft and the club head may be indexed for reproducible placement . in an embodiment , the connection system also includes retaining structures that maintain the connection fastener position when the head and shaft are separated .