Patent Publication Number: US-10758788-B2

Title: Golf club head

Description:
STATEMENT OF RELATED CASES 
     This is a Continuation of application Ser. No. 14/677,742, filed Apr. 2, 2015, which is a Continuation of application Ser. No. 13/568,741, filed Aug. 7, 2012. The disclosures of the prior applications are hereby incorporated by reference herein in their entirety. 
    
    
     COPYRIGHT AUTHORIZATION 
     The disclosure below may be subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the documents containing this disclosure, as they appear in the Patent and Trademark Office records, but otherwise reserves all applicable copyrights. 
     BACKGROUND 
     This invention relates to golf clubs and more particularly golf club heads. Interest among golfers in custom-tailoring their golf equipment has increased over the years. Also, golfers have increasingly demanded golf club head s that include advanced materials, high forgiveness, and generally bet ter performance. However, these desires, i.e. providing easily customizable club head s and high performing club heads, are often incompatible from a design standpoint. 
     As an example, hollow-type iron club heads have recently become popular for golfers interested in game improvement. Because of their large volume, a significant proportion of the mass of such club heads is located outward from their respective centers of gravity. This increases movement of inertia and, thus, provides for a more forgiving club head on off-centered golf shots. To achieve these characteristics, given a predetermined mass budget, hollow-type iron golf club heads generally include thin-walled construction and comprise different materials throughout the club head body to selectively optimize material properties at various locations. However, as a result of their enlarged shape and thin-walled construction, such golf club heads are ill-suited for use with conventional golf club head customization devices (e.g. the STEELC LUB® Signature Angle Machine by the Mitchell Golf Equipment Company of Dayton, Ohio). As a result, attempts at modifying properties of hollow-type iron golf club heads (e.g. loft angle and lie angle) tend to result in damage to the club head that impairs structural integrity and performance. 
     SUMMARY 
     A need exists for a golf club head that incorporates high-performance materials and structural design without foregoing customizability. 
     A golf club head according to an example of the invention may include a striking ace having a face center and an imaginary striking face plane, a sole portion, a top portion having an exterior surface, a hosel extending from the top portion, and a loft angle no less than 18°. When the club head is oriented in a reference position, in an imaginary vertical plane laterally spaced from the face center by no more than 10 mm and perpendicular to the imaginary striking face plane, an imaginary line segment having a length of 25 mm, a first endpoint coplanar with the imaginary striking face plane, and a second endpoint located above the exterior surface, forms an angle θ with the imaginary striking face plane between 55° and 65°. The imaginary line segment is tangent to the exterior surface at a first point that is intermediate the first end point and the second end point. A second point is located on the imaginary line segment and spaced from the first point by no less than 1.0 mm. The second point is spaced from the exterior surface by a gap distance, measured perpendicular to the line segment, that is no greater than 0.15 mm. 
     In another example of the present invention, a golf club head may include a striking face having a face center and an imaginary striking face plane, a sole portion, a top portion having an exterior surface that includes a first surface portion, a second surface portion rearward of the first surface portion, and a third surface portion rearward of the second surface portion, wherein the second surface portion forms a chamfer. The golf club head may also include a hosel extending from the top portion, and a loft angle no less than 18°. In an imaginary vertical plane laterally spaced from the face center by no more than 10 mm and perpendicular to the imaginary striking face plane, the chamfer includes a forwardmost endpoint, a rearwardmost endpoint, and a chamfer length, l 3 , between the forwardmost endpoint and the rearwardmost endpoint that is no less than 2 mm. An imaginary line segment having a length of 25 mm, a first endpoint coplanar with the Imaginary striking face plane, and a second endpoint located above the exterior surface, forms an angle θ with the imaginary striking face plane that is between 55° and 65°. The imaginary line segment is tangent to the exterior surface at a tangent point that is intermediate the forwardmost endpoint and the rearwardmost endpoint of the chamfer. 
     In another example of the present invention, a golf club head may include a striking face having a face center and an imaginary striking face plane, a sole portion, a top portion having an exterior surface that includes a first surface portion, a second surface portion rearward of the first surface portion, and a third surface portion rearward of the second surface portion, wherein the second surface portion forms a chamfer. The golf club head may also include a hosel extending from the top portion and a loft angle no less than 18°. In an imaginary vertical plane laterally spaced from the face center by no more than 10 mm and perpendicular to the imaginary striking face plane, the chamfer forms an angle θ, with a plane parallel to the striking face plane, that is between 55′ and 65°. 
     In another example of the present invention, a method of manufacturing a golf club head may include providing characteristics of at least one generally planar contact surface of an existing customization device, and configuring a portion of an exterior surface of the club head to conform to the contact surface of the customization device when the club head is operatively associated with the customization device. 
     The various exemplary aspects described above may be implemented individually or in various combinations. These and other features and advantages of the golf club head according to the invention in its various aspects and demonstrated by one or more of the various examples will become apparent after consideration of the ensuing description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described below are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. Exemplary implementations will now be described with reference to the accompanying drawings, wherein: 
         FIG. 1  is a front heel-side perspective view of an exemplary golf club head according to one or more aspects; 
         FIG. 1(A)  is a heel-side elevation view of the golf club head of  FIG. 1 , according to one or more aspects; 
         FIG. 1(B)  is a front elevation view of the golf club head of  FIG. 1 , according to one or more aspects; 
         FIG. 1(C)  is a cross-sectional view of the golf club head of  FIG. 1  through an imaginary plane, according to one or more aspects; 
         FIG. 2  is a perspective view of the golf club head of  FIG. 1  in operative association with a customization device, according to one or more aspects; 
         FIG. 2( a )  is a cross-sectional view of the golf club head as shown in  FIG. 2  through an imaginary plane, according to one or more aspects; 
         FIG. 2( b )  is a rear elevation view of the golf club head as shown in  FIG. 2 , according to one or more aspects; 
         FIG. 2( c )  is a rear elevation view of a golf club head in operative association with the customization device of  FIG. 2 , according to one or more aspects; 
         FIG. 2( d )  is a cross-sectional view of the golf club head of  FIG. 2( c )  through an imaginary plane, according to one or more aspects; 
         FIG. 3  is a toe-side elevation view of a golf club head, according to one or more aspects; 
         FIG. 3( a )  is a front elevation view of the golf club head of  FIG. 3 , according to one or more aspects; 
         FIG. 3( b )  is a top plan view of the golf club bead of  FIG. 3 , according to one or more aspects; 
         FIG. 3( c )  is a cross-sectional view of the golf club head of  FIG. 3  through an imaginary plane, according to one or more aspects; 
         FIG. 3( d )  is a partial cross-sectional view of the club head of  FIG. 3( c ) , according to one or more aspects; 
         FIG. 3( e )  is a partial cross-sectional view of the club bead of  FIG. 3( c ) , according to one or more aspects; 
         FIG. 4  is a top plan view of a golf club head, according to one or more aspects; 
         FIG. 5( a )  is a partial cross-sectional view of a golf club head through an imaginary plane, according to one or more aspects; 
         FIG. 5( b )  is a partial cross-sectional view of a golf club head through an imaginary plane, according to one or more aspects; 
         FIG. 5( c )  is a partial cross-sectional view of a golf club head through an imaginary plane, according to one or more aspects; 
         FIG. 5( d )  is a partial dross-sectional view of a golf club head through an imaginary plane, according to one or more aspects; 
         FIG. 6( a )  is a partial cross-sectional view of a golf club bead through an imaginary plane, according to one or more aspects; and 
         FIG. 6( b )  is a partial cross-sectional view of a golf club head through an imaginary plane, according to one or more aspects. 
     
    
    
     DETAILED DESCRIPTION 
     The following examples will be described using one or more definitions, provided below. 
     Referring to  FIG. 1 , in one or more aspects, a golf club bead  100  includes a striking face  102 , a toe portion  106 , a heel portion  108 , and a hosel  110  for securing the golf club head  100  to a shaft (not shown). The golf club head  100  further includes a sole portion  112  and a top portion  114  opposite the sole portion  112 . The golf club head  100  is preferably an iron-type club head and, thus, has a loft angle no less than 18°. 
     Referring to  FIGS. 1(A) and 1(B) , the striking face  102  includes a face center  150 , and is substantially coplanar with an imaginary striking face plane  120 . For example, in some aspects, the striking face  102  is planar. However, in alternative aspects, the striking face  102  includes a bulge and/or roll of a relatively high radius of curvature, i.e. greater than or equal to 4 in. Alternatively, or in addition, the striking face  102  includes a plurality of scorelines  104  that extend rearwardly from the imaginary striking face plane  120 , and/or small-scale recesses or projections that enhance the texture of the striking face  102 . For example, in some aspects, at least a portion of the striking face  102  is sandblasted, milled, etched, and/or laser-milled. In aspects in which the striking face  102  includes a bulge and/or roll, for all purposes herein, the imaginary striking face plane  120  is considered to be an imaginary plane tangent to a face center  150  of the striking face, as defined below. As shown n  FIG. 1(B) , the striking face  102  also includes an uppermost point  152 , and a lowermost point  148 . 
     Referring again to  FIG. 1(B) , the face center  150 , as used herein, denotes a point that is laterally spaced halfway between a heelmost end  172  and a toemost end  170  of the plurality of scorelines  104 , and vertically, halfway between the uppermost point of the striking face  102  and the lowermost point  148  of the striking face  102 . For club heads that are absent any scorelines, the face center  150  denotes the geometric center of the generally planar striking face  102  of the club head  100 . 
     Referring to  FIGS. 1(A) and 1(B) , the golf club head  100  is oriented in a reference position relative to an imaginary ground plane  118 . The hosel  110  include a hosel central axis  116 . The striking face  102  is generally coplanar with the imaginary striking face plane  120 . A first imaginary vertical plane  122  is perpendicular to the striking face plane  120  and passes through the face center  150 . The reference position (of a golf club head), as used herein, denotes a position in which the hosel central axis  116  is coplanar with an imaginary vertical hosel plane  124  that is perpendicular to the first imaginary vertical plane  122 , and the scorelines  104  are generally parallel to the ground plane  118 . 
     As shown in  FIG. 1(C) , the golf club head  100  is shown in cross-section through the plane  122 . In this cross-section, the top portion  114  includes an exterior surface  114 ( a ) and an interior surface  114 ( b ). Preferably, the golf club head  100  is a hollow-type golf club head, i.e. includes a hollow  154  delimited by the striking face  102 , the top portion  114 , and the sole portion  102 . In alternative aspects, the golf club head  100  is substantially, but not entirely, hollow. In other aspects, the golf club bead  100  is solidly formed. In some aspects, the hollow  154  is filled with a material different from a material forming the top portion  114 , sole portion  112 , striking face  102 , and/or hosel  110 . The material filling the hollow  154  may comprise any of a foam, a polymeric material, a metal, a gel, a visco-elastic material, or any combination thereof. Preferably, the material filling the hollow comprises a density less than that of the material forming at least one of the top portion  114 , the sole portion  112 , the striking face  102 , and/or the hosel portion  110 . Preferably, the filling material comprises a specific gravity no greater than 8, more preferably no greater than 7, and most preferable no greater than 5. Such properties enable the golf club head  100  to maintain a high moment of inertia, given a predetermined mass budget, particular about a vertical axis passing through a center of gravity  174  of the club head  100  (I zz ), as discussed in more detail below. 
     Preferably, the golf club head  100  is formed of thin-walled construction. In other words, at least one of the sole portion  112 , the striking face  102 , and/or the top portion  114  have average thicknesses no greater than 10 mm, more preferably no greater than 5 mm, and most preferably no greater than 4 mm. Preferably, in the imaginary plane  122 , at least the top portion  114  comprises an average thickness no greater than 10 mm, more preferably no greater than 5 mm, even more preferably within the range of about 1 mm and about 4 mm, and most preferably substantially equal to about 3 mm. Minimizing the average thicknesses of the various portions of the golf club head  100  increases discretionary mass, i.e. mass which may be positioned primarily to enhance the mass properties and, in turn, performance characteristics, of the club head  100 . It is particularly desirable to form the top portion  114  of thin-wall construction, as a decreased height of the center of gravity  174  of the club head increases dynamic loft and is generally associated with improved ball flight characteristics. However, decreasing average thickness of the club head components below the ranges discussed above may compromise the structural integrity of the golf club head  100 , resulting in damage during use. Of course, acceptable average thickness ranges depend on material selection. Thus, one of ordinary skill in the art would appreciate that, for certain materials, acceptable average thickness ranges may differ from those discussed above. Further, one of ordinary skill in the art would appreciate that, as material properties advance over time, thicknesses below the ranges discussed above may become feasible. 
     Alternatively, or in addition, the top portion  114  includes a minimum wall thickness no greater than 5 mm, more preferably no greater than 3 mm, even more preferably within the range of 0.40 mm and 1.40 mm, and most preferably substantially equal to about 1.0 mm. These ranges ensure that the top portion  114  is capable of withstanding stresses resulting from typical impacts of the golf club head  100  with a golf ball, while increasing discretionary mass, which may be located elsewhere to further enhance the performance of the golf club head  100 . 
     In some aspects, the golf club head  100  preferably includes a club head volume no less than 50 cc, more preferably no less than 55 cc, even more preferably within the range of about 60 cc to about 180 cc. In some embodiments, a correlated set of club heads includes at least two club heads that vary in volume. For example, in some embodiments, a correlated set includes a #3-iron, having a loft between 17° and 20°, with a volume in the range of about 80 cc to about 110 cc, more preferably within the range of about 90 cc to about 105 cc, and most preferably, equal to about 98 cc. The same correlated set, in some embodiments, also includes a pitching wedge (PW), having a loft angle between 42° and 48°, with a volume in the range of about 45 cc to about 70 cc, more preferably within the range of about 50 cc to about 65 cc, and most preferably equal to about 63 cc. Thus, in some embodiments, the volumes of club heads of a correlated eat preferably decrease with increasing loft, for at least two, preferably three, and more preferably each of the, club heads of the set. Of course, in alternative embodiments, volume increases with loft, or, alternatively, does not follow a discernable progression in this regard. 
     Alternatively, or in addition, the golf club head preferably has a club head mass no greater than 320 g, more preferably no less than 175 g, even more preferably within the range of 200 g to 310 g, and most preferably within the range of about 225 g to about 310 g. These combinations of volume and mass ensure that the club head has a relative high moment of inertia (MOI), particularly about an imaginary vertical axis passing through the center of gravity of the club head (I zz ), while maintaining the mass of the club head within ranges that achieve beneficial feel and enable the club bead  100  to be appropriately swing weighted. 
     As discussed above, the golf club  100  includes a hollow construction and, in some embodiments, thin-walled constructions. These attributes enable iron-type golf clubs to achieve higher moments of inertia, particularly about the centers of gravity. For example, the golf club head  100  preferably has a moment of inertia about a vertical axis passing through the center of gravity  174  (e.g. I zz ) no less than 2000 g*cm 2 , more preferably no less than 2200 g*cm 2 , and most preferably no less than 2250 g*cm 2 . In some embodiments, the moment of inertia, I zz , is no greater than 3000 g*cm 2 , and preferably no greater than 2850 g*cm 2 . Such parameters enable high forgiveness of the club head on off-centered golf shots. 
     As discussed above, the golf club head  100  preferably is of hollow, thin-walled construction. Although such construction provides the performance benefits discussed above, such design hinders customizability. 
     With reference to  FIG. 2 , the golf club head  100  is shown in association with a customization device  132 . The customization device  132  includes a base  176 , a clamp  138  secured to, and extending upward from, the base  176 , and a loft/lie gauge  136 . The clamp  138  is adapted to secure the golf club head  100  in a fixed position, preferably in the reference position, so that the loft/lie gauge  136  may statically and/or dynamically measure and indicate the loft angle and/or lie angle of the club head  100 , by association with the shaft  178  of the club bead  100 . 
     In operation, a bending bar  134  is associated with hosel  110  of the golf club head  100 . Manual force is applied to the bending bar  134  resulting in deformation of the hosel  110 . The hosel  110  is relocated to a position in which the golf club  100  has properties (e.g. loft angle and/or lie angle) more favorable to the specific golfer for which the golf club  100  is to be customized. 
     Generally, some customizing devices are configured for use with iron-type golf clubs (e.g. the STEELCLUB® Angle Machine by Mitchell Golf Equipment Company of Dayton, Ohio) and some are intended specifically for wood-type golf clubs. For example, for customization devices specifically configured for use with iron-type club heads, a clamp is provided that includes a plurality of jaws that are positioned, and have contact surfaces angled, to fit typically-shaped iron-type golf clubs without marring, or with minimally marring, the various surfaces of the clamped iron-type club head. Marring may occur by the engagement of the jaws with the club head either (a) by operation of securing the club head to the clamp; or (b) during the forceful manual operation of the bending bar  134 . As hollow-type and/or or thin-walled iron-type golf clubs deviate from the typical shape and structural framework of iron-type club heads, the occurrence and degree of marring is relatively significant, impairing the performance characteristics and structural integrity of the club head  100 . 
     The inventors have discovered that such marring may be prevented by adapting hollow-type iron club heads, through various means, for use with such pr-existing customization devices without appreciably compromising the club heads&#39; performance, structural integrity, and cost of manufacture. These adaptations are described below in farther detail. 
     The following embodiments are described with reference to the customization device  132 , which is similar to a Mitchell STEELCLUB® Angle Machine. However, those of ordinary skill in the art would readily appreciate that like adaptations may be made to club heads for use with other known customization devices, or customization devices that may become known, without departing from the spirit and scope of the invention. 
     Referring to  FIG. 2 , the clamp  138  further includes a downwardly-engaging jaw  140  and a plurality of upwardly-engaging jaws  142 . In operation, the golf club head  100  is positioned to rest on the upwardly-engaging jaws  142 . The downwardly-engaging jaw  140  is moved into contact with the top portion  114  of the club head  100 . Specifically, the downwardly-engaging jaw  140  is positioned on the exterior surface  114 ( a ) of the top portion  114  as to securely fix the golf club head  100  in position. Thus, the effect of this contact on the exterior surface  114 ( a ) is a significant concern. The golf club head  100  is also positioned laterally such that the toe portion  106  of the club head  100  rests against a toe stop  200 . The toe stop  200  is preferably adapted to be adjustable in the lateral direction, such that the customization device  132  is capable of fitting a wide array of club heads. Preferably, the toe stop  200  is positioned such that the face center  150  of the club head  100  is horizontally aligned with the center of the downwardly-engaging jaw  140 . 
     In some embodiments, the golf club bead  100  includes one or more design features directed at reducing or eliminating marring caused by the interaction of the top portion  114  with the downwardly engaging jaw  140  of the customization device  132 . In general, marring is reduced by: (a) configuring the surface contour of the exterior surface  114 ( a ) of the top surface  114  to better accommodate the anticipated contours of the downwardly-engaging jaw  140 ; and/or (b) selectively strengthening the contact region relative to regions proximate the contact region. These aspects will be discussed in further detail below. 
     As shown in  FIG. 2( a ) , in an operating position, the golf club head  100  is secured to the customization device  132 . In this position, the striking face  102  of the club head  100  is flush against the abutment plate  144 . The contact surface, or abutment surface  158 , of the abutment plate  144  is substantially coplanar with an imaginary abutment plane  146  (see  FIG. 2(A) ). The sole portion  112  of the club head  100  rests on the upwardly-engaging jaws  142 . The downwardly-engaging jaw  140  is lowered into fixed association with the exterior surface  114 ( a ) of the top portion  114 . The downwardly-engaging jaw  140  includes an abutment surface  158  that lies flush against the abutment plate  144 . The downwardly-engaging Jaw  140  also includes a contact surface  160  that contacts the exterior surface  114 ( a ) of the top portion  114 . A pin  180  extends through a throughbore  181  in the downwardly-engaging jaw  140  enabling the downwardly-engaging jaw  140  to pivot about a pivot axis  156 . The pivot axis  156  is perpendicular to the abutment plane  146 . The pivotability of the downwardly-engaging jaw  160  enables the downwardly-engaging jaw  140  to accommodate club heads having top portions  114  that are generally inclined or declined toward their respective toe portions  106  in the heel-to-toe direction. 
     Referring to  FIGS. 2( a ) and 2( b ) , the golf club head  100  is shown in association with the customization device  132  in an operating position. In this position, the downwardly-engaging jaw  140  is in a centered position. A centered position, as used herein, refers to the position in which an imaginary plane  182  perpendicular to the contact surface  160  of the downwardly-engaging jaw  140  and coplanar with the pivot axis  156  is vertical relative to the ground plane  118 . Generally, the downwardly-engaging jaw  140  will be in this orientation when associated with a golf club head, e.g. golf club head  100 , that comprises a top portion  114  that is neither inclined nor declined in the heel-to-toe direction. 
     An angle θ, as used herein, denotes the angle formed between the contact surface  160  of the downwardly-engaging jaw  140  and the imaginary abutment plane  146  measured in a vertical plane perpendicular to the abutment plane  146  and passing through the contact point  183 . When the downwardly-engaging jaw  140  is in the centered position, in an Imaginary vertical plane passing through a contact point  183  between the contact surface  160  of the downwardly-engaging jaw  140  and the exterior surface  114 ( a ) of the top portion  114 , the angle θ is equal to θ c . In some aspects, the customization device  132  is configured such that θ c , is equal to 60°. However, in other aspects, θ c  is less than or greater than 60°. The angle θ c  may be considered an inherent property of the customization device  132 . 
     As shown in  FIG. 2( c ) , a golf club head  100 ′ is associated with the customization device  132  in an orientation such that the downwardly-engaging jaw  140  is not in the centered position. Specifically, an imaginary plane  182 ′ is perpendicular to the contact surface and passes through the pivot axis  156 . The imaginary plane  182 ′ forms an angle ϕ with the imaginary vertical plane  182  when projected into the abutment plane  146  (i.e. the plane of the paper as shown in  FIG. 2( c ) ). 
     Referring to  FIG. 2( d ) , the golf club head  100 ′ is shown in a vertical plane  192  that passes through a contact point  183 ′ between the contact surface  160  of the downwardly-engaging jaw  140  and the exterior surface  114 ( a ) of the top portion  114  of the golf club bead  100 ′. In this case, as compared to the golf club head  100  of  FIGS. 2( a ) and 2( b ) , the downwardly-engaging jaw  140  is rotationally offset by an offset angle ϕ from its centered position. As a result, in the imaginary vertical plane  192 , the angle θ also differs from θ c  (measured when the downwardly-engaging jaw  140  is in the centered position). Thus, the angle θ may be viewed as a function of the angle θ c  (an inherent property of the customization device) and the offset angle ϕ (a characteristic of the interaction between a customization device and a specific club head). Specifically, angles θ, θ c , and ϕ are related as follows:
 
θ(ϕ)=tan −1 [tan(θ c )*cos(ϕ)]
 
     On the basis of the constraints and intended operation discussed above, various exemplary golf club heads are configured, as discussed below. 
     EXAMPLE 
     Anticipating the constraints and operation discussed above, referring to  FIGS. 3 through 3 ( c ), a golf club head  100 , according to one or more aspects, is configured to minimize marring in a first example. In this example, the configuration of the club head  100  is adapted for use with a specific customization device, i.e. the customization device  132  discussed above. Also, the orientation and bounds of the contact surface  160  of the downwardly-engaging jaw  140  is modeled by an imaginary planar surface that forms an imaginary planar line segment in a specified imaginary vertical plane, e.g. an imaginary vertical plane passing through the face center  150  of the club head  100 , when the club head  100  is in the reference position. One of ordinary skill in the art would readily appreciate that a club head may be adapted to accommodate other customization devices that are known in the art, or that may become known, in similar manner to this example, or other examples, described herein. In particular, similar adaptations as those described below, but in view of other customization devices having differently-oriented contact surfaces, are within the spirit and scope of the invention. 
     In one or more aspects of the present invention, referring to  FIG. 3 , the golf club head  100  is shown in the reference position. In  FIG. 3( a ) , the golf club head  100  is shown such that the imaginary striking face plane  120  corresponds with the plane of the paper. The exterior surface  114   a  of the top portion  114  of the club head  100  includes a first surface portion  126 , a second surface portion  128 , and a third surface portion  130 . The second surface portion  128  is located between the first surface portion  126  and the third surface portion  130  and, in some aspects, defines a chamfer sandwiched between the first surface portion  126  and the third surface portion  130 , as shown. The striking face  102  of the club head  100  includes the face center  150  and is generally coplanar with the imaginary striking face plane  120 . 
     As shown in  FIGS. 3 through 3 ( b ), the imaginary vertical plane  122  passes through the face center  150 . Specific to the imaginary plane  122 , an uppermost point  184  is located on the top portion  114  of the club head  100  (when the club head is in the reference position, as in  FIG. 3 ). An imaginary tangent line  186  is parallel to the imaginary striking face plane  120  and lies tangent to the uppermost point  184  such that the tangent line  186  does not pass through the exterior surface  114 ( a ) of the top portion  114  of the club head  100  (i.e. excluding the hosel  110 ). The ground plane  118  intersects the imaginary striking face plane  120  to form an imaginary line  200 . The imaginary tangent line  186  forms an angle Δ with the horizontal, measure in the plane  120 . In practical terms, the angle Δ corresponds to the anticipated angle ϕ, as discussed above. 
     Referring to  FIGS. 3( c ) and 3( d ) , the golf club head  100  is shown in cross-section through the imaginary plane  122 . As shown in  FIG. 3( d ) , in the imaginary plane  122 , an imaginary line segment  188  is shown. The imaginary line segment  188  lies tangent to the exterior surface  114 ( a ) at a contact point  183  and does not pass through any portion of the exterior surface  114 ( a ) of the top portion  114 . In this example, the imaginary line segment  188  has a length of 25 mm, a first endpoint  189  coincident with the imaginary striking face plane  120 , and a second endpoint  190  opposite the first end point  189 . The second endpoint  190  is located above the exterior surface  114 ( a ) of the top portion  114 . In practical terms, the imaginary line segment  188  serves to model the extent and orientation of the contact surface  160  of the downwardly-engaging jaw  140 , when the club head  100  is associated with the customization device  132  in an operating position. Accordingly, the imaginary line segment  188  further forms the angle θ with the imaginary striking face plane  120 . Because the angle Δ is intended to correspond to the angle ϕ discussed above, θ may alternatively be represented as a function of Δ as follows:
 
θ(Δ)=tan −1 [tan(θ c )*cos(Δ)]
 
     In this example, based on the intended customization device  132  with which the club head  100  is to be associated with, θ c  is assumed to be 60°. Referring again to  FIG. 3( a ) , the top portion  114  of the golf club head  100  generally inclines from the heel portion  108  toward the toe portion  106 . Thus, when the golf club head  100  is associated with the customization device  132  in an operating position, the downwardly-engaging jaw  140  would pivot about the pivot axis  156  from its centered position. As a result, in the vertical cross-section  122 , the angle θ between the line segment  188  and the striking face plane  120  varies slightly from θ c  (or from 60°). In this example, the angle Δ is 1, and, thus the angle θ is still about 60°. Referring again to  FIG. 3( d ) , preferably, the club head  100  is configured such that the second endpoint  190  of the imaginary line segment  188  is located above the exterior surface  144 ( a ) of the top portion  114 . This ensures that the region of potential contact between the downwardly-engaging jaw  140  and the exterior surface  114 ( a ) is sufficiently large to reduce average stress below a point at which marring, or plastic deformation, is likely to occur. This also prevents the occurrence of high stress due to a corner of the downwardly-engaging jaw  140  compressing the exterior surface  114 ( a ) of the top portion  114  of the club head  100 . 
     Referring again to  FIG. 3( d ) , the second surface portion  128  defines a chamfer and is located between the first surface portion  126  and the third surface portion  130 . In some embodiments, and as shown, a stepped portion  202  is further located at the junction between the second surface portion  128  and the third surface portion  130 . In some embodiments, the second surface portion  128  is also stepped up from the first surface portion  126 . In alternative embodiments, the second surface portion  128  is directly joined to the third, generally planar, surface portion  130 . 
     The second surface portion  128  includes a first, forwardmost, endpoint  196 , and a second, rearwardmost, endpoint  198 . The distance l 3  between the first and second endpoints  196  and  198  is preferably within the range of 2 mm and 6 mm. More preferably, the distance  13  is between 2.5 mm and 4 mm and, most preferably, substantially equal to about 3.4 mm. These ranges ensure that, when in operative association with the customization device  132 , the corners of the downwardly-engaging Jaw  140  remain distanced from, and thereby do not compress, the exterior surface  114   a  of the top portion  114  of the club head. If the distance l 3  is too large, the second surface portion  128 , i.e. the chamfer, detracts from the structural and aesthetic aspects of the top portion  114  of the club head  100 , affecting the acoustic and other vibration-emanation properties of the club head  100 , requiring further remedy. 
     Preferably the contact point  183  is located generally half-way between the endpoint  196  and the point  198 . More specifically, the contact point is located a distance from the endpoint  196  that is between 0.35*l 3  and 0.65*l 3 , more preferably between 0.40*l 3 , and 0.60*l 3 , and most preferably between 0.45*l 3  and 0.55*l 3 . These distances are to be measured along the surface of the second surface portion  128  in the imaginary plane  122 . These ranges ensure that any force applied to the exterior surface  114   a  of the top portion  114  of the club head  100  by the downwardly-engaging jaw  140  is more evenly distributed over the second surface portion  128  and not primarily directed at either of endpoints  196  and  198 . 
     In the reference position, and in the imaginary plane  122  shown in  FIG. 3( c ) , the second surface portion  128  preferably generally extends at an angle formed with the striking face plane  120  that is within 5 degrees of the angle θ. More preferably, the second surface portion  128  is configured to generally extend at an angle with the striking face that is within 2 degrees of θ. Most preferably, the second surface portion  128  generally extends at an angle with the striking face plane  120  that is substantially equal to the angle θ. In this example, the angle θ Is substantially equal to 60°, as discussed above. These ranges ensure that, when the club head  100  is operatively associated with the customization device  132 , any force asserted by the downwardly-engaging jaw  140  is dispersed over a wider area, and such force is generally centered about the intended contact point  183 . 
     Preferably, the second surface portion  128  (i.e. the chamfer) follows a curvilinear path in the imaginary plane  122 . However, in alternative embodiments, the second surface portion  128  follows a generally linear path in the imaginary plane  122 . Where the second surface portion  128  follows a curvilinear path, the radius of curvature is relatively large, i.e. greater than about 5 inches. However, in alternative embodiments, the second surface portion  128  follows a curvilinear path having a radius of curvature that is less than 5 inches. Also, alternatively or in addition, the radius of curvature of the path formed by the second surface portion  128  varies in radius of curvature along its length. Preferably, the second surface portion  128  follows a curvilinear path having an average radius of curvature in the range of between about 5 in and 15 in, more preferably within the range of 81n to about 12 in, and most preferably substantially equal to 10 in. 
     For embodiments in which the second surface portion  128  follows a curvilinear path, in the imaginary plane  122  shown in  FIGS. 3( c ) and 3( d ) , the general angle of its extension relative to the striking face plane  120  is considered to correspond to the angle formed between the striking face plane  120  and an imaginary line that passes through the first endpoint  196  and the second endpoint  198  of the second surface portion  128  and that intersects with the striking face plane  120 . 
     In addition to the above parameters, the forwardmost endpoint  196  of the second surface portion  128  is preferably spaced from the striking face plane  120  by a minimum distance l 1 . Preferably, l 1  is between about 6 mm and about 20 mm. More preferably, the distance l 1  is between 8 mm and 15 mm, and most preferably between 9 mm and 12 mm. A distance, along the imaginary line segment  188 , between the first endpoint  189  and the contact point  183  is within the range of about 10 mm to about 22 mm, more preferably between about 12 mm and about 18 mm, and most preferably within the range of 16 mm to 18 mm. These ranges ensure that the point of contact  183  is sufficiently distanced from the striking face  102  to avoid an overly stiff response to the compression created by contact of the downwardly-engaging jaw  140  with the exterior surface  114   a  of the top portion  114 . Also, such ranges minimizes the risk that marring may occur proximate the striking face  102 , which marring could have an increased effect on structural performance and/or feel associated with impact between the club head  100  and a golf ball. On the other hand, spacing the forwardmost endpoint  196  of the second surface portion  128  of the exterior surface  114   a  of the top portion  114  tends to reduce the effectiveness of the “grip” associated with the contact between the downwardly-engaging jaw  140  of the customization device  132  and the club head  100 . 
     Further, the contact point  183  between the imaginary line segment  188  and the second surface portion  128  lies between the first endpoint  196  and the second endpoint  198 . Preferably, the contact point  183  is generally centered between the first endpoint  196  and the second endpoint  198 . Alternatively, or in addition, the contact point  183  is spaced from the first endpoint  196  by a distance no less than 0.50 mm and, more preferably, no less than 1.0 mm. 
     As discussed above, it is desired to configure the second surface portion  128  to follow a curvilinear path, for example in the imaginary plane  122  shown in  FIGS. 3( o ) and 3( d ) . While such a configuration prevents stress concentrations from forming at various contours, e.g. at either endpoint  196  and  198  of the second surface portion  128 , it is still desirable to configure the second surface portion  128  to generally conform to the contour of the imaginary line segment  188 . As a result, when the club head  100  is operatively associated with the downwardly-engaging jaw  140  of the customization device  132 , as force is exerted from the contact surface  160  of the downwardly-engaging jaw  140 , the surface-conforming second surface portion  128  flexes in a manner as to increase the area of contact between the contact surface  160  of the downwardly-engaging jaw  140  and the exterior surface  114   a  of the top portion  114  of the club head  100 . 
     Thus, referring to  FIG. 3( e ) , a first gap distance g 1 , measured at a location spaced from the contact point  183  by 1 mm (along the length of the imaginary line segment  188 ), between the imaginary line segment  188  and the exterior surface  114   a  of the top portion  114  of the club head  100 , is preferably no greater than 0.15 mm, more preferably no greater than 0.12 mm, and most preferably within the range of 0.05 mm to 0.11 mm. A second gap distance, g 2 , is preferably configured in like manner to the first gap distance g 1 . Alternatively, or in addition, a third gap distance, g 3 , measured at the first endpoint  196  of the second surface portion  128  of the exterior surface  114   a  is preferably configured in like manner to the gap distance g 1 . Alternatively, or in additional, a fourth gap distance, g 4 , measured at the second endpoint  198  of the second surface portion  128 , is configured in like manner to the gap distance g 1 . 
     As discussed above, referring again to  FIG. 3( d ) , the configuration of the second surface portion (i.e. the chamfer)  128  is directed to enabling customization of the club head  100  by typical customization devices, e.g. customization device  132 , without the need to unnecessarily thicken these portions of the club head  100 . Such thickening would likely diminish the performance of the club head  100  by locating greater mass at higher locations, and requiring more mass to be dedicated to providing for the structural integrity of the club head  100  and, thus, not positioned primarily to affect the mass properties of the club head  100 . Thus, an average thickness, t 2 , of the second surface portion  128  is preferably within the range of about 1 mm to about 4 mm, more preferably between about 1.25 mm and about 3.5 mm, and most preferably between about 1.5 mm and about 3 mm. 
     Further, in some embodiments, the average thickness t 2  of the second surface portion  128  varies with loft angle throughout a correlated set of club heads. For example, for a typical #3-iron, having a loft of about 17°, the average thickness t 2  of the second surface portion  128  is within the range of 2 mm and 4 mm. Meanwhile, for a pitching wedge, within the same correlated set, having a loft angle of about 54°, the average thickness t 2  of the second surface portion  128  is within the range of about 1 mm to about 2 mm. Additionally, or alternatively, t 2  decreases with increasing loft angle for at least two golf club heads of a correlated set of golf club heads. More preferably, t 2  decreases with increasing loft angle for at least three golf club heads of a correlated set of golf club heads. Most preferably, t 2  decreases progressively with increasing loft angle for each golf club head within a correlated set of golf club heads. 
     In addition to an average thickness, t 2 , the second surface portion  128  includes a minimum thickness. Preferably, the minimum thickness is no greater than 2 mm, more preferably, no greater than 1.5 mm, and most preferably, no greater than 1.20 mm. 
     An average thickness t 3  of the third surface portion  130  of the exterior surface  114   a  of the top portion  114  is preferably within the ranges discussed above with regard to the second surface portion  128 . Further, an average thickness t 1  of the first surface portion  126  of the exterior surface  114   a  of the top portion  114  is preferably within the ranges discussed above with regards to the second surface portion  128 . 
     As discussed above, one or more of the characteristics of the exterior surface  114   a  of the top portion  114  occurs in a vertical cross-section  122  that passes through the face center  150  of the club head  100 . Preferably, like exterior surface characteristics occur at other vertical cross-sections that are laterally (i.e. in the heel to toe direction) spaced from the face center  150  of the club head  100 . Preferably, like dimensions are found in one or more vertical cross-sections that are laterally spaced from the face center  150  by 10 mm or less, and, more preferably, by 5 mm or less. 
     In addition to adapting the club head  100  for customization with a customization device, e.g. customization device  132 , in the front to rear direction, a discussed above, in some embodiments, adaptations are implemented in the heel to toe direction. For example, referring to  FIG. 4 , in some embodiments, proximate the contact point  183 , in the heel to toe direction, the exterior surface  114   a  of the top portion  114  of the club head  100  follows a curvilinear path such that the contact point  183  coincides with a bulge point. 
     For example, referring again to  FIG. 4 , in some embodiments, proximate the contact point  183 , and between the imaginary line segment  188  and the second surface portion  128 , the exterior surface  114   a  of the top portion  114  follows a curvilinear path  204  in the lateral direction, Specifically, when viewed in top plan view, as shown, the contour of the second surface portion  128  is convex toward the rear, or rearwardly convex. The path of this portion  128  proximate the contact point  183 , in an imaginary horizontal plane, may be considered to have a radius of curvature R and a center point C that is located forward of the striking face  102  of the club head  100 . In some embodiments, the radius of curvature R is no less than Sin, more preferably no less than 8 in, and most preferably between about 8 in and about 25 in. These ranges ensure that, when the club head is operatively associated with the customization device  132 , during use, corners of the downwardly-engaging jaw  140  do not contact any portion of the exterior surface  114   a  in the lateral direction (in addition to the front-to-rear direction as discussed above). 
     In addition to adapting the exterior surface  114   a  of the top portion  114  of the club head  100  to more effectively accommodate a customization device, e.g. customization device  132 , the region proximate the contact point  183  of the exterior surface  114   a , in some embodiments, is strengthened. 
     Referring to  FIGS. 5( a ) through 5( d ) , a portion of the club head  100  is shown in cross-section through the imaginary plane  122 . In these embodiments, a rib (e.g. rib  206 ,  206 ( a ),  206 ( b ), or  206 ( c )) is secured to an interior surface  114   b  of the top portion  114  of the club head  100 . 
     For example, in the embodiment shown in  FIG. 5( a ) , a rib  206  is associated with the region proximate the contact point  183 . In this embodiment, the rib  206  increases in thickness as the rib approaches the contact point  183 , in the font to rear direction. In this embodiment, the rib  206  does not contact the interior surface  114   a  proximate the striking face  102 . 
     In the embodiment shown in  FIG. 5( b ) , a rib  206 ( a ) is secured to the interior surface  114   a  proximate the contact point  183 . In this embodiment, the rib  206 ( a ) is also joined to the interior surface  114   a  proximate the striking face  102 . 
     In the embodiment shown in  FIG. 5( c ) , a rib  206 ( b ) is secured to the interior surface  114   a  proximate the contact point  183 . In this embodiment, the rib  206 ( b ) includes a substantially uniform thickness along its front to rear length. However, the rib  206 ( b ) is not joined to the striking face  102 . 
     In the embodiment shown in  FIG. 5( d ) , the rib  206 ( c ) is secured to the interior surface  114   a  proximate the contact point  183 . In this embodiment, the rib  206 ( c ) is joined to the interior surface  114   a  proximate the striking face  102 . In this embodiment, an aperture  208  is formed by the rib  206 ( c ) and interior surface  114   a  combination. As shown, the aperture  208  extends entirely through the rib  206 ( c ). However, in other embodiments, any of the ribs shown in  FIGS. 5( a ) through 5( d )  may include apertures, recesses, grooves, or fluted portions that extend entirely through, or only partially through the thickness of the rib. Alternatively, or in addition, any of the ribs shown in  FIGS. 5( a ) through 5( d ) , may include projections, struts, or rails extending therefrom. 
     In addition, or alternatively, to any of the embodiments discussed above, plural ribs are secured to the interior surface  114   a  proximate the contact point  183 . Alternatively, or in addition, one or more ribs are secured to the interior surface  114   a  of the club head  100  proximate other regions of the top portion  114 , and/or other regions of the club head  100 , includes any combination of the sole portion  112 , the striking face  102 , the heel portion  108 , and the toe portion  106 . 
     Alternatively, or in addition, ribs may be secured to the interior surface  114   a  proximate the contact point  183 , but not passing through the imaginary plane  122 . For example, in some embodiments, a first and second rib are elongated in the front to rear direction, and straddle an imaginary vertical plane  122  perpendicular to the striking face plane  120  and passing through the contact point  183 . 
     Alternatively, or in addition, one or more ribs are secured to the interior surface  114   a  of the top portion  114  of the club head  100  that are generally elongated in the heel to toe direction, as opposed to the front to rear direction. 
     Referring to  FIG. 6( a ) , in one or more embodiments, the second surface portion  128  of the exterior surface  114   a  of the top portion  114  includes a first material that is different from a second material of at least one of the first surface portion  126  or the third surface portion  130 . In some embodiments, the first material includes a hardness that is greater than a hardness of the second material. Alternatively, the first material includes a stiffness, EI, or Young&#39;s modulus, that is greater than either the stiffness, EI, or Young&#39;s Modulus of the second material. In some embodiments, the first material has a ductility (e.g. percent elongation) that is greater than the ductility (e.g. percent elongation) of the second material. These characteristics ensure that regions of the top portion  114  anticipated to undergo high strain during operative association with the customization device  132 , are particularly suited for such strain. By limiting the use of higher-strength materials to such locations, discretionary mass may be preserved for placement better suited to affect the mass properties (and in turn the performance) of the club head  100 . 
     In some embodiments, the first material has a greater resilience than the second material. For example, in some embodiments, a polymer (e.g. polyurethane or nylons) is particularly located at the second surface portion, while at least one of the first and third surface portions  126  and  130  comprise a stainless steel, such as 17-4 stainless steel, or a titanium alloy, e.g. Ti 8-2 or TI 640. By increasing the resilience of the second surface portion  128 , such region is more capable of conforming, in operative engagement with the customization device  132 , to the contours of the contact surface  160  of the downwardly-engaging jaw  140 . Thus, permanent deformation to the club head  100  may be prevented or minimized. 
     Referring again to  FIG. 6( a ) , the second surface portion  128 , in some embodiments, at least in part constitutes a discrete insert that is secured to the remainder of the club head  100  during construction. In some such embodiments, the second surface portion is welded to the remainder of the top portion  114 , chemically adhered, bonded, brazed, or attached by a mechanical coupling (e.g. press-fitted, expansion fitted, or the like) 
     Referring to  FIG. 6( b ) , in some embodiments, the second surface portion  128  is formed integrally with the remainder of the top portion  114  of the club head  100 . However, the second surface portion  128  is then locally surface treated to gain higher-strength properties. For example, the second surface portion  128  may be locally forged, cold-worked, beat-treated, carbided, nitrided, electroplated, anodized, or otherwise coated, e.g. by a physical vapor deposition process, sputtering or the like, to achieve greater durability and/or resistance to marring. In some embodiments, the surface treatment occurs locally, proximate the contact point  183 . However, in other embodiments, the surface treatment occurs over substantially the entirety of the top portion  114 . In yet other embodiments, the entire club head  100  undergoes one or more surface treatment processes. 
     In any of the embodiments discussed above, the golf club head  100  constitutes a club head of a correlated set of club heads. For example, in some embodiments, the club head  100  is an iron-type club head of a correlated at of like iron-type club heads. Preferably, plural club heads of a correlated set, varying in loft angle, include one or morn of the adaptations discussed above, with reference to the club head  100 , as golfers often desire to customize characteristics of plural club beads of their set. However, operative engagement of the customization device  132  effects club heads differently, at least in part dependent on their respective loft angles. 
     For example, in some embodiments, due to natural changes in the structure of club heads throughout a correlated set, the effect of operative engagement with a customization device, e.g. customization device  132 , tends to be less severe with increasing loft angle. Thus, in some embodiments, a correlated set includes at least a first club head  100  including a top portion  114  with a second surface portion  128  constituting a chamfer in the manner discussed in any of the embodiments discussed above, while at least a second club bead  100 ′ of the set, with a greater loft angle than the first club head, does not. 
     In some embodiments, the degree to which the top portion  114  is specifically adapted to withstand impact with the contact surface  160  of the downwardly-engaging jaw  140  varies through the set. For example, lower-lofted club heads may have internal ribs (e.g. as shown in any of  FIGS. 5( a ) through 5( d ) . Alternatively, or in addition, a correlated set includes a first club head  100  having a first loft angle and a first internal nib  206  proximate a first contact point  183  that has a first average thickness t 1  and a second club head  100 ′ of the correlated set having a second loft angle greater than the first loft angle, and a second internal rib  206 ′ proximate a second contact point  183 ′ that has a second average thickness t 2  less than the first average thickness t 1 . Alternatively, or in addition a correlated set includes at least a first club head  100  having a first loft angle, a surface portion  128  that forms a chamfer, has an angle θ, and a length l 3 , and a second club head  100 ′ having a second loft angle greater than the first loft angle, a surface portion  128 ′ that forms a chamfer, has a angle θ, and a length l 3 ′ that is less than the l 3  of the first club head  100 . 
     Alternatively, or in addition, a correlated set includes at least a first club head  100  having a first angle Δ 1 , a first angle θ 1 , and a first loft angle, and a second club head having a second angle Δ 2  greater than Δ 1  and a second loft angle greater than the first loft angle. Because Δ 2  is greater than Δ 1 , preferably, the second club head  100 ′ also has a second surface portion  128 , forming a chamfer, configured to have an angle θ 2  with the imaginary striking face plane that varies from a first angle θ 1  of the first club head  100 . In some such embodiments, variation of θ through a correlated set of club heads varies for at least two club heads of the set in accordance with the following relationship (where θ c  is equal to 60°):
 
tan −1 [tan(θ c )*cos(Δ)]−2.5°≤θ(Δ)≤tan −1 [tan(θ c )*cos(Δ)]+2.5°
 
     While various features have been described in conjunction with the examples outlined above, various alternatives, modifications, variations, and/or improvements of those features and/or examples may be possible. Accordingly, the examples, as set forth above, am intended to be only illustrative. Various changes may be made without departing from the broad spirit and scope of the underlying principles.