Patent Publication Number: US-11660738-B2

Title: Ergonomic grip for striking tool

Description:
FIELD OF THE INVENTION 
     The present application relates to a grip component for a hand tool, and more specifically to a grip component for a striking tool, such as a hammer or hatchet. 
     DESCRIPTION OF THE RELATED ART 
     The present application relates to a hand tool used to strike another object, such as a hammer used to drive a nail, or a hatchet used to strike and cut or split wood. Such a hand tool may be used in construction, manufacturing, and many other applications. The hand tool may include a head portion and a handle attached to or integral with the head portion. The head portion may be made of steel and have a strike surface used to deliver an impact to the nail, wood, wedge, substrate or other object. The hand tool may be gripped by the handle, which may be formed from wood, plastic, composite, metal, other materials, or combinations thereof. 
     SUMMARY 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     According to an embodiment, a striking hand tool includes a head portion disposed at a first end of the hand tool and a handle attached to or integral with the head portion and extending toward a second and opposite end of the hand tool, the handle comprising a grip component. The grip component extends along a first axis of elongation for the handle, and at any cross sectional plane perpendicularly intersecting the first axis there is a second axis of symmetry for a cross section of the grip component perpendicularly intersecting with the first axis of elongation, and a third axis separating a front half and a rear half of the handle, the third axis perpendicularly intersecting the first axis and the second axis. An external surface of the grip component comprises a front arc half and a rear arc half, the front arc half defined at any cross sectional plane is along the first axis between a frontmost point and side points along the third axis, and the rear arc half defined at any cross sectional plane is between a rearmost point and the side points along the third axis. A first cross sectional area of the grip component defined by the second axis and the third axis is smaller in a first cross sectional plane defined by the second axis and the third axis along the first axis of elongation proximal to the second and opposite end than in a second cross sectional plane defined by the second axis and the third axis along the first axis of elongation proximal to the head portion. A ρ value of the front arc half in the first cross sectional plane is less than approximately 0.45. A measurement from the first axis to the frontmost point in the first cross sectional plane is between 17.5 mm and 19 mm. A ρ value of the front arc half in the second cross sectional plane is less than approximately 0.5. A measurement from the first axis to the frontmost point in the second cross sectional plane is between 18.5 mm and 20 mm. 
     According to another embodiment, a method of manufacturing a striking hand tool, includes forming a head portion disposed at a first end of the hand tool, forming a handle comprising a grip component; and attaching the handle to the head portion or making the handle integral with the head portion, the handle extending toward a second and opposite end of the hand tool. The grip component extends along a first axis of elongation for the handle, and at any cross sectional plane perpendicularly intersecting the first axis there is a second axis of symmetry for a cross section of the grip component perpendicularly intersecting with the first axis of elongation, and a third axis separating a front half and a rear half of the handle, the third axis perpendicularly intersecting the first axis and the second axis. An external surface of the grip component comprises a front arc half and a rear arc half, the front arc half defined at any cross sectional plane is along the first axis between a frontmost point and side points along the third axis, and the rear arc half defined at any cross sectional plane is between a rearmost point and the side points along the third axis. A first cross sectional area of the grip component defined by the second axis and the third axis is smaller in a first cross sectional plane defined by the second axis and the third axis along the first axis of elongation proximal to the second and opposite end than in a second cross sectional plane defined by the second axis and the third axis along the first axis of elongation proximal to the head portion. A ρ value of the front arc half in the first cross sectional plane is less than approximately 0.45. A measurement from the first axis to the frontmost point in the first cross sectional plane is between 17.5 mm and 19 mm. A ρ value of the front arc half in the second cross sectional plane is less than approximately 0.5. A measurement from the first axis to the frontmost point in the second cross sectional plane is between 18.5 mm and 20 mm. 
     According to another embodiment, a striking hand tool includes a head portion disposed at a first end of the hand tool and a handle attached to or integral with the head portion and extending toward a second and opposite end of the hand tool. The handle includes a grip component. The grip component comprises an inner portion and an external portion, the inner portion having a durometer measurement of approximately between 60 Shore A and 70 Shore A, and the external portion having a durometer measurement of approximately between 50 Shore A and 65 Shore A, such that a durometer measurement of the grip component as a whole is approximately between 55 Shore A and 70 Shore A. 
     These and other aspects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and in the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the invention will be apparent from the following description of embodiments hereof as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not necessarily to scale. 
         FIG.  1    is a side view of a hand tool, according to an embodiment hereof. 
         FIG.  2    is a side view of a metal forging including a head, a neck, and handle core for a hand tool, according to an embodiment hereof. 
         FIG.  3    is a sectioned perspective view of a grip component for a handle of a hand tool, according to an embodiment hereof. 
         FIG.  4    is an isolated perspective view of the grip component for a handle of a hand tool, according to an embodiment hereof. 
         FIG.  5    is a perspective view a hand tool including the grip component as according to  FIG.  4   , as being engaged by a hand of a user. 
         FIG.  6 A  illustrates a bisected cross-sectional view of the grip component of  FIGS.  4  and  5   , at a first region thereof. 
         FIG.  6 B  illustrates an embodiment of the cross-sectional view of  FIG.  6 A  with an embodiment of similar view of a conventional grip component overlaid for comparison. 
         FIG.  7 A  illustrates a bisected cross-sectional view of the grip component of  FIGS.  4  and  5   , at a second region thereof. 
         FIG.  7 B  illustrates an embodiment of the cross-sectional view of  FIG.  7    with an embodiment of similar view of a conventional grip component overlaid for comparison. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Embodiments herein relate to a grip component for a handle of a hand tool (e.g., a hammer or hatchet), 
       FIG.  1    illustrates an embodiment of a hand tool  100  that is a hammer (e.g., a 22 oz. framing hammer), though other embodiments may involve a hand tool that is a hatchet or other type of striking tool. The hand tool  100  includes a head portion  110  (e.g., a hammer head) and a handle  120 . The head portion  110  may be used to strike a nail or other object, and may be located at a first end  102  (e.g., an upper end) of the hand tool  100 , while the handle  120  may extend between the head portion  110  and a second, opposite end  104  (e.g., bottom end) of the hand tool  100 . 
     In an embodiment, the head portion  110  may include a bell portion  111  at one end of the head portion  110 , and include a claw portion  113  (e.g., a rip-type or claw-type) at the opposite end of the head portion  110 . The bell portion  111  may have a strike surface  115  for striking the nail or other object. In an embodiment, the strike surface  115  may have a “waffle” pattern machined into or otherwise formed on the strike surface  115 , while in other embodiments the strike surface  115  may be generally smooth. The structure and the material for the head portion  110  are described in more detail in U.S. Patent Application Publication No. 2014/0001426, entitled “Hammer,” to Lombardi et al., the entire content of which is incorporated herein by reference. 
     In an embodiment, a neck  121  may extend from the head portion  110  down towards the second end  104  of the hand tool  100 . In some embodiments, the neck  121  may be integrally formed with the head portion  110 . In an embodiment, the neck  121  may extend to or even into the handle portion  120  to help secure the head portion  110  to the handle portion  120 . As described in greater detail below, in an embodiment, a grip component  123  may define a generally outer portion of the handle  120 , and may be shaped to be engaged by a hand of a user of the hand tool  100 . As seen in  FIG.  2   , where the grip component  123  is removed from the tool  100 , a core  125  of the handle portion  120  may extend from the neck  121  (and in some embodiments may integrally formed with the neck  121 , and may too be integrally formed with the head portion  110 ). While both the neck  121  and the core  125  may be integrally formed with the head portion  110  (e.g., so that the core  125 , neck  121  and head portion  110  are part of a single piece), in other embodiments one or more of the neck  121  and the core  125  may be formed separately from the head portion  110  and attached thereto (e.g., via a weld, bond, friction fit, interference fit, adhesive connection, or mechanical connection such as via fasteners). As discussed in greater detail below, in some embodiments, the core  125  may include one or more apertures  125   a  formed within, which may aid in manufacturing, or assist in holding the core  125  to the grip component  123 . In various embodiments the grip component  123  may be overmolded onto the core  125 , slid onto the core  125 , or may be otherwise secured to the neck  121  and or the head portion  110 . 
     In some embodiments the neck  121  or the core  125  may be formed from a steel alloy. In an embodiment, one or more of the neck  121  and the core  125  may be elongated in shape, and may be substantially straight along an axis A (e.g., an axis of handle elongation) extending along a length of the grip component  123  thereof, or may have a curved shape, such as by curving along an axis B extending from a rear of the grip component  123  to a front of the grip component  123  (as such axes are understood with reference to  FIG.  3   , depicting how the grip component  123  would engage the core  125  in some such embodiments). 
       FIG.  3    illustrates a sectioned perspective of an embodiment of the grip component  123  that includes an external portion  123   a  and an inner portion  123   b . As shown, in an embodiment, the external portion  123   a  forms a shell around the inner portion  123   b . In an embodiment, the external portion  123   a  may form a first layer that is an external layer (also referred to as outer layer) of the grip component  123 , and the inner portion  123   b  may form a second layer that is an inner layer of the grip component  123 . In an embodiment, the grip component  123  may be a two-layer grip that includes only the first layer (formed by the external portion  123   a ) and the second layer (formed by the inner portion  123   b ). In such an embodiment, the external portion  123   a  provides an exposed user contact surface (e.g., grip surface) for the grip component  123 . In other words, in such an embodiment, an external surface  123   e  of the external portion  123   a  is a surface that contacts a user when the handle  120  is being gripped. 
     In various embodiments, the first layer formed by the external portion and the second layer formed by the inner portion may be in contact with and chemically or mechanically bonded to each other (e.g., through overmolding, friction fit, adhesive coupling). In an embodiment, the external portion  123   a  forms an entire external surface of the grip component  123 , such that none of the material of the inner portion  123   b  is exposed to an external environment at a side of the grip component  123 . For instance, the external portion  123   a  may be free of holes or gaps on its external surface, such that the external surface  123   e  is defined entirely by the external portion  123   a . In other embodiments, the external portion  123   a  may have apertures within that allow portions of the inner portion  123   b  to be exposed, such that the external surface  123   a  is formed by the externally facing surfaces of external portion  123   a  and those portions of internal portion  123   b  exposed through the external portion  123   a.    
     The materials of the grip component  123 , including one or more of the external portion  123   a  and the inner portion  123   b  may be of any appropriate construction or configuration, including in various embodiments being formed by one or more of a thermoplastic elastomer (TPE), a thermoplastic urethane (TPU) material, and a thermoplastic rubber (TPR) material. 
       FIG.  3    further illustrates that the inner portion  123   b  may be formed to have a cavity  123   c  for receiving the core  125  and/or portions of the neck  121 . In various embodiments, the grip component  123  may be slid onto the core  125 , or may be entirely overmolded onto the core  125  such that the cavity  123   c  is at least partially filled by the core  125 . In various embodiments, the cavity  123   c  can have a shape that is substantially straight along the axis A of the grip component  123 , or may have a curved shape along the axis A. Further, if the grip component  123  is separated from core  125  (e.g., the cavity  123   c  is not yet filled by the core  125  during assembly of the hand tool  100 ), the cavity  123   c  may have a shape that is substantially the same as at least a portion of the core  125 . Having the same shape may allow the core  125  to more easily pass through the cavity  123   c  during the assembly, and may facilitate better contact between the inner portion  123   b  and the core  125  after the grip component  123  is slid thereon. 
     In other instances, however, when the grip component  123  is configured to be slid onto the core  125 , the cavity  123   c  may have a shape that is different than a shape of the core  125  (or, more specifically, different than a shape of a portion of the core  125  onto which the grip component  123  will be slid). In some embodiments, the grip component  123  may flex or deform so that the cavity  123   c  generally assumes the shape of the core  125 . 
     In various embodiment, one or more of the cavity  123   c  and the core  125  may have a cross sectional shape that is regular or irregular, symmetrical or asymmetrical. In an embodiment the cross section of one or more of the cavity  123   c  and the core  125  may be generally rectangular, (e.g., as a rounded rectangle, or an I-beam shape). Regardless, in some embodiments the cross section may be shaped to prevent rotation of the grip component  123  about the core  125 . In some embodiments, the apertures  125   a  of the core  125  may facilitate the grip component  123  engaging the core  125  (e.g., if the grip component  123  is overmolded onto the core  125 , the material of the grip component  123  may fill in the apertures to prevent the grip component  123  from sliding off of the core  125 ). 
     Regardless of the construction of the grip component  123 , it may be appreciated that the shape of the external surface  123   e  of the grip component  123  may guide an ergonomic engagement between a user and the tool  100 . While such ergonomics may also be impacted by the resilience of the material selections of the grip component  123 , a shape of the grip component  123  provides a unique and beneficial aspect of this disclosure. 
     As such,  FIG.  4    illustrates in isolation the grip component  123 , and in particular the external surface  123   e , while  FIG.  5    illustrates the tool  100  including the grip component  123  being engaged by a hand H of a user. It may be appreciated that the grip component  123  may be elongated sufficiently that the hand H of the user may engage multiple regions of the external surface  123   e  at once, and may even be slid along the external surface  123   e  so as to engage different regions of the grip component  123  during different operations of the tool  100 . For example, moving the hand H to engage the grip component  123  closer to the neck  121  or the first end  102  may allow for greater precision when using the tool  100  to impact a nail (e.g., when the tool  100  is a hammer) or a previous impact when chopping wood (e.g., when the tool  100  is a hatchet). Similarly, moving the hand H closer to the opposite end  104  may increase the power of an impact. 
     Accordingly, in some embodiments, ergonomics may be optimized for different regions of the grip component  123 , to facilitate improved user engagement during precision holds proximal to the neck  121  or power holds proximal to the opposite end  104 . It may be appreciated, however, that based on a length and shape of the grip component  123 , a majority of users may initially pick up the tool  100  by engaging their hand around an intermediate grip position, such as that shown in  FIG.  5   . Accordingly, it may be appreciated that the ergonomics of a grip component  123  may be designed with such a grip position in mind, as is discussed in greater detail below. Regardless, as hand size varies from user to user, a grip component  123  may be designed based on an average hand size across a wide number of users, optimizing the ergonomic feel of the grip component  123  at positions where larger than average hands and smaller than average hands generally agree on ergonomic comfort. 
     With reference to  FIG.  4    and  FIG.  5   , the ergonomics of the grip may be understood with reference to plane C and plane D, wherein the plane C is generally located proximal to where a pinkie P of the hand H would engage the grip component  123 , while the plane D is generally proximal to where the middle finger M and index finger I typically would engage the grip component  123 . It may be appreciated that for many users, the primary engagement between the hand H and the grip component  123  may be through the pinkie P, ring finger R, and middle finger M, while the index finger I and the thumb T typically provide support. Regardless, in some embodiments, the plane C may be located approximately 50 millimeters (e.g., approximately 2 inches) above the end  104  (i.e., approximately 50 millimeters from the end  104  towards the end  102 ), while the plane D may be located approximately 100 millimeters (e.g., approximately 4 inches) above the end  104  (i.e., approximately 100 millimeters from the end  104  towards the end  102 ). In an embodiment where the grip component  123  is shaped so that the external surface flanges outward (e.g., to prevent the tool  100  from inadvertently sliding out of the users grip), it may be appreciated that the plane C may be located generally where the external surface  123   e  begins to flare away from the axis A. In various embodiments, by being approximately a certain distance from the end  104 , it may be understood that that the plane may be plus or minus up to 25% of the distances from the distances from the end  104  noted in the embodiments above. 
     It may be appreciated that in some embodiments, a cross sectional area of the grip component  123  at the plane C may be smaller than a cross sectional area of the grip component at the plane D, as the pinkie P may commonly curl closer to the palm of the hand H around the grip component  123  than the middle finger M as the fingers are curled together. As such, and as may be appreciated from the discussion in greater detail below, in an embodiment a cross sectional area of the grip component  123  at the plane C may be approximately 674.4 mm 2 , while in an embodiment a cross sectional area of the grip component  123  at the plane D may be approximately 766.8 mm 2 , 
     The ergonomics of the grip component  123  at the plane C may be understood further with reference to  FIGS.  6 A and  6 B . As shown in  FIG.  6 A  (and illustrated with exemplary measurements in  FIG.  6 B , as overlaying those of a conventional grip component shown in broken lines), the external surface  123   e  of the grip component  123  may be understood from measurements taken from a center of the grip component  123 , which may be symmetrical over an axis X (which may be parallel to or collinear with the axis B. The axis X may be perpendicular to an axis Y, the intersection of which may generally be understood as a center of the grip component  123 , and may coincide with a center of the core  125  located thereat, and may both be perpendicular to the axis A defined above. As such, the axis A, the axis X, and the axis Y may be orthogonal axes. Similarly, the ergonomics of the grip component  123  at the plane D may be understood further with reference to  FIGS.  7 A and  7 B , reflecting the same axes as those of  FIGS.  6 A  and  6 B. Similarly,  FIG.  7 B  illustrates the view of  FIG.  7 A , however with exemplary measurements, and overlaying those of the conventional grip component shown in broken lines. 
     Returning to  FIGS.  6 A and  6 B , illustrating the ergonomics of the grip component  123  at the plane C, one may appreciate the complex curved shape of the external surface  123   e  as being defined by points relative to the axis A. For example, with the left hand of  FIGS.  6 A and  6 B  showing a front of the grip component  123  more proximal to the bell portion  115  than the claw portion  113  for example, a frontmost point  200   a  of the external surface  123   e  at the plane C may be measurement  210   a  from the axis A. A front angle point  200   b  of the external surface  123  at the plane C may be measurement  210   b  from the axis A, and may be located 45 degrees from the axis X as extending from the axis A towards the frontmost point  200   a  in the plane C. A side point  200   c  may be located at the intersection of the external surface  123   e  and the Y axis, and may be measurement  210   c  from the axis A. A rear angle point  200   d  may be measurement  210   d  from the axis A, and may be located 45 degrees from axis X as extending from the axis A away from the frontmost point  200   a  in the plane C. Finally, a rearmost point  200   e  may be measurement  210   e  away from the axis A in the plane C, along the axis X. As shown in  FIG.  6 B , in some embodiments, the measurement  210   a  may be approximately 18 mm, the measurement  210   b  may be approximately 15.2 mm, the measurement  210   c  may be approximately 12.5 mm, the measurement  210   d  may be approximately 13.9 mm, and the measurement  210   e  may be approximately 15.4 mm 
     Another way for one to understand the curves forming the ergonomic shape of the external surface  123   e  may be through the intrinsic dimensions and shapes of those curves as arc segments defined along the external surface  123   e . For example, a front arc quadrant may be understood as being generally formed between the frontmost point  200   a  and the side point  200   c , while a rear arc quadrant may be understood as formed between the side point  200   c  and the rearmost point  200   e . It may be appreciated that in some embodiments, the arcs quadrants may terminate slightly before or slightly after the side point  200   c  (e.g., where the overall curve between the frontmost point  200   a  and the rearmost point  200   e  is formed by a combination of additional arc segments). According to an embodiment, an arc length between the frontmost point  200   a  and the side point  200   c  at the plane C may be approximately 22.2 mm, while in an embodiment, an arc length between the side point  200   c  and the rearmost point  200   e  at the plane C may be approximately 24.6 mm. It may be appreciated that arc quadrants may be defined between the axis X, the axis Y (or an axis parallel to and adjacent to the axis Y), and the curve of the external surface therebetween. Accordingly, a front arc quadrant may be defined by these axes and the curve between the frontmost point  200   a  and the side point  200   c , while a rear arc quadrant may be defined by the aforementioned axes and the curve between the side point  200   c  and the rearmost point  200   e . In an embodiment, an area of the front arc quadrant may be approximately 153.7 mm 2  while an area of the rear arc quadrant may be approximately 186.4 mm 2 . 
     It may be appreciated that the mathematical ratio ρ (Rho) defines the eccentricity of a conic section, where ρ is the ratio of the distance of the peak of the rounded corner to the sharp corners defined by two points along the curve. In particular a ρ of 0.5 (within manufacturing tolerance) would be understood as generally parabolic in shape. A ρ of less than 0.5 would be generally elliptical in shape, while a ρ of greater than 0.5 would be generally hyperbolic in shape. In an embodiment, a curve defined between the side point  200   c  and a mirror side point  200   c  opposite the axis X, defining a front arc half including the frontmost point  200   a , at the plane C, may have a ρ value of approximately 0.425. In an embodiment, a curve defined between the side point  200   c  and the mirror side point  200   c  opposite the axis X, defining a rear arc half including the rearmost point  200   e , at the plane C, may have a ρ value of approximately 0.475. It may be appreciated that when not bisected by the axis X, the arc lengths of the arc quadrants discussed above may be doubled, such that the front arc half defined between the side point  200   c  and the mirror side point  200   c  opposite the axis X, including the frontmost point  200   a , at the plane C, may have a combined arc length of approximately 44.4 mm, while the rear arc half defined between the side point  200   c  and the mirror side point  200   c  opposite the axis X, including the rearmost most point  200   e , at the plane C, may have a combined arc length of approximately 49.2 mm. 
     For purposes of comparison, with regard to a conventional grip surface such as is shown in broken lines in  FIG.  6 B , a corresponding front arc quadrant measured at a plane C of a conventional grip surface between a frontmost point and a side point similar to frontmost point  200   a  and side point  200   c  may be approximately 25.3 mm, while in an embodiment, an arc length between the side point and a rearmost point similar to the rearmost point  200   e  at the corresponding plane C may be approximately 16.6 mm. Additionally, a conventional front arc quadrant, such as that shown of the example in broken lines, may have an area of approximately 185.4 mm 2  while an area of a corresponding rear arc quadrant at the plane C may be approximately 121.2 mm 2 . In an embodiment, a curve defined between the side point and a mirror side point opposite the axis X of conventional grip surface, defining a rear arc half including the conventional grip surface&#39;s frontmost point at the plane C, may have a ρ value of approximately 0.475. In an embodiment, a curve defined between the side point and the mirror side point opposite the axis X, defining a rear arc half including the rearmost point of the conventional grip surface at the plane C, may have a p value of approximately 0.5. 
     As noted, while the plane C may be proximal to the pinkie P where an average user would commonly grasp the grip surface  123 , the plane D may be proximal to the ring finger R and index finger I of the hand H, so as to define the primary engagement of the grip surface  123  therebetween.  FIGS.  7 A and  7 B  illustrate the ergonomics of the grip component  123  at the plane D, where one may again appreciate the complex curved shape of the external surface  123   e  as being defined by points relative to the axis A. For example, with the left hand of  FIGS.  7 A and  7 B  again showing a front of the grip component  123  more proximal to the bell portion  115  than the claw portion  113  for example, a frontmost point  300   a  of the external surface  123   e  at the plane D may be measurement  310   a  from the axis A. A front angle point  300   b  of the external surface  123  at the plane D may be measurement  310   b  from the axis A, and may be located 45 degrees from the axis X as extending from the axis A towards the frontmost point  300   a  in the plane D. A side point  300   c  may be located at the intersection of the external surface  123   e  and the Y axis, and may be measurement  310   c  from the axis A. A rear angle point  300   d  may be measurement  310   d  from the axis A, and may be located 45 degrees from axis X as extending from the axis A away from the frontmost point  300   a  in the plane D. Finally, a rearmost point  300   e  may be measurement  310   e  away from the axis A in the plane D, along the axis X. As shown in  FIG.  7 B , in some embodiments, the measurement  310   a  may be approximately 19.3 mm, the measurement  310   b  may be approximately 16.2 mm, the measurement  310   c  may be approximately 13.5 mm, the measurement  310   d  may be approximately 15.1 mm, and the measurement  310   e  may be approximately 15.4 mm 
     Similar to that described above with regard to plane C, a front arc quadrant for the plane D may be understood as being generally formed between the frontmost point  300   a  and the side point  300   c , while a rear arc quadrant may be understood as formed between the side point  300   c  and the rearmost point  300   e . It may again be appreciated that in some embodiments, the arcs quadrants may terminate slightly before or slightly after the side point  300   c  (e.g., where the overall curve between the frontmost point  300   a  and the rearmost point  300   e  is formed by a combination of additional arc segments). According to an embodiment, an arc length between the frontmost point  300   a  and the side point  300   c  at the plane D may be approximately 25.4 mm, while in an embodiment, an arc length between the side point  300   c  and the rearmost point  300   e  at the plane D may be approximately 24.3 mm. Arc quadrants may again be defined between the axis X, the axis Y (or an axis parallel to and adjacent to the axis Y), and the curve of the external surface therebetween. Accordingly, a front arc quadrant at the plane D may be defined by these axes and the curve between the frontmost point  300   a  and the side point  300   c , while a rear arc quadrant may be defined by the aforementioned axes and the curve between the side point  300   c  and the rearmost point  300   e . In an embodiment, an area of the front arc quadrant at the plane D may be approximately 198.7 mm 2  while an area of the rear arc quadrant may be approximately 184.7 mm 2 . 
     The eccentricity of the conic sections, ratio ρ at the plane D between the side point  300   c  and a mirror side point  300   c  opposite the axis X, defining a front arc half including the frontmost point  300   a , may be approximately 0.45. In an embodiment, a curve defined between the side point  300   c  and the mirror side point  300   c  opposite the axis X, defining a rear arc half including the rearmost point  300   e , at the plane D, may have a ρ value of approximately 0.5. It may be appreciated that when not bisected by the axis X, the arc lengths of the arc quadrants discussed above may be doubled, such that the front arc half defined between the side point  300   c  and the mirror side point  300   c  opposite the axis X, including the frontmost point  300   a , at the plane D, may have a combined arc length of approximately 50.8 mm, while the rear arc half defined between the side point  300   c  and the mirror side point  300   c  opposite the axis X, including the rearmost most point  300   e , at the plane D, may have a combined arc length of approximately 48.6 mm. 
     Again for purposes of comparison, with regard to a conventional grip surface such as is shown in broken lines in  FIG.  7 B , a corresponding front arc quadrant measured at a plane D of a conventional grip surface between a frontmost point and a side point similar to frontmost point  300   a  and side point  300   c  may be approximately 27.2 mm, while in an embodiment, an arc length between the side point and a rearmost point similar to the rearmost point  300   e  at the corresponding plane D may be approximately 20.7 mm. Additionally, a conventional front arc quadrant, such as that shown of the example in broken lines, may have an area of approximately 217 mm 2  while an area of a corresponding rear arc quadrant at the plane D may be approximately 135.6 mm 2 . In an embodiment, a curve defined between the side point and a mirror side point opposite the axis X of conventional grip surface, defining a front arc half including the conventional grip surface&#39;s frontmost point at the plane D, may have a ρ value of approximately 0.5. In an embodiment, a curve defined between the side point and the mirror side point opposite the axis X, defining a rear arc half including the rearmost point of the conventional grip surface at the plane D, may also have a ρ value of approximately 0.5. 
     While in outward appearance the modifications made between the grip component  123  illustrated in solid line, and conventional grip components such as that overlaid in broken line in  FIG.  6 B  and  FIG.  7 B  may seem relatively insignificant, where millimeters of difference are found in certain measurements, it should be appreciated that prototypes of the grip component  123  were experimentally tested over the conventional grip component illustrated and other conventional grip components, with the grip component  123  being heavily favored for user comfort, providing ergonomic benefits that may otherwise be found in the illustrated conventional grip component, but significantly improving upon them by providing a fuller grip as engaged by at least the pinkie P, middle finger M, and ring finger R to vastly improve user comfort. 
     It may be understood that the ergonomically improved fuller grip discussed above may be understood in terms of the mathematical measures provided herein, and in ratios defined in view of them. For example, the grip component  123  may be understood as having a cross sectional area that is greater at the plane D than at the plane C (e.g. greater at a region more proximal to head portion  110 , where typically engaged by the middle finger M, and lesser at a region more proximal to the bottom end, where typically engaged by the pinkie P). Additionally, a ratio of a measurement between the axis A and the frontmost point  200   a  or  300   a , as compared to the ρ from the side points  200   c  or  300   c  and including the frontmost point  200   a  or  300   a , may define a fullness of the grip by representing a more elliptical rather than parabolic or hyperbolic shape. 
     It may be appreciated that the material selections for the grip component  123  may impact the ergonomic feel of the hand tool  100  in a hand of a user. As noted above, the materials of the grip component  123 , including one or more of the external portion  123   a  and the inner portion  123   b  may be of any appropriate construction or configuration, including in various embodiments being formed by one or more of TPE, TPU, and TPR materials. Without regard to the specific material being used, it may be appreciated that the hardness or resilience of the material may provide an overall different user experience when engaging the external surface  123   e . As an example, when the hand tool  100  is a hammer, hatchet, or other striking tool, having a desired resilience in the grip component  123  may dampen vibration from an impact. Even when simply holding the hand tool  100  in ones hand, a certain amount of resilience, in combination with the ergonomic shape, may give a satisfying feel when squeezed, or when a weight of the hand tool  100  pushes the grip component  123  into the hand of the user even when the hand tool  100  is merely being held steady. 
     According to an embodiment, a durometer value measured on the grip component  123  as a whole (e.g., including both the external portion  123   a  and the inner portion  123   b ) may be approximately between 55 and 70 Shore A. In an embodiment, the overall durometer measurement of the grip component  123  may be approximately 60 Shore A. According to some embodiments, the hardness measured by a durometer may vary for differing layers of material that form the grip component  123 . For example, in an embodiment, the inner portion  123   b  may have an associated durometer measurement of approximately between 60 and 70 Shore A. In an embodiment, the inner portion  123   b  may have an associated durometer measurement of approximately 65 Shore A. In an embodiment, the external portion  123   a  may have a durometer measurement of approximately between 50 and 65 Shore A. In an embodiment, the durometer measurement for the external portion  123   a  may be approximately 57 Shore A. Accordingly, it may be appreciated that in some embodiments the external portion  123   a  may have a softer durometer measurement than the inner portion  123   b . In an embodiment, both the external portion  123   a  and the internal portion  123   b  may be considered between medium soft and medium hard. 
     In molding the grip component  123  around the core  125 , it may be appreciated that in some embodiments the first shot of an injection molding or overmolding process over the core  125  may be of the inner portion  123   b  having a durometer measurement of between 60 and 70 Shore A. The second shot of the injection molding or overmolding process over the core  125  may then be of the external portion  123   a  having a similar hardness or softer material, such as having a durometer measurement of between 55 and 65 Shore A. In some embodiments, a reverse mold technique may be utilized, where the first shot may be the external portion  123   a , while the second shot may be the inner portion  123   b , having similar durometer readings as described above. Regardless, it may be appreciated that having a dual shot grip component  123  with the ergonomic geometry further described herein may provide an enhanced user experience when a user grasps or manipulates a hand tool  100  using such a grip component  123 . 
     While various embodiments have been described above, it should be understood that they have been presented only as illustrations and examples of the present invention, and not by way of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment.