Patent Publication Number: US-2007101576-A1

Title: Blunt tip utility blade

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority to U.S. Provisional Application No. 60/736,013, filed Nov. 10, 2005, the contents of which are hereby expressly incorporated by reference as part of the present disclosure. 
    
    
     BACKGROUND  
      The present invention relates to utility knife blades, and more particularly, to safety utility knife blades having an exposed side edge which reduces the risk of inadvertent injury to the user while providing suitable penetration through a work piece.  
      Utility knives having disposable blades are well known in the art. These knives have many industrial as well as home uses, such as for opening boxes, cutting cord, or carving wall board or wood. A typical utility knife has a plastic or metal handle with a retractable blade. When not in use, the blade is retracted into the body of the handle so that the knife can be safely stored or handled. When in use, the blade can extend outwardly from the handle, exposing the cutting edge of the blade.  
      Utility knife blades come in a variety of shapes, depending upon the intended use. As partially shown with reference to  FIG. 1 , a typical form of blade has a generally trapezoidal shape, with a wide cutting edge. The two side edges (only one shown) converge from the outer ends of the blade toward a narrower back edge. The side edges and the back edge are blunted. The blade may additionally have an aperture pattern through a center portion of the blade which enables the blade to be secured within the handle. The trapezodial shape blades are popular since they have pointed cutting corners formed at the intersections between the side edges and the cutting edge. These cutting corners form an acute angle by intersection of the side edges with the cutting edge and enable a user to puncture through a material which is desired to be cut, such as sealing tape closing a box or the cardboard defining the box. Once the object has been punctured, the user can slice open the material by dragging the knife along the surface of the material and allowing the cutting edge to pull through the material.  
      Although blades having acute angle cutting corners may be preferred for the reasons described above, the acute angle cutting corner can cause injury to a user. For example, the blade can cause inadvertent injury when being used, such as by the cutting corner puncturing the skin of the operator. In addition, care must be taken when loading a fresh blade into the holder, in order to reduce the risk of receiving a puncture wound as a result of contact with the cutting corner. The user must hold the blade by contacting only the broad surfaces of the blade, such as between the thumb and forefinger.  
       FIG. 2  illustrates a utility blade with a rounded point that effectively removes the possibility of accidental puncture wounds. In practice, some users do not like the rounded cutting corner blades because they do not penetrate the work piece very well. For example, the rounded point is less efficient as a box cutter. Many users will remove the “safety” rounded point blades and replace them with sharp point blades that they feel are more functional. However, this often violates applicable safety policies. Thus, although the blade of  FIG. 2  reduces the threat of injury to a user, it is less efficient in puncturing a work piece because of the rounded tips.  
       FIG. 3  illustrates a utility blade formed with obtuse angle cutting corners while  FIG. 4  illustrates a utility blade formed with right angle cutting corners. The utility blade of  FIG. 3  is the subject of U.S. Pat. No. 5,337,482 to Schmidt. Each of  FIGS. 3 and 4  define the respective cutting edge corners via a side edge having a first end extending from the cutting edge, and a second end intersecting a major side edge and thereby forming an outboard pointed end.  FIGS. 3 and 4  represent utility blades having cutting corners that are better suited to penetrate a work piece than the utility blade of  FIG. 2 , but are not as effective at reducing the risk of puncture wounds to a user because of the exposed pointed end on each outboard side edge of the blade.  
      It is an object of the present invention to overcome one or more of the above-described drawbacks and/or disadvantages of prior art utility knife blades.  
     SUMMARY OF THE INVENTION  
      The present invention is directed to a blade for a utility knife having blunt side edges to prevent injury, but while still having a cutting corner for puncturing workpieces, such as for box cutting. In accordance with one aspect of the present invention, a utility blade includes a blade body of a generally planar shape, a cutting edge, a back edge opposite the cutting edge, and a pair of opposing side edges. At least one first side edge includes a first end and a second end. The first end of the first side edge extends substantially normal to the cutting edge from a terminal end defining the cutting edge, and a convex radiused edge extends from the second end of the first side edge. The convex radiused edge provides a substantially blunt profile configured to limit puncture wounds to a user, while the first end of the first side edge intersects the cutting edge at approximately 90° to thereby provide a sharp profile for penetration through an object.  
      In accordance with another aspect of the present invention, a utility blade includes a trapezoidal blade body of a generally planar shape and having at least one notch enabling engagement with a handle configured to receive the blade body, a cutting edge, a blunt back edge, and a pair of opposing side edges. Each side edge includes a first side edge having a first end and a second end. The first end of each first side edge extends substantially normal to the cutting edge at opposing terminal ends defining the cutting edge. A pair of opposing convex radiused edges each extend from the second end of a respective first side edge and has a radius of about ¼ inch. The intersection of each first side edge with the cutting edge defines a substantially right angle cutting corner. Each cutting corner is substantially laterally aligned with a corresponding convex radiused edge, such that each convex radiused edge provides a substantially blunt profile configured to limit puncture wounds to a user while the corresponding cutting corner provides a sharp profile to facilitate penetration through an object.  
      In accordance with yet another aspect of the present invention, a utility knife includes a blade body of a generally planar shape, a cutting edge and a pair of opposing side edges. At least one first side edge of the pair of opposing side edges includes a first end and a second end. The first end of the at least one first side edge extends substantially normal to the cutting edge from a terminal end defining the cutting edge. A convex radiused edge extends from the second end of the at least one first side edge. A handle is configured to receive the blade body, wherein the at least one first side edge and at least a portion of said cutting edge are exposed during use. The convex radiused edge provides a substantially blunt profile configured to limit puncture wounds to a user, and the first end of the first side edge provides a sharp profile for facilitating penetration through an object.  
      One advantage of the utility blades of the present invention is that at least one corner region of the cutting edge includes a first portion formed at the intersection of the side edge and cutting edge that is substantially perpendicular to the side edge to thereby form a sharp profile that facilitates piercing an object. The corner region also includes a second portion located on an opposite end of the corner region relative to the first portion and defining a convex radiused edge, to thereby provide the corner region with a blunt lateral profile that prevents a user from being inadvertently injured by the corner region as encountered in the above-described prior art utility blades.  
      Other objects and advantages of the present invention will become more readily apparent in view of the following detailed description of preferred embodiments and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a partial, side elevational view of a prior art trapezoidal utility blade;  
       FIG. 2  is partial, side elevational of a prior art rounded tip utility blade;  
       FIG. 3  is a partial, side elevational view of a prior art utility blade having a cutting edge that intersects opposing side edges at an obtuse angle;  
       FIG. 4  is a partial, side elevational view of a prior art utility blade having a cutting edge that intersects opposing side edges at a right angle;  
       FIG. 5  is a side elevational view of a first embodiment of a utility blade of the present invention having a cutting edge that intersects opposing side edges at respective first ends at a substantially right angle, while respective second ends of the side edges define a convex radiused portion that intersects a major side edge of the blade;  
       FIG. 6  is a partial, enlarged view of a corner region of the utility blade of  FIG. 5 ;  
       FIG. 7  is a front elevational view of the utility blade of  FIG. 5 ;  
       FIG. 8  is an enlarged view of a corner region of the utility blade of  FIG. 7 ; and  
       FIG. 9  is a side elevational view of the utility blade of  FIG. 5  used in conjunction with a utility knife handle.  
       FIG. 10  is a side elevational view of a second embodiment of a utility blade of the present invention that is usable in the utility knife handle of  FIG. 9  and that includes four notches in the back edge of the blade to provide two cutting positions on the blade carrier of the handle for each side of the cutting edge of the blade.  
       FIG. 11  is a partial, side elevational view of a third embodiment of a utility blade of the present invention wherein the blade includes a plurality of cutting edge segments separated by score lines to allow each worn exposed cutting edge to be manually engaged, snapped off and discarded, and thereby expose a fresh cutting edge segment for use, and wherein the exposed corner edge of each cutting edge segment is defined by a cutting edge intersecting a side edge at a first end forming a right angle, while a second end of the side edge defines a convex radiused portion that intersects a major side edge of the blade. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      In  FIG. 5 , a blunt tip utility knife blade embodying the present invention is indicated generally by the reference numeral  10 . The utility knife blade  10  defines a back edge  12 , a cutting edge  14  located on an opposite side of the blade relative to the back edge, and two side edges  16 ,  18  located on opposite sides of the blade relative to each other and extending between the back and cutting edges of the blade. As shown typically in  FIG. 5 , in the currently preferred embodiment of the present invention, the back, cutting and side edges of the blade preferably define an approximately trapezoidal peripheral configuration. However, as described further below with reference to  FIG. 9 , for example, the utility knife blade of the present may take any of numerous different shapes or configurations that are currently known or later become known, including, for example, a square or parallelogram shape.  
      In the exemplary embodiment of  FIG. 5 , the blade  10  is a bi-metal blade defining a blade body  24  including a first metal portion  26  and a second metal portion  28 . The first metal portion  26  extends between the back edge  12  and the second metal portion  28 , and further extends from approximately one side edge  16  to the other side edge  18 . In the illustrated embodiment, the first metal portion  26  is formed of a steel, typically referred to as an “alloy” steel, that is heat treated to a surface hardness within the range of approximately 38 Rockwell “c” (referred to herein as “Rc”) to approximately 52 Rc. The second metal portion  28  defines the cutting edge  14  and extends from approximately one side edge  16  to the other side edge  18 . In accordance with the present invention, the second metal portion  28  is formed of a steel, typically referred to as a “high speed” or “tool” steel, that is heat treated to a surface hardness within the range of approximately 60 Rc to approximately 75 Rc.  
      The first metal portion  26  defines a spring-like backing that is relatively pliable, tough, and thus highly resistant to fatigue and cracking. The second metal portion  28 , on the other hand, is relatively hard and highly wear resistant, and thus defines an ideal, long-lasting cutting blade. As a result, the composite utility knife blades define highly wear-resistant, long-lasting cutting edges, combined with virtually unbreakable or shatter-proof backings.  
      The first metal portion  26  of blade  10  is preferably made of any of numerous different grades of steel capable of being heat treated to a surface hardness within the range of approximately 38 Rc to approximately 52 Rc, such as any of numerous different alloy steels or standard AISI grades, including without limitation 6135, 6150 and D6A. The second metal portion  28 , on the other hand, is preferably made of any of numerous different types of wear-resistant steel capable of being heat treated to a surface hardness within the range of approximately 60 Rc to approximately 75 Rc, including any of numerous different tool steels or high-speed steels, such as any of numerous different standard AISI grades, including, without limitation, M Series grades, such as M1, M2, M3, M42, etc., A Series grades, such as A2, A6, A7 A9, etc., H Series grades, such as H10, H11, H12, H13, etc., T Series grades, such as T1, T4, T8, etc., and W, S, O, D and P Series grades.  
      As further shown in  FIG. 5 , the blade  10  defines a weld region indicated generally with a dashed line  32  formed between the first and second metal portions  26  and  28 , respectively, and defining an approximate line of joinder extending from one side edge  16  to the other side edge  18 . The second metal portion  28  is joined to the first metal portion  26  by applying thermal energy to the interface, such as by electron beam welding, to thereby weld the first metal portion to the second metal portion and form a resulting weld region defining a line of joinder between the two different metal portions.  
      Further details of the composite utility blades and the manufacture of such blades are disclosed in the following patent and co-pending patent applications that are assigned to the assignee of the present invention and are hereby expressly incorporated by reference as part of the present disclosure: U.S. Pat. No. 6,701,627 issued Mar. 9, 2004, entitled “COMPOSITE UTILITY KNIFE BLADE AND METHOD OF MAKING SUCH A BLADE”; U.S. patent application Ser. No. 10/202,703 filed Jul. 24, 2002, entitled “Composite Utility Knife Blade and Method of Making Such a Blade”; and U.S. patent application Ser. No. 10/793,593 filed Mar. 4, 2004, entitled “COMPOSITE UTILITY BLADE AND METHOD OF MAKING SUCH A BLADE”.  
      As may be recognized by those skilled in the pertinent art based on the teachings herein, the currently preferred materials used to construct the first and second metal portions  26  and  28  and disclosed herein are only exemplary, and any of numerous other types of metals that are currently known or later become known for performing the functions of the first and/or second metal portions may be equally employed to form the composite utility knife blades. Alternatively, it will be recognized that the utility blades of the present invention need not define a bi-metal or other composite structure, but rather may be made with only a single metal substrate, such as with traditional carbon steel blades, and/or may include any of numerous different coatings to enhance cutting performance and/or wear characteristics, and/or for decorative purposes, including any of numerous different PVD coatings, such as TiN, AlTiN, other carbide-forming coatings, and combinations of the foregoing. Exemplary coatings and the application of such coatings to utility blades are disclosed in further detail in the following co-pending patent application that is assigned to the assignee of the present invention and is hereby expressly incorporated by reference as part of the present disclosure: U.S. patent application Ser. No. 10/793,593 filed Mar. 4, 2004, entitled “Composite Utility Knife Blade and Method of Making Such a Blade”.  
      As further shown in  FIG. 5 , each composite utility knife blade  10  defines a pair of cut outs or notches  30  formed in the back edge  12  and laterally spaced relative to each other. As shown typically in  FIG. 5 , each notch  30  defines a concave, approximately semi-circular profile, and is provided to engage a corresponding locator mounted within a blade holder (not shown) in order to retain the blade in the blade holder. As may be recognized by those skilled in the pertinent art based on the teachings herein, each notch  30  may take any of numerous different shapes and/or configurations and may be located in any of numerous different locations, and the blade may include any number of such notches or apertures or other recesses that are currently known or later become known to those skilled in the pertinent art for performing the function of engaging a blade holder, or the blade actuating mechanism or locator of such a holder.  
      As also shown in  FIG. 5 , the cutting edge  14  defines an approximately straight cutting edge extending from one side edge  16  to the other side edge  18 . As shown in  FIGS. 7 and 8 , the cutting edge  14  preferably defines first facets  34  located on opposite sides of the blade relative to each other, and second facets  36  spaced laterally inwardly and contiguous to the respective first facets  34 . As shown typically in  FIG. 8 , the first facets  34  define a first included angle “A”, and the second facets  36  define a second included angle “B”. Preferably, the second included angle B is greater than the first included angle A. In the currently preferred embodiment of the present invention, the first included angle A is approximately 14° and the second included angle B is approximately 10°. However, as may be recognized by those skilled in the pertinent art based on the teachings herein, these included angles are only exemplary, and may be set as desired depending upon the physical properties and/or proposed applications of the blade. As may be further recognized by those skilled in the pertinent art, the utility knife blades of the present invention may include any number of facets.  
      Referring now to  FIGS. 5 and 6 , side edges  16  and  18  each define a respective squared corner  20  and a convex radiused edge  22  extending from the squared corner  20 .  FIG. 6  is a partial enlarged view of the left side edge  16  of  FIG. 5  illustrating the junction of the squared corner  20  with the respective convex radiused edge  22 . Each squared corner  20  is defined by an intersection of the cutting edge  14  with a corresponding first side edge  40 ,  42 . Each first side edge  40 ,  42  is defined by a first end  44  and an opposing second end  46 . Each first end  44  is joined with a corresponding terminal end of the cutting edge  14  and is oriented substantially normal to the cutting edge. Each second end  46  is joined with the respective convex radiused edge  22  and also extends substantially normal to the cutting edge  14 . Each first side edge  40 ,  42  forms a substantially right angle cutting corner with respect to the cutting edge  14 . In this manner, the blade  10  includes opposing cutting corners  20  each configured to penetrate a work piece, while simultaneously presenting blunt lateral surfaces defined by the convex radiused edges  22  to prevent inadvertent injury to a user.  
      Each of the opposing convex radiused edges  22  extend from the respective first side edges  40 ,  42  and provide blunt edges which prevent or reduce the risk of puncture wounds to a user. It is contemplated that a bend radius “R” of each convex radiused edge  22  is between about ⅛ inch and about ⅜ inch. In an exemplary embodiment as shown in  FIGS. 5 and 6 , the radius R is about ¼ inch.  
      Each of the opposing convex radiused edges  22  includes one end extending from the respective first side edge  40  or  42  and another opposite end extending from a respective second side edge  50  or  52  that extends to the back edge  12 . In this manner, the convex radiused edges  22  are intermediate the respective first side edges  40 ,  42  and second side edges  50 ,  52 , respectively.  
      As shown typically in  FIG. 5 , in the illustrated embodiment of the present invention, the back, cutting and side edges of the blade define an approximately trapezoidal peripheral configuration. However, as described further below, as well as with reference to  FIG. 9 , for example, the utility knife blades of the present invention may take any of numerous different shapes or configurations that are currently known or later become known, including, for example, a square or parallelogram shape, and/or any desired shape having at least one substantially squared cutting corner and a convex radiused edge extending from the squared cutting corner.  
      In the exemplary embodiment as shown in  FIG. 5 , the second side edges  50  and  52  form an angle C relative to either the cutting or back edges. In the exemplary embodiment, the angle C is about 52°; however, other angles suitable to the desired end purpose are also contemplated. Although the second side edges  50 ,  52  have been described and shown as being straight edges, the second side edges  50 ,  52  alternatively may be curved or take a number of other shapes as each extends from a convex radiused edge  22  to the back edge  12 .  
       FIG. 9  illustrates the blade  10  of  FIG. 5  seated on a blade carrier of a utility knife handle  60  with the notches  30  of the blade engaging the blade-engaging bosses of the blade carrier. The utility knife handle  60  includes a manually engageable button  62  for moving the blade between extended and retracted positions relative to a blade aperture  68  defined by the handle  60 . When the extended portion of the cutting edge  14  of the blade  10  becomes dull, the blade can be flipped over and the other half of the blade used. The blade  10  can be removed from the holder and held with the operator contacting either the side edges  16 ,  18 , at the convex radiused edges  22  and/or the first side edges  40 ,  42  of the blade substantially without the risk of a puncture wound. As may be recognized by those of ordinary skill in the pertinent art based on the teachings herein, the utility blades of the present invention are usable with any of numerous different types of handles in blade carriers that are currently known, or that later become known, including for example any of numerous different types of retractable blade utility knife handles and fixed blade utility knife handles. Alternatively, the utility knife blades of the present invention can be designed for use without a handle, such as in a rectangular form similar in shape to that of a conventional safety razor or utility blade.  
      In  FIG. 10 , another embodiment of a utility blade of the present invention is indicated generally by the reference numeral  10 ′. The primary difference of the utility blade  10 ′ in comparison to the utility blade  10  described above, is that the utility blade  10 ′ defines in its upper edge two inner notches or u-shaped apertures  94  and two outer notches or u-shaped apertures  95 . Accordingly, each side of the blade defines two cutting positions, a first cutting position with the blade-engaging bosses  90  received within the two inner notches  94 , and a second cutting position with the blade-engaging bosses  90  received within one inner notch  94  and a respective outer notch  95 . In the illustrated embodiment, when the blade  10 ′ is located in the first cutting position, about 45% of the cutting edge extends outwardly of the blade aperture  68  and is exposed for cutting in the fully-extended position of the carrier. In the second cutting position, on the other hand, a greater portion of the cutting edge extends outwardly of the blade aperture  68  in comparison to the first cutting position. In the illustrated embodiment, in the second cutting position, about 55% of the cutting edge extends outwardly of the blade aperture  38  and is exposed for cutting in the fully-extended position of the carrier. One advantage of the blunt tip utility blades of the present invention is that if the corner of the blade is not fully retractable within the handle, as can be the case when the blade  10 ′ is located in the second cutting position, the convex radiused edge  22 ′ can extend outwardly of the blade aperture of the handle substantially without risk of puncturing a user.  
       FIG. 11  illustrates a partial side elevational view of a blunt tip segmented utility knife blade in accordance with an alternative embodiment of the present invention and indicated generally by the reference numeral  100 . The utility knife blade  100  defines a back edge  112 , a cutting edge  114  located on an opposite side of the blade relative to the back edge, and two outboard side edges  118  (only the right side edge shown) located on opposite sides of the blade relative to each other and extending between the back and cutting edges of the blade. As partially shown typically in  FIG. 11 , in the illustrated embodiment, the back, cutting and side edges  114 ,  112 , and  118 , respectively, of each blade section resemble the corresponding cutting edge  14 , back edge  12 , and side edge  18  of the utility blade of  FIG. 5   
      In particular,  FIG. 11  illustrates a snap-off blade segment configuration in which the blade  100  includes a plurality of score lines  128 , each defining the profile of a respective side edge  118 . In this manner, when an outboard blade segment becomes unusable due to dulling or breakage, the outboard segment may be manually snapped off at a proximate score line  128  subsequently exposing a new side edge  118  having a new cutting corner  120  defined by the intersection of the cutting edge  114  and new side edge  118 . The score lines  128  are axially spaced relative to each other on the blade and each extends from the cutting edge  114  to the back edge  112 .  
      As with the side edge  18  described above with reference to  FIGS. 5 and 6 , the outboard side edge  118  and each of the plurality of score lines  128  are defined by a first side edge  142  having a first end  144  and an opposing second end  146 , and a convex radiused edge  122  extending from the opposing second end  146  of the first side edge  142 . Each first end  144  is joined with a corresponding terminal end of the cutting edge  114 . The first side edge  142  extends substantially normal to the cutting edge  114  and is joined with a respective convex radiused edge  122 . Each first side edge  142  substantially forms a right angle cutting corner with respect to the cutting edge  114 . In this manner, the blade  100  provides a plurality of cutting corners  120  (only one exposed at a time) with each configured to penetrate a work piece.  
      Each of the exposed convex radiused edges  122  extending from the respective first side edges  142  provide blunt edges which prevent or reduce the risk of puncture wounds to a user. It is contemplated that a bend radius “R” of each convex radiused edge  122  is between about ¼ inch and about ⅜ inch. In the illustrated embodiment of  FIG. 10 , the radius R is about ¼ inch.  
      Each of the opposing convex radiused edges  122  include one end extending from the respective first side edge  142 , and another opposite end extending from a respective second side edge  152  that extends to the back edge  112 . In this manner, the convex radiused edges  122  are intermediate the respective first side edges  142  and second side edges  152 .  
      As may be recognized by those skilled in the pertinent art based on the teachings herein, the utility blades  100  may be made of any of numerous different material that are currently known, or that later become known, such as conventional carbon steel, bi-metal or other composite constructions, and/or may include any of numerous different coatings, such as wear-resistant coatings and/or decorative coatings. In addition the scoring instrument used to provide the plurality of scoring lines  128  may take any of numerous different configurations that are currently known, or later that become known for performing the function of scoring the strip forming the utility blades, such as a carbon steel strip or a bi-metal or other composite strip as described above in the above-mentioned patent and co-pending patent applications. For example, a progressive die may be employed to form the score lines  128 . The term score line is used herein to mean a line defined by a recess or indentation in the surface of the blade  100 .  
      In accordance with a currently preferred embodiment of the present invention, the depth of score is within the range of about 40% to about 50% of the thickness of the blade, and most preferably within the range of about 45% to about 48% of the thickness of the blade. In the illustrated embodiment, the blade is approximately 0.6 mm thick, and the depth of score is within the range of about 0.27 mm to about 0.29 mm. Also in accordance with the currently preferred embodiment of the present invention, each score line is approximately v-shaped, and the included angle of each v-shaped score line is preferably within the range of about 50° to about 60°. In the illustrated embodiment, the included angle of each score line is about 55°. The greater the included angle of the score line, the greater is the pressure on the back side of the blade upon scoring, and thus the greater is the likelihood that the scoring tool will create a ripple effect on the back side of the blade. The smaller the included angle, on the other hand, the more rapid will be the scoring tool wear during use.  
      In an alternative embodiment with reference to  FIG. 11 , the segmented utility knife blade may include a plurality of the notches  160  (shown in broken lines). Each notch  160  is formed at a juncture of a respective score line  128  and the cutting edge  114  of the blade to facilitate bending and snapping a respective cutting edge segment from the blade. For example, the utility knife blades may be bi-metal having high speed or tool steel cutting edges  114  defined by a cutting metal portion  228  and a relatively tough, spring-like backing  226  extending to the back edge. Notches  160  formed in the high speed or tool steel portion of the blade facilitate snapping off of a respective cutting segment of the blade by snapping off just the spring-like backing  226  extending to the back edge without having to snap the harder cutting metal portion  228 .  
      As may be recognized by those skilled in the pertinent art based on the teachings herein, numerous changes and modifications may be made to the above described and other embodiments of the blunt tip utility knife blades of the present invention without departing from the scope of the invention as defined in the appended claims. For example, as shown in  FIGS. 5 and 11 , the blades may take any of numerous different shapes and/or configurations. As shown in  FIGS. 5 and 11 , the second side edge  52 ,  152  may define straight edges extending from the convex radiused edge to the back edge. Alternatively, as shown with dashed line  218  in  FIG. 11 , the second side edge  152  may define a convex portion. The blade  100  of  FIG. 11  is designed for use in a “snap-off” blade holder of a type known to those of ordinary skill in the pertinent art whereby each substantially parallelogram-shaped segment (or other shaped segment, if desired) may be snapped off when the respective cutting edge segment  114  and/or cutting corner  120  becomes worn to, in turn, expose a fresh cutting edge segment. Similarly, although the utility knife blades  10 ,  100  described above define a bi-metal construction, the blades of the present invention may equally define a single metal, tri-metal or other composite or material construction. Accordingly, this detailed description of preferred embodiments is to be taken in an illustrative, as opposed to a limiting sense.