Patent Publication Number: US-9404523-B2

Title: Bolt retention apparatus and method

Description:
CLAIM OF PRIORITY 
     This application is a division of U.S. patent application Ser. No. 13/080,972, filed Apr. 6, 2011, which claims priority to U.S. Provisional Patent Application No. 61/323,913, filed Apr. 14, 2010, the entire disclosures of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to fasteners. 
     BACKGROUND OF THE INVENTION 
     When securing components with fasteners, the fasteners are typically provided separately from the components themselves and must be brought to the components using either an automated or manual process during assembly of the components. For example, when securing two components by a bolt, the two components are often first brought together in their final assembled positions, the bolt is then brought to the pre-assembled components, and lastly the bolt is inserted through respective apertures in the components and tightened to secure the components together. 
     SUMMARY OF THE INVENTION 
     Unitizing fasteners with one or more of the components which the fasteners will secure can reduce the number of steps required to assemble the components and subsequently decrease the amount of time spent on the component assembly. 
     The present invention provides, in one aspect, a unitized component assembly including an component having an aperture, and a plurality of discrete projections extending into the aperture and spaced apart from one another about the perimeter of the aperture. The unitized component assembly further includes a fastener having a head and a shank extending from the head. The shank includes a necked portion and a threaded portion adjacent the necked portion. The shank is positioned in the aperture such that the necked portion is in facing relationship with the projections. The threaded portion is engageable with the projections to provide an axial stop for limiting movement of the fastener relative to the component. 
     The present invention provides, in another aspect, a method of unitizing a fastener and a component. The method includes providing the component with an aperture, and a plurality of discrete projections extending into the aperture and spaced apart from one another about the perimeter of the aperture. The method further includes providing the fastener with a head and a shank having a necked portion and a threaded portion adjacent the necked portion, inserting the shank into the aperture, at least partially deforming each of the projections during insertion of the threaded portion of the shank into the aperture, positioning the necked portion of the fastener in facing relationship with the projections after the projections have been deformed by the threaded portion of the shank, and engaging the threaded portion of the shank with the projections to provide an axial stop for limiting movement of the fastener relative to the component. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a first construction of a unitized component assembly of the invention, including a component and a fastener unitized to the component. 
         FIG. 2  is a top view of the component of  FIG. 1 , illustrating an aperture and a plurality of discrete projections extending into the aperture. 
         FIG. 3  is a perspective view of the component of  FIG. 1 , illustrating one of the discrete projections. 
         FIG. 4  is a top view of a portion of the component of  FIG. 1 , illustrating a first series of manufacturing steps used to create the projections. 
         FIG. 5  is a bottom view of the portion of the component of  FIG. 4 , illustrating a second series of manufacturing steps used to create the projections. 
         FIG. 6  is a cross-sectional view of the unitized component assembly of  FIG. 1 , illustrating a threaded portion on the shank of the fastener engaging the projections to prevent removal of the shank from the aperture in the component. 
         FIG. 7  is a cross-sectional view of the unitized component assembly of  FIG. 1 , illustrating the head of the fastener engaging the component to prevent removal of the shank from the aperture in the component. 
         FIG. 8  is a cross-sectional view of a second construction of a unitized component assembly of the invention, including a component and a fastener unitized to the component. 
         FIG. 9  is a top view of the component of  FIG. 8 , illustrating an aperture and a plurality of discrete projections extending into the aperture. 
         FIG. 10  is a top perspective view of the component of  FIG. 8 , illustrating two of the projections in the aperture. 
         FIG. 11  is a top perspective view of a component of a third construction of a unitized component assembly of the invention. 
         FIG. 12  is a top perspective view of the component of  FIG. 11 . 
         FIG. 13  is a cross-sectional view of the component of  FIG. 11 . 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a first construction of a unitized component assembly  10  according to the invention. The assembly  10  includes a component (e.g., an engine component  14 ) and a fastener  18  coupled to the engine component  14 . The illustrated engine component  14  is configured as a rocker arm pivot of an engine valve train. Alternatively, the engine component  14  may be configured as any of a number of different components that are secured to the engine using the fastener  18 . The fastener  18  includes a head  22  and a shank  26  extending from the head  22 . Although the illustrated fastener  18  is in the form of a bolt, the fastener  18  may be configured in any of a number of different ways. The shank  26  includes a non-threaded necked portion  30  spaced from the head  22  and having a reduced diameter relative to the portions of the shank  26  adjacent the necked portion  30 . The shank  26  also includes a threaded portion  34  adjacent the necked portion  30 . Alternatively, the necked portion  30  of the shank  26  may be spaced from the threaded portion  34  of the shank  26 . Further, the necked portion  30  of the shank  26  is adjacent the head  22 . The necked portion  30  of the shank  26  is defined between the head  22  and a shoulder on the shank  26 , which substantially coincides with an upper extent  38  of the threaded portion  34 . At least part of the threaded portion  34  (e.g., the first few lower threads) may be heat treated to increase the hardness of the threaded portion  34 . 
     The engine component  14  includes an aperture  42  ( FIG. 3 ) and a plurality of discrete projections  46   a ,  46   b ,  46   c  ( FIG. 2 ) extending into the aperture  42 . As shown in  FIG. 2 , the projections  46   a ,  46   b ,  46   c  are spaced apart from one another about the perimeter of the aperture  42 . Specifically, the engine component  14  includes three projections  46   a ,  46   b ,  46   c  that are equidistantly spaced from each other by an angle A of about 120 degrees ( FIG. 4 ) with respect to a central axis  48  of the aperture  42 . Each of the projections  46   a ,  46   b ,  46   c  includes an apex  50  and respective curved or arcuate surfaces  54 ,  58  on either side of the apex  50 . Respective planes  62   a ,  62   b ,  62   c  pass through the central axis  48  and the apices  50  of the respective projections  46   a ,  46   b ,  46   c . As such, the planes  62   a ,  62   b ,  62   c  separate the arcuate surfaces  54 ,  58  of each of the projections  46   a ,  46   b ,  46   c.    
     With reference to  FIG. 5 , the projections  46   a ,  46   b  are separated from each other by an arc length AL 1  defined by a constant radius R 1  with respect to the central axis  48 . Likewise, the projections  46   b ,  46   c  and the projections  46   c ,  46   a  are separated from each other by respective arc lengths AL 2 , AL 3  each defined by the constant radius R 1  with respect to the central axis  48 . With continued reference to  FIG. 5 , the arcuate surface  54  of the projection  46   a  is defined by a continually decreasing radius having an origin coaxial with the central axis  48 , sweeping in a counterclockwise direction from the arc length AL 3 , having a maximum value corresponding with the radius R 1  of the arc length AL 3 , and a minimum value corresponding with a radial dimension R 2  ( FIG. 4 ) between the apex  50  of the projection  46   a  and the central axis  48 . Likewise, with reference to  FIG. 5 , the arcuate surface  58  of the projection  46   a  is defined by a continually increasing radius having an origin coaxial with the central axis  48 , sweeping in a counterclockwise direction from the apex  50 , having a minimum value corresponding with the radial dimension R 2  ( FIG. 4 ) between the apex  50  of the projection  46   a  and the central axis  48 , and a maximum value corresponding with the radius R 1  of the arc length AL 1  ( FIG. 5 ). The projection  46   b  is defined in a similar manner relative to the arc lengths AL 1 , AL 2  on either side of the projection  46   b , and the projection  46   c  is defined in a similar manner relative to the arc lengths AL 2 , AL 3  on either side of the projection  46   c.    
     With reference to  FIG. 4 , the projection  46   a  is defined by the outer peripheral surface of a first cylinder  66  having a central axis  70  oriented substantially parallel to the central axis  48 , and the outer peripheral surface of a second cylinder  74  having a central axis  78  oriented substantially parallel with the central axis  48 . Specifically, the central axis  70  is aligned with a plane  82  passing through the central axis  48  and angularly offset from the plane  62   a  by about 60 degrees in a counterclockwise direction from the point of view of  FIG. 4 . Likewise, the central axis  78  is aligned with a plane  86  passing through the central axis  48  and angularly offset from the plane  62   b  by about 60 degrees in a counterclockwise direction from the point of view of  FIG. 4 . Each of the axes  70 ,  78  is spaced from the central axis  48  in a radial direction by a dimension D 1  (shown in  FIG. 5  with respect to reoriented axes  70 ′,  78 ′, which are equidistant to the central axis  48  as the axes  70 ,  78  in  FIG. 4 , respectively), in which the ratio of the dimension D 1  to the radius R 1  of each of the arc lengths AL 1 , AL 2 , AL 3  is between about 0.05:1 and about 0.15:1. In the illustrated construction of the engine component assembly  10 , the ratio of the dimension D 1  to the radius R 1  of each of the arc lengths AL 1 , AL 2 , AL 3  is about 0.10:1. 
     With reference to  FIG. 4 , the projection  46   b  is defined by the outer peripheral surface of the second cylinder  74 , and the outer peripheral surface of a third cylinder  90  having a central axis  94  oriented substantially parallel with the central axis  48 . Specifically, the central axis  94  is aligned with a plane  98  passing through the central axis  48  and angularly offset from the plane  62   c  by about 60 degrees in a counterclockwise direction from the point of view of  FIG. 4 . The axis  94  is also spaced from the central axis  48  in a radial direction by the dimension D 1 . The projection  46   c  is defined by the outer peripheral surface of the third cylinder  90  and the outer peripheral surface of the first cylinder  66 . 
     With reference to  FIG. 1 , each of the projections  46   a ,  46   b ,  46   c  includes an axial length L 1  that is less than the axial length L 2  of the aperture  42 . Specifically, the ratio of the axial length L 1  of each of the projections  46   a ,  46   b ,  46   c  to the axial length L 2  of the aperture  42  is about 0.150:1 or less. In the illustrated construction of the engine component assembly  10 , the projections  46   a ,  46   b ,  46   c  are positioned toward the upper end of the aperture  42 . Alternatively, the projections  46   a ,  46   b ,  46   c  may be positioned toward the bottom end of the aperture  42 , the middle of the aperture  42 , or at any location along the length of the aperture  42 . The aperture  42  includes a substantially circular cross-section, defining a diameter D 2 , below the projections  46   a ,  46   b ,  46   c . In the illustrated construction of the engine component assembly  10 , the diameter D 2  is equal to twice the radius R 1  ( FIG. 5 ) of each of the arc lengths AL 1 , AL 2 , AL 3 . Alternatively, the diameter D 2  may not coincide with twice the radius R 1  of each of the arc lengths AL 1 , AL 2 , AL 3 . The apices  50  ( FIG. 4 ) of the respective projections  46   a ,  46   b ,  46   c  are tangent to a circle  102  ( FIG. 2 ) concentric with the aperture  42  and having a diameter D 3 . Preferably, the ratio of the diameter D 3  to the diameter D 2  is between about 0.92:1 and about 0.98:1. In the illustrated construction of the engine component assembly  10 , the ratio of the diameter D 3  to the diameter D 2  is about 0.95:1. 
     To manufacture the engine component  14 , the body of the component  14  is first created (e.g., using a powdered metal process, a casting process, a forging process, etc.). Then, the projections  46   a ,  46   b ,  46   c  are machined into the body of the engine component  14  such that the projections  46   a ,  46   b ,  46   c  are integral with the engine component  14  as a single piece. To machine the projections  46   a ,  46   b ,  46   c , a drill bit having a diameter coinciding with the diameter of the first cylinder  66  is used during a first boring process to bore a hole into the body of the engine component  14 , from the top of the engine component  14 , that is coaxial with the axis  70  (see  FIG. 4 ) to create the arc length AL 3 . The drill bit is then used in a second boring process, in which the bit is aligned with the axis  78 , to create the arc length AL 1 . The drill bit is then used in a third boring process, in which the bit is aligned with the axis  94 , to create the arc length AL 2 . The projections  46   a ,  46   b ,  46   c , with an axial length L 1  corresponding to the axial length L 2  of the aperture, are created from the first, second, and third boring processes. 
     As mentioned above, the first, second, and third boring processes are performed with the drill bit being inserted from the top of the engine component  14 . After the first, second, and third boring processes are completed, the engine component  14  is re-oriented such that the drill bit may be inserted from the bottom of the engine component  14  (shown in  FIG. 5 ). A series of three additional boring processes is used to create the circular profile of the aperture  42  beneath the projections  46   a ,  46   b ,  46   c . With reference to  FIG. 5 , the drill bit is aligned with the axis  70 ′, which corresponds with the position of the axis  70  if the axis  70  were angularly shifted about the central axis  48  in a clockwise direction by about 60 degrees relative to the top view of the engine component  14  in  FIG. 4 . Then, the drill bit is plunged into the bottom of the engine component  14  during a fourth boring process to remove some of the material that is left over from the first and second boring processes. However, the drill bit is only partially plunged through the engine component  14 , thereby leaving the projection  46   a  after completion of the fourth boring process. 
     Likewise, the drill bit is then aligned with the axis  78 ′, which corresponds with the position of the axis  78  if the axis  78  were angularly shifted about the central axis  48  in a clockwise direction by about 60 degrees relative to the top view of the engine component  14  in  FIG. 4 . The drill bit is plunged into the bottom of the engine component  14  during a fifth boring process to remove some of the material left over from the second and third boring processes. However, the drill bit is only partially plunged through the engine component  14 , thereby leaving the projection  46   b  after completion of the fifth boring process. Finally, the drill bit is aligned with the axis  94 ′, which corresponds with the position of the axis  94  if the axis  94  were angularly shifted about the central axis  48  in a clockwise direction by about 60 degrees relative to the top view of the engine component  14  in  FIG. 4 . The drill bit is plunged into the bottom of the engine component  14  during a sixth boring process to remove some of the material left over from the first and third boring processes. However, the drill bit is only partially plunged through the engine component  14 , thereby leaving the projection  46   c  after completion of the sixth boring process. The boring processes discussed above include machining a pre-manufactured engine component body. Alternatively, the fourth, fifth, and sixth boring processes may be substituted with a single boring process using a drill bit having a diameter corresponding with the machined diameter D 2  of the aperture  42 . As a further alternative, the projections  46   a ,  46   b ,  46   c  may be integrally formed with the body of the engine component  14  as a single piece, during the creation of the engine component body itself (e.g., using a powdered metal process, a casting process, a forging process, etc.). 
     To unitize the fastener  18  and the engine component  14 , the shank  26  is initially aligned with the central axis  48  and inserted into the aperture  42 . During insertion of the shank  26  into the aperture  42 , the threaded portion  34  of the fastener  18  contacts the projections  46   a ,  46   b ,  46   c , thereby preventing continued axial movement of the fastener  18  into the aperture  42 . Then, the fastener  18  is rotated in a clockwise direction (i.e., for right-handed threads) to at least partially deform at least one thread into each of the discrete projections  46   a ,  46   b ,  46   c . As the fastener  18  forms the threads in the discrete projections  46   a ,  46   b ,  46   c , the fastener  18  also moves axially into the aperture  42 . The fastener  18  is capable of forming threads into the engine component  14  because the fasteners  18  (i.e., at least the first few threads of the threaded portion  34 ) are made from a harder material than the engine component  14 . Also, because the three discrete projections  46   a ,  46   b ,  46   c  are used on the engine component  14  to simulate “point” contact with the fastener  18 , and the ratio of the diameter D 3  to the diameter D 2  is between about 0.92:1 and about 0.98:1, the fasteners  18  may be hand-threaded into the aperture  42  without the aid of tools. In other words, the projections  46   a ,  46   b ,  46   c  need not be pre-threaded before insertion of the fastener  18  into the aperture  42 , thereby eliminating a manufacturing process (e.g., threading the projections  46   a ,  46   b ,  46   c  prior to insertion of the fastener  18 ) and its associated costs. 
     Upon continued rotation of the fastener  18 , the threaded portion  34  of the fastener  18  eventually disengages the projections  46   a ,  46   b ,  46   c , such that the projections  46   a ,  46   b ,  46   c  are in facing relationship with the necked portion  30 . In other words, once the threaded portion  34  of the fastener  18  disengages the projections  46   a ,  46   b ,  46   c , the fastener  18  may be axially slidable within the aperture  42  by an amount corresponding to the length of the necked portion  30 .  FIG. 6  illustrates the fastener  18  in a first position with respect to the engine component  14 , in which the threaded portion  34  of the shank  26  is engaged with the projections  46   a ,  46   b ,  46   c  to prevent removal of the shank  26  from the aperture  42 . In other words, the threaded portion  34  is engageable with the projections  46   a ,  46   b ,  46   c  to provide an axial stop for limiting movement of the fastener  18  relative to the engine component  14 .  FIG. 7  illustrates the fastener  18  in a second position with respect to the engine component  14 , in which the head  22  is engaged with the top of the engine component  14 . Because the necked portion  30  has a smaller diameter than that of the projections  46   a ,  46   b ,  46   c , the fastener  18  is axially movable between the first and second positions without being rotated. However, should one desire to remove the fastener  18  from the aperture  42 , the fastener  18  must be positioned to re-engage the threaded portion  34  and the projections  46   a ,  46   b ,  46   c , and then rotated in a counterclockwise direction to unscrew the fastener  18  from the engine component  14 . 
     The projections  46   a ,  46   b ,  46   c  facilitate handling of the fastener  18  and the engine component  14  as a unit, without substantial concern that the fastener  18  and the engine component  14  may become unintentionally separated. For example,  FIGS. 6 and 7  illustrate the retention of the fastener  18  to the engine component  14  while the engine component  14  is situated in an inverted orientation and a non-inverted orientation, respectively. When the engine component  14  is handled in an inverted orientation ( FIG. 6 ), the threaded portion  34  of the shank  26  is abutted or engaged with the projections  46   a ,  46   b ,  46   c , such that the fastener  18  is prevented from falling out of the aperture  42  by the engine component  14  itself. When the engine component  14  is handled in a non-inverted or upright orientation ( FIG. 7 ), the head  22  of the fastener  18  is directly supported on the engine component  14 . As a result, the movement of the fastener  18  relative to the engine component  14  is constrained between the first position, in which the threaded portion  34  and the projections  46   a ,  46   b ,  46   c  are engaged ( FIG. 6 ), and the second position, in which the head  22  of the fastener  18  is directly supported on or engaged with the engine component  14  ( FIG. 7 ). 
       FIG. 8  illustrates a second construction of a unitized component assembly  106  according to the invention. The assembly  106  includes a component (e.g., an engine component  110 ) and a fastener  18  coupled to the engine component  110 . Although the illustrated engine component  110  is a rocker arm pivot, the engine component  110  may be configured as any of a number of different components that are secured to the engine using the fastener  18 . The fastener  18  is substantially identical to the fastener  18  utilized with the engine component assembly  10  of  FIG. 1 . Therefore, like reference numerals are used to describe like features of the fastener  18 . 
     The engine component  110  includes an aperture  114  ( FIG. 8 ) and a plurality of discrete projections  118   a ,  118   b ,  118   c  ( FIG. 9 ) extending into the aperture  114 . As shown in  FIG. 9 , the projections  118   a ,  118   b ,  118   c  are spaced apart from one another about the perimeter of the aperture  114 . Specifically, the engine component  110  includes three projections  118   a ,  118   b ,  118   c  that are equidistantly spaced from each other by an angle A of about 120 degrees with respect to a central axis  122  of the aperture  114 . Each of the projections  118   a ,  118   b ,  118   c  includes a radially inwardly-extending, arcuate surface  126 . 
     With continued reference to  FIG. 9 , the projections  118   a ,  118   b  are separated from each other by an arc length AL 4  defined by a constant radius R 3  with respect to the central axis  122 . Likewise, the projections  118   b ,  118   c  and the projections  118   c ,  118   a  are separated from each other by respective arc lengths AL 5 , AL 6  each defined by the constant radius R 3  with respect to the central axis  122 . The arcuate surfaces  126  of the respective projections  118   a ,  118   b ,  118   c  are each defined by a constant radius R 4 . 
     With reference to  FIG. 8 , each of the projections  118   a ,  118   b ,  118   c  includes an axial length L 3  that is less than the axial length L 4  of the aperture  114 . Specifically, the ratio of the axial length L 3  of each of the projections  118   a ,  118   b ,  118   c  to the axial length L 4  of the aperture  114  is about 0.07:1 or less. In the illustrated construction of the engine component assembly  106 , the projections  118   a ,  118   b ,  118   c  are positioned toward the upper end of the aperture  114 . Alternatively, the projections  118   a ,  118   b ,  118   c  may be positioned toward the bottom end of the aperture  114 , the middle of the aperture  114 , or at any location along the length of the aperture  114 . 
     With continued reference to  FIG. 8 , the aperture  114  includes a substantially circular cross-section, defining a diameter D 4 , below the projections  118   a ,  118   b ,  118   c . In the illustrated construction of the engine component assembly  106 , the diameter D 4  is equal to twice the radius R 3  of each of the arc lengths AL 4 , AL 5 , AL 6 . Alternatively, the diameter D 4  may not coincide with twice the radius R 3  of each of the arc lengths AL 4 , AL 5 , AL 6 . With reference to  FIG. 9 , the radially inwardly-facing arcuate surfaces  126  of the respective projections  118   a ,  118   b ,  118   c  each include a curvature defined by a circle  130  concentric with the aperture  114  and having a diameter D 5 . Preferably, the ratio of the diameter D 5  to the diameter D 4  is between about 0.92:1 and about 0.98:1. In the illustrated construction of the engine component assembly  106 , the ratio of the diameter D 5  to the diameter D 4  is about 0.95:1. In the illustrated construction of the engine component assembly  106 , the diameter D 5  is equal to twice the radius R 4  of each of the projections  118   a ,  118   b ,  118   c . Alternatively, the respective surfaces  126  of the projections  118   a ,  118   b ,  118   c  may not be defined by the constant radius R 4 , such that one or more portions of each of the projections  118   a ,  118   b ,  118   c  may be tangent with the circle  130 . 
     With continued reference to  FIG. 9 , the arcuate surfaces  126  of the respective projections  118   a ,  118   b ,  118   c  each include an arc length AP. In the illustrated construction of the engine component assembly  106 , the arc length AP of each of the projections  118   a ,  118   b ,  118   c  is about 20 degrees. Alternatively, the arc length AP of each of the projections  118   a ,  118   b ,  118   c  may be greater than or less than about 20 degrees. To facilitate hand-threading the fastener  18  to the engine component  14  as discussed below, the ratio of the sum of the arc lengths AP of the respective projections  118   a ,  118   b ,  118   c  to the circumference of the aperture  114  (i.e., an arc length of 360 degrees) is between about 0.15:1 and about 0.20:1. In the illustrated construction of the engine component assembly  106 , the ratio of the sum of the arc lengths AP of the respective projections  118   a ,  118   b ,  118   c  to the circumference of the aperture  114  is about 0.17:1. 
     To manufacture the engine component  110 , the projections  118   a ,  118   b ,  118   c  are integrally formed with the body of the engine component  110  as a single piece (e.g., using a powdered metal process, a casting process, a forging process, etc.). The illustrated engine component  110  is manufactured as a single piece using a powdered metal process. Alternatively, one or more machining processes may be employed to create the projections  118   a ,  118   b ,  118   c  subsequent to creation of the body of the engine component  110 . 
     The fastener  18  may be unitized to the engine component  110  using the same process described above, in which the threaded portion  34  of the fastener  18  is hand-threaded into the aperture  114 , without the aid of tools, to at least partially deform at least one thread into each of the projections  118   a ,  118   b ,  118   c . In other words, the projections  118   a ,  118   b ,  118   c  need not be pre-threaded before insertion of the fastener  18  into the aperture  114 , thereby eliminating a manufacturing process (e.g., threading the projections  118   a ,  118   b ,  118   c  prior to insertion of the fastener  18 ) and its associated costs. After the fastener  18  is unitized to the engine component  110 , the threaded portion  34  is engageable with the projections  118   a ,  118   b ,  118   c  to provide an axial stop for limiting movement of the fastener  18  relative to the engine component  110 . As a result, engagement of the threaded portion  34  and the projections  118   a ,  118   b ,  118   c  substantially prevents removal of the shank  26  from the aperture  114 . 
       FIGS. 11-13  illustrate a component (e.g., an engine component  150 ) for use with a third construction of a component assembly according to the invention. Although the illustrated engine component  150  is a rocker arm pivot, the engine component  150  may be configured as any of a number of different components that are secured to the engine using the fastener  18  shown in  FIGS. 1 and 6-8 . Although not shown, the fastener  18  of  FIGS. 1 and 6-8  may be unitized to the engine component  150  in a similar manner as described above with reference to the engine component assemblies  10 ,  106 . 
     With reference to  FIGS. 11-13 , the engine component  150  includes an aperture  154  and a plurality of discrete projections  158   a ,  158   b ,  158   c  extending into the aperture  154 . As shown in  FIG. 12 , the projections  158   a ,  158   b ,  158   c  are spaced apart from one another about the perimeter of the aperture  154 . Specifically, the engine component  150  includes four projections  158   a ,  158   b ,  158   c  (only three of which are visible in  FIGS. 11-13 ) that are equidistantly spaced from each other by an angle A of about 90 degrees ( FIG. 11 ) with respect to a central axis  162  of the aperture  154 . With reference to  FIG. 12 , each of the projections  158   a ,  158   b ,  158   c  includes an apex  166  and respective surfaces  170 ,  174  on either side of the apex  166 . In the illustrated construction of the engine component  150 , each of the surfaces  170 ,  174  is substantially flat. Alternatively, the respective surfaces  170 ,  174  of each of the projections  158   a ,  158   b ,  158   c  may include a curvature (e.g., a generally concave or convex curvature). 
     With reference to  FIG. 13 , each of the projections  158   a ,  158   b ,  158   c  includes an axial length L 5  that is less than the axial length L 6  of the aperture  154 . Specifically, the ratio of the axial length L 5  of each of the projections  158   a ,  158   b ,  158   c  to the axial length L 6  of the aperture  154  is about 0.150:1 or less. In the illustrated construction of the engine component  150 , the projections  158   a ,  158   b ,  158   c  are positioned toward the upper end of the aperture  154 . Alternatively, the projections  158   a ,  158   b ,  158   c  may be positioned toward the bottom end of the aperture  154 , the middle of the aperture  154 , or at any location along the length L 6  of the aperture  154 . The aperture  154  includes a substantially circular cross-section, defining a diameter D 6 , below the projections  158   a ,  158   b ,  158   c . The apices  166  of the respective projections  158   a ,  158   b ,  158   c  are tangent to a circle  178  ( FIG. 12 ) concentric with the aperture  154  and having a diameter D 7  ( FIG. 13 ). Preferably, the ratio of the diameter D 7  to the diameter D 6  is between about 0.92:1 and about 0.98:1. In the illustrated construction of the engine component  150 , the ratio of the diameter D 7  to the diameter D 6  is about 0.95:1. 
     The projections  158   a ,  158   b ,  158   c  may also be sized to include a radial dimension R 5  ( FIG. 13 ), extending radially inwardly from the wall defining the aperture  154  toward the central axis  162 , such that about 50% or less of the thread depth of the fastener  18  is engaged with the projections  158   a ,  158   b ,  158   c  when the fastener  18  is unitized with the engine component  150 . In the illustrated construction of the engine component  150 , the projections  158   a ,  158   b ,  158   c  are sized having a radial dimension R 5  such that about 50% of the thread depth of the fastener  18  is engaged with the projections  158   a ,  158   b ,  158   c  when unitized with the engine component  150 . As shown in  FIG. 13 , the inner extent of the radial dimension R 5  is aligned with the apex  166  of the projection  158   a.    
     To manufacture the engine component  150 , the projections  158   a ,  158   b ,  158   c  are integrally formed with the body of the engine component  150  as a single piece (e.g., using a powdered metal process, a casting process, a forging process, etc.). The illustrated engine component  150  is manufactured as a single piece using a powdered metal process. Alternatively, one or more machining processes may be employed to create the projections  158   a ,  158   b ,  158   c  subsequent to creation of the body of the engine component  150 . 
     The fastener  18  (see  FIGS. 1 and 6-8 ) may be unitized to the engine component  150  using the same process described above, in which the threaded portion  34  of the fastener  18  is hand-threaded into the aperture  154 , without the aid of tools, to at least partially deform at least one thread into each of the projections  158   a ,  158   b ,  158   c . In other words, the projections  158   a ,  158   b ,  158   c  need not be pre-threaded before insertion of the fastener  18  into the aperture  154 , thereby eliminating a manufacturing process (e.g., threading the projections  158   a ,  158   b ,  158   c  prior to insertion of the fastener  18 ) and its associated costs. After the fastener  18  is unitized to the engine component  150 , the threaded portion  34  is engageable with the projections  158   a ,  158   b ,  158   c  to provide an axial stop for limiting movement of the fastener  18  relative to the engine component  150 . As a result, engagement of the threaded portion  34  and the projections  158   a ,  158   b ,  158   c  substantially prevents removal of the shank  26  from the aperture  154 . 
     Various features of the invention are set forth in the following claims.