Patent Publication Number: US-2022213919-A1

Title: Self-drilling self-tapping fastener

Description:
PRIORITY 
     This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 63/134,785, filed Jan. 7, 2021, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Fasteners are well known and widely used throughout the world to secure one object to another object. Various known fasteners include: (a) a head including a mechanical engaging structure engageable by a tool, (b) a shank extending from the head, and (c) a helical thread formation outwardly extending from the shank for frictionally engaging the objects into which the fastener is driven. Certain known self-drilling self-tapping fasteners have a shank that also includes a drill tip and at least one flute. The drill tip and the flute(s) enable the self-drilling self-tapping fastener to form holes in the objects into which the fastener is driven. 
     There is a continuing need for self-drilling self-tapping fasteners that have improvements to performance in one or more of the following categories without decreasing performance in any of the other categories: (i) drilling times; (ii) ductility; (iii) tapping torque; (iv) torsional strength; (v) tensile strength; and (vi) pullout force. 
     SUMMARY 
     The present disclosure provides a self-drilling self-tapping fastener that has: (1) an improved performance in drilling time and specifically a relatively lower drilling time, and (2) improved performance in pullout force and specifically a relatively higher pullout force, both without decreasing performance in any of the ductility, the tapping torque, the torsional strength, and the tension strength of such self-drilling self-tapping fastener. 
     In various embodiments of the present disclosure, the self-drilling self-tapping fastener includes a head, a shank integrally connected to and extending from the head and including a first shank portion and a second shank portion, and a helical thread formation integrally connected to and extending radially outwardly from the first shank portion and part of the second shank portion. The second shank portion defines a longitudinally extending first flute and a longitudinally extending second flute. The first flute extends through three threads of the thread formation on a first side of the second shank portion The second flute extends through three threads of the thread formation on a second side of the second shank portion and to a fourth thread formation on the second side of the second shank portion. The second shank portion includes a first chip breaker positioned in the first flute and a second chip breaker positioned in the second flute. The second shank portion includes a drill tip. The drill tip includes a first cutting blade having a first cutting edge and a second cutting blade having a second cutting edge. The first cutting edge and the second cutting edge are tapered toward each other. The second shank portion is suitably formed such as by milling or forging in various different embodiments of the present disclosure. The head, the shank, and the helical thread formation are specifically configured and sized such that the self-drilling self-tapping fastener has improved performance in drilling time and pullout force without decreased performance in any of the ductility, the tapping torque, the torsional strength, and the tension strength of the self-drilling self-tapping fastener. 
     Other objects, features, and advantages of the present disclosure will be apparent from the following detailed disclosure and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a side perspective view of one example embodiment of a self-drilling self-tapping fastener of the present disclosure. 
         FIG. 2  is a first side view of the self-drilling self-tapping fastener of  FIG. 1 . 
         FIG. 2A  is also a first side view of the self-drilling self-tapping fastener of  FIG. 1 , identical to  FIG. 2  but with dimensional indicators. 
         FIG. 2B  is an enlarged fragmentary first side view of the free end part of the second shank portion of the self-drilling self-tapping fastener of  FIG. 1 . 
         FIG. 3  is a second side view of the self-drilling self-tapping fastener of  FIG. 1 , with the self-drilling self-tapping fastener rotated 180 degrees from  FIG. 2 . 
         FIG. 3A  is also a second side view of the self-drilling self-tapping fastener of  FIG. 1 , identical to  FIG. 3  but with dimensional indicators. 
         FIG. 3B  is an enlarged fragmentary second side view of the end part of the second shank portion of the self-drilling self-tapping fastener of  FIG. 1 . 
         FIG. 4  is a third side view of the self-drilling self-tapping fastener of  FIG. 1 , with the self-drilling self-tapping fastener rotated 90 degrees in a first direction from  FIG. 2 . 
         FIG. 4A  is also a third side view of the self-drilling self-tapping fastener of  FIG. 1 , identical to  FIG. 4  but with dimensional indicators. 
         FIG. 5  is a fourth side view of the self-drilling self-tapping fastener of  FIG. 1 , with the self-drilling self-tapping fastener rotated 90 degrees is an opposite second direction from  FIG. 2 , and rotated 180 degrees from  FIG. 4 . 
         FIG. 6  is a bottom end view of the self-drilling self-tapping fastener of  FIG. 1 . 
         FIG. 6A  is also bottom end view of the self-drilling self-tapping fastener of  FIG. 1 , identical to  FIG. 6  but with dimensional indicators. 
         FIG. 7  is a top end view of the self-drilling self-tapping fastener of  FIG. 1 . 
         FIG. 8  is a fragmentary cross-sectional view of part of the self-drilling self-tapping fastener of  FIG. 1  taken substantially along line  8 - 8  of  FIG. 2 . 
         FIG. 9  is Table  1  showing a general parameter comparison of the self-drilling self-tapping fastener of  FIG. 1  and six example commercially available self-drilling self-tapping fasteners. 
         FIG. 10  is Table  2  showing a dimensional comparison of the self-drilling self-tapping fastener of  FIG. 1  and six example commercially available self-drilling self-tapping fasteners. 
         FIG. 11  is Table  3  showing ductility test results vs core hardness for the self-drilling self-tapping fastener of  FIG. 1  in comparison to six example commercially available self-drilling self-tapping fasteners. 
         FIG. 12  is Table  4  showing torsional strength vs root diameter test results for the self-drilling self-tapping fastener of  FIG. 1  in comparison to six example commercially available self-drilling self-tapping fasteners. 
         FIG. 13  is Table  5  showing tensile strength vs root diameter test results for the self-drilling self-tapping fastener of  FIG. 1  in comparison to six example commercially available self-drilling self-tapping fasteners. 
         FIG. 14  is Table  6  showing pullout force vs thread engagement test results for the self-drilling self-tapping fastener of  FIG. 1  in comparison to six example commercially available self-drilling self-tapping fasteners. 
         FIG. 15  is Table  7  showing drilling time/tapping torque vs point geometry test results for the self-drilling self-tapping fastener of  FIG. 1  in comparison to six example commercially available self-drilling self-tapping fasteners. 
     
    
    
     DETAILED DESCRIPTION 
     While the systems, devices, and methods described herein may be embodied in various forms, the drawings show and the specification describes certain exemplary and non-limiting embodiments. Not all components shown in the drawings and described in the specification may be required, and certain implementations may include additional, different, or fewer components. Variations in the arrangement and type of the components; the shapes, sizes, and materials of the components; and the manners of connections of the components may be made without departing from the spirit or scope of the claims. Unless otherwise indicated, any directions referred to in the specification reflect the orientations of the components shown in the corresponding drawings and do not limit the scope of the present disclosure. Further, terms that refer to mounting methods, such as mounted, connected, etc., are not intended to be limited to direct mounting methods but should be interpreted broadly to include indirect and operably mounted, connected, and like mounting methods. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the present disclosure and as understood by one of ordinary skill in the art. 
     Turning now to the drawings,  FIGS. 1, 2, 2A, 2B, 3, 3A, 3B, 4, 4A, 5, 6, 6A, 7, and 8  illustrate one example embodiment of the self-drilling self-tapping fastener of the present disclosure, generally indicated by numeral  50  and sometimes called the “fastener” herein for brevity.  FIGS. 9 and 10  show tables comparing the features and dimensions of the self-drilling self-tapping fastener  50  to six example commercially available self-drilling fasteners.  FIGS. 11, 12, 13, 14, and 15  show tables comparing various tests results on the self-drilling self-tapping fastener  50  to these same six example commercially available self-drilling self-tapping fasteners. 
     Various embodiments of the example fastener  50  are particularly configured for use in connecting steel objects (such as but not limited to connecting a ⅛ inch (0.315 cms) steel plate to a ¼ inch (0.635 cms) steel plate). However, the fastener may be employed for a variety of different uses in accordance with the present disclosure. In this example, fastener  50  is a #12-24×1¼ inch fastener. It should be appreciated that the fastener length may vary in other alternative embodiments of the present disclosure as further discussed below. 
     The fastener  50  has a longitudinal central axis X and includes: (a) a head  100 ; (b) a shank  200  integrally connected at one end to the head  100 ; and (c) a helical thread formation  400  integrally connected to and extending outwardly from parts of the shank  200 . The shank  200  includes a first shank portion  220  integrally connected to and extending from the head  100 , and a second shank portion  300  integrally connected to and extending from the first shank portion  220  opposite the head  100 . Line C in  FIG. 3A  illustrates the plane along which the first shank portion  220  is integrally connected to the second shank portion  300  in this example embodiment. The second shank portion  300  functions as the drilling portion of the shank  200  and enables the fastener  50  to be used to drill a hole in one or more objects into which the fastener  50  will be tapped, fastened and secured. 
     In this example embodiment, the head  100 , the shank  200 , and the thread formation  400  are monolithically formed. More specifically, in this example embodiment, the fastener  50  is made by: (1) cutting (or otherwise forming) a carbon steel member (not shown but further described below) that is sometimes initially called a blank having a suitable length and a suitable width; (2) then forming (such as by forging) the carbon steel member to form the head  100 ; (3) then forming (such as by forging or milling) the carbon steel member to form the second shank portion  300 ; (4) then forming (such as by roll threading) the carbon steel member to form the thread formation  400 ; (5) then heat treating the carbon steel member; and (6) then coating the carbon steel member with a suitable corrosion resistance coating and curing this coating on the carbon steel member. It should be appreciated that one or more suitable cleaning and/or deburring processes may be employed in accordance with the present disclosure to form the fastener  50 . 
     It should be appreciated that the self-drilling self-tapping fastener  50  of this example embodiment is made from a low carbon steel (such as but not limited to an AISI 1022 low carbon steel). It should be also be appreciated that the heat treatment of case hardening is to provide a hardened fastener surface, so that the fastener point can self-drill into steel objects, and the thread formation can self-tap its own way to engage with steel objects. It should further be appreciated that hardened fastener surface case depth should be maintained in a reasonable range because if the case depth is too deep, it can make the fastener too brittle. It should also be appreciated that the case hardening process also provides a lower fastener core hardness, which ensures that the fastener has enough ductility. If the core hardness is too high, it will make the fastener too brittle, and become vulnerable to hydrogen embrittlement failure and/or hydrogen assisted stress corrosion. It should further be appreciated that the fastener&#39;s coating not only provides corrosion protection, but also provides lubrication when the fastener drills into one or more steel objects. 
     The head  100  includes a generally annular bottom portion  110  and a top portion  140  integrally connected to the bottom portion  110 . The annular bottom portion  110  has an outer diameter of 0.412 inches (1.04648 cms) and a height of 0.035 inches (0.0889 cms). The annular bottom portion  110  has a bottom surface  112 , a top surface  114 , and a generally cylindrical outer edge  116  extending from and connect the bottom surface  112  to the top surface  114 . The outer edge  116  is somewhat rounded or convex along its entire surface. The bottom portion  110  is also integrally connected to the first shank portion  220 . In this example embodiment, as best shown in  FIG. 7 , the top portion  140  of the head  100  defines an external hexagonal mechanical engaging structure having six sides  142   a ,  142   b ,  142   c ,  142   d ,  142   e , and  142   f  that define an upper recessed portion  150 . The six sides  142   a ,  142   b ,  142   c ,  142   d ,  142   e , and  142   f  are engageable by an appropriate wrench or hex socket (not shown) configured to rotate and drive the self-drilling self-tapping fastener  50 . It should be appreciated that other suitable mechanical engaging structures (not shown) may be employed in accordance with the present disclosure, such as but not limited to: (1) a straight slot (engageable by a flathead screwdriver), (2) a cross-shaped slot (engageable by a Phillips head screwdriver), (3) an internal star or six lobe shaped cavity (engageable by a six lobe driver), or (4) an internal hexagonal shaped cavity (engageable by an Allen wrench). As also best shown in  FIG. 7 , the top portion  140  of the head  100  has six corners  144   a ,  144   b ,  144   c ,  144   d ,  144   e , and  144   f , respectively between sides  142   a  and  142   b ,  142   b  and  142   c ,  142   c  and  142   d ,  142   d  and  142   e ,  142   e  and  142   f , and  142   f  and  142   a.    
     In this example embodiment, the top portion  140  of the head  100  has a height of 0.150 inches (0.381 cms). The top portion  140  has an outer diameter of 0.306 inches (0.77724 cms) from side  142   a  to side  142   d , from side  142   b  to side  142   e , and from side  142   c  to side  142   f.  The top portion  140  has an outer diameter of 0.351 inches (0.89154 cms) from corner  144   a  to corner  144   d , from corner  144   b  to corner  144   e , and from corner  144   c  to corner  144   f.    
     The shank  200  has a length (LS) indicated in  FIG. 3A , which in this example embodiment is 1.245 inches (3.162 cms), and includes: (1) the first shank portion  220 ; and (2) the second shank portion  300 . 
     The first shank portion  220  is integrally connected to the head  100  at an inner end  222  and is integrally connected to the second shank portion  300  at an outer end  226 . The first shank portion  220  is annular and has a constant outer diameter (OD) from the inner end  222  (adjacent to the head  100 ) to the outer end  226  (adjacent to the second shank portion  300 ). This outer diameter in this example embodiment is 0.214 inches (0.544 cms). The first shank portion  220  has a length (LFSP) as indicated in  FIG. 3A  and which in this example embodiment is 0.632 inches (1.605 cms). 
     The second shank portion  300  includes an inner end  302  that is integrally connected to the first shank portion  220  and an outer end  306 . The outer end  306  is a free end and includes a drill tip  380  as described below. The second shank portion  300  is configured to enable the fastener  50  to be self-drilling. In particular, the second shank portion  300 : (1) defines a longitudinally extending first flute  310  (best seen in  FIGS. 1, 2, 2A, 2B, and 8 ); (2) defines a longitudinally extending second flute  330  (best seen in  FIGS. 3, 3A, 3B, and 8 ); (3) includes a first chip breaker  350  (best seen in  FIGS. 1, 2, 2A, 2B, and 8 ); (4) includes a second chip breaker  370  (best seen in  FIGS. 3, 3A, 3B, and 8 ); and (5) includes the drill tip  380 . 
     The second shank portion  300  is partially annular and has multiple different outer surfaces and outer diameters, as further described below. In this example embodiment, the second shank portion  300  has a length (LSSP) indicated in  FIG. 3A , and which in this example embodiment is 0.711 inches (1.806 cms). When viewed from the side shown in  FIGS. 1, 2, 2A, and 2   b , and the side shown in  FIGS. 3, 3A, and 3B , the second shank portion  300  has a first constant outer diameter until reaching the drill tip  380 . When viewed from the side shown in  FIGS. 4 and 4A , and the side shown in  FIG. 5 , the second shank portion  300  has a first decreasing outer width, until reaching the drill tip  380 . This decreasing outer width first decreases as at a greater angle and then decreases at a smaller angle. The elongated opposite outer surfaces  301  and  303  of the second shank portion  300  are rounded or convex and extend between the respective opposite flutes  310  and  330 . 
     The first flute  310  defined in the second shank portion  300  includes a longitudinally extending first surface  312  and a longitudinally extending second surface  320 . The longitudinally extending first surface  312  and the longitudinally extending second surface  320  meet along a longitudinally extending connection line  318  (best seen in  FIGS. 2, 2A, 2B, and 8 ). The first flute  310  narrows almost to a point at the first end  302  of the second shank portion  300 , widens toward the central section (not labeled) of the second shank portion  300 , and remains wide through the drill tip  380  to the second end  306  of the second shank portion  300  (as best seen in  FIGS. 1, 2, 2A, and 2B ). 
     Likewise, the second flute  330  defined in the second shank portion  300  includes a longitudinally extending first surface  332  and a longitudinally extending second surface  340 . The longitudinally extending first surface  332  and the longitudinally extending second surface  340  meet along a longitudinally extending connection line  338  (best seen in  FIGS. 3, 3A, 3B, and 8 ). The second flute  330  narrows almost to a point at the first end  302  of the second shank portion  300 , widens toward the central section (not labeled) of the second shank portion  300 , and remains wide through the drill tip  380  to the second end  306  of the second shank portion  300  (as best seen in  FIG. 3, 3A , and  3 B). 
     The first and second flutes  310  and  330  provide part of the self-drilling functionality of the fastener  50 , and particularly provide areas for the debris cut by the drill tip  380  and the chip breakers  350  and  370  to move along the length of the shank  200  of the fastener  50  and out of the hole(s) being formed by the fastener  50  in the objects to which the fastener will be tapped, fastened, and secured. 
     For each flute  310  and  330 , the flute length in this example embodiment is 0.141 inches (0.35814 cms). This is indicated by the P1 indications on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). It should be appreciated that this length is 0.060 inches (0.1524 cms) longer than the flute length of example Fastener-A as shown in  FIG. 10 . This longer flute length in part enables the fastener  50  to be drilled through one or more thicker objects. 
     For each flute  310  and  330 , the flute angle in this example embodiment is 13.6 degrees at one or more designated points along each respective flute. This is indicated by the P2 indications on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). 
     For each flute  310  and  330 , the flute relief length in this example embodiment is 0.711 inches (1.80594 cms). This is indicated by the P3 indication on  FIG. 2A  and on Table  2  ( FIG. 10 ). 
     As best shown in  FIG. 2B , the first chip breaker  350  of the second shank portion  300  includes first, second, third, and fourth connected surfaces  352 ,  354 ,  356 , and  358  positioned in the flute  330  adjacent the second end  306  of the second shank portion  300 . Likewise, as best shown in  FIG. 3B , the second chip breaker  370  of the second shank portion  300  includes first, second, third, and fourth connected surfaces  372 ,  374 ,  376 , and  378  positioned in the flute  360  adjacent the second end  306  of the second shank portion  300 . These chip breakers  350  and  370  of the second shank portion  300  reduce tapping torque by cutting chips into smaller pieces from the object(s) that the fastener  50  is/are tapping into, which in turn reduces jamming. The chip breakers  350  and  370  thus provide part of the self-drilling functionality of the fastener  50 , and particularly function with the drill tip  380  to form the hole(s) in the object(s) being formed by the fastener  50  in the object(s) to which the fastener will be tapped, fastened, and secured. 
     The drill tip  380  of the second shank portion  300  extends from a transition plane indicated by dotted reference line TP shown in  FIGS. 4, 4A, and 5  to the drill tip point  398 . The drill tip  380  has a length (LDT) or point height P7 indicated in  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ) which in this example embodiment is 0.060 inches (0.1524 cms). 
     As best shown in  FIGS. 2, 2A, 2B, 3, 3A, and 3B , the drill tip  380  includes: (1) a first cutting blade  382  having a first cutting edge  384 , a first cutting surface  385 , and an outer surface  386 ; and (2) a second cutting blade  392  having a second cutting edge  394 , a first cutting surface  395 , and an outer surface  396 . The first cutting blade  382  and the second cutting blade  392  are tapered toward each other and specifically the first cutting edge  384  and the second cutting edge  394  are tapered toward each other. 
     The outer diameter of the drill tip  380  decreases moving along the longitudinal axis X in the direction of or toward the pointed end  398  from: (1) a point outer diameter (OD) adjacent the transition plane TP of 0.199 inches (0.50546 cms) indicated by the P5 indication on  FIGS. 2A and 3A , to (2) an outer diameter of 0.005 inches (0.013 cms) at the drill point  398  indicated by the P11 indication on  FIG. 6A . 
     As best shown in  FIGS. 2A and 3A , the first cutting edge  284  extends at an angle P8 to the outer surface of the second shank portion  300 . The second cutting edge  294  also extend at an angle P8 to the outer surface of the second shank portion  300 . In this example embodiment, P8 which is called the point cutting edge angle is 110.6 degrees. 
     It should be appreciated that in this example embodiment, the drill tip  380  has a rounded point (and particularly a slightly rounded point). In certain embodiments, the drill tip  380  point is formed as a sharp point and slightly rounded during a finishing manufacturing process. In other embodiments, the drill tip  380  is otherwise suitably rounded or formed. In other embodiments of the present disclosure, the drill tip  380  is not rounded but rather formed with a sharp point. 
     It should also be appreciated that in this example embodiment, the drill tip  380  is preferably directly positioned along the longitudinal axis X as shown in  FIGS. 2, 2B, 3, and 3B , but may slightly vary from being along the longitudinal axis due to manufacturing tolerances. 
     The relief angle of the drill tip  380  in this example embodiment is 5.2 degrees. This is indicated by the P4 indication on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). 
     The point thickness of the drill tip  380  in this example embodiment is 0.119 inches (0.30226 cms). This is indicated by the P6 indication on  FIG. 4A  and on Table  2  ( FIG. 10 ). 
     The point flute angle of the drill tip  380  in this example embodiment is 90.0 degrees. This is indicated by the P9 indication on  FIG. 4A  and on Table  2  ( FIG. 10 ). 
     The drill point&#39;s web thickness of the drill tip  380  in this example embodiment is 0.013 inches (0.03302 cms). This is referred to herein as the drill point web thickness. This is indicated by the P10 indication on  FIG. 6A  and on Table  2  ( FIG. 10 ). 
     The center distance of the drill tip  380  in this example embodiment is 0.005 inches (0.0127 cms). This is indicated by the P11 indication on  FIG. 6A  and on Table  2  ( FIG. 10 ). 
     The flute detail radius of the drill tip  380  in this example embodiment is 0.011 inches (0.02794 cms). This is indicated by the P12 indication on  FIG. 6A  and on Table  2  ( FIG. 10 ). 
     The point outside radius of the drill tip  380  in this example embodiment is 0.072 inches (0.18288 cms). This is indicated by the P13 indication on  FIG. 6A  and on Table  2  ( FIG. 10 ). 
     The point eccentricity or total indicator reading (TIR) of the drill tip  380  in this example embodiment is 0.0023 inches (0.0058 cms) (but can be up to 0.005 inches (0.0127 cms) due to manufacturing tolerances) in accordance with the present disclosure. This is indicated by the P14 indication on Table  2  ( FIG. 10 ). It should be appreciated that for the purposes of the present disclosure, the point eccentricity or TIR is the difference between the maximum and minimum measurement readings of an indicator on the planar or cylindrical contoured surfaces of the drill tip  380  representing its/their respective amount(s) of deviation from flatness or roundness. It should also be appreciated that the extremely low point eccentricity or TIR of the drill tip  380  of the present disclosure maximizes the rotation of the second shank portion  300  with minimal deviation from along the longitudinal center axis X of the first and second shank portions  200  and  300  of fastener  50 . In various embodiments, this extremely low point eccentricity or TIR of the drill tip  380  is at least partially achieved in the fastener  50  by forging the second shank portion  300  of the fastener  50 , but it should be appreciated that such extremely low point eccentricity or TIR of the drill tip  380  could alternatively be achieved in the fastener  50  by milling the second shank portion  300  of the fastener  50  with extremely tight manufacturing tolerances. This configuration of the drill tip  380  and the second shank portion  300  is at least partially responsible for the relatively lower drilling time provided by the fastener  50  of the present disclosure. This configuration provides a more precise tapped thread (and/or slightly smaller hole(s)) in the object(s) in which the fastener  50  is tapped, fastened, and secured. This more precise tapped thread in the object(s) in combination with the enhanced thread engagement provided by the thread formation  400  (as described below) of the fastener  50  is considered to be at least partially responsible for the relatively higher pullout force provided by the fastener  50  of the present disclosure. 
     The helical thread formation  400  is integrally connected to and extends radially outwardly from respective sections of both the first and second portions  220  and  300  of the shank  200 . In this illustrated embodiment, the helical thread formation  400  extends along substantially the entire first shank portion  220  and an initial part of the second shank portion  300 . The helical thread formation  400  includes: (1) a first helical thread portion  420 ; and (2) a second helical thread portion  440 . 
     The helical thread formation  400  has a substantially constant outer diameter from start of the thread formation  400  adjacent to the head  100  to almost the end of the thread formation  400  on the second shank portion  300 . At the third thread from the end of the thread formation  400  on the second shank portion  300 , the outer diameter or height of the thread formation  400  begins to decrease until gradually terminating at the outer surface of the second shank portion  300 . In other words, once reaching that point, the outer diameter of the thread formation  400  tapers radially inwardly until reaching the outer surface of the second shank portion  300 . 
     The helical thread formation  400  has a length (LHTF) indicated on  FIG. 3A  which in this example embodiment is 0.659 inches (1.67386 cms). This is also indicated by the T4 indication on  FIG. 4A  and in  FIG. 10  Table  2 . 
     The root diameter to the head of the helical thread formation  400  in this example embodiment is 0.075 inches (0.1905 cms). This is indicated by the T2 indication on  FIG. 4A  and on Table  2  ( FIG. 10 ). 
     The thread outer diameter (OD) of the helical thread formation  400  in this example embodiment is 0.217 inches (0.55118 cms). This is indicated by the T3 indication on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). 
     The pitch distance of the helical thread formation  400  in this example embodiment is 12-24 tpi (and preferably 24 threads per inch (9.449 threads per cm). This is indicated by the T5 indication on  FIG. 4A  and on Table  2  ( FIG. 10 ). 
     The root outer diameter (OD) of the helical thread formation  400  in this example embodiment is 0.186 inches (0.47244 cms). This is indicated by the T6 indication on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). 
     The blank outer diameter (OD) of the helical thread formation  400  in this example embodiment is 0.195 inches (0.4953 cms). This is indicated by the T7 indication on Table  2  ( FIG. 10 ). 
     The thread at run-out of the helical thread formation  400  in this example embodiment is 1 thread, which means the thread outer diameter gradually decreased and merges with shank. This is indicated by the T8 indication on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). 
     The quantity of threads of the helical thread formation  400  that are adjacent the flutes in this example embodiment is 3 threads. This is indicated by the T9 indication on  FIGS. 2A and 3A  and on Table  2  ( FIG. 10 ). 
     The thread up taper of the helical thread formation  400  in this example embodiment is 0.002 (0.00508 cms). This is indicated by the T10 indication on Table  2  ( FIG. 10 ). 
     As mentioned above, the fastener  50  of the present disclosure provide a plurality of advantages. These advantages are shown in the tables discussed below. These tables are based on actual comparison tests on six commercially available self-drilling self-tapping fasteners and the fastener  50 . More specifically, as shown in Tables  1 ,  2 ,  3 ,  4 ,  5 ,  6 , and  7  respectively provided in  FIGS. 9, 10, 11, 12, 13, 14, and 15 , the fastener  50  has: (1) an improved performance in drilling time and specifically a relatively lower drilling time, and (2) an improved performance in pullout force and specifically a relatively higher pullout force, both without decreasing performance in any of the ductility, the tapping torque, the torsional strength, and the tension strength of the fastener  50 , in comparison to such other fasteners. 
     More specifically, Table  3  of  FIG. 11  shows ductility test results for the self-drilling self-tapping fastener  50  of  FIG. 1  in comparison to six example commercially available self-drilling self-tapping fasteners. Table  3  shows that the ductility of the fastener  50  is not different than the ductility of the six commercial fasteners. It should be appreciated that suitable fastener ductility is necessary to avoid hydrogen embrittlement failure, hydrogen assisted stress corrosion failure, and the effects of thermal expansion and contraction of the objects in which the fastener is tapped, fastened, and secured. It should be also be appreciated that industrial standards use suitable bend tests to evaluate a fastener&#39;s ductility. As shown in Table  3  of  FIG. 1 , the tests used to test the ductility of the fasteners tested was a 10 degree head bend test, and. five samples of each fastener were tested. All samples passed the 10 degree bend test except the Fastener-D sample. The failure appears to be due to such fasteners having a higher core hardness and a deeper case. It should thus be appreciated that core hardness and case depth are the two more important factors that determine the fastener&#39;s ductility. 
     Table  4  of  FIG. 12  shows torsional strength vs root diameter test results for the self-drilling self-tapping fastener  50  of  FIG. 1  in comparison to six commercially available self-drilling self-tapping fasteners. Table  4  shows that the torsional strength of the fastener  50  has the best torsional strength comparing to six commercial fasteners except the Fastener-D sample. It should be appreciated that in addition to material and heat treating, root diameter is one of the more important factors that determines a fastener&#39;s torsional strength (i.e., typically, the larger of root diameter, the higher of the torsional strength). It should also be appreciated that, as shown in Table  4 , the root diameter of Fastener-B, Fastener-A, and Fastener-F are 88%, 92%, and 84% of the fastener  50 , respectively, so their respective torsional strengths are lower than that of the fastener  50 , and only 76%, 76%, and 71% of the fastener  50 . It should also be appreciated that the Fastener-D has the highest torsional strength, not only because its root diameter is similar (101%) to the fastener  50 , but also because it has the highest core hardness. It should be appreciated that higher core hardness will provide higher torsional strength, but high core hardness will reduce fastener&#39;s ductility as mentioned above regarding ductility. Fastener-A has a similar root diameter as fastener  50 , so it has a good optimum balance of tensile strength and ductility. To reach the optimum balance of ductility and torsional strength, fastener  50  has a root diameter in the range of 0.183-0.189 inches (0.46482 to 0.48006 cms). 
     Table  5  of  FIG. 13  shows tensile strength vs root diameter test results for the self-drilling self-tapping fastener  50  of  FIG. 1  in comparison to six commercially available self-drilling self-tapping fasteners. Table  5  shows that the fastener  50  has the best tensile strength comparing to six commercial fasteners. It should also be appreciated that in addition to material and heat treating, root diameter is the more important factor that determines fastener&#39;s tensile strength (e.g., generally the larger the root diameter, the higher of the tensile strength). As Table  5  shows, the root diameter of Fastener-B, Fastener-A, and Fastener-F are 88%, 92%, and 84% of the fastener  50 , respectively, so their respective tensile strengths are lower than the fastener  50 , and only 72%, 82% and 83% of the fastener  50 . On the other hand, Fastener-A has a similar root diameter as fastener  50 , so it also has a comparable tensile strength. To reach the best performance of fastener tensile strength, the fastener  50  has a root diameter in the range of 0.183 to 0.189 inches (0.46482 to 0.48006 cms). 
     Table  6  of  FIG. 14  shows pullout vs thread engagement test results for the self-drilling self-tapping fastener  50  of  FIG. 1  in comparison to six commercially available self-drilling self-tapping fasteners. If fastener material, heat treatment, and thread profile are the same, screw thread engagement with the substrate, or the difference of thread OD and drill point OD, appears to be the more important factor that determines the fastener pullout value from the substrate (e.g., the larger the difference, the higher of the pullout value). However, the larger the difference, the harder it is for the threads to tap into the substrate, and thus the higher the tapping torque. Table  6  shows that the fastener  50  has the best pullout performance, followed by Fastener-A and Fastener-D that respectively have 97% and 96% of the pullout value of Fastener  50 . Fastener-D has 98% of thread engagement of fastener  50 , so it has 96% of the pullout value of fastener  50 . Fastener-A has a little larger thread engagement (101%) than fastener  50 , but a little lower pullout force (97%) than fastener  50  because Fastener-A has a larger point eccentricity, so the actual hole size Fastener-A drilled is larger than the point OD, which reduced its pullout value. Fastener-B, Fastener-C, Fastener-A, and Fastener-F have much lower pullout values (84%, 88%, 85%, 79%, respectively) since their thread engagements are also smaller (92%, 83%, 66%, 92% compared to fastener  50 ). Table  6  thus shows that the pullout force of the fastener  50  is significantly higher than the pullout force of each of the six commercial fasteners. It should be appreciated that if the fastener material, heat treatment, and thread profile are the same, the thread engagement with the steel object or the difference of thread OD and drill point OD thus appear to be the more important factor(s) that determine the fastener pullout value from an object (e.g., generally the larger of the difference the higher of the pullout value). It should further be appreciated that the larger the difference, the harder for the threads to tap into the object(s), or the higher the tapping torque will be. It should also be appreciated from Table  6  that the fastener  50  has the best pullout value in part due to the thread engagement of around 0.018 inches (0.046 cms). To reach the best pullout performance and a reasonable drill tapping torque, the fastener  50  has a thread engagement in the range of 0.018 to 0.019 inches (0.0457 to 0.0483 cms), and the drill point eccentricity is less than 0.005 inches (0.00127 cms). It should be appreciated that this drill point eccentricity may be achieved via forging the second shank portion  300  or by milling this second shank portion with tight manufacturing tolerances. 
     It should further be appreciated that to reach the best pullout performance and at the same time to keep the tapping torque at a reasonable low level, the fastener  50  has a second shank portion  300  with the combination of the chip breakers and the thread formation  400  with only 3 threads at the flute transition section on one side of the fastener  50 . 
     Table  7  of  FIG. 15  shows drilling time/torque vs point geometry test results for the self-drilling self-tapping fastener  50  of  FIG. 1  in comparison to six commercially available self-drilling self-tapping fasteners for both tests on ⅜ inch thick steel plate and ½ inch thick steel plate. As mentioned above, Table  7  shows that the drilling time of the fastener  50  is significantly lower than the drilling times of each of the six commercial fasteners. These comparisons show that drill point geometry is an important factor that determines drilling time. Generally, the sharper the drill point is, the faster it can drill into a steel substrate, and the less drilling time is needed to drill through the steel substrate. However, since the self-drilling self-tapping fastener  50  must be able to drill through at least ½ inch thick steel plate, if the drill point is too sharp, it will be worn easily, and then cannot drill through such substrate or may need more time to do so. Thus, the drill point sharpness of the fastener  50  appears to be important in obtaining this lowest drilling time. The fastener  50  has a cutting edge center distance in the range of 0.003 inches to 0.005 inches, a drill point web thickness in the range of 0.010 inches to 0.015 inches, and a point cutting edge angle in the range of 109 to 111 degrees. These features appear to provide the fastener  50  with this significantly lower drilling time. It should be appreciated from the above that the fastener  50  has: (1) an improved performance in drilling time and specifically a relatively lower drilling time, and (2) an improved performance in pullout force and specifically a relatively higher pullout force, all without decreasing performance in any of the comparative ductility, tapping torque, torsional strength, or tension strength of the fastener  50 , when compared to various known commercially available self-drilling self-tapping fasteners of the similar size and form. 
     It should be appreciated that the above dimensions are subject to reasonable variation due to manufacturing tolerances in accordance with the present disclosure. It should also be appreciated that the above dimensions are based on actual measurements and thus take into account manufacturing tolerances. It should further be appreciated that the actual designed dimensions may be different and result in such actual manufacturing tolerances in accordance with the present disclosure. 
     In further embodiments of the present disclosure, the fastener length may vary. In one example alternative embodiment, the fastener is a #12-24×1½ inch fastener and is ¼ inches longer than fastener  50 . In another example alternative embodiment, the fastener  50  is a #12-24×1¾ inch fastener and is ½ inches longer than fastener  50 . In another example alternative embodiment, the fastener  50  is a #12-24×2.0 inch fastener and is ¾ inches longer than fastener  50 . In these example alternative embodiments, the respective thread lengths have increased by a ¼ inch, a ½ inch, and ¾ inches for each of above respective fasteners, but the other dimensions are identical. 
     It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, and it is understood that this application is to be limited only by the scope of the claims.