MXPA00000970A - Self-riveting fastening element - Google Patents

Abstract

An improved self-riveting fastening element for permanent attachment to a metal panel within a panel opening by a die member having an annular concave die cavity. The fastening element includes a tubular riveting portion and a radial flange portion and a fastening portion. The internal and external surfaces of the tubular riveting portion are relatively uniformly inclined toward the radial flange portion such that the thickness of the tubular riveting portion at the free end is less than the thickness adjacent the radial flange portion. In the preferred embodiment, the internal surface of the tubular riveting portion is cylindrical and the external surface is slightly conical tapering inwardly toward the free end to reduce the force required to radially deform the free end of the tubular portion radially outwardly. Further, the outer surface of the radial flange portion is generally polygonal having arcuately radially inwardly concave side surfaces spaced by relative thin convex arcuate edge surfaces reducing the force required to drive the flange portion into the panel during final installation of the fastening element.

Description

SELF-REACHED FASTENER ELEMENT FIELD OF THE INVENTION The present invention relates to an improved self-clamping or self-joining fastener element, preferably a male fastener element of self-marking such as a stud, bolt or the like, which is attached to a panel in a hole in the panel. More specifically, the present invention relates to a self-locking fastener element having a tubular rivet portion that is received through a hole in the panel in a concave annular die cavity to permanently rivet the fastener element to the panel.

BACKGROUND OF THE INVENTION The self-locking male fastener elements of the type described herein were first developed by Profil Verbindungstechni GmbH & Ce .. KG de Alemán- '\, a company related to the assignee of the present application, as described in U.S. Patent No. 5,092,724. The fastener includes a tubular or annular piercing and riveting portion or barrel portion which, in the preferred embodiment, pierced a hole in the panel which is then received through the panel hole in a die element having a cavity of annular concave die. The die then deforms the free end of the barrel portion or rivets radially outward to permanently attach the fastener element to the panel. The fastener element is furthermore a radial flange portion which is moved to the panel as •• as e '.

The free end of the tubular rivet portion is deformed radially outwardly to form a stiff firm installation in a panel. In the preferred embodiment, the fastener element further includes an integral male fastener portion with the radial flange or body portion coaxially aligned with the tubular rivet portion. Female fastener elements of this type were also developed, where the body portion includes an internal thread that forms a nut-type fastener. Alternatively, the hole may be smooth to receive a self-rolling or self-tapping screw or bolt. Self-joining fastener elements of this type have been widely used in particular in automotive and other applications that require a secure rigid installation of a fastener element such as a stud, bolt, or nut in a metal panel or sheet metal including body panels, supports, structural elements and the like. However, self-piercing fastener elements of this type are generally limited to applications where the metal panel has a thickness generally less than about 2.5 mm or 0.098 inches. In automotive applications, for example, a problem solved by the self-piercing fastener described in the above-referenced US Patent was to permanently attach a fastener element to relatively thin panels having a thickness of approximately 0.787 milli (0.031 inches) in thickness. a continuous operation. Later, fastener elements of this type were developed for the permanent joining of fastener elements in relatively thick or large gauge metal panels as described, for example, in U.S. Patent Nos. 4,713,872; 5,237,733; and 5,564,873. In applications that require the installation of a self-locking fastener element This type of large gauge metal panels having a thickness in the order of from about 2.03 to 6.35 mm (0.08 to 0.25 inches) or more, is first formed in the panel a hole configured for receiving the tubular riveting portion of the fastener element. The tubular riveting portion of the clamping element is then received through the panel hole in a concave annular die cavity and the clamping member approaches the punch element which deforms the free end of the tubular riveting portion radially outward, riveting permanently the fastener element to the panel. The fastener element may include a radial flange portion that is moved to the panel to trap the panel portion adjacent the panel hole and form a mortise assembly as described in U.S. Patent Nos. 5,237,733 and 5,564,873. Alternatively, the body portion may include a conical surface adjacent to the tubular riveting portion that forms a snap fit as described in U.S. Patent No. 4,713,872. In the most preferred embodiment, however, the body portion includes a radial flange portion that forms a stiffer and firmer fastener and panel assembly.

There are, however, problems in installing a self-locking fastener element of the type described having a radial flange portion for installation in larger gauge metal panels, particularly, but not exclusively, self-locking male fastener elements. A self-locking male fastener element, for example, is approximated to the die element by a plunger having an annular end portion surrounding the male fastener portion as described in the above-referenced US Patents. The annular drive surface of the plunger is moved against a surface The annular portion of the radial flange portion of the body portion of the fastener element deforms considerathe radial flange portion during installation as shown in Figure 9, described below, because of the force required for the installation. As described in the above-referenced US Patents, self-locking fasteners of this type are normally installed in a stamping press that generates several tons of force and the stamping press can simultaneously form the sheet or panel in a contoured shape. First, several tons of force are required to deform the free end of the tubular branch portion or barrel radially outward in the arcuate concave annular cavity, because of the extreme resistance to friction and large developed tangential stresses. These forces have been reduced by including an internal tapered conical surface at the free end of the self-tapping portion and by friction-resistant coatings; however, these approaches have not eliminated this problem. In addition, the force required to deform the radial flange portion of the self-locking fastener member to the panel results in additional deformation of the radial flange portion during final installation of the fastener element in the panel. During the installation of a self-clamping fastener of the type described above, the radial flange portion is deformed by the piston or plunger driving surface towards and to the tubular riveting portion and radially, resulting in less structural integrity of the assem bra and panel element. This problem has reduced the applications of this type of self-locking fastener element in larger gauge metal panels and problems after installation. As it is exposed later, this problem has been solved by the improved self-bonding fastener element of this invention by reducing the force required to install the self-fastening fastener element in a panel, thereby reducing the deformation of the radial flange portion during installation.

COMPENDIUM OF THE INVENTION As described above, the improved self-locking fastener element of this invention is designed for permanent attachment to a metal panel or sheet metal within a panel hole by a die element having an annular concave die cavity. The self-tapping fastener includes a tubular rivet portion having generally cylindrical inner and outer surfaces and a free end. The self-tapping fastener element further includes a radial flange portion integral with the tubular riveting portion opposite the free end having a larger diameter than the tubular barrel portion and adapted "to enter the panel when the tubular rivet portion is passed. through the panel hole to the annular die cavity Where the self-retaining fastener element is a male fastener element, the radial flange portion forms part of a body portion of the fastener element, which bypasses the tubular rivet portion and closes the end of the tubular barrel portion opposite the free end and a male fastener portion such as a stud or bolt is integral with the flange or body portion opposite the tubular riveting portion and is preferaaligned coaxially with the tubular portion This is how an annular drive surface is defined around of the male fastener portion. Where the self-retaining fastener element is installed in a preformed hole, as will be required for installation in higher-gauge panels, the tubular rivet portion is first aligned with the panel hole, then inserted through the panel hole by a plunger to a annular concave die cavity of a die element. The die element then deforms the free end of the tubular rivet portion radially outwardly preferably in the form of a hook or U and the radial flange portion is simultaneously moved to the panel which traps the panel metal between the rivet portion in the form of radially deformed hook and flange portion, forming a fixed assembly of bra and panel element. The force required to deform the free end of the tubular rivet portion in the concave punch cavity is greatly reduced by reducing the thickness of the tubular rivet portion adjacent to the free end, where the inner and outer surfaces of the tubular barrel portion generally The cylindrical members are inclined slightly towards the radial flange portion, such that the thickness of the tubular riveting portion increases uniformly from the free end toward the radial flange portion. In the most preferred embodiment of the self-retaining fastener element of this invention, the inner surface of the tubular riveting portion is cylindrical and parallel to the longitudinal axis of the tubular rivet portion and the outer surface is conically tapered towards the free end of the rivet portion. the riveted portion. Most preferably, the free end of the tubular rivet portion includes an outer arcuate surface that joins smoothly with the outer conical surface providing a smooth transition from the outer surface arched to the outer conical surface. The conical angle of the outer surface is between about one and five degrees or most preferably between two and three degrees. As more fully described below, this relatively simple modification of the tubular portion of riveting results in a considerable reduction in the force required to deform the free end of the tubular riveting portion radially outward, greater than ten percent. . The reduction of the required force is achieved without considerably reducing the strength of the hook-shaped deformed free end of the tubular riveting portion. The force required to move the radial flange portion of the self-locking fastener of this invention to the panel is reduced by arranging a plurality of arcuately radially concave inward surfaces on the radially outer or outer surface of the radial flange portion. This modification reduces the area of the radial flange portion moved to the panel adjacent to the hole and further increases the torque required to rotate the self-locking fastener relative to the panel, after installation. Torque resistance is also an important feature of a self-locking fastener member of the type described herein because the fastener element is used to attach a second element to the fastener and panel assembly. For example, the self-locking male fastener element of this invention may include an integral threaded pin portion extending from the panel. The bolt is then used to join an automotive component, for example, to the fastener and panel assembly which is fixed in place by a conventional nut. During the engagement of the nut, however, the bolt may be subjected to twisting forces, in particular when the nut is damaged or a thread nut or bolt is used and a torque wrench is used. The fastening portion can therefore be subjected to substantial torsional loads and must be able to withstand the rotation of the fastener element relative to the panel after installation. In the most preferred embodiment of the self-healing fastener element, the radial flange portion is generally polygonal having, for example, six or eight sides. The radially inwardly concave surfaces are defined on the lateral surfaces of the polygonal radial flange portion located between the points or edges. In the most preferred embodiment, the "edges" of the polygonal radial flange portion include a thin convex arcuate surface and the radially inwardly concave surfaces are located between the fine convex edges of the edges. The radially inwardly concave surfaces between the arcuate concave surfaces most preferably have a relatively large radius. The radius of curvature of the arcuate concave surfaces is defined such that the arc is spaced from the outer surface of the tubular rivet portion. In the most preferred embodiment, the radius of the arcuate radially concave inward surface is greater than the radius of the outer surface of the tubular rivet portion. Other advantages and meritorious features of the self-fastening fastener element of this invention method of installation will be better understood by the following description of the preferred embodiments, the claims and the accompanying drawings, the brief description of which follows.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an end perspective view of a preferred embodiment of a self-locking male fastener element of this invention. Fig. 2 is an end view of the embodiment of the self-locking male fastener element shown in Fig. 1. Fig. 3 is a partial sectional side view of Fig. 2 in the direction of the observation arrows 3-3. Figure 4 is a partially cross-sectional side view of the fastening element - self-tapping member of Figures 1 to 3 with the fastener located in a panel hole supported in a die element prior to installation. Figures 5 to 7 are side views partly in section of the self-locking fastener element illustrated in Figures 1 to 4 illustrating the installation of the self-locking male fastener element in a panel. Figure 8 is a graph comparing the installation forces of the improved self-locking fastener element of this invention with the aforementioned self-riveting fastener element. And Figure 9 is a side view in cross section illustrating the installation of a fastener element in a panel that does not include the improvements claimed herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 illustrate a preferred embodiment of the self-locking male fastener element 20 of this invention. The self-tapping male fastener element 20 includes a tubular or barrel portion 22, a polygonal radial flange portion 24 that forms a portion of the body portion 26 as shown in FIG.

Figure 3, and a male fastener portion 28 which in the embodiment described is threaded by 30 as shown in Figures 1 and 3. The tubular portion ds riveted 22 includes a free end 32 having an arched outer surface. 34 and an internal conical chamfered surface 36 well represented in Fig. 3. The tubular riveting portion 22 further includes an inner surface 38 and an outer surface 40 that are generally cylindrical. The radial flange portion further includes an annular drive surface 42 which in the described embodiment of the self-locking male fastener element surrounds the male fastener portion 28. As best shown in FIG. 2, the outer surface of the radial portion is generally polygonal. to the. which in the described embodiment includes eight "edges" '44 and eight side surfaces 46. As described, in the preferred embodiment of the self-stitching fastener element of this invention, side surfaces 46 include radially concave inwardly curved surfaces that They have a relatively large radius. The "edges" or corners 44 are most preferably fine convex arcuate surfaces; that is, the surfaces 44 have a relatively short arc length, but all have the same radius generated from the longitudinal axis A of the fastener. In a MIO fastener, for example, the arc length or "width" of the surfaces 44 will be 0.254 to 0.762 mm (0.010 to 0.30 'inch). These thin concave arcuate surfaces 44 are, however, important for the control of the fastener during installation. First, fasteners of this type are fed through a flexible plastic tube having an internal diameter only slightly larger than the diameter of the convex arcuate surfaces 44, and these ri The surfaces therefore control the orientation of the fasteners in the feed tube and prevent tilting. Second, the convex arcuate surfaces 44 control the position and orientation of the fastener in the installation head, which is important to properly orient the fastener for installation. The radius of curvature of the arcuate concave surfaces 46 is defined in such a way that the arc is preferably spaced from the outer surface 40 of the tubular portion remapped., as shown in Figure 2. Finally, the arcuate concave surfaces 46 end near the "edges", leaving the convex fine arcuate surfaces 44 for control of the fastener. In the preferred embodiment, the radius of the convex arcuate surfaces 44 is greater than the radius of the outer surface 40 of the tubular rivet portion 22. Further, as described above, the generally cylindrical inner and outer surfaces, 38 and 40 , respectively, of the tubular barrel portion 22 are relatively inclined, and Uniform to the radial flange portion 24 such that the thickness of the tubular riveting portion at the free end 32 increases uniformly to the portion of radial tab. Stated differently, the inner and outer surfaces 38 and 40 converge towards the free end 32 of the tubular rivet portion 22. In the most preferred embodiment, the inner surface 38 is cylindrical and parallel to the longitudinal axis A of the barrel portion. tubular 22 and the self-tapping male fastener element 20 in this embodiment, and the outer surface 40 is tapered tapering inward towards the free end 32 and joining smoothly with the arcuate surface 34 om is shown in Figure 3. The tapered angle B is preferably between one and five degrees and most preferably between two and three degrees. Having described a preferred embodiment of the self-locking male fastener element of this invention, the function and advantages of the improved fastener element will be better understood by the description of the installation method illustrated in Figures 4 to 7. As depicted in Figure 4, firstly A hole 50 is formed in the panel 52 configured and adapted to receive the fastener element 20. In the embodiment shown, the hole 50 is cylindrical or circular having an internal diameter that is larger than the external diameter of the outer surface 40 of the tubular riveting portion 22 and less than the diameter of the radial flange portion 24. The panel 52 is supported on a die element 54 having an annular concave die cavity 56 coaxially aligned with the hole in the panel. The die element further includes a central relief hole 58 in that the body portion 26 closes the end of the tubular rivet portion 22 opposite the free end 32 and the hole 58 allows air to escape during the installation of the fastener element 20, The fastener element 20 is installed by a plunger 60 which in the described embodiment includes a cylindrical hole 62 that receives the male stud or bolt portion 28 as shown in Figure 4. The free end of the plunger includes an annular driving surface 64 which engages the driven surface '42"of the radial flange portion during installation As previously described and more particularly in the aforementioned Patents, the fastener 20 is normally installed in a stamping press having a installation head attached to a roller of the stamping press (not shown) and the die or button element of matrix 54 is installed in the opposite stamp. A fastener element is then installed with each stroke of the stamping press. During installation, the riveting portion 22 is disposed through the hole 50 of the panel 52 in such a manner that the inner conical chamfered surface 36 of the free end 32 of the riveting portion 22 engages an inner surface of the annular concave die cavity. 56. The fastener element 20 is then ready for installation. The annular driving surface 64 of the plunger 60 is then moved against the annular surface 42 of the radial flange portion 24 which moves the conical conical surface 36 of the free end 32 of the riveting portion 22 against the annular concave die cavity 56. as shown in Fig. 5. This deforms the free end 32 of the riveting portion 22 radially outwardly as shown in Fig. 6. As the free end 32 of the tubular rivet portion becomes more deformed, the inner surface 38 'of the tubular barrel 22 is deformed against the annular concave die cavity 56 creating very substantial resistance to friction to further deformation. Finally, as shown in Figure 7, the tubular rivet portion is deformed to a hook shape 66 and the radial flange portion 24 is deformed to panel 54 by trapping portion 68 of the panel adjacent to the panel hole. The radial flange portion 24 is not deformed substantially radially outwardly or axially during the final installation of the fastener element 20 in the panel 52, forming a very secure and rigid installation. Figure 8 is a graph that sequentially compares the forces required to install the improved self-stitching fastener element of this invention with elements previous bras of this type. The X axis defines the path of the plunger 60 in the previous figures 4 to '7. The Y axis defines the force in thousands of pounds required for the installation of the fastener element 20 in the panel 52. Thus, the force required to install the improved self-locking male fastener element 20 described above is represented by the broken line 70. and the force required to install an identical self-tapping male fastener element that does not include a relatively inclined outer or inner conical surface and outer surfaces (38 and 40) or a radial flange portion 24 having arcuately radially concave inward surfaces 46 is shown at 72. Otherwise, the tested fasteners were identical. First, it should be noted that the rate of increase in force required to install the improved self-locking male fastener member 20 represented at 70 is relatively constant as compared to the force required to install a self-fastening male fastener element without the improvements as depicted in FIG. 72. This is important because the piston force of a stamping press is generally constant. The arcuate line 74 represents an arcuate concave surface 56 of the die cavity that has been traced in Figure 8 to allow the determination of the installation status of the self-locking male fastener element 20. At point 76, the radial flange portion 24 is moved first to the panel 54 just after the installation step shown in Figure 6. The graph depicted in Figure 8 thus allows a direct comparison of the improved self-crimped fastener element of this invention with such a fastener element which does not include the improvements claimed here. More specifically, it should be noted from Figure 8 that the force required for the installation of the ele- The self-tapping fastener before point 76 results only from the radial deformation of the tubular rivet portion 22. As noted above, the force indicated by line 70 is relatively constant and considerably less than the force required to install a fastener element. similar that does not include an outer conical surface 40. For example, at point 78, the force required to install the improved self-locking fastener element 20 of this invention is approximately twelve thousand pounds compared to approximately fifteen thousand pounds for an element Self-tapping fastener which does not include an outer conical surface 40 in the tubular riveting portion 22 or a tapered riveting portion. At the point 80 where the ra-dial flange portion 24 is moved to the panel 52 and the free end of the radial flange portion 24 is deformed to the final hook shape 66 as shown in Figure 7, the force is reduced from more than thirty-eight thousand pounds to about thirty-two thousand pounds as a result of the radially concave arcuate surfaces inwardly 46 on the outer surface of the radial flange portion. Expressed differently, it takes ten percent less energy to install a bra of improved design. As described above, these reductions in the force required to install the self-locking fastener element 20 results in substantially less deformation of the radial flange portion 24 during the installation of the self-locking fastener element of this invention and a set of Improved fastener element and panel. The final force at 82 is identical because the installation is now complete as shown in FIGS. 7, where the radial flange portion 24, the trapped portion 68 of the panel 52 and the hook shape 66 is a metal-to-metal laminate.

Any additional force would result in an excessive shock condition that should be avoided during installation. Figure 9 illustrates the problems associated with an installation of a self-locking fastener element 120 that does not include the improvements of this invention. That is, the tubular rivet portion does not include an outer conical surface 40 and the flange does not include arcuate concave surfaces 46 between the convex arcuate edges 44 as described above with respect to Figures 1 to 7. The side surfaces are flat Otherwise, the fastener 120 is identical to the fastener 20 described above. The installation force of the self-locking fastener element 120 is shown at 72 in FIG. 8 as described above. Figure 9 is similar to Figure 7 except that it represents only the right side of the assembly. The plunger 160 and the die member 154 are identical to the plunger 60 and the die member 54 shown in Figures 4 to 7. As described above, the plunger 160 includes a hole 162 that receives the male threaded portion 128 of the element. fastener 120. Male fastener portion 128 includes external threads 129 having a crest diameter slightly smaller than internal diameter 162 of the plunger. As described above, the tubular barrel portion is deformed on the concave annular die surface 156 to a hook shape 166 when the plunger moves the fastener 120 towards the die element 154. In addition, the radial flange portion 124 is moved to panel 152 as described. The greater force required to deform the tubular barrel portion to the hook-shaped end portion 166 and the greater force required to deform the flange portion 124 to the panel 152 as presented at 72 in FIG. 8 (compared to 70 for fastener 20), deforms radial flange portion 124 both radially and axially. In real installations, the radial flange portion 124 is axially deformed a distance C as shown in FIG. 9. In other words, FIG., the driven surface 142 was actually located at 125 prior to installation, but this surface was axially deformed to the position shown in Fig. 9. In addition, the flange portion 124 deforms radially outwardly as shown. This permanent deformation of the radial flange portion results in reduced structural integrity of the fastener and panel assembly and few applications of this type of fastener element in larger gauge metal panels. As will be understood by those skilled in the art, various modifications may be made to the self-fastening fastener element of this invention within the scope of the appended claims. For example, various male fastener portions 28 may be used including, for example, an unthreaded stud or ball joint or the improvements described herein may be used in connection with female fasteners where a threaded or non-threaded hole is provided through of the body portion 26 of the fastener element. It is also possible to use features of this invention in self-piercing and riveting fasteners of the type described above. The self-retaining fastener element of this invention is adapted in particular, but not exclusively for mass production applications such as those used by the automotive and home appliance industries, where the fastener element can be installed, for example, in low steel panels. carbon having a thickness in the order of from about 2.03 to 6.35 mm (0.08 to 0.25 inches) or more, such as SAE 1010 steel and the fastener can be formed of steel with medium carbon content, such as SAE 1035 steel and the fastener is preferably heat treated. As will be understood, however, the preferred material for the self-stitching fastener element of this invention will depend on the application that includes the panel metal.

Claims (20)

Claims

1. A self-tapping male fastener element for permanent attachment to a panel within a panel hole by a die element having an annular concave die cavity, said self-tapping fastener element including a tubular portion of riveting having generally inner and outer surfaces cylindrical and a free end, a radial flange portion integral with said tubular riveting portion opposite said free end having a larger diameter than said panel hole adapted to be inserted into said panel, and an integral male fastening portion with said portion of flange in front of said tubular riveting portion, said improved radial flange portion including a plurality of radially concavely spaced arcuate inwardly spaced surfaces that reduce the force required to introduce said flange portion into said panel and which increase the torque required to turn said ele- He claimed self-fastening bra with regard to said panel after installation.

2. The self-locking male fastening element defined in claim 1, wherein said flange portion is generally polygonal having a plurality of lateral surfaces separated by edges, said concave arcuate surfaces being defined radially inwardly on said lateral surfaces of said radial flange portion between said edges.

3. The self-locking male fastener element defined in claim 2, wherein said polygonal radial flange portion has at least six lateral surfaces and six edges and where each of said edges has a narrow arched outer convex surface.

4. The self-locking male fastening element defined in claim 1, wherein said generally cylindrical inner and outer surfaces of said tubular riveting portion are relatively inclined towards said radial flange portion such that the thickness of said tubular riveting portion at said end Free is less than the thickness adjacent said radial flange portion, thereby reducing the force required to radially deform said tubular riveting portion in said annular die cavity.

5. The self-locking male fastening element defined in claim 4, wherein said inner surface of said tubular riveting portion is cylindrical and parallel to the axis of said tubular riveting portion, and said outer surface is conical tapering uniformly toward said free end and said free end of said tubular riveting portion having an arcuate surface that is smoothly joined to said outer conical surface.

6. The self-locking male fastening element defined in claim 5, wherein said male fastening portion is a generally cylindrical stud portion having a diameter smaller than said radial flange portion and said radial flange portion including an annular surface surrounding said portion asparagus, adapted to receive an annular actuation element.

7. The self-retaining male fastener element defined nest in claim 5, wherein the conical angle of said outer conical surface of said tubular riveting portion is between one and five degrees.

8. A self-tapping fastener element for permanent attachment to a panel within a panel hole by a die element having an annular concave die cavity, said self-tapping fastener element including a tubular portion of riveting having inner and outer surfaces generally cylindrical and a free end, a radial flange portion integral with said tubular riveting portion opposite said free end, said tubular riveting portion including an outer surface having a diameter less than said panel hole and having said flange portion radial a greater diameter than said panel hole and adapted to be introduced into said panel when said free end of said tubular riveting portion deforms radially outwardly in said concave die cavitysaid radial flange portion having a polygonal side surface that includes at least six arcuate concave surfaces that reduce the force required to introduce said flange portion into said panel and that increase the torque required to rotate said self-crimped fastener element. in relation to said panel after installation.

9. The self-locking fastener element defined in claim 8, wherein said generally cylindrical inner and outer surfaces of said tubular riveting portion are slightly inclined relative to said radial flange portion such that the thickness of said tubular barrel portion at said end free is less than the thickness adjacent said radial flange portion, thereby reducing the force required to initially deform said tubular riveting portion in said annular die cavity.

10. The self-locking fastener element defined in claim 9, wherein said inner surface of said tubular riveting portion is cylindrical and parallel to the axis of said tubular riveting portion and said outer surface of said tubular riveting portion is tapered by uniformly tapering toward inwardly towards said free end and said free end of said tubular riveting portion having an arcuate surface which is smoothly joined to said outer conical surface.

11. The self-stitching fastener element defined in claim 8, wherein said polygonal side surface of said radial flange portion includes relatively thin convex arcuate surfaces and said arcuate concave surfaces are spaced apart by said convex arched edge surfaces having a relatively large diameter. large spacing of said outer surface of said tubular riveting portion.

12. A self-locking male fastener element for permanent attachment to a panel within a panel hole by a die element having an annular concave die cavity, said self-locking fastener member including a tubular rivet portion having a free end , an integral radial flange portion with said tubular riveting portion opposite said free end bridging said tubular riveting portion and having a larger diameter than said tubular portion for riveting, an integral male fastening portion with said radial flange portion facing said tubular riveting portion and coaxially aligned with said tubular riveting portion, said tubular riveting portion having an internal cylindrical surface extending parallel to the axis of said portion tubular riveting and an outer conical surface that tapers uniformly towards said free end and that joins smoothly with an arcuate outer surface of said free end in such a way that the thickness of said tubular riveting portion in said free end is less than the thickness of said tubular riveting portion adjacent said radial flange portion, thereby reducing the force required to radially deform said tubular riveting portion in said annular die cavity.

13. The self-stitching male fastener element defined in claim 12, wherein said flange portion includes a plurality of spaced-apart radially concave outwardly curved outer surfaces which reduce the force required to introduce said flange portion into said panel and which increase the torque required to rotate said self-locking male fastener element relative to said panel after installation. -

14. The self-clamping male fastening element defined in claim 13, wherein the outer surface of said radial flange portion is generally polygonal having at least six lateral surfaces separated by edge surfaces, said radially concave arcuate surfaces being spaced apart. inwards defined in each of said lateral surfaces of said radial flange portion by said surfaces of 2- "4 edge.

15. The self-stitching male fastener element defined in claim 13, wherein each of said edge surfaces is defined by a fine convex arcuate surface separating said concave surfaces radially inwardly and said convex-shaped arcuate edge surfaces having the same radius of curvature .

16. A self-tapping male fastener element for permanent attachment to a panel within a panel hole by a die element having an annular concave die cavity, said self-tapping male fastener element including a tubular rivet portion having a free end, an integral radial flange portion with said tubular riveting portion in front of said free end and an integral male fastening portion with said radial flange portion opposite said tubular riveting portion, said tubular riveting portion having a diameter less than said hole. panel for receiving through said panel hole a in said annular die cavity to deform said free end radially outwardly and said radial flange portion having a larger diameter than said panel hole to fit said panel, said tubular portion of riveted surfaces in The outer and outer generally cylindrical relatively inclined slightly uniformly towards said radial flange portion such that the thickness of said tubular riveting portion at said free end is less than the thickness of said tubular riveting portion adjacent said radial flange portion , thereby reducing the force required to initially deform said por- tubular riveting in said die cavity and said radial flange portion including a plurality of arcuately spaced arcuate radially inwardly concave surfaces that reduce the force required to introduce said flange portion into said panel and that increase the torque required to rotate said self-tapping male fastener element relative to said panel after installation.

17. The self-locking male fastener element defined in claim 16, wherein the outer surfaces of said radial flange portion are generally polygonal having a plurality of side surfaces each of which has a concave surface radially inwardly.

18. The self-locking male fastening element defined in claim 16, wherein said inner surface of said tubular barrel portion is cylindrical and parallel to the axis of said tubular barrel portion and said outer surface being tapered uniformly inward toward said free end and having said free end an arcuate outer surface that joins smoothly with said outer conical surface.

19. The self-locking male fastener element defined in claim 16, wherein the outer surface of said radial flange portion is polygonal having at least six side surfaces and six edge surfaces, each of said edge surfaces defined by a surface of relatively thin convex arcuate edge and said concave surfaces being defined radially inwardly in said lateral surfaces are- paced by said convex arched edge surfaces.

20. The self-locking male fastener element defined in claim 19, wherein the radius of curvature of said convex arcuate surfaces is greater than the radius of said outer surface of said tubular rivet portion.