Method of forming a nut and panel assembly
United States Patent 1191 Ladouceur et al.  
 14 1 Apr. 22, 1975 METHOD OF FORMING A NUT AND PANEL ASSEMBLY Inventors: Harold A. Ladouceur, Livonia; John H. Steward, Bloomfield, both of Mich.  
 Multifastener Corporation, Detroit, Mich.  
 Filed: Sept. 14, 1973 Appl. No.: 397,559  
 Related US. Application Data Continuation-impart of Scr. No. 63,316, Aug. l2,  
 Assignee:  
 I970. abandoned, which is a division of Ser. No.  
 84l ,037, July ll, I969, abandoned.  
 u.s. c1. 29/4322; 29/509; 29/523; 151/4113 Int. Cl B23p 11/00 Field of Search 29/432, 432.2, 509, 523, 29/4321; 151/4113 References Cited UNITED STATES PATENTS 6/l936 Jcsscr 285/202 X 3.234.987 2/l966 Hentzi 29/432 X 3,253,631 5/1966 Reusser 29/432 X 3,282,3l5 ll/l966 Zahodiakin 29/432 X 3,282,317 ll/l966 Zahodiakin l51/4l.73 3,299,500 l/l967 Double l5l/4l.73 X 3,337,946 8/1967 Anderson 29/432.l 3,648,747 3/l972 Steward l5l/4l.73  
 Rl5.4l3 7/1922 Reynolds 285/202 Primary Examiner-Charlie T. Moon Attorney, Agent, or FirmCullen, Settle, Sloman &amp; Cantor [57] ABSTRACT 17 Claims, 16 Drawing Figures HIENTEC APRZ 2 i9?5 SHEET 2 OF 5 &#39;METIIOI) OF FORMING A NUT AND PANEL ASSEMBLY REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part application of our copending application for United States patent, Ser. No. 63,316, filed Aug. 12, 1970, now abandoned, which application was a divisional application of Ser. No. 841,037, filed July 1 l, 1969, now abandoned.  
 BACKGROUND OF THE INVENTION The present invention is especially directed to pierce and clinch nuts of the type designed to provide for a flush installation in a panel; i.e. where the installed nut projects from only one surface of the panel. Nuts and installations of this general type are disclosed in U. S. Pat. Nos. 3,299,500; 3,314,138 and 3,315,345. These patents in general disclose pierce type nuts for flush mounted installations in which the nut is either formed with an undercut groove or in which metal from the nut is staked and folded over in the panel metal. In the prior art arrangements in which an undercut groove is employed, as in U.S. Pat. No. 3,315,345, the forcing of the panel metal into the undercut portions of the grooves is accomplished by deforming the panel metal under pressure sufficient to cause the metal to flow. Because of the fact that the sheet metal with which nuts of this type are employed has a permissable variation in thickness, the retention characteristics of such an arrangement can vary considerably with variations in panel thickness because of variations in the volume of metal displaced in the flowing of the metal. Where primary reliance for retention is placed on a staking of a portion of the pilot into overlying relationship with metal in the groove, the retention is dependent upon the amount of metal staked from the pilot, and this arrangement frequently requires an undesirable compromise between achieving adequate retention while at the same time avoiding distortion of the nut threads.  
  The present invention is designed to avoid the foregoing problems in that panel metal is forced into an undercut wall of the groove by force applied solely in a direction away from the thread cylinder during the piercing or clinching operation to achieve positive retention without having to rely on flowing of the metal and without thread distortion.  
  In the present invention, the outer wall of the groovei.e. the wall most remote from the nut threads-diverges from the nut axis in its inward extent to provide the undercut retaining surface of the groove. In the pierce nut embodiment, the inner wall of the groove is parallel to the nut axis. The inner half of the bottom of the groove is deeper than the outer portion of the bottom of the groove to provide a recess which receives the tip of the piercing or clinching tool so that the end of the tool can project inwardly into the groove beyond a flat panel metal abutment wall which forms the outer portion of the groove bottom. The tip of the tool has a bevel or chamfer on its outer surface, and the thickness of the tool is less than the width of the groove.  
  When the nut is used as a piercing tool, the inner side of the punch travels down the inner wall of the groove to shear the panel, while the bevelled or chamfered outer surface acts as a wedge forcing the sheared panel edge outwardly into engagement with the undercut inclined outer wall of the groove. Because the tip of the LII tool can pass inwardly into the groove beyond the abutment wall bottom portion, the panel metal is positively forced by the wedging action into the undercut region of the groove. The depth to the wall portion of the bottom is somewhat less than the width of the groove, hence the panel metal, which is depressed into the groove, in some instances, may be compressed against the abutment wall portion or, more commonly, is folded upon itself to extend beneath the bevelled outer surface. When the panel is pre-pierced, the pilot may be eliminated, permitting a larger diameter threaded bore in the nut. The groove or channel surrounds the bore to define a counter-bore having an inclined outer wall and a greater depth adjacent the bore than at the outer wall, as described above.  
  The method of this invention then includes: positioning the nut against one face of the panel; engaging the opposed panel face with a tool configured to be received within the recess at the bottom of the groove; deforming the panel edge into the groove opening and against the groove outer side wall; and, continuing to advance the tool into the groove recess, beyond the panel edge, to securely retain the nut on the panel.  
  Other objects and features of the invention will become apparent by reference to the following specification and to the drawings.  
 IN THE DRAWINGS FIG. 1 is a cross-sectional view of one form of nut which may be utilized in the method of this invention, showing the nut positioned beneath a panel with the piercing tool about to begin its downward stroke;  
  FIG. 2 is a view similar to FIG. 1, showing the nut and piercing tool at the conclusion of the piercing stroke;  
  FIG. 3 is an end elevational view of one form of nut employing the grooved configuration of FIG. 1 and 2;  
  FIG. 4 is an end elevation view of a nut of square configuration which may be utilized in the method of this invention;  
  FIGS. 5, 6, 7, 8, 9 amd 10 are partial cross-sectional views showing successive steps in the piercing and interlocking method of this invention;  
  FIG. 11 is an end elevational view of another nut embodiment used in the method of the invention;  
  FIG. 12 is a cross-sectional view taken on the line 12-12 of FIG. 11 showing the nut of FIG. 11 installed in a panel;  
  FIG. 13 is a top elevation of another nut embodiment which may be utilized in the method of this invention;  
  FIG. 14 is a cross-sectioal view of the nut embodiment shown in FIG. 13, in the direction of view arrows 14-14;  
  FIG. 15 illustrates the nut embodiment shown in FIGS. 13 and 14 received against a panel, prior to clinching; and  
  FIG. 16 illustratesthe clinching operation utilizing the nut, panel and tool illustrated in FIG. 15.  
  DESCRIPTION OF THE PREFERRED EMBODIMENTS AND METHOD OF THIS INVENTION Referring first to FIGS. 1 and 2, there is shown in cross-section a nut body designated generally 10 having a centrally located tapped bore 12. The upper or panel engaging end surface 14 of the nut is flat and is grooved as generally indicated at 16 on opposite sides of the tapped bore 12. Y  
  Referring briefly to FIGS. 3 and 4, the nut shown in FIGS. 1 and 2 will be assumed to be the circular nut of FIG. 3, with FIGS. 1 and 2 being taken approximately at the section line indicated at 1-l. However, it is believed apparent that the cross-sectional view of FIG. 1 might equally well have been taken on the section line l&#39;l&#39; of FIG. 4, the reference numerals I4 and 16&#39; of FIG. 4 representing the flat end surface 14 and the grooves 16 of FIG. 1.  
  Returning to FIGS. 1 and 2, the groove 16 is defined by an inner wall 18 which extends parallel to the axis of bore 12 and an outer wall 20 which diverges from inner wall 18 in its extend inwardly from end surface 14. At the bottom of outer wall 20, a flat abutment surface 22, parallel to end surface 14 of the nut body, extends across approximately one-half of the width of groove 16 to a bevel surface 24 inclined inwardly toward the nut axis at an angle of approximately 45 to terminate at a flat bottom surface 26. The surfaces 24 and 26, and the lower portion of inner wall 18 cooperatively define a recess at the bottom of groove 16 which extends inwardly of the nut body to a depth greater than that of the abutment surface 22.  
  FIG. 1, the nut is supported from beneath by an anvil, not shown, and a sheet metal panel 28 is supported upon the nut in face-to-face engagement with end surface 14, again by suitable means, not shown. Spaced above panel 28 is shown the lower end of a tubular piercing tool 30 whose tip is defined by an annular flate surface 32 at the inner side of the tool and a bevelled surface 34, inclined upwardly at a 45 angle. Tool 30 is of hollow, annular construction having an inner wall surface 36 of a diameter, in the circular nut configuration of FIG. 3, slightly greater than the diameter of the inner groove wall 18. The width of the flat annular bottom surface 32 of the tool is slightly smaller than the width of the flat bottom wall 26 defining the bottom of the recess in the grooves so that the tool can be driven into the groove until surface 32 of the tool contacts surface 26 of the nut.  
  Referring now to FIG. 2, the tool is shown at the conclusion of its piercing stroke, with the lower end of the tool being received in the recess defined by walls 24 and 26 of the groove. The panel metal has been mechanically forced outwardly into engagement with the inclined surface 20 of the groove and has been compressed or deformed somewhat in that the volume of the groove left after the insertion of the tool is somewhat less than the actual volume of the panel metal forced into the groove.  
  Referring now to FIGS. -10, there are shown in these figures the progressive steps in the piercing and interlocking of the panel to the nut.  
  In FIG. 5, the tip of tool 36 has just entered the panel surface, and shearing of the panel has commenced at the inner or right-hand edge of the tool tip and also at the shoulder at the upper end of inner wall 18 of the groove. At this particular stage, the only displacement of panel metal which has occured is in the region immediately below the tool tip.  
  In FIG. 6, the tool tip has advanced nearly completelythrough the panel, and the bevelled surface 34 of the tool is substantially completely in face-to-face engagement with the upper surface of the panel. The panel has been bent downwardly about the shoulder formed at the upper end of the outer wall of the groove, but the panel has still retained its original thickness at all points because the closest point on the surface of the tool to the shoulder at the upper end of outer wall 20 still exceeds the thickness of the panel.  
  In FIG. 7, the tool has been advanced into the groove to a point at which the bevelled surface 34 is now entirely within the groove. It will be noted that the difference f between the thickness of the tool 36 and the width of the groove at its opening is less than the thickness of the metal of panel 28 and that the thickness of the panel has thus been reduced between the shoulder at the upper edge of outer wall 20 and the outer surface of tool 36. The downward movement of the tool relative to the stationary nut and panel as viewed in FIG. 7 thus forceably displaces some of the panel metal during movement of the tool between the FIG. 6 and FIG. 7 positions, and the metal which is displaced is displaced by the bevelled surface 34. Thus, the force tending to displace the metal acts, in general, in a direction normal to the bevelled surface 34 of the tool so tht the displaced metal is not only moved downwardly, as viewed in FIG. 7, into the groove, but at the same time is forced outwardly toward the outer grooved wall 20.  
  It will further be noted from FIG. 7 that because of the downward component of metal displacement, the upper surface of panel 28 is, in effect, stretched and drawn downwardly into the groove, resulting in a smoothly flared curved surface on the panel adjacent the outer wall of the tool.  
  It will further be noted from FIG. 7 that the sheared edge 40 of the panel is now in a position where it becomes apparent that further downward movement of the tool 36 will force the lower surface of the panel into engagement with abutment surface 22.  
  In FIG. 8, the tool 36 has advanced inwardly of the groove from its FIG. 7 position, and the lower surface of the panel has engaged abutme&#39;nt surface 22 and is being forced outwardly across surface 22. In effect, a reverse bend has now been created in the panel metal tending to force metal in toward the corner at the intersection of abutment surface 22 and the outer wall 20 of the groove.  
  In FIG. 9, the tool has reached almost the end of its stroke, and the undercut outer wall of the groove has been substantially filled with the panel metal.  
 In FIG. 10, the tool has reached the end of its stroke.  
  The progressive steps illustrated in FIGS. 5-10 show the idealized siutation in which, as shown in FIG. 10, the inner surface of the panel metal in the completed assembly forms a cyclindrical surface which projects upwardly from precisely the juncture between abutment surface 22 and the inclined wall 24 of the tool receiving recess. In the case where the panel metal is slightly thicker than that illustrated in FIGS. 5-10, when the stage shown in FIG. 9 is reached, some metal will be left over and will extend downwardly along the inclined wall 24 of the tool receiving recess in the completed nut. In the event that the panel metal is slightly thinner than illustrated in FIGS. 5-10, the panel metal in the completed assembly may have a configuration more like that of FIG. 9, or even of FIG. 8. It will be noted, however, that the bevelled surface 34 on the tool, positively assures that the panel metal will be forced or wedged radially outwardly into engagement with the undercut outer wall 20, regardless of whether the amount of metal in the groove is increased or decreased relative to the amount illustrated in FIGS 5-10.  
 Width of groove at end surface l4 Groove depth from end surface l4 to abutment wall 22 Depth of groove from end surface 14 to bottom of recess at wall 26 Panel thickness Difference between radius of outer surface of tool 30 and outer wall 20 of groove at surface 14 The relationship between these various dimensions should be approximately as follows:  
 The width of groove a should be greater than depth b by about -20 percent The depth d of the groove should exceed the groove width a The radial difference f between the outer surface of the tool and the outer edge of groove should be approximately one-half of the maximum panel thickness t.  
  Because of variations in the panel thickness t, the relationship involving the panel thickness can permissably vary from those specified above. Sheet metal, as supplied to the automotive industry for example, cannot be supplied in precise uniformity of thickness, mainly for economic reasons. The ranges specified above will be normally satisfactory for panel metal of a given nominal thickness. A slight expansion of the range of panel thicknesses which may be handled for a nut of given groove dimensions can be achieved by using tools of differing wall thickness so that the dimension f is regulated to remain at approximately one-half the panel thickness. If the dimension fbecomes much less than half the panel thickness, the panel metal as it is wrapped around the upper edge of wall 20, becomes too thin, and thus is easily sheared. If the dimensionf becomes much greater than half the panel thickness, the panel metal is not forced quite as firmly against wall 20, and a loss of retention or holding strength is the result.  
  The angle of inclination of wall 20 to the nut axis is preferably somewhere in the neighborhood of 15 percent. At an angle of 10, a noticable reduction in retention occurs, while at an angle of greater than difficulties are encountered in forcing the metal back into the undercut, thus resulting in a reduction of holding strength.  
  In the round nut configuration of FIG. 3, torque resistance is achieved by providing a series of notches, such as 38, in the outer wall of groove 16. The bottom of the notches may be located at the level of abutment surface 22 or, if increased torque resistance is desired, the notches may extend inwardly to the level of the recess bottom 26 as shown at 38a. Panel metal is forced into the notches 38 during the piercing operation.  
  The above description applies in general to the square nut embodiment of FIG. 4 in which two grooves 16 extend in parallel relationship on opposite sides of the tapped bore, the grooves being of the same crosssectional configuration as those shown in FIGS. 1 and 2. In the case of the. FIG. 4 embodiment, the tool will consist of two parallel members. The nut of FIG. 4 possesses some advantages over that of FIG. 3 in that it can be formed from rolled strip stock, but has the disadvantage of requiring orientation in some installations. The undercut in the nut of FIG. 3 is constructed by making a blank with the walls 18 and 20 of the groove initially in parallel relationship to each other with surface 14 lying on a conical surface and subsequently cold forming the nut to, in effect, bend the wall 18 into the conical relationship shown in FIGS. 1 and 2.  
  The retention characteristics of the annular groove embodiment of FIGS. 1 and 2 are far superior to those of the square nut of FIG. 4 insofar as resistance to forces tending to move the nut away from the panel are concerned. This is because in the case of the nut of FIGS. 1 and 2, a continuous annular band of panel metal underlies the overcut groove and the nut cannot be separated from the panel without compressing this annular band of metal around its entire circumference. In the square nut embodiment of FIG. 4, separation of the nut from the panel is opposed solely by the resistance of the panel metal to bending along the shoulder at the upper end of the inclined outer wall of the groove.  
  In FIGS. 11 and 12, there is shown another embodiment of the invention in which an annular groove 116 (FIG. 11) is formed in one face of a nut body, designated generally 110, by retaining the cylindrical surface configuration of the inner wall 118 while forming the outer wall 120 in an oval or generally elliptical configuration. For purposes of illustration, the out-ofroundness of the eliptical outer wall 120 has been greatly exaggerated in FIG. 1l-in one example of a nut of the FIG. 11 type, the major diameter of the ellipse is 0.593 inch with a minor diameter of 0.562 inch. The nut of FIGS. 11 and 12 retains the advantage of not requiring orientation for installation, because the nut is installed in the panel by the use of a circular tool identical to that employed in installing the nut of FIGS. 1 and 2.  
  Because of the fact that the width of the groove 116 in the FIGS. 11 and 12 embodiment is not uniform, it is apparent that the general relationships of relative dimensions previously set forth is only approximated in the FIG. 11 embodiment. However, the groove, tool and panel thickness dimensions of the FIG. 11 embodiment are selected in terms of the average groove width.  
  A cross-sectional view of a nut of the FIGS. 11 and 12 embodiment installed in a panel 128 appears in FIG. 12, the left-hand portion of FIG. 12 showing a crosssection at a position of maximum groove width, while the right-hand portion of the figure shows the crosssection at a location of minimum groove width. Because a circular tool is employed, to eliminate the necessity of orienting the nut, the panel metal configuration in the position differs as between the minimum and the maximum groove width sections. The effect, as illustrated in FIG. 12, is similar to the effect produced by a relative increase or decrease in panel thickness previously described in connection with the progressive steps of the installation of a nut of the FIGS. 1 and 2 embodiment. As best seen in the right-hand portion of FIG. 1, where the volume of panel metal within the groove is relatively large as compared to the groove dimensions, a portion of the panel metal extends down the inclined wall 124 of the tool receiving recess.  
 5 At the left-hand portion of FIG. 12, where the volume of the groove is relatively large as compared to the amount of panel metal forced into the groove, the end result is a panel metal configuration which falls somewhat short of optimum filling of the undercut of the groove, however, it will be noted that even where under-filling is present, the major portion of the undercut groove wall 120 is engaged by the panel metal.  
  The embodiment of the nut 210 shown in FIGS. 13 to 16 differs from the nut embodiments described above in that the nut is clinched to a pre-pierced panel, rather than utilized as a piercing tool. The central piercing pilot portion surrounding the nut bore has been eliminated in the embodiment shown in FIGS. 13 to 16, permitting enlargement of the tapped bore 212. This configuration has an advantage in certain applications, particularly where the bore diameter is important, such as a bung or plug application for containers and the like. Enlarging the bore diameter in the nut embodiment shown in FIG. 1, for example, would weaken the wall, requiring a larger diameter nut, which may not be possible in certain applications.  
  The clinch nut embodiment shown in FIGS. 13 to 16 includes a flat panel engaging face 214 and a groove or channel 216 surrounding the nut bore and defining a counter-bore. The configuration of the groove or channel may be similar to the groove 16 in FIG. 1 described above, except that the inner wall 18 has been elimianted with the piercing pilot. The groove shown in FIG. 14 includes an inclined outer wall 220, an abutment wall 222 generally parallel to the end face 214 of the nut, an arcuately inclined surface 224 and a bottom wall 226. In the clinching operation, the inclined or bevelled surface 224 and the bottom wall 226 define a tool receiving recess, as described above.  
  It will be further noted from FIG. 13 that this embodiment of the nut is generally hexagonal, however the corners are truncated. It has been found that this configuration is particularly suitable for pierce and clinch nuts of the type disclosed. The hexagonal channel or groove prevents rotation of the nut on the panel after securement and is easily formed in a die or cold header apparatus. The corners have been truncated to prevent tearing of the panel and to reinforce the nut body.  
  The clinching method of this invention is shown in FIGS. 15 and 16. The nut is received against one face of the panel 228 with the channel 216 opening toward the panel face. The panel, in the clinching operation, includes a hole 229 which has been previously formed, as by punching. The configuration of the panel opening will depend upon the particular application, however in the disclosed embodiment a circular opening is preferred. The diameter of the panel opening has been choosen such that the panel edge may be extruded into the groove or channel 216, as shown in FIG. 16, against the abutment wall 222, but not against the bottom wall 226 of the groove which receives the tool edge 232. Stated another way, the diameter of the panel opening should be equal to approximately the hole diameter pierced by the pierce nuts described hereinabove. The diameter of the opening xshown in FIG. 15 is equal to the inside diameter of the bottom wall 226 of the groove. It will be noted that the wall 226 is inclined at approximately a angle to permit parting of the nut in the cold operation.  
  In the clinching method, the nut bore 212 is aligned in registry with the panel opening and the nut is normally supported on an anvil or the like, not shown. The tool or punch 230 is located above the nut groove, coaxially aligned with the nut bore and the punch opening. The panel and punch may then be moved toward the punch, or vice-versa. The punch in the disclosed embodiment includes an annular projection 232 which is configured to be received in the tool receiving recess, as shown in FIG. 16. Except for the piercing operation, which has been eliminated in the clinching operation shown in FIGS. 15 and 16, the nut is secured to the panel by the method described above. The panel edge is first deformed or folded over the inclined outer wall 220 of the groove and then extruded into the groove opening by the annular projection 232 of the punch 230. It will be noted that the outer edge 234 includes an arcuate camming surface which provides the same function as the chamfer 34 of the tool 30 shown in FIG. 1.  
  The method of clinching the nut 210 to the panel 228 then includes disposing the nut against one face of the panel 228 with the groove 216 opening toward the panel and the nut bore 212 coaxially aligned with the panel opening 229. The punch 230 is then advanced against the opposed side of the panel with the projection 232 coaxially aligned with the panel opening. The panel edge surrounding the panel opening 229 is then deformed into the nut groove, over the inclined outer side wall 220. Finally, the annular projection 232 of the punch is advanced beyond the panel edge into the tool receiving recess defined by the arcuate groove wall 224 and the bottom wall 226 to deform the panel edge against the abutment wall 222 adjacent the outer wall and deform and compress the panel edge beneath the inclined outer groove wall 220 to securely retain the nut on the panel.  
 We claim:  
  1. The method of interlocking a nut to a sheet metal panel of a known nominal thickness t comprising the steps of engaging in face-to-face relationship with one side of the panel a nut having a groove in the engaged face of the nut spaced from opposite sides of the tapped bore of the nut, the groove being undercut at the side remote from the bore and having a depth less than the width of the groove at said engaged face, and a tool receiving recess in the bottom of the groove at the side of the groove adjacent the tapped bore, and in a single uninterrupted stroke displacing said nut and said panel relative to a tool located on the opposite side of the panel from said nut a. to cause said tool in cooperation with the engaged face of the nut to shear the panel at opposite sides of said bore along the side of the groove adjacent the bore,  
 b. to bend into the groove that portion of saidpanel overlying the groove by bending the same about the shoulder of the groove remote from the tapped bore,  
 c. to compress the panel metal along the last mentioned shoulder to approximately one-half of its original thickness 1, and  
 d. to wedge the panel metal in said groove outwardly from said bore into the undercut remote side of the groove by the advancement of the tip of the tool receiving recess.  
  2. The method of interlocking to a sheet metal panel of thickness t a generally circular nut having an annular groove in one face concentric with the tapped bore of the nut and having a width at said one face greater than I and a depth less than its width, the radially outer side wall of the groove being undercut and the bottom of the groove being recessed to a depth greater than the width of the groove adjacent the radially inner side wall to define a tool receiving recess; comprising the steps of:  
 a. engaging the panel between the one face of the nut and a hollow cylindrical tool having an inner diameter approximately equal to the diameter of the inner side wall of the nut groove and a wall thickness less than the width of the groove at said one face by approximately one-half I, the tool tip being beveled at its outer side and the tool and nut bore being coaxially aligned;  
 b. axially advancing the tool relative to the nut to shear the panel along the radially inner side wall of the groove and to force the panel axially into the groove and radically outwardly against the outer side wall of the groove by the wedging action of the beveled tool tip and the engagement of the panel with grooved bottom, and  
 c. continuing to advance the tool tip axially into the groove beyond the panel into the tool receiving recess.  
  3. In the method of locking a nut to a flat sheet panel member in which the nut is provided with a bore and a groove in its panel engaging surface extending alongside said bore between the bore and the outer edge of said nut; said groove being formed to have an inner side surface parallel with the axis of the bore and an outer side surface inclined at an angle of from between 10 to degrees relative to said axis so that the open end of said groove is smaller in width than the bottom of said groove to provide an undercut; said bottom providing a first portion along the inclined outer side and a second portion along the inner side disposed on a lower level than the first portion and connected thereto by an inclined surface, the steps comprising:  
 placing said nut with said panel engaging surface against one side of said panel and holding said nut;  
 advancing a hollow punch having a tapered end onto said panel from the other side in axial alignment with said axis to cut out a slug from said panel to permit said punch to enter said groove;  
 displacing that portion of said panel overlying said groove into said groove by advancement of said punch into said groove; and  
 further advancing said punch to compress the portions of the panel in the groove in locking engagement into the first, undercut portion of the groove by wedging action of the taper of said punch along the inclined bottom surface between said first and second portion as said punch advances into the second portion of said groove.  
  4. In the method as defined in claim 3, in which said nut is further provided with a plurality of radial recesses intersecting said groove, the further step comprising: compressing material from said panel into said recesses upon advancement of said punch into said groove to retain said nut against rotation relative to said panel.  
  5. In the method as defined in claim 3, in which said groove in said nut is of oval shape having undercut portions further remote from the axis of said bore than the remainder of said groove and the further step compris ing: compressing material from said panel into said undercut portions further remote from said axis by advancement of said punch into said groove to thereby prevent said nut from rotation on said panel.  
  6. In the method as defined in claim 3, in which said nut is of rectangular shape and said groove comprising a pair of longitudinal parallel grooves extending along opposite sides of said bore, the further step comprising: compressing material from said panel into said undercut first portions of both of said grooves simultaneously by advancement of said punch into said grooves to thereby lock said nut against rotation on said panel.  
  7. In the method of making a nut and panel assembly, said panel being of a thickness I, said nut having an axial bore and a lateral outer surface and is provided with a groove in the panel engaging surface of the nut between said bore and the outer surface providing an undercut having a shoulder along one edge thereof closest to the outer surface. and a continuous recess in the bottom of said groove nearest to said bore having a greater axial depth than the undercut portion of said groove to which the recess is connected by a tapered surface, the steps comprising:  
 placing said panel engaging surface of said nut against one side of said panel; locating a punch at the other side of said panel having a bore in axial alignment with said bore of said nut defining a cutting edge, said punch further having a tapered outer surface;  
 displacing said nut and said panel relative to said punch to cause said punch in co-acting relationship with said nut defining a cutting edge, said punch further having a tapered outer surface; displacing said nut and said panel relative to said punch to cause said punch in co-acting relationship with said nut to shear a slug from said panel of a size corresponding to the inner surfaces of said groove; further advancing said punch in to said groove to cause the portions of said panel overlying said groove immediately adjacent from the severed slug to be bent into said groove around said shoulder;  
 and still further advancing said punch into said recess of said groove to cause wedging engagement of said tapered outer surface of said punch with said tapered surface of said groove to thereby exert an axial and radial outwardly directed compression force on said portions of said panel to displace the material of said portions into said undercut in locking engagement therewith.  
  8. In the method as defined i claim 7, in which said groove is of circular shape and concentric with said bore of said nut and said nut is further provided with a plurality of radial recesses intersecting said groove, the further step comprising: compressing material from said panel into said recess upon advancement of said punch into said groove.  
  9. In the method as defined in claim 7, in which the inner surface of said groove is being circular and concentric with said bore and the outer surface of said groove extends along an oval path providing undercut portions further remote from the axis of said bore of said nut than the remainder of said groove, the further step comprising: compressing material from said panel into said undercut portions further remote from said axis by advancement of said punch into said groove.  
  10. In the method as defined in claim 7, in which said nut is of rectangular shape and said groove comprising a pair of longitudinal parallel grooves extending along opposite sides of said bore, the further step comprising: compressing material from said panel into said undercut first portions of both of said grooves simultaneously by advancement of said punch into said grooves to thereby lock said nut against rotation on said panel.  
  11. In the method of making a nut and locking said nut on a panel the steps comprising:  
  providing a nut body having an axial bore and a panel engaging surface, providing a continuous groove in said panel engaging surface having an inner lateral surface equally spaced from the axis of said bore to define a central hub portion of said nut surrounded by an outer rim portion, said outer rim portion initially having an inclined surface relative to the planar surface of said hub portion, axially compressing said outer rim portion into co-planar alignment with said planar surface to thereby provide an undercut, outer, radial surface of said groove, providing said groove witha bottom recess along said inner lateral surface of a greater axial depth than the undercut portion of said groove; placing said panel engaging surface of said nut against one side of said panel; disposing a tool against the other side of said panel, relatively moving said panel and nut against said tool for advancement of said tool through said panel and into said groove to (a) sever a slug from said panel corresponding to the size of said central hub portion of said nut, (b) advancing said tool into said groove to align said inner lateral surface to bend the portions of said panel overlying said groove into said recess of said groove to thereby compress said portions of said panel into said undercut of said groove in locking engagment therewith. 12. In the method as defined in claim 11 in which said recess and the undercut portion of said groove are connected by an inclined surface and said tool having a chamfered outer surface for engagement with the inclined surface in the bottom of said groove the further steps comprising:  
 advancing said tool into said recess of said groove in wedging engagement against said inclined surface;  
 to exert an axial and radially outwardly directed force on said portions of said panel bend into said groove to forceably compress said portions into said undercut.  
  13. A method of making a nut and panel assembly, said nut having a panel engaging surface, said surface having a groove defined therein having an inner side wall defining a piercing face and an outer side wall inclined towards said piercing face defining a restricted groove opening, the bottom wall of said groove, at said inner side wall, spaced farther from said surface than at said outer side wall, comprising the steps of:  
 placing said nut piercing face against one side of said panel; advancing a hollow punch against the opposed side of said panel, said punch having an opening closely receiving said piercing face and cutting a slug from said panel;  
 further advancing said punch, into said nut groove, to  
 deform the pierced panel edges into said groove, over said groove outer side wall; and  
 continuing to advance said punch, into said nut groove, against said groove bottom wall adjacent said inner wall and beyond said pierced panel edge, to (l) deform said pierced panel edge against said bottom groove wall at said outer side wall, and (2) deform and compress said panel beneath said inclined outer side wall, wedging said panel within said groove.  
  14. The method of making a nut and panel assembly defined in claim 13, wherein said punch includes an inclined outer edge at the piercing end, including radially deforming said pierced panel edge, beneath said outer side wall with said inclined punch edge.  
  15. The method of making a nut and panel assembly defined in claim 13, wherein said groove bottom wall includes a distinct tool receiving recess at said inner side wall, including the step of continuing to advance said punch into said tool receiving recess, beyond said pierced panel edge, to deform and compress said panel edge against said outer side wall.  
  16. The method of making a nut and panel assembly defined in claim 13, wherein said punch includes an inwardly inclined end surface and said groove bottom wall has a conforming inclined surface, including (1) radially deforming said pierced )anel edge with said inclined punch surface against said outer side wall, and (2) continuing to advance said punch to abut said inclined surfaces, beyond said pierced panel edge.  
  17. The method defned in claim 1, characterizedin that said nut includes an annular pilot having a piercing face substantially parallel to said nut panel supporting surface and surrounding said bore, the radial outer wall of said pilot defining the inner wall of said groove, including the step of piercing a slug from said panel with said nut pilot and the inner surface of said hollow punch forming said panel aperture.