JP2012250279A - Piercing nut manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing apparatus with which high stress type square piercing nuts, which are high in dimensional accuracy and with which stable clinching force is obtained, are mass-produced.SOLUTION: There is provided a piercing nut manufacturing apparatus for performing heading of a nut blank 11 for the high stress type piercing nut by using a nut former: the nut blank 11 wherein an end surface slants the circumferential sidewall surface of a cylindrical pilot portion 13 working as a punch for punching a metallic sheet and the sidewall 14 to the axial line and wherein an annular groove 15 is formed in a dovetail groove of a back spread. The apparatus is configured such that the end faces of four corners in the diagonal directions of the nut blank 11b which finishes a heading step where the circumferential sidewall surface of the pilot portion 13 for defining the annular groove 15 is slanted and enlarged with the prepared screw hole 12 punched and with the end surface portion of the pilot portion 13 pushed and expanded in a radial direction are pushed out with four knockout pins 77 and they are pushed in between a pair of fingers 58, 58 of a transfer mechanism located in the vicinity of the end surface.

Description

  The present invention relates to an apparatus for manufacturing a pierce nut in which a nut itself punches a metal plate, and a peripheral portion of a punching hole is fixed to the metal plate. In particular, the inventor of the present application discloses Japanese Patent Publication No. 8-29362 (Patent Document 1). It is related with the improvement of the manufacturing apparatus of the high stress type pierce nut obtained from the big clinch force proposed and implemented by this.

  The pierce nut manufacturing apparatus described in the above-mentioned Japanese Patent Publication No. 8-29362 is a cylindrical shape which is implemented by a nut homer and whose end face provided at the center of a square nut body serves as a punch for punching a metal plate. And the opposite side wall surfaces defining an annular groove formed between the pilot portion and the side wall protruding along the outer peripheral edge of the nut body so as to surround the pilot portion are inclined with respect to the axis. When the annular groove is formed into a dovetail having a depth, the dimensional accuracy of the inner dimension and the outer dimension of the annular groove is high, the punching by the pilot part is good, and a high quality with a constant and large clinch force can be obtained. It has a great advantage that high-stress type pierce nuts can be mass-produced.

  When manufacturing the above-mentioned high stress type pierce nut using a nut former, the nut blank which finished each forging process shown in Drawings 1-3 of the above-mentioned patent documents 1 (Japanese Patent Publication No. 8-29392), It is pushed to the front of the dies of each process, and is gripped by a pair of opposing fingers of a transfer mechanism that reciprocates along the vicinity of the front surface of the dies and transferred to the dies of the next process to perform the next forging process. However, when the nut blank that has been subjected to the hole punching and pilot part expansion process shown in FIG. 2 of the above-mentioned Patent Document 1 is transferred to the sidewall inclined forging process shown in FIG. was there.

  14 and 15 show that the nut blank 11 that has been subjected to the hole punching and pilot portion expansion process shown in FIG. 2 of Patent Document 1 (Japanese Patent Publication No. 8-29392) is pushed out of the die 31, and the die 31 is used. It is explanatory drawing which shows the operation | work process hold | gripped by a pair of opposing fingers 39 and 39 of the transfer mechanism which reciprocates along the front surface. Both fingers 39, 39 are biased toward each other by a spring (not shown), and the distance therebetween is slightly smaller than the opposite side dimension of the nut blank 11.

  An outwardly expanding taper wall 34 is provided at the base of the punching punch 33 provided in the recess 32 of the die 31, and the tapered wall 34 is provided on the end face of the cylindrical insert 35 provided by being fitted around the punching punch 33. An annular projection 36 is provided so as to surround the cylindrical insert 35, and the cylindrical insert 35 is held and fixed to a holder 37.

  When the nut blank 11 inserted into the recess 32 of the die 31 is pressed by the cylindrical punch 38, the cylindrical punch 38 and the punching punch 33 cooperate to punch out a preliminary pilot hole that does not penetrate the nut blank 11. Then, the screw pilot hole 12 is forged, and then the end surface portion of the pilot portion 33 is expanded in the radial direction by the taper wall 34 in a state where the annular protrusion 36 of the cylindrical insert 35 is inserted into the annular groove 15. The side wall surface 16 is inclined with respect to the axis, and the cross-sectional shape of the annular groove 15 is formed as a dovetail groove that is widened. The outer diameter of the end face of the pilot portion 13, that is, the inner dimension of the annular groove 15 is finished to an accurate constant dimension by being restricted by being in contact with the inner side surface and preventing excessive tilt deformation. That.

  When the process of punching out the screw hole 12 and the enlargement process of the pilot portion 13 is completed, as shown in FIG. 14, first, the cylindrical punch 38 is retracted away from the die 31, and both fingers 39, 39 are in front of the die 31. Move to the vicinity. At this time, the scrap piece 12c punched out by the punching punch 33 is accommodated in the cylindrical hole of the cylindrical punch 38 and removed. Subsequently, as shown in FIG. 15, when the punch 33 is advanced and protrudes from the die 31, and the nut blank 11 is pushed up and pushed between the fingers 39 and 39, the punch 33 is moved into the die 31. The nut blank 11 held by the fingers 39 and 39 is transferred to the front face of the next die.

  On the other hand, the outer diameter d of the tip 33 a of the punching punch 33 is substantially the same as that of the screw hole 12 punched into the nut blank 11, so that the tip of the punching punch 33 is retracted into the die 31. 33a interferes with the nut blank 11, and a stress is generated to pull the nut blank 11 back into the die 31. However, in normal work operation, there is no problem because the spring pressure for urging both fingers 39, 39 is strong, but during long-time work operation, the urging force by the springs of both fingers 39, 39 is weakened. When the hole punch 33 is retracted, the nut blank 11 is pulled back into the die 31 and the nut blank 11 cannot be transferred to the next process. Serious accidents such as shutdowns occurred.

  The present invention has been made for the purpose of solving the above-mentioned problems, and the nut blank that has undergone the hole punching and pilot portion expansion process is arranged so as to surround the hole punch instead of the hole punch. To provide an apparatus for manufacturing a pierce nut which can be pushed out by four provided knockout pins and can be securely pushed between both fingers to be gripped and does not hinder the transfer of the nut blank. Is an issue.

  In order to solve the above problems, the present invention provides a cylindrical pilot portion whose end face serves as a punch for punching a metal plate at a central portion including a screw pilot hole of a nut body having a square outer shape, and the nut body. A side wall projecting so as to surround the pilot part along an outer peripheral edge of the pilot part, forming an annular groove between the pilot part and the side wall, and a peripheral side wall surface of the pilot part defining the annular groove; In the manufacturing apparatus of a pierce nut for forming a nut blank of a high stress type pierce nut in which the side wall is inclined with respect to the axis and the annular groove is formed into a wide dovetail groove using a nut former, the screw pilot hole Forging and expanding the end surface portion of the pilot portion in the radial direction to incline and enlarge the peripheral side wall surface of the pilot portion that defines the annular groove Extruding the end faces of the diagonal direction of the terminated the nut blank corners by four knockout pins, characterized by being configured to push between a pair of fingers of a transfer mechanism located near the end face of the die.

  The invention according to claim 2 is a manufacturing apparatus according to the present invention, in which the configuration of the forging die punch in the main process of forging a nut blank by a nut former is specifically specified. It has a knockout pin that can be moved forward and backward in the axial direction in the recessed portion of the die to be inserted and is biased to the retracted position by a spring, and is fixedly placed inside the recessed portion by externally fitting to the knockout pin An annular protrusion is provided on the end surface of the first cylindrical insert, and a protrusion for forming a preliminary screw hole is provided on the front end surface of the punch opposite to the die. The inserted blank is pressed so as to be sandwiched between the punch and the knockout pin, the preliminary hole which does not penetrate is formed, and the annular protrusion is formed into the blank. A cylindrical pilot portion whose end face works as a punch for punching out a metal plate is provided in the center portion including the preliminary hole of the nut body having a square outer shape by press-fitting, and the pilot portion along the outer peripheral edge of the nut body A nut blank forging die punch in which an annular groove is formed between the pilot part and the side wall, and a recess for the next step for inserting the nut blank is provided. A taper wall that extends outward is provided at the base of the punched punch provided, and an annular protrusion that is inserted into the annular groove is provided on the end surface of the second cylindrical insert that is fitted on the punched punch. The nut blank is inserted into the concave portion of the die for the next step and pressed, and the preliminary hole is punched out by a cooperative action of the cylindrical punch and the punching punch. The end surface portion of the pilot portion is formed in the radial direction by the tapered wall, and the peripheral side wall surface of the pilot portion that defines the annular groove is inclined to form the annular groove in a dove groove that is widened. , A hole punching and pilot part enlarged forging die punch having a configuration in which the outer peripheral edge of the pilot part is brought into contact with the inner side surface of the annular protrusion to regulate, and the nut blank in which the hole punching and pilot part are enlarged are inserted. It has a knockout pin that is arranged to be able to advance and retreat in the axial direction in the recess of the die of the next process, and is biased to the retracted position by a spring, and the side wall of the nut blank is on the axis side inside the recess An annular protrusion is provided on the end surface of the third cylindrical insert disposed at the bottom of the recess of the die in the subsequent process. When the nut blank is inserted into the concave portion of the die of the next process with a punch with a punch opposite to the die of the next process and pressed, the side wall is inclined to the axis side by the tapered wall and An annular groove is formed in the dovetail that is widened, and a sidewall inclined forging die punch configured to abut on the outer side surface of the annular protrusion to contact the inner edge of the side wall inclined toward the axial line side is provided. In the apparatus for manufacturing a pierce nut by a nut former, the hole punching and the second cylindrical insert of the hole punching and pilot portion expanding die punch are fixedly held in a recess of the die of the next step, and Four knockout pins are provided so as to surround the hole punch, and the nut blank is inserted into the concave portion of the die in the next step and pressed. Due to the cooperative action of the punch and the punch, the end faces of the four corners in the diagonal direction of the nut blank after the drilling of the screw hole and the enlargement of the pilot portion are pushed out by the four knockout pins. The structure is such that it is pushed between a pair of fingers of the transfer mechanism located in the vicinity of the end face of the die.

  The invention according to claim 3 is the pierce nut manufacturing apparatus according to claim 2, more specifically specifying the configuration of the punched pilot portion enlarged forging die punch, the punched punch and the The second cylindrical insert is fixedly held via a holder in the recess of the die for the next step, and the four knockout pins are pivoted on the holder with a phase of 90 degrees around the punching punch. And is urged to a retracted position by a spring, and when in the retracted position, the front end surface is flush with the front end surface of the second cylindrical insert, The nut blank is configured to abut against the end faces of the four corners in the diagonal direction, push out the nut blank, and push it between the pair of fingers.

  As described above, the pierce nut manufacturing apparatus according to the present invention, when forming a nut blank with a nut homer, forcibly forms a ring-shaped groove by expanding the hole surface of the pilot hole and the end face of the pilot part in the radial direction. The transfer mechanism located in the vicinity of the end face of the die is formed by pushing out the four corner end faces of the nut blank with the four knockout pins after the forging process for inclining and enlarging the peripheral side wall face of the pilot part to be defined is finished. Since the nut blank is pushed between the pair of fingers, the nut blank is reliably and smoothly pushed out of the die and is held by the fingers, and there is no possibility of hindering the transfer to the next process. Therefore, high-quality high-stress type square pierce nuts with high dimensional accuracy and stable clinching force can be mass-produced more efficiently.

It is a front view which shows the nut homer principal part which implements this invention. It is explanatory drawing which shows the process order of the nut blank which is forge-molding by a nut former same as the above. It is a top view which shows the outline of the transfer mechanism which transfers the nut blank processed at each forging process of the nut homer to the next process sequentially. It is a front view which shows the operation state which the transfer mechanism same as the above moved from the position shown in FIG. It is a principal part cross-sectional top view of a forging die punch which shows the state which each forging process of the nut blank shape | molded by a nut former same as the above was completed, and was extruded from the forging die. It is a principal part cross-sectional top view of the forging die punch which shows the state which shows the state in which the nut blank which complete | finished the main forging process by a nut former same as the above is each transferred to the following process. It is a principal part cross-sectional top view of a forging die punch which shows the state which the nut blank which complete | finished the main forging process by a nut former same as the above was conveyed ahead of the forging die of the following process, respectively. The nut blank which finished the main forging process by a nut former same as the above is a principal part transverse plane view of a forging die punch which shows the middle of being formed by pressing to a forging die of the next process, and pressing with a punch, respectively. The nut blank which finished the main forging process by a nut former same as the above is the principal part transverse plane view of the forging die punch which shows the state by which the forging die of the next process and the forging forming by a punch were each completed. FIG. 10 is a cross-sectional plan view of the main part of the forging die punch showing the state in which the forging die and the forging of the next step shown in FIG. 9 have been completed, and the punches of each forging step have moved backward away from the forging die. It is a principal part enlarged front view of a hole formation of a nut former same as the above, and a pilot part expansion forging die. It is explanatory drawing which shows the state which extrudes the nut blank which finished the drilling of a screw pilot hole, and expansion of a pilot part by the punching of a nut homer, and pilot part expansion forging die punch same as the above with four knockout pins. It is a perspective view of the square piercing nut completed by tapping the nut blank manufactured by the device of the present invention. It is explanatory drawing which shows the extrusion preparation of the nut blank which complete | finished the hole punching and pilot part expansion process shown by FIG. 2 of Japanese Patent Publication No. 8-29392. It is explanatory drawing which shows the state which extrudes the nut blank shown in FIG. 14 from a forging die, and is hold | gripped with a pair of fingers which a transfer mechanism opposes.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a main part of a four-stage nut former embodying the present invention, and dies for each forging step for forging a nut blank to a die block 50, that is, a preforming die 51 and a nut blank forging die 52. , Hole punching and pilot part expansion forging dies 53 and side wall inclined forging dies 54 are incorporated in parallel in the transverse direction at equal intervals. Incidentally, in the pre-process of the pre-forming die 51, the technical means for cutting a material of a certain size from the coil material, correcting the end face and supplying it to the pre-forming die 51 is provided in the existing nut former as standard. It is omitted because it is a conventional technical means.

  A transfer mechanism 55 that reciprocates in the horizontal direction along the vicinity of the front surface of the die block 50 is provided. Since the transfer mechanism 55 is also a conventional technical means that is standardly provided in the existing nut homer, a detailed description thereof will be omitted. However, as shown in FIGS. Three spindles 57 extending in the vertical direction on the connecting plate 56 that reciprocally moves in the lateral direction along the vicinity of the front surface can be rotated around the axis line with an interval equal to the interval between the forging dies 51 to 54. A pair of opposing fingers 58 and 58 are assembled to each spindle 57 so as to be movable in the lateral direction, and are urged to approach each other by leaf springs 59 and 59. Then, only the fingers 58 and 58 arranged in front of the preforming die 51 in FIG. 1 are reversed by 180 degrees when the preformed blank 10 is moved in front of the forging die 52 as shown in FIG. The remaining two pairs of fingers 58, 58 are adapted to translate in the lateral direction.

  FIG. 5 shows a state in which the nut blanks 11a, 11b, and 11c of each forging step that have been forged by the nut former are pushed out from the forging dies 52, 53, and 54, respectively, and transferred to the next step.

  The nut blank forging die 52 is disposed so as to be capable of moving back and forth in the axial direction in a recess 61 into which the blank 10 (see FIG. 2) preliminarily swung by the preforming die 51 is inserted, and is attached to the retracted position by a spring 63. The knockout pin 62 is biased, and the knockout pin 62 is pushed out against the spring 63 by a main pin 64 disposed behind the knockout pin 62. In addition, an annular protrusion 66 is provided on the end surface of the first cylindrical insert 65 that is fitted around the knockout pin 62 and fixedly arranged in the interior of the recess 61. On the other hand, a protrusion 68 for forming a preliminary hole for a screw-down hole is provided on the front end surface of the punch 67 provided opposite to the forging die 52. Then, the blank 10 inserted into the recess 61 is pressed so as to be sandwiched between the punch 67 and the knockout pin 62 to form the preliminary holes 12a and 12b of the screw-down holes not penetrating, and the annular protrusion 66 is formed into the blank 10 The cylindrical pilot portion 13 whose end face works as a punch for punching a metal plate is formed in the central portion of the nut body including the preliminary hole 12a, and the pilot portion 13 is surrounded along the outer peripheral edge of the nut body. A nut blank 11a in which a side wall 14 protruding in parallel with the axis is formed and an annular groove 15 is formed between the pilot portion 13 and the side wall 14 is formed by forging (see FIG. 2). As shown in FIG. 5, the nut blank 11 a thus forged is first retracted so that the punch 67 is separated from the forging die 52, and then pushed out of the forging tie 52 by the knockout pin 62. It is pushed and held between 58 and 58.

  In the punching pilot part enlarged forging die 53, the hole 74 is inserted into the recess 71 into which the nut blank 11a is inserted, and the second cylindrical insert 73 that is externally fitted to the hole punch 72 is provided with the holder 74. Is held through. An outwardly expanding taper wall 75 is provided at the base of the punching punch 72, and an annular protrusion 76 that is inserted into the annular groove 15 of the nut blank 11 a is provided on the end surface of the second cylindrical insert 73. On the other hand, four elongated knockout pins 77 are provided so as to surround the punching punch 72. The knockout pin 77 is arranged around the punching punch 72 with a phase of 90 degrees (see FIG. 11), is attached to the second cylindrical insert 73 and the holder 74 so as to be capable of moving forward and backward in the axial direction. The spring 78 is biased to the retracted position, and when in the retracted position, the front end surface is flush with the end surface of the second cylindrical insert 73 or slightly lower than the end surface (see FIGS. 7 to 10). ). The four knockout pins 77 are pushed forward against the spring 78 by a main pin 79 disposed on the rear side. On the other hand, a cylindrical punch 80 facing the forging die 53 is provided. Then, when the nut blank 11a is inserted into the recess 71 by the cylindrical punch 80 and pressed, the preliminary holes 12a, 12a, and 12b are brought about by the cooperative action of the cylindrical punch 80 and the punching punch 72 as shown in FIGS. 12b is punched out to form the screw prepared hole 12, and the end wall portion of the pilot portion 13 is radially expanded by the tapered wall 75 of the punching punch 72 so as to define the annular groove 15. Is inclined with respect to the axial line, and the cross-sectional shape of the annular groove 15 is formed into a dovetail having a depth, and the outer peripheral edge of the end face of the pilot part 13 is in contact with the inner side surface of the annular protrusion 76 and is regulated, and excessive inclination deformation is caused. As a result, the nut blank 11b in which the outer diameter of the end surface of the pilot portion 3, that is, the inner dimension of the annular groove 15, is finished to a precise and constant dimension is formed by forging. At this time, the punched piece 12c punched by the punching punch 72 is accommodated in the cylindrical hole of the cylindrical punch 80 and discharged. As shown in FIG. 10, the nut blank 11 b thus forged is first retracted so that the cylindrical punch 80 is separated from the forging die 53, and the pair of fingers 58, 58 of the transfer mechanism 55 is connected to the forging die 53. Move to the vicinity of the front. Subsequently, as shown in FIG. 5, the four knockout pins 77 are pushed out against the spring 78 by the main pins 79 and come into contact with the end faces of the diagonal corners of the nut blank 11b. It pushes out from the recessed part 71 of the forging die 53. FIG. When the nut blank 11b is pushed out by the four knockout pins 77 in this way, the nut blank 11b is pushed out accurately in the axial direction, so that the nut blank 11b is pushed out of the recess 71 smoothly and reliably without interfering with the punching punch 72. Then, it is pushed and held between a pair of opposing fingers 58 and 58.

  The side wall inclined forging die 54 is disposed so as to be capable of moving forward and backward in the axial direction in the recess 81 into which the nut blank 11b in which the pilot hole 13 is expanded and the pilot portion 13 is enlarged, and is biased to the retracted position by the spring 83. The knockout pin 82 is pushed out against the spring 83 by a main pin 84 disposed behind the knockout pin 82. In addition, a tapered wall 85 that inclines the side wall 14 of the nut blank 11b toward the axial line is provided in the inner part of the recess 81. Furthermore, the end face of the third cylindrical insert 86 externally fitted to the knot-out pin 82 and fixedly arranged in the inner part of the recess 81 is opposed to the taper wall 85 and has a constant interval, and the nut blank 11b. An annular protrusion 87 to be inserted into the annular groove 15 is provided. On the other hand, a punch 88 facing the forging die 54 is provided. When the nut blank 11b inserted into the recess 81 of the forging die 54 is pressed by the punch 88 (see FIGS. 8 to 9), as shown in FIG. 9, the annular protrusion 87 of the third cylindrical insert 86 is formed into the annular groove 15 as shown in FIG. In this state, the side wall 14 is inclined toward the axis by the taper wall 85, the inner wall surface 17 defining the annular groove 15 is inclined with respect to the axis, and the cross-sectional shape of the annular groove 15 is formed into a dovetail having a depth. In addition, the inner edge of the inclined side wall 14 abuts against the outer surface of the annular protrusion 87 and is restricted, and excessive inclination deformation is prevented, so that the outer dimension of the annular groove 15 is finished to an accurate constant dimension. . As shown in FIG. 10, the nut blank 11c forged by the side wall inclined forging die 54 retreats so that the punch 88 moves away from the forging die 54, and then, as shown in FIG. It is pushed out from the recess 81 of the forging die 54, falls free, and is conveyed to a tapping process (not shown).

  FIG. 13 shows a high-stress type square pierce nut 1 completed by tapping a female screw 2 into the screw pilot hole 12 of the nut blank 11c formed by forging as described above.

DESCRIPTION OF SYMBOLS 1 Square piercing nut 2 Screw hole 10 Blank 11 Nut blank 11a, 11b, 11c Nut blank 12 Screw pilot hole 13 Pilot part 14 Side wall 15 Annular groove 50 Die block 51 Pre-formation die 52 Nut blank forging die 53 Hole extraction and pilot part expansion Die 54 Side wall inclined forging die 55 Transfer mechanism 58, 58 A pair of fingers 59, 59 Leaf spring 61 Recessed portion (forging die 52)
62 Knockout pin 65 First cylindrical insert 66 Annular projection 67 Punch 71 Recess (Forging die 53)
72 Hole punch 73 Second cylindrical insert 74 Holder 75 Tapered wall 76 Annular projection 77 Knockout pin 80 Cylindrical punch 81 Recess (forging die 54)
82 Knockout pin 85 Tapered wall (concave 81)
86 Third cylindrical insert 87 Annular projection 88 Punch

Japanese Patent Publication No. 8-29362

Claims (3)

  A cylindrical pilot part whose end face works as a punch for punching out a metal plate is provided at the center part including the screw hole of the square nut body, and the pilot part is surrounded along the outer peripheral edge of the nut body. Protruding side walls are provided, an annular groove is formed between the pilot part and the side wall, the peripheral side wall surface of the pilot part defining the annular groove and the side wall are inclined with respect to the axis, and the annular groove is formed. An apparatus for manufacturing a pierce nut in which a nut blank of a high-stress type pierce nut formed in a dovetail having a depth is formed by using a nut former, and the end face portion of the pilot portion is punched in a radial direction. Diagonal direction of the nut blank after the forging process in which the peripheral side wall surface of the pilot portion defining the annular groove is inclined and expanded is finished. Of extruding the end faces of the four corners by four knockout pins apparatus for manufacturing a pierce nut, characterized in configuration and the be pushed into between the pair of fingers of a transfer mechanism located in the vicinity of an end face of the die. It has a knockout pin that is disposed so as to be able to advance and retreat in the axial direction in a recess of a die for inserting a preformed blank, and is biased to a retracted position by a spring. An annular projection is provided on the end surface of the first cylindrical insert fixedly arranged in the inner side of the inner side, while a protrusion for forming a preliminary hole for a screw hole is provided on the front end surface of the punch opposite to the die. The blank inserted in the recess is pressed so as to be sandwiched between the punch and the knockout pin, the preliminary hole not penetrating is formed, the annular protrusion is press-fitted into the blank, and an outer shape is formed. A square nut body is provided with a cylindrical pilot portion whose end face works as a punch for punching out a metal plate at the central portion including the preliminary hole, and along the outer periphery of the nut body. It provided projecting sidewalls so as to surround the pilot portion, and the forming die punch nut blank to form an annular groove between the said pilot portion sidewalls,
A second cylinder provided with a taper wall extending outwardly at the base of the punching punch disposed in the concave portion of the die for the next step of inserting the nut blank, and being fitted over the punching punch. An annular projection for inserting into the annular groove is provided on the end face of the cylindrical insert, and the nut punch is inserted into the concave portion of the die in the next step and pressed by the cooperative action of the cylindrical punch and the punching punch. The pilot hole is punched to form a screw hole, and the end face portion of the pilot portion is radially expanded by the tapered wall to incline the peripheral side wall surface of the pilot portion that defines the annular groove. Forming a groove in the dovetail that expands to the back, and punching and pilot part expansion forging die punch with a configuration that restricts the outer peripheral edge of the pilot part against the inner side surface of the annular protrusion, and
A knockout pin which is disposed so as to be capable of moving forward and backward in the axial direction in a recess of a die in the subsequent process for inserting the nut blank with the hole punched and enlarged pilot portion, and having a knockout pin biased to a retracted position by a spring, A tapered wall for inclining the side wall of the nut blank toward the axial line side is provided in the inner part of the recess, and is inserted into the annular groove at the end surface of the third cylindrical insert disposed at the bottom of the recess of the die in the subsequent process. When the nut blank is inserted and pressed into the concave portion of the next-stage die with a punch opposite to the next-stage die, the side wall is inclined toward the axis by the tapered wall. The annular groove is formed into a dovetail having a deepened width, and the side wall is tilted so that the inner edge of the side wall inclined toward the axial line is in contact with the outer surface of the annular protrusion and is regulated. In the manufacturing apparatus of the pierce nut according to the nut Homer with a forming die punch,
The hole punching and pilot portion expansion die punch and the second cylindrical insert are fixedly held in the concave portion of the die for the next step, and four holes are provided so as to surround the hole punch. Knockout pins are provided, and the nut punch is inserted into the concave portion of the die in the next step and pressed by the cylindrical punch and the punching punch, thereby punching the screw-down hole and the The end face of the four corners in the diagonal direction of the nut blank after the expansion of the pilot part is pushed out by the four knockout pins and pushed between the pair of fingers of the transfer mechanism located near the end face of the die. The pierce nut manufacturing apparatus characterized by the above-mentioned. The punching punch and the second cylindrical insert are fixed and held via a holder in the recess of the die for the next process,
The four knockout pins are attached to the holder so as to be able to advance and retreat in the axial direction around the hole punching punch and are urged to a retreating position by a spring, and are in a retreating position. When the front end surface is flush with the front end surface of the second cylindrical insert, abuts against the end surfaces of the diagonal corners of the nut blank at the time of advance, the nut blank is pushed out, The pierce nut manufacturing apparatus according to claim 2, wherein the apparatus is configured to be pushed between fingers.

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