US3255623A

US3255623A - Method and apparatus for forming ball studs

Info

Publication number: US3255623A
Application number: US246985A
Authority: US
Inventors: Bernard E Ricks
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1962-12-26
Filing date: 1962-12-26
Publication date: 1966-06-14
Anticipated expiration: 1983-06-14
Also published as: FR1374200A; GB1061193A

Description

June 14, 1966 B. E. RICKS 3,255,623

METHOD AND APPARATUS FOR FORMING BALL STUDS Filed Dec. 26, 1962 2 Sheets-Sheet 2 4g Eg- 42a 4 g INVENTOR.

M 1 Bernard 5 6/065 AT ()RNEYS United States Patent 3,255,623 METHOD AND APPARATUS FOR FORMING BALL STUDS Bernard E. Ricks, Birmingham, Mich, assignor to TRW Inc., a corporation of Ohio Filed Dec. 26, 1962, Ser. No. 246,985 17 Claims. (Cl. 72-456) The present invention relates generally to the formation of a ball stud from 'a metal rod. The invention is more particularly concerned with improvements in a method and apparatus for manufacturing ball studs by punch and die extrusion techniques.

The present application is an improvement upon the techniques disclosed in my earlier issued US. Patent No. 3,036,367 entitled, Method of Making Ball Studs.

The method disclosed in my earlier patent illustrated how a blank of predetermined diameter and length was formed into a ball stud by locating the blank in alignment with a die having a cavity substantiallycorresponding to the outer shape of the final stud with the exception of the entire head thereof, and directing against one end of the blank a sliding gather punch to provide upon the blank, the stem, taper, shank and portion of the head ultimately desired. An extrusion punch was then vdirected at the center of the partially-shaped head to form a thimbleshaped cavity therein, and then a die was employed to reduce the open end of the partially-shaped head into the desired ball-shaped spherical configuration. This patent disclosed the technique for forming the thimble-shaped recess into an essentially round inner cavity in the head providing a lubricant reservoir for the tie rod socket or other structure within which the ball stud is normally received.

In the practice of my new method, essentially the same steps are employed in the formation of the ball stud described in my issued patent, but each of the steps has been improved. During the initial forming step and according to important features of my invention, I have found that by providing a constricting shoulder on a sliding punch sleeve that a locking metal mass may be formed upstream of the die cavity for developing a forward force vector in excess of a backward force vector enabling the sliding punch to be held in face-to-face contact with the die member to prevent rod metal leakage between these engaged faces. After the rod metal has been substantially displaced into the die cavity, the locking metal mass is also forced into the cavity and free of the constricting shoulder whereupon a conical recess is formed in the spherical head portion of the rod by the end of-the metal rod at the end of its stroke.

According to still other important features of this invention, the thus formed rod is placed into a second die member and an extrusion punch is forcefully engaged against the spherical head portion at the area of the conical recess and this extrusion punch is provided with a conical end having an included angle larger than the included angle of the conical recess whereby an oil trap is provided between the sliding punch and the conical recess to permit oil to flow axially from the oil trap with' the metal of the spherical head portion as the extrusion punch is forced into the spherical head portion displacing the material of the head portion around the extrusion punch to form an extended skirt portion.

According to yet other important features of this invention, as the extrusion punch is urged against the spherical head portion to form the extended skirt portion, a portion of the metal in the shank of the blank is displaced into a lockingc'avity in the second die member locking the shank with the second die member to enable the extrusion punch to be withdrawn and disengaged from the extended skirt portion. Thereafter, a knock-out pin is ac- Patented June 14, 1966 tuated to eject the ball stud blank from the second die member while simultaneously wiping back or displacing the bulge of metal lodged in the locking cavity or metal trap into the shank of the blank.

The thus formed blank is then rigidly held while being struck by a floating punch permitting the punch cavity to be properly aligned with the extended skirt portion as the skirt portion is displaced to provide a spherical head on the ball stud.

Other important features of this invention relate to the provision of a new and improved apparatus for securing engaged ends of a tubular punch holder and a die member in face-to-face relation while a punch is being actuated causing a spherical head portion to be formed in the die cavity on the end of a metal rod.

It is, therefore, an important aim of the present invention to provide improvements in the ball stud forming methods disclosed in my aforesaid patent. Another object of this invention lies in the provision of a method of providing a new andimproved oil trap between the extrusion punch and the ball stud blank for forming an annular skirt on a partially shaped head of the blank.

Still another object of this invention is to provide a new and improved method for separating an extrusion punch from a partially formed ball stud blank.

Yet another object of this invention is to provide a new and improved method for aligning a skirt shaping punch with respect to a partially formed ball stud blank so that the skirt portion can be more readily collapsed to provide a spherical head portion on a ball stud..

Other objects and advantages of the present invention will more fully become apparent in view of the following detailed description taken in conjunction with the accompanying drawings illustrating a single embodiment and in which:

FIGURE 1 is a view of a typical blank from which the finished ball stud may be formed;

FIGURE 2 is a sectional view of a first forming die showing the stud blank being directed therein by a sliding gather punch;

FIGURE 3 is a sectional view of the die of FIGURE 2 and showing the manner in which a locking metal mass is built up for securing the punch and the die member in.

face-to-face engagement as the metal of the rod is displaced into the die cavity;

FIGURE 4 is a sectional view of the die of FIGURE 3 showing the partially formed ball stud having a lubricant recess in the head portion thereof;

FIGURE 5 is a sectional view of a second die illustrating the method for forming an extended skirt portion on the head end of the ball stud blank; 7

FIGURE 6 is a fragmentary enlarged view illustrating the relationship of the punch shown in FIGURE 5 with respect to the enlarged head portion of the ball stud as shown in FIGURE 4 for the purpose of illustrating the oil trap;

FIGURE 7 is an enlarged vertical section of a third die for collapsing the extended skirt portion;

FIGURE 8 is an enlarged vertical section similar to FIGURE 7 only illustrating the manner in which the stud head portion is formed to final shape; and

FIGURE 9 is a side elevation of a finished ball stud of the type produced from the operation of the dies shown in FIGURES 1-8.

Referring now to the drawings,- and first to FIGURE 9, a full ball stud 10 as produced in accordance with this invention comprises a stem 11 of generally uniform diameter, which is illustrated as being threaded and as having a tapered end portion 11a. The ball stud 10 is also provided with

tapered portions

12 and 13 having diameters greater than the stem 11. Integral with the tapered portions is a shank 14 of generally uniform cross section throughout its length and upon which an integral head is received. The head is generally circular in cross section, as shown, and is provided interiorly thereof with a generally dome or bell-shaped cavity 16 (FIG- URE 8) connected with an open ended passage 17. The passage 17 provides a fluid path for lubricant into and out of the cavity, and said cavitythereby constitutes an elfective grease reservoir that can be drawn upon throughout the life of the tie rod socket or other structure with which the ball stud 10 is associated.

Illustrated in FIGURE 1 is a blank 20 which may be cut from coil stock to the desired diameter and length. The blank is adapted to be located partially within and in alignment with the axis of a die cavity 21 of a die member 22. The cavity 21 corresponds in general to the outer shape essentially of the ball stud 10, with the exception of the open end 17. It will be noted that the stern, taper and shank portions of the final ball stud are of lesser diameter and greater length than the forming surfaces of the cavity 21. Specifically, the die 22 includes a die case 23, a top die insert 24, a die liner 25 and a knock-out pin 26. The die cavity 21 includes a section 27 of relatively uniform diameter which provides the stem 11 of the stud. The cavity 21 is further comprised of

tapered sections

28 and 29 which preliminarily form the

portions

12 and 13 on the stud 10. It will, of course, be appreciated that for certain applications in practice, only a single taper on the stud is required, and accordingly the die cavity design may be suitably modified.

At the outer end of the cavity 21 is a semi-circular or semi-spherical shape within which a configuration is shaped comprising a ball head portion as shown in FIG- URES 3 and 4.

Mounted adjacent the die 22 is a punch assembly 30 which includes a punch casing or sleeve 31, a sliding punch or sleeve punch or punch guide 32 and a sliding gather punch 33 having a conical head 33a.

In the initial practice of the first step of the present process, the blank 20 is located with respect to the die cavity 21 in the manner shown and circumferentially surrounded by the sleeve punch or guide 32. In this position, the guide 32 has its end 32a engaged in face-toface relation with end 24a of the die insert 24. The sliding gather punch 33 is then forcefully urged against the end of the blank 20 at which moment the blank is forced to move into the die cavity 21 causing the blank to extrude into the cavities or bores 29, 28 and 27 of die liner 25 until the blank comes in contact with the end of the knock-out pin 26. While the blank is being extruded in this manner, the inside diameter of the tubular punch 32 supports the outside diameter of the blank and thereby prevents snaking of the blank. The forward motion of the punch pin 33 then continues after the blank comes into contact with the knock-out pin 26 and since the blank cannot move deeper into the die cavity at this point, the blank begins to bulge or upset into a spherical cavity 24b of the die insert 2 As the material is caused to flow, a force vector P develops which tends to cause the

faces

24a and 32a to move apart leaving a gap. If these faces were to separate, a dual gathering would occur, leaving a step on the end of the blank. Therefore, according to an important feature of this invention, the tubular punch holder 32 is provided with an annular rib 32b providing a stricture shoulder 32c upstream from the face 32a. Thus, as the blank is forced into the die, a locking metal mass 20a is upset behind the shoulder 32c developing a forward force vector P on the sliding punch 32. Because metal from the mass 29a must extrude past the shoulder and is confined to a smaller diameter by the rib 32b and because the metal gathering in the cavity 21 has not yet filled the cavity, the forward force vector F is greater than the backward force vector P. As a result the

faces

24a and 32a are held together in tight contact as the metal is upset into the semi-spherical cavity 24b.

The stricture or rib 32b is only a few thousandths of an inch and there is a gradual taper from the large diameter at the shoulder 32c to the opposite end'of the stricture 3212. When the rib 3212 becomes worn, the tubular punch holder 32 will move backward and produce defective ball studs unless the holder 32 is held against the die face 24a.

At the end of the forward stroke of the sliding gather punch 33, a conical indent 20b is coined in the end of the blank 20 by the conical end 33a of the punch 33. It will further be appreciated that as the conical end 33a of the punch 33 moves past the rib 32b, the locking metal mass is caused to flow from behind the shoulder 32c and is forced into the die cavity 21 so that the engaged

faces

24a and 32a may be separated by moving the punch assembly 34) away from the die assembly 22. The knockout pin 26 is then actuated to force a partially formed ball stud blank 36 from the die cavity 21.

The partially formed ball stud blank 36 is then placed into a second die cavity 39 provided in a second die 40. The die 40 includes a die case 41 having a die insert 42, a taper insert 43, a bottom insert 44, a filler insert 45, and a knock-out pin 46. The insert 42 is provided with an annular recess 42a defining a metal trap which is only a few thousandths of an inch larger than the inside diameter of the cavity 39 at the area of the trap 42a.

A sliding extrusion punch assembly 47 is mounted adjacent the die assembly 40 and includes a punch holder 48 and an extrusion punch 49 having a conical end 49:: with an included angle that is larger than the included angle of the conical indent or recess 20b in the end of the ball stud blank 36 as illustrated in FIGURE 6.

The purpose of the metal trap 42a is to permit the outside diameter of the blank 36 to swell into the trap under the heading pressure developed by the extrusion punch 49 as it is projected against the partially formed ball stud blank 36, as shown in FIGURE 5. The swell or displaced portion of the blank is identified at 47'. This displaced portion 4'7' functions to secure the blank 36 in the die while the extrusion punch 49 is retracted out of the die cavity 39. The bulge or displaced portion 47 is then wiped back to the taper of the blank 36 in the die upon actuation of the knock-out pin 46.

The depth of the metal trap 42a must be limited to a few thousandths of an inch in order for the bulge 47' to be wiped back to the shank of the blank and in order to avoid giving the blank a poor appearance. If the metal trap 42a is too shallow, the blank will stick on the punch 49 and this will result in the blank 36 being re-struck in the die unless the operator stops the machine before the ram again actuates the punch 49.

The included angle at the conical indent 20b in the end of the blank 36 is smaller than the included angle of the conical end 49a of the extrusion punch. When the extrusion punch 49 initially contacts the blank 36 as shown in FIGURE 6, an oil trap is formed at the face of the extrusion punch and the oil trapped at the face of the punch prevents metal to metal contact as the metal in the blank 36 is caused to flow radially of the punch during the punching operation. As the metal is caused to flow radially at the face of the punch, oil is metered out of the oil trap along with the metal flow thereby lubricating the bearing portion 49b of the extrusion punch. An extrusion lubricant or oil of any suitable type is directed at the extrusion punch when the punch is moving through the rear half of the stroke cycle. The lubricant has a dual purpose to lubricate the punch and to keep the temperature of the punch down to a minimum. The extrusion of lubricantion spray must be carefully controlled to prevent inadequate lubrication so that excessive heat will not be generated during extrusion of the blank. If the spray oil density is excessive and the air velocity is insufficient, the punch will be flooded with oil and excessive oil will be trapped between the extrusion punch and the end of the blank which may tend to cause ruptures in the blank and/ or an excessive amount of smoke. It is also undesirable to spray the .punch and allow the punch to enter the empty die cavity, for oil will then be trapped in the die cavity and will prevent proper forming of the blank. Skin ruptures are a common result of oil trapped in the die cavity.

In order to enable the blank 36 to be removed from the die 40, the die cavity is provided with an angled flared mouth surface 39a. The angle at the mouth of the die cavity is not discernible to the eye, but it is nevertheless flared slightly outwardly in a direction away from the cavity 39 permitting easier stripping of the punch out of the blank and easier stripping of the blank 36 from the die cavity 39.

After the blank 36 is removed from the second die 40, a-third die 50 is provided having a die cavity 51 for receipt of the blank. The die assembly 50 includes a die case 52, a top die insert 53, a taper die insert 54, a pointing die insert 55, a filler insert 56, and a knock-out pin 57. Mounted adjacent one end of the die assembly 50 is a punch assembly 58 including a punch holder 59 and v a floating forming punch 60. A relatively large clearance 61 is provided between the outside diameter of the punch and the inside diameter of the punch holder to permit a limited float of the punch with respect to thepunch holder. This float permits the forming punch to align itself to the blank as the blank is being formed and eliminates the need for precise alignment of a rigid punch with respect to a rigidly held blank.

The floating punch 60 has a semi-spherical recess 60a for forming the annular skirt portion 36a into a generally spherical shape with the head portion 36b of the blank.

In order to assist in the collapsing of the skirt portion 36oz of the blank, the punch die cavity 60a has a small lead radius 6% at the mouth of the forming punch to avoid scraping of the blank surface by the leading edge of the punch. After the annular skirt portion 36a is formed in the manner illustrated in FIGURE 8, the punch assembly 58 is retracted and the knock-out pin 57 is actuated to free the hollow head ball stud 10 from the die 50. The stem 11 of the stud 10 may be threaded in a subsequent machine operation.

It will be seen-from the foregoing that applicant has provided a new and improved method for manufacturing a ball stud as Well as improved apparatus for manufacturing ball studs. By practicing the described method, it is not necessary to heat the dies or the metal being worked. The die structures required to produce the ball studs are of relatively simple construction. By employing the method and apparatus described herein, the percentage of ball stud rejects may be materially reduced and the apparatus may be maintained. in continuous operation for longer periods without mechanical failure.

It is to be understood that variations and modifications may be practiced in the method and apparatus herein disclosed without departing from the spirit of the invention or the scope of the claims.

I claim as my invention:

1. In a method of forming a ball stud from a metal rod,'the steps of disposing an end of the metal rod within a die cavity defined between a punch holder and a die member and moving the punch holder in flush engagement with the die member, moving a sliding gather punch having a conical end face axially through the punch holder against the end of the rod and forming a locking metal mass upstream of the cavity developing a forward force vector in. excess of a backward force vector acting to separate engaged faces of the punch holder and the die member locking the punch guide and the die member together at the die cavity while directing the metal into the die cavity and while confining the path of metal flow in an opposite axial direction to form a segmented spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke,

placing lubricant in said recess,

directing an extrusion punch against the spherical head portion while disposed in a second cavity of a second die member with the included angle on a conical end of the extrusion punch being larger than the included angle of the conical end on the sliding gather punch providing an oil trap preventing metal to metal contact between the conical end and the conical recess causing the oil to flow axially from the oil trap with the metal of the head portion as the extrusion punchis pushed against the spherical head portion displacing a central portion of said head portion axially around said extrusion punch to form an extended skirt portion while contemporaneously displacing a portion of a shank of said rod into the second die member locking the shank with the second die member to enable the extrusion punch to be retracted and disengaged from the extended skirt portion,

knocking the thus formed ball stud blank from the second die member while contemporaneously wiping' ofi the displaced portion onthe shank of the rod, and die forming said extended skirt portion to a contour complementing the contour of said head portion. 2. In a method of forming a ball stud from a metal rod, the steps of disposing an end of the metal rod within a die cavity defined between a punch holder and a die member :and moving the punch holder in flush engagement with the die member, moving a sliding gather punch having a conical end \face axially through the punch holder against the end of the rod and forming a locking metal mass upstream of the cavity developing a forward force vector in excess of a backward force vector act-ing to separate engaged faces of the punch holder and the die member locking the punch guide and the die member together at the die cavity while directing the metal into the die cavity and while confining the path of metal flow in an opposite axial direction to form a segmented spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke, placing lubricant in said recess, directing an extrusion punch against the spherical head portion while disposed in a secondcavi-ty of a second die member thereby displacing a central oprtion of said head portion axially around said extrusion punch to form an extended skirt portion, knocking the thus formed ball stud blank from the second die member, and die forming said extended skirt portion radially inwardly to form a generally spherical contour cornplementing the contour of said head portion. 3. In a method of forming a ball stud from a metal rod, the steps of disposing an end of the metal rod within av die cavity defined between a punch holder and a die member, moving a sliding gather punch having a conical end :face axially through the punch holder against the end of the rod directingthe metal into the die cavity While confining the path of metal flow in an opposite axial direction to form a segmented sphericalhead portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke, placing lubricant in said recess, directing an extrusion punch against the spherical head portion while disposed in a second cavity of a second die member with the included angle on a conical end of the extrusion punch being larger than the included angle of the conical end on the sliding gather punch providing an oil trap preventing metal to metal contact between the conical end and the conical recess causing the oil to flow axially from the oil trap with the metal of the head portion as the extrusion punch is pushed against the spherical head portion thereby displacing a central portion of said head portion axially around said extrusion punch to form an extended skirt portion while contemporaneously displacing a portion of a shank of said rod into the second die member locking the shank with the second die member to enable the extrusion punch to be retracted and disengaged from the extended skirt portion,

knocking the thus formed ball stud blank from the second die member While contemporaneously wiping oh the displaced portion on the shank of the rod, and

die forming said extended skirt portion to a contour complementing the contour of said head portion.

4. In a method of forming a ball stud from a metal rod, the steps of disposing an end of the metal rod within a die cavity defined between a punch holder and a die member and moving the punch holder in flush engagement with the die member,

moving a sliding gather punch having a conical end face axially through the punch holder against the end of the rod and forming a locking metal mass upstream of the cavity developing a forward force vector in excess of a backward force vector acting to separate engaged faces of the punch holder and the die member there-by locking the punch guide and the die member together at the die cavity while directing the metal into the die cavity and while confining the path of metal flow in an opposite axial direction to form a segmented spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke,

directing an extrusion punch against the spherical head portion while disposed in a second cavity of a second die member thereby displacing a central portion of said head portion axially around said extrusion punch to form an extended skirt portion while contemporaneously displacing a portion of a shank of said rod into the second die member locking the shank with the second die member to enable the extrusion punch to be retracted and disengaged from the extended skirt portion,

knocking the thus formed ball stud blank from the second die member while contemporaneously wiping ofl? the displaced portion on the shank of the rod, and

5. In an apparatus for forming a ball stud from a metal rod,

a die member having a die cavity for receiving an end of the metal rod,

means including a tubular punch holder and a sliding gather punch mounted therein with the punch holder being movable in flush engagement with the die member,

said sliding gather punch having a conical end for engagement against an end of the rod,

said punch holder having a constricting shoulder adjacent the area of engagement between said punch and said punch holder providing means for forming a locking metal mass upstream of the cavity for developing a forward force vector in excess of a backward force vector acting to separate engaged faces of the punch holder and the die member thereby locking the punch guide and the die member together at the die cavity while the metal of the rod is displaced into the die cavity and while the path of metal flow in an opposite axial direction is confined to form a segmented spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke. 6. in an apparatus for forming a ball stud from an unheated metal rod of constant cross section,

a die member having a die cavity for receiving an end of the metal rod, means including a tubular punch holder and a sliding gather punch mounted therein with the punch holder being movable in flush engagement with the die member, said sliding gather punch having a conical end for engagement against an end of the rod, said punch holder having a constricting shoulder adja cent the area of engagement between said punch and said punch holder providing means for forming a locking metal mass upstream of the cavity for developing a forward force vector in excess of a backward force vector acting to separate engaged faces of the punch holder and the die member for thereby locking the punch guide and the die member together at the die cavity while the metal of the rod is flowed into the die cavity and while the path of metal fiow in an opposite axial direction is confined to form a segmented spherical head portion, i said sliding gather punch being movable axially across said constricting shoulder to force the locking metal mass into said cavity and to permit the locked faces of the tubular punch holder and the die to be disengaged. 7. In -an apparatus for forming a ball stud from an unheated metal rod of constant cross section,

a die member having a die cavity for receiving an end of the metal rod, means including a tubular punch holder and a sliding gather punch mounted therein with the punch holder being movable in flush engagement with the die member, said sliding gather punch having a conical end for engagement against an end of the rod, said punch holder having a constricting shoulder adjacent the area of engagement between said punch and said punch holder providing means for forming a locking metal mass upstream of the cavity for developing a forward force vector in excess of a backward force vector acting to separate engaged faces of the punch holder and the die member and thereby locking the punch guide and the die member together at the die cavity while the metal of the rod is flowed into the die cavity and while the path of metal flow in an opposite axial direction is confined to form a segmented spherical head portion, said sliding gather punch being movable axially across said constricting shoulder to force the locking metal mass into said cavity and to permit the locked faces of the tubular punch holder and the die to be disengaged, said constricting shoulder comprising an annular rib disposed in the tube defined by the tubular punch holder. 8. In a method of forming a ball stud from an unheated metal rod of constant cross section, the steps of disposing an end of the metal rod within a die cavity defined between a punch holder and a die member, moving a sliding gather punch having a conical end face axially through the punch holder against the end of the rod thereby directing the metal into the die cavity while confining the path-of metal flow in an opposite axial direction to form a segmented 9 spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke, placing lubricant in said recess,

pushing an extrusion punch against the spherical head portion while disposed in a second cavity of a second die member with the included angle on a conical end of the extrusion punch being larger than the included angle of the conical recess providing an oil trap preventing metal-to-metal contact between the conical end and the conical recess with the oil preventing metal-to-metal contact during the radial flow of metal at the face of the extrusion punch causing the oil to be metered out of the oil trap along with the metal flow axially of the extrusion punch to lubricate an extrusion punch bearing at its outer diameter forming an extended skirt portion at the outer diameter of the extrusion punch,

removing the thus formed ball stud blank from the second die member, and

die forming said extended skirt-portion to a contour complementing the contour of said head portion.

9. In a method of forming a ball stud from a metal rod, the steps of disposing an end of the metal rod within a die cavity defined between a punch holder and a die member and moving the punchholder in flush engagement with the die member,

moving a sliding gather punch having "a conical end face axially through the punch holder against the end of the rod and forming a locking metal mass upstream of the cavity developing a forward force vector on the sliding gather punch in excess of a backrward force vector exerted between the die cavity and the punch holder acting to separate engaged faces of the punch holder and the die member thereby locking the punch guide and the die member together at the die cavity while directing the metal into the die cavity and while confining the path of metal flow in an opposite axial direction to form a segmented spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke,

directing an extrusion punch against the spherical head portion while disposed in a second cavity of a second die member thereby displacing a central portion of said head portion axially around said extrusion punch to form an extended skirt portion while contemporaneously displacing a portion of a shank of said rod into the second die member locking the shank with the second die member to enable the extrusion punch to :be retracted and disengaged from the extended skirt portion.

knocking the thus formed ball stud blank from the second die member while contemporaneously wiping off the displaced portion on the shank of the rod, and

rigidly holding the ball stud blank while moving a floating punch axially against said extended skirt portion effecting alignment of the extended skirt portion with a punch cavity in the floating punch and causing the extended skirt portion to be collapsed radially inwardly to a contour complementing the contour of said head portion.

10. In a method of forming a ball stud from an unheated metal rod of continuous cross section, the steps of disposing an end of the metal rod within a die cavity defined between a punch a holder and a die member and moving the punch holder in flush engagement with the die member,

moving a sliding gather punch having a conical-end face axially through the punch holder against the end of the rod and thereby directing the metal of the rod into, the die cavity while confining the path of metal flow in an opposite axial direction to form a segmented spherical head portion and with the sliding gather punch forming a conical recess in the spherical head portion of the metal rod at the end of its stroke,

directing an extrusion punch against the spherical head portion while disposed in a second cavity of a second die member thereby displacing a central portion of said head portion axially around said extrusion punch to form an extended skirt portion while contemporaneously displacing a portion of a shank of said rod into the second die member thereby locking the shank with the second die member to enable the extrusion punch to be retracted and disengaged from the extended skirt portion,

rigidly holding't-he ball stud blank while moving a floating punch axially against said extended skirt portion effecting alignment of the extended skirt portion with a punch cavity in the floating punch and causing the extended skirt portion to be collapsed radially inwardly to a contour complementing the contour of said head portion.

11. In a method of making headed metal articles by upsetting in a die, the improvement which comprises seating a hollow punch holder against a face of the die around the upsetting cavity of the die, providing a reduced diameter extrusion throat in the punch holder adjacent the die face engaging end of the punch,

confining a metal blank in the die and punch holder, and V feeding a punch in the holder against the blank to upset the blank in the die cavity and behind the extrusion throat thereby forming a locking metal mass upstream from the throat effective to create a force vector on the punch holder from the punch force to hold the punch holder against the die face.

12. A method of forming a ball stud, which comprises seating a hollow punch holder against a face of a die around an upsetting cavity in the die, and

feeding a sliding gather punch in the holder against a metal blank in the die and the holder to extrude a portion of the blank through an extrusion throat in the holder and to upset the blank in the die cavity adjacent the extrusion throat so that a deformed portion of the blank between the extrusion throat and the punch exerts on the holder a force which urges the holder against the die face.

13. A method as claimed in claim 12, in which the punch, the punch holder and the die cavity cooperate to form the upset portion of the blank into a segmental spherical head in the die cavity, and the punch has a conical end face which forms a conical recess in such head, in which the blank is subsequently disposed in a second die cavity in a second die and an extrusion punch having a conical end is pushed into such recess to extr-ude the head of the blank to form a skirt around the extrusion punch, and in which the skirt is subsequently die formed in a further die to form the head into a ball shape.

14. A method as claimed in claim 12, in which the conical end of the extrusion punch has an inclined angle greater than that of the conical recess in the head of the blank and lubricant is placed in such recess before the extrusion punch is pushed into such recess, and the lubricant is trapped in such recess by the extrusion punch to prevent metal-to-metal contact between the conical end of the extrusion punch and the bottom of the recess during radial flow of the metal of the blank at the conical end of the extrusion punch, the oil being squeezed from the recess to lubricate axial flow of such metal at the outer diameter of the extrusion punch.

15. A method as claimed in claim 12, in which during the formation of the skirt a portion of a shank on the blank is displaced radially outwardly into locking engagement with the second die to facilitate subsequent retraction and disengagement of the extrusion punch from the skirt, and the radially outwardly displaced portion of the shank is wiped oil on knocking of the blank from the second die.

16. Apparatus for forming a ball stud, comprisifig a die formed with an upsetting die cavity, a hollow punch holder arranged to be seated against the die around the die cavity with an extrusion throat in the punch holder disposed adjacent the die cavity, and a sliding gather punch arranged to be fed in the punch holder to extrude a portion of a blank through the extrusion throat and to upset the blank in the die cavity beyond the extrusion throat, such throat being shaped so that the portion of the blank between the throat and the punch exerts on the holder a force which folds the holder against the die. 17. Apparatus as claimed in claim 16, in which the die cavity is shaped to form the upset portion of the blank into a segmented spherical head, and the punch has a conical end for forming a conical recess in such head.

References Cited by the Examiner UNITED STATES PATENTS 5/1962 Ricks 29--l49.5 5/1962 Ricks 29149.5

Claims

1. IN A METHOD OF FORMING A BALL STUD FROM A METAL ROD, THE STEPS OF DISPOSING AN END OF THE METAL ROD WITHIN THE DIE CAVITY DEFINED BETWEEN A PUNCH HOLDER AND A DIE MEMBER AND MOVING THE PUNCH HOLDER IN FLUSH ENGAGEMENT WITH THE DIE MEMBER, MOVING A SLIDING GATHER PUNCH HAVING A CONICAL END FACE AXIALLY THROUGH THE PUNCH HOLDER AGAINST THE END OF THE ROD AND FORMING A LOCKING METAL MASS UPSTREAM OF THE CAVITY DEVELOPING A FORWARD FORCE VECTOR IN EXCESS OF A BACKWARD FORCE VECTOR ACTING TO SEPARATE ENGAGED FACES OF THE PUNCH HOLDER AND THE DIE MEMBER LOCKING THE PUNCH GUIDE AND THE DIE MEMBER TOGETHER AT THE DIE CAVITY WHILE DIRECTING THE METAL INTO THE DIE CAVITY AND WHILE CONFINING THE PATH OF METAL FLOW IN AN OPPOSITE AXIAL DIRECTION TO FORM A SEGMENTED SPHERICAL HEAD PORTION AND WITH THE SLIDING GATHER PUNCH FORMING A CONICAL RECESS IN THE SPHERICAL HEAD PORTION OF THE METAL ROD AT THE END OF ITS STOKE, PLACING LUBRICANT IN SAID RECESS, DIRECTING AN EXTRUSTION PUNCH AGAINST THE SPHERICAL HEAD PORTION WHILE DISPOSED IN A SECOND CAVITY OF A SECOND DIE MEMBER WITH THE INCLUDED ANGLE ON A CONICAL END OF THE EXTRUSION PUNCH BEING LARGER THAN THE INCLUDED ANGLE OF THE CONICAL END ON THE SLIDING GATHER PUNCH PROVIDING AN OIL TRAP PREVENTING METAL TO METAL CONTACT BETWEEN THE CONICAL END AND THE CONICAL RECESS CAUSING THE OIL TO FLOW AXIALLY FROM THE OIL TRAP WITH THE METAL OF THE HEAD PORTION AS THE EXTRUSION PUNCH IN PUSHED AGAINST THE SPHERICAL HEAD PORTION DISPLACING A CENTRAL PORTION OF SAID HEAD PORTION AXIALLY AROUND SAID EXTRUSION PUNCH TO FORM AN EXTENDED SKIRT PORTION WHILE CONTEMPORANEOUSLY DISPLACING A PORTION OF A SHANK OF SAID ROD INTO THE SECOND DIE MEMBER LOCKING THE SHANK WITH THE SECOND DIE MEMBER TO ENABLE THE EXTRUSION PUNCH TO BE RETRACTED AND DISENGAGED FROM THE EXTENDED SKIRT PORTION, KNOCKING THE THUS FORMED BALL STUD BLANK FROM THE SECOND DIE MEMBER WHILE CONTEMPORANEOUSLY WIPING OF THE DISPLACED PORTION ON THE SHANK OF THE ROD, AND DIE FORMING SAID EXTENDED SKIRT PORTION OF TO A CONTOUR COMPLEMENTING THE CONTOUR OF SAID HEAD PORTION.