IE56897B1 - Method for producing a composite center electrode for spark plug - Google Patents

Abstract

The invention is directed to an improved method for producing a composite spark plug electrode 58. Initially, a cup (15, Fig. 2), is formed from a corrosion resistant first metal and is partially filled with a billet (20) to form a composite billet (22). The composite billet (22) is partially extruded to form an electrode blank (30, Fig. 4). A cup opening (39, Fig. 8) is formed in the end of the electrode blank which was formed from the open end of the cup (15). An end of a terminal wire 40 is positioned within the cup opening (39) and the electrode blank walls adjacent the cup opening (30) are deformed inwardly to interconnect the electrode blank 30 with the terminal wire 40. The method may be used to attach a wire to a solid electrode.

Description

This invention relates to spark plug electrodes and more particularly to a method for producing a composite center electrode for a spark plug.

I έ r fc Each particular internal combustion engine design operates most efficiently with a spark plug having a heat range selected for such engine.

Various factors go into determining the heat range for a spark plug, such as the thermal properties of the insulator and the center electrode and the length of the Insulator firing tip extending from the insulator seat. If the insulator firing tip is too short, for example, the center electrode and the Insulator firing tip will operate too cold and tend fo foul with combustion deposits.

On the other hand, if the insulator and center electrode extend too far from the insulator seat, the center electrode will over heat and may cause preignltion. By providing a thermally conductive core to tbe center electrode, heat will be dissipated more rapidly from the electrode and, consequently, a longer electrode and insulator nose may be used without causing pre-ignition. < This in turn increases the fouling path and the amount of deposits which can be tolerated without ? t failure. · In one type of spark plug design, the portion ' of the center electrode located within and projecting * from the insulator nose comprises a sheath formed from a corrosion resistant nickel alloy which surrounds a thermally conductive copper core. An iron terminal wire is welded to the internal end of this electrode. The iron terminal wire extends through a compacted powder seal within the Insulator bore and Is connected either directly to a high voltage terminal for the spark plug or is connected through, for example, an ignition noise suppressor and/or an auxiliary spark gap to the high voltage terminal. In forming the electrode, it is necessary to completely enclose the copper core within the nickel sheath so that no copper is exposed to the combustion gases in the combustion chamber and also so that a solid nickel end is provided for welding to the iron wire.

Various methods are known in the prior art for forming spark plug center electrodes having a high thermal conductivity, such as electrodes having a nickel sheath surrounding a copper core. One commercial method for forming such electrodes consists of placing a copper billet within a nickel cup having cylindrical sidewalls, a closed end and an open end. The copper billet is recessed from the open end of the cup and the open end is rolled over to partially enclose the copper billet. The resulting composite billet then Is forced, closed end first, partially through an extrusion orifice. The resulting extrusion is pushed back and withdrawn from the orifice, leaving an electrode having a closed lower end which forms one side of the spark gap in the completed spark plug and a larger diameter upper end In which the nickel extends over and encloses the copper. An Iron terminal wire then Is welded to the nickel sheath to extend coaxially from the larger diameter end of the extruded electrode. In assembling the spark plug, the center electrode is inserted into a stepped bore in a spark plug insulator until the larger diameter portion seats against the bore step.

A seal is positioned in the annular space above the enlarged diameter portion of the electrode and between tbe iron terminal wire and the * insulator, in a conventional manner.

Xn a modified prior art method for manufacturing spark plug electrodes of this type, a composite billet is again formed by inserting a copper billet within a closed bottom nickel cup to form a composite billet. The nickel may be rolled over the end of the billet to retain the copper billet within the cup and then the composite billet is extruded hy passing the open end first through an extrusion orifice. During the extrusion process, the nickel wall at the open end of the cup is closed over the copper core. The extrusion then is backed from the extrusion orifice, the remaining larger diameter shoulder is sheared from the extrusion, a head is formed on the extruded end of the extrusion and an iron wire then is welded fo the head. Xn a modification of this method, a copper billet is positioned within a nickel cup so as fo be recessed from the open end of the cup and the end of an iron terminal wire is then held within the nickel cup while the nickel cup 9 is extruded, open end first. During the extrusion process, the end of the terminal wire within the cup is deformed to form a mechanical connection e between the nickel cup and fhe terminal wire.

The electrode then is completed hy forming a suitable shoulder for seating against fhe insulator bore step. Although each of these methods produces a high quality electrode, the manufacturing process for fhe electrode is relatively expensive, particularly in electrodes in which the terminal wire must be welded fo the extrusion. φ In accordance with the present invention, an Improved method is provided for manufacturing spark plug electrodes of the type having a low cost terminal wire attached to an upper or interior end of fhe electrode. A composite billet Is formed initially by positioning a copper billet within a nickel alloy cup. An extruded electrode blank is formed by passing at least a portion of the composite billet through an extrusion orifice having a diameter less than the exterior diameter of the cup. An end of fhe electrode blank which is completely formed from nickel will form one side of a spark gap while the other or interior end of the electrode blank is connected to a low cost iron terminal wire to complete the electrode. The terminal wire is attached fo the electrode blank by forming a cup in fhe interior end of the electrode blank, positioning an end of the electrode wire in fhe formed cup and deforming the walls of the cup to cause metal to flow inwardly into contact with the terminal wire to mechanically and electrically interconnect the terminal wire and the electrode blank. If desired, a slightly Increased diameter flange or head may be formed on fhe end of the β wire prior fo Inserting fhe headed wire end into the cup to strengthen the connection between the terminal wire and the electrode blank.

In the improved electrode formed by the method of the present invention, the electrode wire is connected to the electrode blank without the use of welding and without the need for totally enclosing the copper core within the nickel alloy cup at the point of connection. The method also can be used to attach a terminal wire to a headed end of a solid electrode of a nickel alloy, for example, without welding. As a consequence, the cost for manufacturing the electrode is reduced over prior art techniques for manufacturing welded center electrodes.

The invention will now be more particularly described, by way of example, with reference to the accanpanying drawings, in which:Fig. 1 is a vertical cross sectional view showing a corrosion resistant metal cup and a 2o cylindrical billet of a metal having a high thermal conductivity prior to being inserted into the cup in accordance with a first step of an embodiment of a method of the present invention? Fig. 2 is a cross sectional view showing a composite billet after the thermally conductive billet is Inserted into the corrosion resistant cup, upset or staked in place and the edges of the cup crimped inwardly to retain the copper billet in place; Fig. 3 is a fragmentary cross sectional view showing the composite billet position within the bore of an extrusion die prior to extrusion; Fig. 4 is a fragmentary cross sectional view, similar to Fig. 3, but showing the billet within the extrusion die at completion of extrusion; Fig. 5 is a cross sectional view through the eJ electrode blank after extrusion and after excess metal is axially sheared from the butt at the nonextruded end of the electrode blank; Fig, 6 is a fragmentary cross sectional view 5 showing the electrode blank positioned within a first die for initially shaping the upper or interior end of the electrode blank; Fig. 7 is a fragmentary cross sectional view showing the electrode blank within the first die of Fig. 6 with a punch advanced to initially shape * the interior end of the electrode blank; Fig. 3 is a fragmentary cross sectional view through a second die showing the completion of formation of a cup at the interior end of the electrode blank; Fig. 9 is a fragmentary cross sectional view showing one method for attaching a terminal wire to the electrode blank; Fig. 10 is an enlarged fragmentary cross 20 sectional view through the completed electrode formed by the method illustrated in Figs, l through 9; Fig. 11 is a fragmentary cross sectional view showing a modified method for attaching a terminal wire to the electrode blank; Fig. 12 is an enlarged fragmentary cross sectional view of an electrode formed by the method illustrated in Fig. 1-8 and 11; Fig. 13 is a vertical cross sectional view showing a cylindrical billet of a metal of a high thermal conductivity prior to being inserted into a corrosion resistant metal cup for forming an m electrode blank by a modified embodiment of the Invention; Fig. 14 is a fragmentary cross sectional view 4 35 showing the composite billet positioned within the s bore of an extrusion die prior to extrusion; Fig. 15 is a fragmentary cross sectional view, similar to Fig. 14, showing the composite billet within the extrusion die at completion of extrusion; Fig. 16 is a cross sectional view of an extruded electrode blank and terminal wire prior to assembly by a modified embodiment of the invention; Fig. 17 is a fragmentary cross sectional view showing the extruded electrode blank of Fig. 16 positioned in a die and the terminal wire aligned with the electrode blank prior to advancing a tool ύ to attach the terminal wire to the electrode blank; Fig. 18 is an enlarged fragmentary cross sectional view showing the metal deformation in the electrode blank end when the tool of Fig. 16 is advanced; and Fig. 19 is a cross sectional view of the composite electrode produced by the die and tool of Fig. 17.

Referring to the drawings and particularly to Fig. 1, a cup 15 is illustrated formed from a corrosion-resistant material, such as a nickel alloy.

The cup 15 is formed to have a generally tubular sidewall 16, a closed end 17 and an open end 18.

The cup sidewall 16 and end 17 define a right cylindrical opening 19. A billet 20 of a metal having a high thermal conductivity such as copper is positioned within the cup opening 19. The billet 20 is shaped slightly smaller than and generally to conform with the interior surfaces of the cup end 17 and the tubular sidewall 16. However, the billet 20 is formed to have a longitudinal dimension shorter than the longitudinal dimension of the cup opening 19 so that an upper end 21 on the billet 20 will be spaced interiorly of the open cup end 18 when the & billet 20 ls positioned within the opening 19. Preferably, pressure is applied to the billet end 21 after the billet is inserted into the cup opening fo expand the billet 20 into contact with the 5 cup sidewall 16 and thereby retain the billet 20 within the cup 15. The assembled cup 15 and billet form a composite billet 22, as shown in Fig. 2. Optionally, a crimp 23 is formed in the portion of the cup side 16 above the billet end 21 and adjacent the open end 16. The crimp 23 slightly reduces the diameter of the open end to retain more positively the copper billet 20 within the cup 15.

After the composite billet 22 is completely formed, it is inserted, either open end first as shown, or closed end first Into the upper end of a close fitting bore 34 of an extrusion die 25, as shown in Fig. 3. The bore 34 has a diameter slightly larger than the exterior diameter of the billet 22 to confine the billet 22 to slide axially within the bore 24. A reduced diameter extrusion orifice 26 is located within the bore 24 and spaced from the upper surface 27 of the die 25 by a distance greater than the length of the composite billet 23. After the composite billet 22 is inserted into the bore 24, a tool or extrusion punch 23 having a flat end 29 is inserted into the bore 24 until the end *9 abuts the flat closed end 17 on the composite billet 22. The flat punch end 29 also has a diameter only slightly smaller than the diameter of the bore 24 so that the punch can be advanced ln the bore 24 to apply pressure across the entire closed billet end 17.

The punch 26 is advanced in the extrusion die bore 24 fo force most of the composite billet 22 through the extrusion orifice 26, as shown in Fig. 4.

As the composite billet 22 is forced through the extrusion orifice 26, an extruded electrode blank is formed. Since the punch 28 has a diameter greater than that of the extrusion orifice 26, the entire composite billet 22 cannot be forced through the orifice 26, leaving an enlarged diameter annular butt 31 at a closed end 32 on the electrode blank . After extrusion, the punch 28 is retracted from the die bore 24 and the electrode blank 30 is pushed by a suitable plunger (not shown) back through the orifice 26 and Is withdrawn from the bore 24.

During the extrusion process, the corrosion resistant metal in the crimped end 23 of the cup 1 portion of the billet 22 is forced together at an end 33 of the electrode blank 30 to enclose entirely a core 34 which was formed from the copper billet . It will be noted that the core 34 has an end adjacent to the closed end of the electrode blank 30 which is somewhat flat. This configuration provides for better heat flow from the electrode end than that achieved in prior art electrodes wherein the composite blank closed end 17 was first passed through the extrusion orifice 26. By passing the open end 18 of the composite blank 22 first through the orifice 26, the location of the core end 35 is more easily controlled than in prior art methods.

After the electrode blank 30 is removed from the extrusion die 25, the enlarged diameter butt is sheared from the electrode blank 30, as illustrated in Fig. 5. When the billet 22 is extruded closed end first, it may be unnecessary to trim the butt 31. The resulting electrode blank 30 has a uniform diameter throughout its length and a flat end 32 extending perpendicular * ii ri ill to the axis of the electrode blank 30 for forming one side of a spark gap in a spark plug.

As illustrated in Figs. 6-8, a head 36 is formed at the end 33 of the electrode blank 30.

The head 36 has a larger diameter than a shank portion 37 of the electrode blank 30 to form a shoulder 38 for seating within a stepped bore in a spark plug insulator (not shown). The head 36 also defines a cup 39 to which an iron terminal wire 40 is attached, as illustrated in Fig. 9.

Figs. 6 and 7 show an initial forming step on the end 33 of the extruded blank 30. The electrode blank 30 is inserted into an opening 41 in a die 42 so that the electrode blank end 32 abuts an ejector end 43. The shaped end 44 of a punch 45 is advanced into an enlarged diameter upper end 46 of tbe die opening 41 so as fo form the electrode blank end 33 into a slightly flattened end 36' having a configuration intermediate between the straight sides at the end 33 on the electrode blank and the head 36 which is ultimately formed on the electrode blank 30. The electrode blank 30 then is transferred to an opening 47 within a die 48, as illustrated in Fig. 8, and a stepped end 49 on a punch 50 is advanced Into an enlarged diameter upper end 51 of the die opening 47 to complete formation of the electrode blank head 36.

Referring to Fig. 9, the terminal wire 40 is attached to the electrode blank 30 by positioning the end 32 of the electrode blank 30 within an opening 52 in a die 53 with the electrode blank shoulder 38 seated against a die surface 54. An end 55 on the terminal wire 40 is positioned within the cup 39 and a tool 56 is advanced towards the die surface 54 to crimp sidewalls of the cup 39 radially inwardly against the terminal wire end 55. The tool 56 then is retracted and a completed composite electrode 53 is ejected from the die 53.

Fig. 10 is a fragmentary enlargement showing details of the completed composite electrode 58.

The closed end 32 from the electrode blank 30 forms a lower end of the composite electrode which will form one side of a spark gap when the composite electrode is assembled into a spark plug. The ι 3 ·♦ lower end of fhe composite electrode 58 includes a sheath or outer surface 59 formed from fhe corrosion resistant material, such as a nickel alloy, which initially formed the cup 15 in Fig. 1, and the core 34 of fhe lower end of fhe composite electrode is formed from a thermally conductive material, such as copper, which Initially formed the billet 20 in Fig. 1. By extruding the electrode blank 30 in a direction in which fhe open end 18 of fhe composite billet 22 was passed first through the extrusion orifice 26, quite accurate control is achieved over fhe location of the lower end 35 of fhe copper core 34 relative fo the lower end 32 of fhe composite electrode 58. The described method of manufacturing the composite electrode 58 also provides accurate control over fhe spacing between the lower electrode end 32 and fhe shoulder 38.

When the cup sidewall 57 was pressed inwardly against fhe terminal wire end 55, sufficient force was applied fo slightly deform the terminal wire end 55 fo provide a strong mechanical lock between fhe terminal wire end 55 and fhe deformed cup sidewall 57. Thus, the electrode wire 40 is attached to the extruded electrode blank 30 without welding, as in fhe prior art. The resulting composite electrode 58 is less expensive to manufacture than a similar electrode having a weld connecting the terminal wire fo the electrode blank and better coaxial alignment between the terminal wire 40 and the electrode blank 30 is achieved In fhe composite electrode 58 over a welded electrode Fig. 11 shows a modified method for attaching a terminal wire 80 to an extruded electrode blank 61 to form a composite center electrode 62 i ί 41 for a spark plug. The electrode blank 61 is similar to tbe electrode blank 37 described above and may be formed, for example, by the method illustrated in Figs. l-β. The electrode blank is positioned within an opening 63 in a die 34 so that a shoulder 65 abuts against a surface on the die 64. The terminal wire 60 is formed with a headed end 67 having a diameter slightly greater than the diameter in the remainder of the wire 60. The headed wire end 67 is positioned within a cup shaped open upper end 63 of the extruded electrode blank 61 and a tool 69 is advanced towards the die 64 to deform the upper electrode blank end 68 Inwardly over the headed wire end 67 and against the shank of the wire 60. The tool then is retracted and the composite electrode is completed.

Fig. 12 is an enlarged view illustrating details of the composite electrode 62. Composite electrode 62 has a lower end 69 which will form one side of a spark gap when the electrode 62 is assembled into a spark plug Insulator (not shown).

The lower electrode end 69 comprises a tubular sheath 70 formed from a corrosion resistant material, such as a nickel alloy, surrounding a thermally conductive core 71 formed, for example, from copper. The shoulder 65 is spaced a predetermined distance from the lower electrode end 69. Above the shoulder 65, tbe headed wire end is mechanically locked to the extruded electrode blank 61 by the nickel formed inwardly over the headed wire end 67 and against the shank of the wire 60. Accordingly, a strong bond is provided between the extruded electrode blank 61 and tbe terminal wire 30 without the need for welding. ι as Figs. 13-15 illustrate a modified series of steps for forming an extruded electrode blank 75 from a cup 76 formed from a corrosion resistant metal, such as a nickel alloy, and a billet 77 formed from a metal having a high thermal conductivity, such as copper. The billet 77 is initially inserted into an opening 76 ln the cup 76 to abut against a closed lower cup end 79. Optionally, the billet 77 may then be staked within the cup 76 to retain the billet 77 within the cup 76 during subsequent handling.

The assembled cup 76 and billet 77 form a composite billet 80 which is inserted into an opening 81 through an extrusion die 82. The composite billet 80 and the opening 61 have substantially the same diameter, with only a small clearance provided to allow the composite billet 80 to be received by and move axially in the opening 81.

The composite billet 80 moves downwardly within the opening 81 until the end 79 abuts a restricted diameter extrusion orifice 83. As illustrated in Fig. 14, the core 77 of the composite billet 80 has an upper surface 84 which ls recessed from an open upper end 85 of the cup 76. A punch 86 ls provided with a stepped lower end 87 which is shaped to conform with the upper end of the composite billet 80 so that a lower surface 88 on the punch 86 contacts the core surface 84 and a surface 89 on the punch 86 contacts the cup end 85. The punch 86 then is advanced downwardly, as illustrated in Fig. 15, to force a substantial portion of the composite billet 80 through the extrusion orifice 83, thereby forming an extruded electrode blank 75. Advancement of the punch 86 is stopped just short of extrusion orifice 83. V/hen the punch 86 is withdrawn from the die opening 81 and the extruded electrode blank 75 is removed from the die 82, the resulting electrode blank 75 has a cup shaped upper end 90 having an interior opening 91 of a diameter slightly smaller than the exterior diameter of a lower shank portion 92 of the electrode blank 75 which had passed through the extrusion orifice 83. For example, if the shank portion 92 of the electrode blank 75 has a diameter of 0.1 inch (0.254 an), the cup opening 91 may have a diameter on the order of 0.092 inch (0.233 cm) for receiving an iron terminal wire having a diameter on the order of 0.090 inch (0.228 an).

It will be appreciated that the terminal wire can be attached to the extruded electrode blank 75 by either of the methods Illustrated in Figs. 9 and 11.

A shoulder 93 is formed on the electrode blank 75 between the upper end 90 and the lower shank portion 92. Since the punch 86 is stopped at a precise location within the die 82, the length of the electrode blank 75 between the shoulder 93 and a lower end 94 will vary with changes in the volume of metal in the core 77 and the cup 76 within normal manufacturing tolerances. Accordingly, it is necessary to trim the electrode blank end 94 to obtain a desired distance between the shoulder 93 and the end 94.

Referring to Figs. 16-19, a modified method is illustrated for assembling an extruded electrode blank 98 and a terminal wire 99 (Fig. 16) into a composite center electrode 100 (Fig. 19) for a spark plug. The electrode blank 98 may be of a solid material, such as a nickel alloy, or it may have an outer surface 101 of a hard, corrosion resistant i 35 fl? material such as a nickel alloy and a core 102 of a high thermal conductivity material such as copper. The terminal wire 99 is of a low cost material, such as iron. The electrode blank 98 has an enlarged diameter cup shaped end 103 having an opening 104 sized to receive an end 105 of the terminal wire 99. A step 106 is formed on the electrode blank 98 where the cup shaped end 103 joins a shank portion 107 of the electrode blank 98.

Referring to Fig. 17, the electrode blank 98 is shown positioned in an opening 108 in a die 109. The die opening 108 is sized to receive the shank portion 107 and the step 106 abuts a die surface 110. Thus, the cup opening 104 faces away from the die surface 110. The terminal wire 99 is positioned in axial alignment with the electrode blank 98 by a suitable mechanism, not shown. A tool 111 is positioned with a stepped opening 112 spaced from an end 113 of the terminal wire 99 opposite the end 105. The tool opening 112 also is axially aligned with the terminal wire 99 and the electrode blank 98.

The tool 111 has a surface 114 which is moved parallel to and towards the die surface 110 to attacn the terminal wire 99 fo the electrode blank 98 to form the composite center electrode 100. As the tool 111 is advanced towards the die 109, the opening 112 receives the terminal wire 99. At the surface 114, an end 115 of the opening 112 has a diameter sized to receive the diameter of the cup shaped end 103 of the electrode blank 98. Adjacent the opening end 115, the opening 112 has an inwardly angled conical region 116. The conical region 116 preferably has an Included angle of about 30° to facilitate metal flow. Inwardly from the conical β region 116, there is an expansion region 117 having a diameter greater than the terminal wire 99 and less than the cup shaped end 103 of the electrode blank 98. The opening 112 has a long section 118 interior to the expansion region 117 which is sized to just receive the terminal wire 99. At an interior end of the section 118, the opening 112 has another inwardly tapered conical region 119 which forms a chamfer on the end 113 of the terminal wire 99. The conical region 119 preferably has an included angle of about 30° to facilitate metal flow. The interior end of the opening 112 is closed by an ejector pin 120.

As the tool 111 is advanced toward the die 109, the terminal wire end 113 passes through the tool opening end 115, the conical region 116, the expansion region 117 and into the opening section 118. When the terminal wire end 113 reaches the conical region 119, further advancement of the tool 111 forces the terminal wire end 105 into the cup opening 104 on the electrode blank 98. The cup end 103 also passes through the tool opening end 115. As the tool 111 is advanced further, the cup end is extruded along the terminal wire 99 and into the expansion region 117 of the opening 112, as shown in the enlarged fragmentary cross sectional view of Fig. 18, to form a joint 121 connecting the terminal wire 99 to the electrode blank 98.

As the tool 111 advance approaches completion, the terminal wire end 105 abuts an interior end 122 in the cup opening 104. During the final advance of the tool 111, the terminal wire cannot move and its end 113 is forced into tbe conical end region 119 of the tool opening 112 to form a chamfer 123 on the end 113 of the terminal wire 99. Thus, a © separate manufacturing step to form the chamfer 123 on the terminal wire 99 is eliminated. The chamfer 123 aids in aligning the center electrode 100 during assembly of a spark plug.

After the tool 111 is advanced to the point that the tool surface 114 contacts the die surface 110, the center electrode 100 is completed and the tool 111 is withdrawn. The ejector pin 120 in the tool 111 and an ejector pin 124 in the die 109 eject the composite center electrode 100 from the openings 108 and 112 as the tool 111 is moved away from the die 109. The resulting center electrode 100 has a higher degree of concentricity and a significantly lower manufacturing cost over a similar composite center electrode in which the terminal wire is welded to the electrode blank.

The present invention has been described for a spark plug electrode of the type having a core formed from a material having a high thermal con20 ductivity. In its broadest aspects, the Invention is equally applicable to attaching a terminal wire to a solid electrode formed, for example, from a nickel alloy. A cup is formed in the end of a solid rod or wire formed from tbe material by the method illustrated in Figs. 6-8, for example. The terminal wire then is attached by the method illustrated either in Fig. 9 or Fig. 11 or Fig. 17, thus eliminating welding.

Various modifications and changes may be made in the above described preferred method without departing from the scope of the following claims.

Claims (8)

CLAIMS:

1.L. A method for producing a composite spark plug electrode comprising the steps of: forming from a corrosion resistant first metal a cup having a tubular side of a predetermined exterior diameter, an open first end and a closed second end, partially filling said cup with a second metal having a high thermal conductivity with said second metal contacting interior surfaces of at least said closed end and being spaced inwardly from said open end, passing at least a portion of said partially filled cup through an extrusion orifice of a diameter less than the exterior cup diameter to form an electrode blank having first and second ends formed from the corresponding open and closed cup ends, forming a cup in said first blank end, positioning an end of a terminal wire in said blank^cup, and deforming the walls of said blank cup to cause metal to flow inwardly into contact with said terminal wire to provide a strong mechanical and electrical connection between said terminal wire and said electrode blank.

2. A method according to claim l, wherein said partially filled cup is passed open end first partially through said extrusion orifice, and further including the step of trimming the unextruded portion of said electrode blank to substantially the diameter of the extruded portion of said electrode blank. t

3. A method according co claim 1, wherein said partially filled cup is passed closed end first partially through said extrusion orifice by advancing a punch having a shaped end. and wherein said shaped punch 5 end forms the cup in said first blank end as said partially filled cup is passed partially through said extrusion orifice.

4. A method according to any one of the preceding claims, wherein the deforming of the walls of said blank LO cup inwardly also slightly deforms said terminal wire end to provide a strong mechanical and electrical connection between said terminal wire and said electrode blank.

5. A method according to any one of the preceding 15 claims, and further including the step of forming a chamfer on a second end of the terminal wire opposite said terminal wire end simultaneously with the step of deforming the walls of said blank cup.

6. A method according co any one of claims 1-3, and 20 further including the step of forming a head on said terminal wire end. wherein said wire head is positioned in said blank cup. and wherein the walls of said blank cup are deformed inwardly over said wire head to provide a strong mechanical connection between said wire 25 terminal and said electrode blank. 7 · A method for producing a spark plug electrode comprising the steps of: forming a metal electrode blank having a corrosion resistant surface and first and second ends, said second 5 end defining one side of a spark gap when said electrode is assembled in a spark plug; forming a cup in said first blank end; positioning an end of a terminal wire in said blank cup; and advancing a punch having a shaped cavity over said terminal *

7. 10 wire and said blank cup, said punch cavity deforming the walls of said blank cup to cause metal to flow inwardly into contact with said terminal wire to provide a strong mechanical ang electrical connection between said terminal wire and said electrode blank.

8. 15 8. A method according to claim 1 or 7 for. producing a spark plug electrode, substantially as hereinbefore described with reference to the accompanying drawings.