US3879976A

US3879976A - Starter slide and blade assembly for thread roller

Info

Publication number: US3879976A
Application number: US424870A
Authority: US
Inventors: Robert D Morton
Original assignee: Hartford Special Machinery Co
Current assignee: National Machinery Co
Priority date: 1973-12-14
Filing date: 1973-12-14
Publication date: 1975-04-29
Anticipated expiration: 1992-04-29
Also published as: BR7410115A; GB1473406A; DE2457922A1; JPS5092847A

Abstract

A starter blade assembly for a thread roller starter mechanism which comprises a reciprocable starter slide mounted for precision rectilinear movement throughout its full range of travel, a starter blade supported on the slide for gating and feeding a work blank between starting ends of a pair of thread rolling dies, and an adjustable biasing means acting directly on the slide for providing a preselected starting force responsive to a return movement of a one-way drive lever, permitting following movement of the slide and starter blade in a blank feeding direction under the force of the biasing means.

Description

United States Patent 11 1 Morton 1 i STARTER SLIDE AND BLADE ASSEMBLY FOR THREAD ROLLER [75] Inventor: Robert D. Morton. West Hartford.

Conn.

[731 Assignee: The Hartford Special Machinery Company. Simshurg. Conn.

[22] Filed: Dec. 14. 1973 I21] Appl. No.: 424.870

[52] U.S. Cl. 72/90; 10/162 R [51] Int. Cl BZlh 3/06: B2lh 9/02 [52%| Field of Search 10/111 R. 162 R. 165: 72/88. 90. I04

[56] References Cited UNITED STATES PATENTS 1.584.264 5/1926 Wilcox 72/90 1.696.225 12/1928 Blood 72/90 3.314.261 4/1967 Grohoski ct a1. 72/90 Apr. 29, 1975 3.371.820 3/1901'4 Grohoski et al. 72/90 X Primary Iimminvr-C. W. Lanham Assistant li.\'mninerE. M. Combs Armrnev. Agent. or I-'irmPrutzman. Hayes. Kalb &

Chilton 1571 ABSTRACT A starter blade assembly for a thread roller starter mechanism which comprises a reciprocable starter slide mounted for precision rectilinear movement throughout its full range of travel. a starter blade supported on the slide for gating and feeding a work blank between starting ends ofa pair of thread rolling dies. and an adjustable biasing means acting directly on the slide for providing a preselected starting force responsive to a return movement of a one-way drive lever. permitting following movement of the slide and starter blade in a blank feeding direction under the force of the biasing means.

8 Claims. 3 Drawing Figures STARTER SLIDE AND BLADE ASSEMBLY FOR THREAD ROLLER This invention generally relates to thread rollers and specifically concerns an improved starter mechanism for such machines of a type generally described in US. Pat. No. 3.371.820 entitled "Starter Mechanism for Thread Rolling Machine" issued Mar. 5. I968 in the names of Edward G. Grohoski and Robert D. Morton and assigned to the assignee of this invention.

A principal object of this invention is to provide an improved starter mechanism having a starter blade assembly the weight and inertia of which is significantly reduced for rolling threads on lightweight blanks at normal high speed operation.

Another object of this invention is to provide an improved starter mechanism ol an overload release type which is independent of its drive fo pacing operation of the starter blade.

A further object of this invention is to provide an improved starter mechanism wherein the length of the starter blade stroke is readily adjusted to accommodate blanks of different diameters without requiring change in the throw of a drive actuating cam.

Still another object of this invention is to provide an improved starter mechanism which reliably operates at a normal high operating speed the same way it does during slow speed adjustment during the step up when the machine is being turned over manually to insure correct adjustment ofthe machine at normal high operating speeds with the machine in match.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

A better understanding of the objects. advantages. features. properties and relationships of this invention will be obtained from the following detailed description and accompanying drawings which set forth an illustrative embodiment and is indicative ofa way in which the principle of this invention is employed.

In the drawings:

FIG. I is a partial plan view of a thread rolling ma chine showing a starter mechanism which is the subject of this invention;

FIG. 2 is a side elevational view, partly broken away. showing certain component parts of a starter blade assembly on an enlarged scale; and

FIG. 3 is an enlarged cross-sectional view taken generally along line 33 of FIG. I.

Referring to the drawings in detail. a thread rolling machine I is illustrated in FIG. 1. The machine l0 includes an elongated frame on table 12 to which is mounted a feed chute or guide track I4 for conveying blanks 15 in line from a hopper. not shown. to a pair of cooperating stationary and reciprocable dies 16 and 18 respectively. The stationary die I6 is mounted on a stationary die block 20. and the reciprocable die is mounted to a slide 22 by an adjustable clamp assembly 24.

Slide 22 is supported for reciprocable movement on a slide block 26 which can be adjusted on table 12 by suitable fasteners 28 for insuring alignment of the spacing between the stationary and reciprocable dies 16 and 18. A suitable clamp assembly 30 is provided for holding stationary die in place on die block 20.

Guide track 14 will be understood to be downwardly inclined so that blanks are fed between rails 34 to track 14. A combination gate and starter blade 36 is mounted adjacent an open end of track 14 for reciprocable movement between stationary and reciprocable dies [6 and I8. Blade 36 is driven for successively feeding each end blank from track 14 to between the starting ends of dies l6. 18. The feeding of each blank is initiated and timed to cooperate with reciprocable movement of slide 22 by a cam 38 driven by a main crank. not shown. of the machine It).

To reciprocate slide 22 and therefore the driven reciprocable die 18. crank wheel 40 has one end of a pit man arm 42 eccentrically pivotally mounted on crank wheel 40. and the other end of pitman arm 42 is pivotally connected to slide 22 by pivot pin 44. For each revolution ofcrank wheel 40. reciprocable die [8 is driven through one complete cycle with the stroke of die 18 being dependent upon the eccentricity of the pivotal mounting of pitman arm 42 to crank wheel 40.

To pace operation of starter blade 36. a drive mechanism 46 is provided which serves to retract starter blade 36 in one linear direction to open the end of track 14 and to remain open long enough for the single end work blank to be admitted from track I4 into position between the starting end of each die l6. 18. The end blank is to be positioned against the face of the moving die 18 at least by the time the moving die 18 comes to a position at the completion of its backstroke and reverses direction. Then the work blank is wedged between the starting ends ofthe dies I6. 18 by blade 36 to be accurately provided with a thread rolled onto the outer periphery of the blank upon movement olthe reciprocable die I8 relative to the fixed die 16. Drive mechanism 46 includes a one-way drive lever or operating lever 48. supported on a fixed pivot pin 50 secured to table I2. for movement in a plane parallel to the table 12. and a cam follower or cam roll lever 52 having a cam roll 54 shown mounted on a free end of lever arm 56 of the cam roll lever 52. The operating lever 48 likewise has a cam roll 58 for engaging a depending ear 60 (FIG. 2) of a bar slide 62 on which starter blade 36 is mounted. Operating lever 48 includes an angularly offset adjustment arm 64 which is biased in a counter-clockwise direction as viewed in FIG. I by a drive return spring 66. Drive return spring 66 has one end seated against arm 64 in surrounding relation to a head of a plunger 68 fixed to operating lever arm 64. The opposite end of spring 66 is seated on an L-shaped bracket 70 suitably fixed to table I2 and retained in position by a plunger 72 received within the confines of spring 66 with plunger 72 fixed to an upstanding car 74 of bracket 70.

Extending generally parallel to the operating lever adjustment arm 64 is an adjustment arm 76 of cam roll lever 52 which is spaced from the operating lever adjustment arm 64 in operative relation thereto by a roller 78 establishing a pivot point connection between the operating lever 48 and the cam roll lever 52. The latter is shown having its lever arm 56 extending in generally perpendicular relation to its adjustment arm 76.

During normal operation. cam roll lever 52 is supported for pivotal movement about a pivot pin 80 to which an arm 82 ofa starter engage lever 84 is secured. Starter engage lever 84 in turn is supported for pivotal movement about a fixed pivot pin 86 mounted to table 12 whereby both starter engage lever 84 and interconnected cam roll lever 52 are supported for selective movement in parallel overlying relation to table 12.

Starter engage lever 84 has a second arm 88 with an upstanding car 90 which will be understood to have an oversized opening, not shown, through which a bolt 92 extends. A similarly enlarged opening. not shown, is formed in an upstanding car 94 of a bracket 96 fixed to table 12. Bolt 92 extends through car 94 which serves as a stop for one end of a spring 98 having its other end seated against a washer 100 adjustably fixed in position on a threaded end portion of bolt 92 against an adjustment nut 102. Spring 98 accordingly will retain starter engage lever 84 in a selected position within the limits of the enlarged openings through which bolt 92 extends. to establish pivot pin 80 as a normally fixed pivot point for cam roll lever 52 for an operating cycle of machine with cam roll 54 in engagement with the contoured profile of driving cam 38 on the outer periphery of crank wheel 40.

While generally circular, the outer peripheral feed control contour of cam 38 has a high point or position of maximum radius 106 which forces cam roll lever 52 counterclockwise about its pivot pin 80 to drive operating lever 48 clockwise about its pivot pin 50 and against the bias of drive return spring 66. This action opens the discharge end of feed rails 34 of track 14 in timed relation to movement of reciprocable die 18 away from stationary die 16 by retracting starter blade 36 in one linear direction to the left of its illustrated position shown in FIG. 1 by the action of cam roll 58 mounted on arm 107 of operating lever 48 which is in one-way driving engagement with slide 62 in one angular direction (clockwise) of operating lever 48 to permit blank discharge.

Subsequent to blank discharge, cam roll 54 passes high point 106 of cam 38 to permit drive return spring 66 to move operating lever arm 64 in the opposite angular direction (counterclockwise) into its illustrated position in FIG. 1 and return cam roll lever 52 in a clockwise direction to continuously maintain cam roll 54 in constant engagement with driving cam 38.

Drive mechanism 46 and, specifically, its operating lever 48 provide the sole connection and sole drive to starter blade 36. In accordance with this invention, a starter blade assembly of significantly reduced weight and reduced inertia is provided without any associated conventional linkage required to support starter blade 36 which would introduce undesired added mass and turning moments. This reduced weight and inertia is critical at high operating speeds to provide a machine production rate, e.g., of 750 pieces per minute when handling lightweight blanks which in finished diameter range from 0.062 to 0.156 inch diameter sizes. It will be seen that the blanks must each be wedged between the rolling dies 16, 18 with an exceptionally low starting force to ensure that the blank is not driven beyond the match point of the dies 16, 18, i.e., the time and position at which dies 16 and 18 are matched with the thread crests opposite the thread roots to ensure rolling the blank with a thread which accurately tracks both dies without shaving the thread flanks.

[n the specifically illustrated embodiment, slide 62 is mounted, within a housing or cage 108 bolted to talbe 12, for reciprocable movement toward and away from the work station between dies 16, 18. More specifically, slide 62 has an exposed working end protruding from cage 108. Starter blade 36 is mounted in a dovetail groove 110 (FIG. 2) formed on a side face 112 of the exposed end of bar slide 62, and a keeper clamp 113 is releasably secured to fix blade 36 in position on slide 62. Blade 36 is in a plane generally perpendicular to the discharge end of feed rails 34 when operating lever cam roll 58 is engaged by slide 62 to terminate movement of blade 36 in a blank feeding direction at its illustrated starting position. Additionally. blade 36 is of such a length that it extends opposed surfaces of dies 16, 18 a sufficient amount to insure proper starting of the blank between the dies upon termination of the starter blade stroke in a blank feeding direction to push the blank across into the throat between moving die 18 and onto the roll-on portion of stationary die 16.

An opposite end of slide 62 is received within cage 108 and is shown apertured to receive an end of a starter assembly return spring 114 directly acting on slide 62 and having the opposite end of spring 114 seated against a plate 116 within cage 108 and selectively positioned therein by a releasable adjustment device 118 threadably secured to an end plate 120 fixed to cage 108 by suitable machine fasteners 122. Adjustmerit device 118 further includes a lock nut 124 to secure adjustment device 118 in a desired position to provide a selected biasing force urging slide 62 and its starter blade 36 in a blank feeding direction.

To continuously maintain bar slide 62 and blade 36 in a desired aligned position and to virtually elminate any possibility whatsoever of slide 62 and its blade 36 from tilting or otherwise being angularly offset from its desired position relative to the longitudinal axis of slide 62. a flat cut-out 126 is shown formed along one side of slide 62 and a f-shaped bracket 128 having an inwardly projecting center post 130 is fixed by machine fasteners 132 to cage 108 withpost 130 received in cutout 126 of slide 62. Post 130 thereby cooperates with cut-out 126 in slide 62 to guide and continuously maintain it and blade 36 in precisely oriented alignment during reciprocation to repetitively establish the starting position of blade 36, as determined by cam 38, between the stationary and reciprocable dies 16, 18 without any danger of driving blade 36 into the moving die path.

By virtue of such construction, the weight and inertia of the slide and starter blade assembly is reduced, particularly since the double lever arrangement of the drive mechanism 46 is driven by a spring separate and isolated from the starter blade 36, whereby the only force actually imposed on blade 36 in a blank feeding direction is that of the isolated slide return spring 114 which may be finely adjusted to a minimal driving force precisely tailored to a selected blank diameter size for each specific thread rolling operation.

The starter assembly inertia can further be reduced by virtue of the disclosed arrangement wherein the stroke length of the blade 36 may be varied, e.g., between a maximum of about 0.180 inch and a minimum of about 0.090 inch simply by selectively changing the pivot point connection between the

adjustment arms

64 and 76 of drive levers 48 and 52.

More specifically, an adjustment means or yoke 134 is shown in FIG. 1 in an intermediate position between minimum and maximum stroke length adjustment positions illustrated respectively by broken lines at 136 and 138 of HO. 1. Adjustment is quick and easy in view of the disclosed adjustment yoke arrangement which affects only the retracted position of blade 36 and its actuating slide 62, responsive to a constant cam throw, depending on the selected position of adjustment yoke 134. As described, the terminal position of the operating lever cam roll 58 in a blank feeding direction (as seen in HO. 1) is established by cam 38. and cam roll 58 of operating lever 48 serves as a positive stop for blade 36 in such blank feeding direction.

More specifically. yoke 134 has a generally U-shaped cross-section having a bight 140 with a pair of legs I42. 144 extending from bight I40 and interconnected by roller 78 rotatably supported on legs I42. N4 of yoke 134 by any suitable means such as the illustrated snap rings 146. By virtue of this construction. yoke I34 may be easily locked in a selected position at any point along the elongated operating lever adjustment arm 64 with roller 78 in operative relation to a co-extending portion of cam follower adjustment arm 76 to selectively establish the pivot point between

arms

64, 76 to provide the starter blade stroke length. Fastener I48 is threaded through bight 140 of yoke I34 for engagement with arm 64, and a releasable lock nut 150 is shown securing the pivot point adjustment means in selected position. lt will be understood that the disclosed adjustment means could alternatively be reversely mounted on the cam roll lever adjustment arm 76 and also provide the same desired function.

The disclosed construction also entirely eliminates any need for rod ends and turnbuckles conventionally used in machines of this type which must be grease lubricated but remain exposed to shavings from the thread rolling operating and which also must be carefully tightened and maintained to prevent undesired force reversals tending to cause fatigue failure. In the disclosed construction. optimum location of the support and guide system for blade 36 is provided while definitely insuring that straight line starter blade movement is also achieved in that the starter blade parts may be sealed and lubricated within the disclosed cage 108 while protecting such parts against any shavings or chips produced by the metal deforming operation of machine 10.

If desired, drive mechanism 46 may be rendered inoperative and cam roll 54 may be disengaged from cam 38 upon retraction of the positive adjustment stop 104 from its position illustrated in FIG. I. This action permits starter engage lever 84 to be rotated to a limited extent within the previously noted over-sized openings through which bolt 92 extends in

ears

90 and 94. Starter engage lever 84 is then forced in a counterclockwise direction by spring 98 and arm 76 ofcam roll lever 52 will engage a pin I52 projecting from T- shaped bracket [28 to permit the pivot point 80 between starter engage lever 84 and cam roll lever 52 to be moved in a counter-clockwise direction about pivot pin 86 and to disengage cam roll 54 from cam 38.

In view of the foregoing disclosure. it will be seen that the described construction will provide a thread rolling starter blade assembly of reduced weight and reduced inertia while at the same time providing easy adjustment of the starter blade stroke length for accommodating exceptionally small screw blanks of different diameters without requiring any change in the throw to drive actuating cam 38. In addition, it will be seen that the selected biasing force of the isolated starter return spring 114, which directly acts on the slide. can be precisely adjusted to be sufficient to overcome the inertia of the starter assembly and to effect a precisely linear starting vector which produces a following motion in a blank feeding direction responsive to a return movement of the operating lever 48 but insufficient to initiate movement of the starter blade 36 upon occurrence of an abnormal condition such as in the case of a jammed blank obstructing normal feeding of machine 10. It will be apparent that when blade 36 is disabled. the drive will continue to operate under influence of the main drive assembly without any undesired effects on the machine parts. A quick and easy arrangement is also provided for changing the relationship between the two

drive levers

48 and 52 by simple adjustment of the stroke adjustment yoke 134 to establish a pivot point providing the desired stroke length. In addition. the support and guiding system for the starter blade 36 not only insures straight line reciprocating but also enables the component parts of the starter assembly to be com pletely sealed and lubricated.

As will be apparent to persons skilled in the art. vari ous modifications. adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

I claim:

1. A starter mechanism usable in a thread rolling machine for high speed feeding of work blanks from a feed chute to a work station between starting ends of a pair of thread rolling dies and comprising a stationary frame. a starter blade movable toward and away from a starting position at the work station. the starter blade effecting both wedging of a work blank between the starting ends of the dies and gating the feed chute. a slide supporting the starter blade for rectilinear reciprocation throughout its full range of movement. a oneway drive lever including a slide actuator engageable with the slide. the one-way drive lever mounted for pivotal movement on the frame for moving the slide actuator in opposite angular directions toward and away from a terminal position of the slide actuator. the slide actuator positively engaging and driving the slide in one linear direction to retract the starter blade away from its starting position responsive to movement of the slide actuator in one angular direction away from its terminal position. biasing means acting directly on the slide. the biasing means urging the slide in the opposite linear direction for blank feeding to cause the slide to follow a return movement of the drive lever and its slide actuator in the opposite angular direction while exerting a sole starting force on the starter blade in returning it to its starting position. the slide actuator upon its return in said opposite angular direction to said terminal position serving to establish a positive stop for the slide and. accordingly, to establish the starting position of the starter blade, a cam rotatably mounted on the frame, a cam follower pivotally mounted on the frame. the cam follower having one end engageable with a contoured cam surface of the cam and an angularly offset elongated adjustment arm, the drive lever having an enlongated adjustment arm disposed adjacent the adjustment arm of the cam follower. a pivot pin being disposed between the adjustment arms maintaining them in spaced apart relation, a drive return spring for urging said one end of the cam follower into engagement with the cam and biasing the one-way drive lever in said opposite angular direction. and adjustment means being mounted on one of the adjustment arms for selectively positioning the pivot pin along the length of said one arm for varying the angular displacement of the drive lever to establish a desired stroke length of the starter blade from its starting position without varying the cam contour and without affecting the starting position of the starter blade as established by the terminal position of the drive lever slide actuator.

2. A starter mechanism usable in a thead rolling machine for high speed feeding of work blanks front a feed chute to a work station between starting ends of a pair of thread rolling dies and comprising a stationary frame. a starter blade movable toward and away from a starting position at the work station for wcdging a work blank between the starting ends of the dies and gating the feed chute. a slide supporting the starter blade for rectilinear reciprocation throughout its full range of movement. a one-way drive lever mounted for pivotal movement on the frame for positively driving the slide in one linear direction to retract the starter blade away from its starting position responsive to movement of the drive lever in one angular direction, biasing means acting directly on the slide. the biasing means urging the slide in the opposite linear direction to cause it to follow a return movement of the drive lever in the opposite angular direction while exerting a sole starting force on the starter blade in returning it to its starting position. a cam rotatably mounted on the frame. a cam follower pivotally mounted on the frame, the cam follower having one end engageably with a contoured cam surface of the cam and an angularly offset enlongated adjustment arm the drive lever having an elongated adjustment arm disposed adjacent the adjustment arm of the cam follower, a pivot pin disposed between the adjustment arms maintaining them in spaced apart relation. a drive return spring urging said one end of the cam follower into engagement with the cam and biasing the one-way drive lever in said opposite angular direction, and adjustment means mounted on one of the adjustment arms for selectively positioning the pivot pin along the length of said one arm for varying the angular displacement of the drive lever to establish a desired stroke length of the starter blade from its starting position without varying the cam contour.

3. The starter mechanism of claim 2 wherein the ad- 8 justment means comprises a generally U-shaped yoke having a bight with a pair of legs extending from the bight and interconnected by said pivot pin, the yoke being movable along said one adjustment arm, and releasable locking means for securing the adjustment yoke in a selected position on said one adjustment arm.

4. The starter mechanism of claim 2 wherein said biasing means comprises a spring directly acting on the slide for urging it into following movement with the pivotable one-way drive lever when the drive lever is operated in said opposite angular direction 5. The starter mechanism of claim 2 wherein said biasing means is adjustable to establish a preselected starting force urging the starter blade in said opposite linear direction toward the work station.

6. The starter mechanism for claim 1 further including a housing fixed to the frame, wherein the slide is mounted for rectilinear reciprocation within the housing and has an exposed end protruding therefrom, the starter blade is mounted on said exposed end of the slide, wherein a spring constituting said biasing means is received within the housing, one end of the spring acts directly on the slide, and adjustable spring seating means is provided for adjusting the opposite end of the spring relative to the slide to vary the starting force exerted on the starter blade to return it to its starting position,

7. The starter mechanism of claim 2 further including a housing secured to the frame, the slide being mounted in the housing for rectilinear reciprocation and having an exposed end protruding from the housing for mounting the starter blade. the biasing means being received within the housing and shielded thereby from by-products of the thread rolling operation.

8. The starter mechanism of claim 2 further including guide means cooperating with and engaging the slide for limiting its movement to said rectilinear reciproca-

Claims

1. A starter mechanism usable in a thread rolling machine for high speed feeding of work blanks from a feed chute to a work station between starting ends of a pair of thread rolling dies and comprising a stationary frame, a starter blade movable toward and away from a starting position at the work station, the starter blade effEcting both wedging of a work blank between the starting ends of the dies and gating the feed chute, a slide supporting the starter blade for rectilinear reciprocation throughout its full range of movement, a one-way drive lever including a slide actuator engageable with the slide, the one-way drive lever mounted for pivotal movement on the frame for moving the slide actuator in opposite angular directions toward and away from a terminal position of the slide actuator, the slide actuator positively engaging and driving the slide in one linear direction to retract the starter blade away from its starting position responsive to movement of the slide actuator in one angular direction away from its terminal position, biasing means acting directly on the slide, the biasing means urging the slide in the opposite linear direction for blank feeding to cause the slide to follow a return movement of the drive lever and its slide actuator in the opposite angular direction while exerting a sole starting force on the starter blade in returning it to its starting position, the slide actuator upon its return in said opposite angular direction to said terminal position serving to establish a positive stop for the slide and, accordingly, to establish the starting position of the starter blade, a cam rotatably mounted on the frame, a cam follower pivotally mounted on the frame, the cam follower having one end engageable with a contoured cam surface of the cam and an angularly offset elongated adjustment arm, the drive lever having an enlongated adjustment arm disposed adjacent the adjustment arm of the cam follower, a pivot pin being disposed between the adjustment arms maintaining them in spaced apart relation, a drive return spring for urging said one end of the cam follower into engagement with the cam and biasing the one-way drive lever in said opposite angular direction, and adjustment means being mounted on one of the adjustment arms for selectively positioning the pivot pin along the length of said one arm for varying the angular displacement of the drive lever to establish a desired stroke length of the starter blade from its starting position without varying the cam contour and without affecting the starting position of the starter blade as established by the terminal position of the drive lever slide actuator.

2. A starter mechanism usable in a thead rolling machine for high speed feeding of work blanks from a feed chute to a work station between starting ends of a pair of thread rolling dies and comprising a stationary frame, a starter blade movable toward and away from a starting position at the work station for wedging a work blank between the starting ends of the dies and gating the feed chute, a slide supporting the starter blade for rectilinear reciprocation throughout its full range of movement, a one-way drive lever mounted for pivotal movement on the frame for positively driving the slide in one linear direction to retract the starter blade away from its starting position responsive to movement of the drive lever in one angular direction, biasing means acting directly on the slide, the biasing means urging the slide in the opposite linear direction to cause it to follow a return movement of the drive lever in the opposite angular direction while exerting a sole starting force on the starter blade in returning it to its starting position, a cam rotatably mounted on the frame, a cam follower pivotally mounted on the frame, the cam follower having one end engageably with a contoured cam surface of the cam and an angularly offset enlongated adjustment arm, the drive lever having an elongated adjustment arm disposed adjacent the adjustment arm of the cam follower, a pivot pin disposed between the adjustment arms maintaining them in spaced apart relation, a drive return spring urging said one end of the cam follower into engagement with the cam and biasing the one-way drive lever in said opposite angular direction, and adjustment means mounted on one of the adjustment arms for selectIvely positioning the pivot pin along the length of said one arm for varying the angular displacement of the drive lever to establish a desired stroke length of the starter blade from its starting position without varying the cam contour.

3. The starter mechanism of claim 2 wherein the adjustment means comprises a generally U-shaped yoke having a bight with a pair of legs extending from the bight and interconnected by said pivot pin, the yoke being movable along said one adjustment arm, and releasable locking means for securing the adjustment yoke in a selected position on said one adjustment arm.

4. The starter mechanism of claim 2 wherein said biasing means comprises a spring directly acting on the slide for urging it into following movement with the pivotable one-way drive lever when the drive lever is operated in said opposite angular direction.

5. The starter mechanism of claim 2 wherein said biasing means is adjustable to establish a preselected starting force urging the starter blade in said opposite linear direction toward the work station.

6. The starter mechanism for claim 1 further including a housing fixed to the frame, wherein the slide is mounted for rectilinear reciprocation within the housing and has an exposed end protruding therefrom, the starter blade is mounted on said exposed end of the slide, wherein a spring constituting said biasing means is received within the housing, one end of the spring acts directly on the slide, and adjustable spring seating means is provided for adjusting the opposite end of the spring relative to the slide to vary the starting force exerted on the starter blade to return it to its starting position.

7. The starter mechanism of claim 2 further including a housing secured to the frame, the slide being mounted in the housing for rectilinear reciprocation and having an exposed end protruding from the housing for mounting the starter blade, the biasing means being received within the housing and shielded thereby from by-products of the thread rolling operation.

8. The starter mechanism of claim 2 further including guide means cooperating with and engaging the slide for limiting its movement to said rectilinear reciprocation.