US2367612A

US2367612A - Thread rolling machine

Info

Publication number: US2367612A
Application number: US472135A
Authority: US
Inventors: Reed Arthur Bradford
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-01-12
Filing date: 1943-01-12
Publication date: 1945-01-16
Anticipated expiration: 1962-01-16

Description

Jan 36 1945. A. B. REED 2,367,612

THREAD ROLLING MACHINE Filed Jan. 12, 1945 3 Sheets-Sheet l 3nventor Uhtne s A. Bradford Reed Her-bn*t E. Cove 1 Ittorneg Jan. 16, 1945.

A. B. REED THREAD ROLLING MACHINE Filed Jan. 12, 1943 5 Sheets-Sheet. 2

wilhesa Herberi 6. Covey Isnnentor A.Br-adfor-d Reed. I J

' (Ittorneg Jan. 16, 1945.. A. B. REED 2,367,612

THREAD ROLLING MACHINE Filed Jan. 12, 1943 3 Sheets-Sheet 3 X 3nnentor witness W Herbert 5.. Cove A. Bradfpr'd Reed Cit torneg Patented Jan. 16, 1945 UNITED STATES PATENT OFFICE THREAD ROLLING MACHINE Arthur Bradford Reed, Worcester, Mass. Application January 12, 1943, Serial No. 472,135

14 Claims.

This invention relates to a thread rolling machine and more particularly to one in which threads are formed by positively rotated and synchronized cylindrical thread dies.

In a thread rolling machine of the type set forth in my prior application Serial No. 444,130 filed May 22, 1942, threads are rolled by means of a plurality of positively driven cylindrical dies which are forced inwardly towards the work center by means of toggle arms or cams operated through a stress ring which is oscillated in a predetermined cycle by means of a reversible electric motor connected thereto by a rack and pinion.

One object of the present invention is to provide adjustable mechanism in a thread rolling machine which will roll threads according to a controllable and variable cycle of penetration, dwell and release of the rolling dies, and particularly to provide such a mechanism which may be readily changed or adjusted to give a suitable cyclic movement as required by different types of metal work blanks to be treated.

A further object of the invention is to provide a variation in the length of time of the thread rolling operation or the output of the machine and particularly to control the number of contacts between the rolling dies and the work piece during the production cycle, regardless of the frequency of the cycle.

A further object is to provide a machine having a stress ring arranged to absorb the stresses set up by the rolling operation which is so constructed that adjustments may be made for rolling threads on work pieces of different diameters without disturbing the matching of the die threads.

A further object of the invention is to provide a multiple die machine of this general type having a three point supporting and rolling contact between the dies and the Work, and wherein two of the contact members may be thread rolling dies and the third die serves primarily as a support to hold the work in proper position and distribute the thrusts of the thread rolling operation.

A further object of the invention is to provide an easily controlled starting and stopping mechanism which makes it possible to roll a series of work pieces in a continuous succession or to roll only a single work piece.

A further object is to provide a thread rolling machine wherein very small pieces of work may be rolled by means of three contacting cylindrical members. Further objects will be apparent in the following disclosure.

Referring to the drawings which illustrate preferred embodiments of this invention:

Fig. 1 is a vertical section, partly broken away, through the machine;

Fig. 2 is a top plan View of the machine;

Fig. 3 is a top plan view showing a modification arranged for rolling a very small piece of work;

and

Fig. 4 is a top plan view of another modification in which only one die roll is fed forward positively.

In the embodiment illustrated in Figs. 1 and 2 of the drawings, a work piece l0 has threads rolled in its surface by means of cylindrical dies H, I2 and I3 which are mounted to be rotated about either parallel or tilted axes in contact with the work piece. The surface of each die roll is provided with single or multiple threads suitably shaped for the rolling operation. Each die roll is mounted on an arbor I4 carried by two spaced arms l5'and l6 of a supporting yoke ll. The construction of this supporting yoke and the associated parts may be as set forth in my prior application. As shown in Fig. 2, the yoke has a vertically arranged dovetailed groove slidably interfitting with a wedge portion on a pivot block 20. The pivot block has a partial cylindrical convex surface mating with a similarly shaped concave bearing surface of a block 22. The yoke l1 and the pivotally connected

blocks

20 and 22 form the two arms of a toggle having a vertical axis, and the parts are so arranged that when the linked arms of the toggle are moved to bring their center lines towards a straight line, the die supported thereby is moved inwardly toward the work center. A pair of guide links 24 have axially aligned bearings at their inner ends which pivotally bear on sleeves 25 and 26 (Fig. 1) surrounding the arbor M of each of the die rolls. The other ends of these guide links are pivotally mounted on the reduced end 28 of a stationary post 29 suitably mounted on the frame of the machine. The structures of the three sets of die supports, toggles and guides may be made alike or modified as herein described.

In order to operate the toggle, the outer toggle arm or block 22 is mounted for revolving through a short are about the work axis while the inner toggle arm is held by the links 24. That is, the block 22 is adjustably secured on a stress ring assembly comprising the two spaced

stress rings

32 and 33 which are carried by an outer supporting ring 34. The ring groove carrying a set of ball bearings 35 which ride in a raceway formed in a top ring 36 of the machine frame and are held in place by a ring 31. When the stress ring assembly is oscillated 34 has a !ball raceway through a short arc, the two arms of the toggle are moved relative to the center line of the die roll, while the die roll is obliged to travel in an arc required by the link arms 24 which can oscillate only about the fixed center line of the pivot post 28, 29.

A primary feature of this invention resides in so moving the stress ring assembly that the cycle of penetration, dwell and release of the rolling dies relative to the work may be controlled and varied as required by different types of metal. A preferred construction comprises a cam which is conncted to oscillate the stress ring assembly through a cycle that is determined by the shape of the cam. This cam of predetermined shape is mounted for rotation about its axis by means of power driving mechanism. This cam is suitably supported on a shaft 4| carried by ball bearings 42 mounted on a top plate of the machine. The lower end of the vertical shaft 4| carries a suitable clutch member 45 arranged to mesh with a movable clutch member 43 which is mounted for vertical sliding movement on the drive shaft 44.

The peripheral face of the cam engages a roller 46 pivotally mounted between two swinging arms 41. These two arms 41 are pivoted at their outer ends to a post 48 fixed on the plate 42. The innerends of the arms connect through a pin 49 with a short link 50 which is in turn pivotally connected by a pin 5| to a block 52 suitably secured,

as by a screw, to the ring 34 of the stress ring assembly. A compression spring 54 is secured at one end by a link 55 to one of the rock arms 41. The spring is supported by and surrounds a short sleeve 56 telescoping on a guide rod. The sleeve is carried by the rocking link 51 which is pivotally mounted on the top plate of the machine frame. This spring tends to hold the cam roller 46 against the cam 40 and to move the stress ring assembly towards the left, as shown in Fig. 2.

Rotation of the cam moves the stress ring to wards the right against the pressure of the spring and at a rate and in accordance with the cycle determined by the shape of the cam 40. In order to change that cycle, it is merely required to remove the cam 40 and replace it with another suitably shaped dam. The strength of the spring is merely enough to move the die rolls away from the work, while the cam is required to force the dies into the work to roll the thread. By changing the cam, it is possible to varythe rate of penetration of the die rolls into the work. Some types of steel can be rolled rapidly, while others require a slow penetration per revolution of the work. Also, the period of dwell, represented by the upper cylindrical portion of the cam of minimum diameter, can be varied as required for removing and replacing the work piece. The cam form shown in the drawings provides a rapid infeeding period, during which the roller 46 rides up the portion A of the cam and the die roll is moved up into contact with the work. The part B of the cam may be a spiral of a uniform incline which provides a suitable rate of penetration of the die threads. The cam surface portion C is cylindrical and thus provides a dwell period during which the threads are finished and their surfaces brought to a smooth burnished appearance. The part D of the cam causes the die rolls to leave the work. By changing the shapes of any or all of these portions of the cam the penetration cycle may be varied as desired.

A further feature of this invention comprises rotating the die rolls and oscillating the stress ring and the dies carried thereby in different and predetermined speed ratios. To this end, I provide a driving motor 60, which may be a constant speed electric motor of suitable construction and a desired rate. This motor 60 is suitably mounted in the base of the machine and it drives through a v-belt 6! a pulley 62 on a horizontal shaft 63 suitably mounted on the machine framework. The right hand end of this shaft 63 carries two gears 64 and 65 (Fig. 2). The gear 65 mesheswith a gear of suitable size 66 located thereabove. This gear 66 is on the end of a short horizontal shaft 61 carrying a worm 68 meshing with a worm gear 69 which is on the bottom of the clutch shaft 44. The gear 64 (Fig. 2) meshes with a gear 10 at the front thereof. That gear 10 is on the end of a long shaft ll (Fig. 1) located in front of the shaft 53. This shaft H, which is suitably mounted inbearings, has a Worm 13 on its left hand end meshing with a worm gear 14 arranged on a short vertical shaft 15 suitably mounted on the framework. The upper end of the shaft 15 carries a central gear 16 which meshes with a cluster of three ars 18 of equal sizes. Each of these gears 18 (only one of which is shown) is mounted on a short shaft 19 suitably carried in bearings and the upper end of each short shaft 19 is keyed to the bottom member of a universal driving coupling of standard construction. The upper half 8| of this coupling is slidably keyed to the lower half 82 of a second universal coupling, the upper part 83 of which is threaded onto the lower end of the roll die shaft I4.

The sleeve 26 rotates with the coupling member 83 and with the shaft l4. The yoke arm I6 is provided with a suitably shaped bearing for the sleeve. The upper portion of this sleeve 26 is shaped to provide clutch teeth which project into a narrow slot cut out of the lower face of the die roll, so that the sleeve and the die roll rotate together. This clutch transmits the torque directly from the coupling to the sleeve and thence to the die roll so as to prevent strain being imposed 0n the shaft [4.

By rotating the drive gear 16 and the gear cluster, each one of the die rolls H, I2 and I3 is rotated in synchronism at a speed determined by the sizes of the gears and the motor speeds. Suitable gears may be substituted for gears 16 and 18 to obtain any desired rotational speed of the dies. The relative speeds of the dies and the cam 40 may be changed by means of the change gears 64, 65, 66 and 10. These are conveniently mounted in an external pocket 85 in the framework of the machine. Each of these gears is so mounted on its shaft that it may be readily replaced by other gears of suitable gear ratios so that the speed of the cam may be thus changed relative to a given speed of the die rolls, or vice versa. That is, the cam speed may be left unchanged and the die rolls moved faster or slower, or for a given speed of die rolls the rate of penetration caused by the cam may be made faster or slower. It will be appreciated that a suitable change speed mechanism may be substituted for the change gears and that the latter have been illustrated to simplify the drawings.

The clutch 43, 45 has been provided in order that the machine may be made to operate either continuously or intermittently. In order to effect an intermittent operation, the lower member 43 of the clutch assembly is slidably mounted on the shaft 44 in accordance with standard procedure and it is thrown into and out of engagement by means of a lever 90 having a yoke arm which carries rollers riding in a groove on the clutch member 43. The lever 90 is centrally mounted on a pivot carried by a support 93. The right hand end 94 of the yoke lever 90 has a tension spring 95 secured thereto. The spring is fixed at its other end and it tends to hold the clutch parts disconnected. Pivoted at 96 on the fixed support 93 is a pawl 9'! arranged to ride along the under side of the yoke arm 90 and to connect the clutch when moved towards the left.

When the pawl is moved to the right, the spring 95 operates to disengage the clutch. Fixed to this pawl 91 so as to rock it about the pivot 96 is a lever 98 which passes upwardly through the top of the machine where it may be manually operated.

A small latch 99 suitably pivoted on the machine frame is arranged" to contact the right hand end 94 of the lever and hold the clutch feet engaged for a continuous operation of the machine. If the latch 99 is held out of position, the cam may be caused to operate through a single cycle and then stop. This is effected by means of a knock off cam I00 fixed to the vertical shaft 44 which carries the lower clutch member. The knock off cam has a projecting portion so shaped and arranged that its periphery strikes the lower end of the lever 98 or the pawl 97 and thus moves the pawl towards the right at the same time that the cam 40 has finished its cycle of forcing the dies into the work piece and then removingthe the outer ring 34 and by means of a pointer H5 secured to the lower ring and projecting over a scale placed on the top ring.

A further feature of the invention comprises a simple type of construction which serves to secure the two stress rings 32 and 33 in a fixed relationship and to hold the toggle block 22 immovable but adjustably positioned thereon. This comprises, as shown particularly in Fig. 1, a pair of lugs I20 formed on the outside of each of the toggle blocks 22. A draw bolt I 2I is pivotally connected to the lugs and it passes outwardly through a hole in a central flange on the outer stress ring 34. The draw bolt I2I is adjustably secured in place by means of a screw I22 threaded into the bolt. An enlarged head on the screw engages a washer and the latter, is seated against a shoulder within a recess formed in the outer ring 34. Each of the blocks 22 is provided with two concave grooves within which are seated short metal strips I24 having outer vertical faces lying in contact with the inner scroll cam faces H0. The inner faces of these metal strips are convex and slidably fit within the grooves in the toggle blocks 22. The strips I24 are loosely positioned and thereby move freely to make proper adjustment so that the toggle block 22 may be tilted and fit against a high part on one stress ring and a lower part on the other. By means of the draw bolt I2I, the toggle blocks 22 are clamped agains the stress rings through the indies to the maximum distance fromthe work.

This permits the.spring 95 to disengage the clutch parts and to hold them out of engagement until the hand lever 98 is again moved toward the right to force the clutch into an operating position. Thus the cam goes through a single cycle although the dies rotate continuously in their synchronized relationship. This gives the operator opportunity for removing the work piece l0 and replacing it by a fresh one, after which the lever 98 may be thrown to cause the pawl 91 to connect the clutch parts. Since the cam 40 has been stopped on its low point, the cam will thus be in proper position for starting a new cycle and causing the die threads to roll properly into the work. If the latch 99 is left in its lowermost position, the clutch parts are held engaged and the knock off cam I00 merely moves the pawl 9'! to the right where it stays in an inoperative position.

Each of the stress rings 32 and 33 is provided with three scroll or cam faces I I 0, and the toggle blocks 22 are arranged to be clamped in desired adjusted positions against those scroll faces. If each of the blocks is moved toward the low end of the scroll cam, then the roll die carried thereby is moved away from the work center. One of the stress rings, such as the upper ring 32, may also be rotated relative to the other ring into a non-symmetrical arrangement so that when the block 22 is clamped in place it contacts with a high point on one cam face and a lower point on the other and thereby is tilted. This causes a tilting of the roll die and thus makes it possible to roll a tapered thread. This relative movement may be effected by means of a small pinion II2, Fig. 1, which is suitably mounted in the upper ring 32 and may be rotated by a hand knob II3 projecting therefrom. The pinion meshes with a short section of a rack bar II4 fixed on the outer stress ring 34. The positions of the two rings may be determined by means of suitable scale markings on the top stress ring 32 and termediate adjusting strips I24, and the stress rings 32 and 33 are likewise held immovable relative to the outer stress rings 34.

The threads of the three die rolls may be brought initially into a helical alignment so that when the dies are rotated in synchronism in the same direction the crests of the threads at the points of contact between the dies and the work blank remain at all times on a perfect helix, in which relation the threads of the dies may be considered as being in a helical alignment. This initial alignment is accomplished, as described in my prior application, by vertically moving any of the die rolls through a distance suflicient to match the threads. To this end the toggle yoke I1 is actually made in two parts I I and 20, one being vertically slidable on the other. The outer end of the member 20 is shaped to provide a partial cylindrical bearing surface which pivots within the toggle block 22. The opposite side of this piece has a dovetailed portion I29 (Fig. 2) which slidably interfits with a mating slid'eway formed in the outer end of the yoke IT. The yoke may be split and provided with a cap screw adapted to draw the parts together and thus clamp the two slide portions in a relatively immovable position. The yoke is supported by means of the micrometer head I28. A central bore formed within the pivot block 20 carries slidably mounted therein a rod I30 having a toe on its lower side projecting laterally through a slot in a wall of the dovetailed portion of the pivot member 20. This toe interfits with an undercut recess formed in the body of the yoke I! so that the-yoke is supported on the toe. The rod I30 may be adjusted vertically by means of a suitable micrometer screw I3I threaded into a recess in the upper part of the rod, and the upper end of this micrometer screw carries the dial head I28 which is adapted to be turned to register with markings on the stationary portion of the block 20. This provides a fine vertical adjustment of the die roll. These parts are so con-v structed and arranged that any vertical adjustment for helical alignment of the die rolls will not be affected by loosening the draw bolt HI and again returning it to a clamping position.

A further feature of this invention comprises the modified arrangement shown in Fig. 3 whereby a very small work piece may be rolled by means of comparatively large dies. In this construction, the stress ring assembly and the roll die mounts and driving mechanism may be made as above described, but the roll dies themselves are made of different sizes and in relatively different positions. In the construction of Figs, 1 and 2, the dies are of the same size and are arranged at approximately 120 apart relative to radial lines of the work. In the construction of Fig. 3, the two dies I40 and MI are made of sufficiently large size to accomplish the desired rolling operation. The centers of these dies and the work make an angle between 120 and 180 degrees, and preferably an angle a little less than 180. Two lateral supports may engage the work at the opposite sides, but I preferably employ only one support I42 which is made small enough to enter the comparatively narrow space between the dies I40 and MI and act as a steadyrest which takes the thrust of the two main dies I40 and MI. The roll I42 may be a plain faced cylindrical body which serves merely to take the thrust and hold the work in place between the dies I40 and MI, but it is preferably provided with suitable threads. The diameter of each large die is a multiple of the diameter of the small threaded roll, and the number of threads on each is inversely proportional to the size ratio. The two large roll dies I40 and HI may be, for example, six times the diameter of the work and the third roll may be approximately equal in size to the work. The small roll I42 may be provided with a thread having a single start, while the larger rolls have six threads or six starts. The three rolls are power driven by the above described mechanism but at speeds inversely proportional to their diameters so that the threads properly match with the work. That is, the six lead dies have one-sixth of the speed of the little roll.

It is desirable that the dies have such an angular relationship relative to the work as to avoid the formation of a non-cylindrical but equal diameter work piece. To this end, the dies are so located that the angle between the centers of any two of the die rolls relative to the work is not a multiple of the angle between any other two dies and is not divisible into 360 degrees. For example, the line a passing through the small roll I42 and the work center may make an angle of 103 with the center line b of the roll die MI and an angle of 113 with the center line of the roll die I40. Thus the two dies I40 and MI may be disposed almost diametrically opposite each other and do most of the work, while the roll I 42 acts primarily as a steadyrest against the work surface.

A further modification, which will serve for certain non-precision operations, is shown in Fig. 4, an accordance with which only one or two of the die rolls, such as the roll I50, is mounted on a toggle mechanism arranged to force the die toward the work center. The other two dies I5I and I52 are arranged to be held stationary relative to the work axis. To this end, each of the stress rings may be provided with a scroll face I54 adapted to cooperate with a toggle block I55 and its associated toggle arm I56 and the guide link I51 which locate and serve to move the die roll I50 inwardly toward the work center as the stress ring assembly is oscillated. One of the other rolls I5I or I52 may be similarly mounted if desired. In the construction illustrated, each is mounted on a plate I60. The latter is pivotally carried on the post ISI suitably secured on the framework of the machine and constructed similar to the post 29 above described. Each plate I60 carries a roller I64 pivotally mounted thereon, and each of these rollers engages a cylindrical portion I62 on each of the stress rings. This construction is such that when the stress rings are oscillated, the rollers I64 ride on cylindrical portions of the stress rings and thus do not cause the dies I5I and I52 to move inwardly. At the same time the rollers transmit the thrust from the thread rolling operation to the stress ring assembly. The other die I50 is, however, forced inwardly by the toggle mechanism when the stress ring is oscillated and thus causes the thread to be rolled in the work. The toggle block I55 may be moved to any desired position on the scroll cam I54 to accommodate different diameters of work.

It is important that a die roll be in the same helical alignment with the other rolls after adiustment along the scroll face of the stress ring. The construction shown in Fig. 1 insures this. The toggle block 22 has a projection I10 lying between the two stress rings 32 and 33 and the upper and lower flat faces of the block are shaped and arranged to fit snugly between the stress rings. The lower stress ring is supported solely by a clamp ring I1I which is carried by a bolt I12 threaded therein. The head of the bolt rests on a second ring I13 which in turn rests on the top stress ring 32. The upper ring 32 rests on a shoulder I14 on the inwardly projecting flange of the outer stress ring 34. The lower ring 33 does not touch this flange. When the draw bolt I2I is loosened and the toggle block 22 is to be moved along the scroll faces of the stress rings, the bolt I12 is also loosened slightly. When the parts are to be reassembled, the bolt I12 is turned by a wrench applied to its head. The upper stress ring 32 is positioned by the shoulder I14. Hence, tightening the bolt first draws the upper clamp ring I13 into place against ring 32. Then the lower clamp ring I 1| raises the stress ring 33 until it strikes the lower face of the projection I10 on the toggle member 22 and raises it until the upper face of the projection I10 strikes the under side of stress ring 32. The clamp screw I22 may then be turned and form a rigid assembly of stress rings and toggle. The sole support for the assembly is the set of ball bearings 35 and these locate the upper stress ring correctly. All of the other parts are located relative to that upper ring and the supporting shoulder I14 on the outer ring 34. It is therefore unnecessary to change the setting of the dial head I28 when the die rolls are moved to accommodate a different size of work piece.

The operation of the machines will be apparent in view of the above description of my inventions. The speeds of the various parts are coordinated so that the rate of die rotations and the rate of penetration are best suited for a given work piece. For a given speed of the main drive shaft, the change gear ratio for the die roll shaft may give a rate of, say, 3 revolutions per second for each die roll. The other set of change gears and the worm drive may give a cam shaft rotation of approximately 1 revolution per 3 seconds. Assuming the cam to be so shaped that about ascacra two thirds of its surface causes the die to roll the work. then two seconds are consumed e cotively. In that two seconds. the three dies with 4 threads or starts on each will make 72 starting contacts with the work. Assuming that the depth v of thread is 0.024 inch, this means that the penetration for each contact is only about 0.00033 inch. The cam is preferably shaped to provide a dwell when the cam roller rides over the cylindrical surface portion C. This results in the thread being shaped accurately and provided with a smooth or burnished surface. By chang ing the gears, the ratio of die rotation to work penetration may be made as desired.

The various parts of the machine may be made in accordance with the disclosure in my prior application except as modified by the requirements of this invention. Various modifications will be readily apparent to one skilled in the art,

and mechanically equivalent parts may be substituted for those herein described. Hence, the above disclosure is to be considered as setting forth the principles of my invention and preferred embodiments thereof and not as imposing limitations on the appended claims.

I claim:

1. A thread rolling machine comprising three rotatable roll dies arranged in helical alignment to roll a thread on a work blank rotatably supported therebetween and which hold the blank axially immovable relative to the dies while the thread is being rolled, power mechanism for rotating the dies positively and in peripheral synchronism, and power mechanism including a replaceable cam of required shape and a cam follower connected to move all of the rotating dies simultaneously through equal distances towards and from the work axis in a predetermined and variable cycle of approach, penetration and release, said die rotation and cam movement being coordinated and the operating surface of the cam being shaped to cause the dies to penetrate the work progressively during more than one die revolution and to roll the entire thread length simultaneously at a controlled rate.

2. A thread rolling machine comprising three rotatable roll dies maintained in a substantially equal spacing to roll the entire thread length on an axially immovable work piece rotatably supported therebetween, power mechanism for rotating the dies positively and in synchronism, means for adjusting the separation of the dies and positioning them in helical alignment for rolling different sizes of work pieces, and mechanism including a cam follower and a replaceable cam moved through a definite cycle for forcing all of the dies simultaneously towards the work axis through equal distances, said work and cam movement being coordinated and the operating surface of the cam being shaped to cause the dies to penetrate the work progressively and gradually in a predetermined cycle of approach during a plurality of rotations of the work.

3. A thread rolling machine comprising three rotatable roll dies arranged to roll a thread on a work blank rotatably supported therebetween and which hold the blank axially immovable relative to the dies while the thread is being rolled, driving mechanism for rotating the dies positively and in peripheral synchronism, power driven mechanism including a cam connected to move all of the dies simultaneously and equally towards the work axis to roll the thread, and a power driven change speed mechanism connected to coordinate the die and cam movements to provide a predetermined but variable relationship of rate of die rotation to the rate of penetration of the die into the work, the operative cam surface being shaped to cause the dies to penetrate the entirethread length simultaneously and progressively during a plurality of die revc lutions and in a predetermined cycle of approach, penetration and release.

4. A thread rolling machine comprising three rotatable roll dies arranged to roll the entire thread length simultaneously on a work piece rotatably supported therebetween and which hold the blank axially immovable relative to the dies while the thread is being rolled, precision means for tilting each of the dies axially to roll tapered work or to control the straightness thereof, mechanism connected to rotate the dies positively and in synchronism, power mechanism including a cam and a follower connected to move the dies simultaneously through equal distances towards the work axis, means for coordinating the rates of die rotation and work penetration, said cam having its operative surface shaped to cause the dies to penetrate the work progressively during a plurality of work rotations and in a predetermined cycle of penetration, dwell and removal.

5. A thread rolling machine comprising three rotatable roll dies arranged to roll the entire thread length of an axially immovable work piece rotatably supported therebetween, precision means for tilting the dies axially to roll tapered work or to control the straightness thereof, mechanism connected to'rotate the dies positively and in synchronism, a replaceable cam driven through a fixed cycle, and a cam follower connected to move all of the dies simultaneously and equally towards the work axis, said cam having its operative surface shaped to cause the dies to penetrate the work progressively and at a controlled rate during a plurality of work revolutions, and means for varying the ratio of the rate of die rotation to the rate of work penetration.

6. A thread rolling machine comprising two die rolls arranged in helical alignment to roll a thread on an axially immovable work piece rotatably supported therebetween, the centers of said rolls and the work making an angle between 120 and 180", a steadyrest holding the work positioned between the die rolls, the angles formed by the centers of said rolls and rest relative to the work being indivisible in each other and in 360 degrees, means for rotating the die rolls positively and in synchronism, means for forcing said rotating die rolls towards the work axis to roll the entire thread length simultaneously and means for coordinating the rates of die rotation and work penetration so that the dies penetrate the work progressively during a plurality of work rotations and in a controlled cycle of penetration, dwell and release.

7. A thread rolling machine comprising two die rolls arranged to roll simultaneously the entire thread length on an axially immovable work piece rotatably supported therebetween, the centers of said rolls and the work making an angle between 120 and 180, a steadyrest comprising a third roll of smaller diameter than the others which forms therewith a three point support for the work, the angles formed by lines connecting the axes of said rolls with the work axis being indivisible in each other and in 360 degrees, means for rotating the rolls in synchronism and at rates inversely proportional to their sizes. means for moving the rolls simultaneously to- W ds the work, center and holding the work axially immovable during the thread rolling operation and means for controlling the rates of die rotation and work penetration so that the dies penetrate the work progressively at a controlled rate of penetration per work rotation.

8. A thread rolling machine comprising two die rolls arranged to roll simultaneously the entire thread length on an axially immovable small work piece rotatably supported therebetween, the centers of said rolls and the work making an angle between 120 and 180, a third threaded roll of smaller diameter than the others which forms therewith a three point support for the work, the angles formed by the centers of said rolls relative to the work being indivisible in each other and in 360 degrees, the larger rolls having diameters which are multiples of the diameter of the smaller roll and the number of threads thereon being inversely proportional to the size ratio,

means for rotating the rolls in synchronism and at rates inversely proportional to their sizes, means for moving said two die rolls simultaneously towards the work center and means for coordinating the rates of die rotation and work penetration so that the dies penetrate the work progressively at a controlled rate during a plurality of work rotations.

9. A thread rolling machine comprising three die rolls arranged to roll the entire thread length on an axially immovable work piece rotatably supported therebetween, a stress ring having a portion of its inner periphery lying in a cylindrical surface, means for oscillating the ring, means including a die roll support moved by oscillating the ring which causes the roll to move towards and from the work center, a support for another die roll which engages the cylindrical surface portion of the ring and transmits thrust without causing the roll to move, means for rotating the die rolls in synchronism, and means for coordinating the rates of die rotation and work penetration so that the dies penetrate the work progressively during a plurality of work rotations.

10. A thread rolling machine comprising three die rolls arranged to roll simultaneously the entire thread length of a work piece rotatably supported therebetween and which hold the blank axially immovable relative to the dies while the thread is being rolled, driving mechanism for rotating the rolls positively and in peripheral synchronism, power mechanism for moving all of the rotating die rolls through equal distances towards and from the work axis and causing the roll to penetrate the work progressively during a plurality of work rotations and in a controlled cycle of penetration, dwell and release, a clutch for controlling said power mechanism, means operated in timed relationship with the die roll movement tending to disconnect the clutch at the end of a thread rolling cycle, and means for holding the clutch connected and causing the machine to operate continuously.

11. A thread rolling machine comprising a plurality of rotatable roll dies arranged to roll a thread on an axially immovable work blank rotatably supported therebetween, power mechanism for rotating the dies positively and in synchronism, an oscillatable stress ring. means operated by oscillation of the ring which moves the die rolls simultaneously and equally towards and from the work axis, a rotatable cam, a cam tollower operated by the cam and connected to oscillate the ring, said cam having an inclined surface which causes the die rolls to penetrate the entire thread length of the work progressively during a plurality of rotations of the work, and power mechanism including a change speed mechanism to rotate the cam in a controlled and variable timed relation to the die rotation and thereby control the work penetration per contact of die and work and cause the dies to move in a predetermined cycle of approach, penetration and release relative to the work.

12. A thread rolling machine comprising a plurality of rotatable roll dies arranged to roll a thread on an axially immovable work blank rotatably supported therebetween, an oscillataole stress ring, means operated by oscillation of the ring which moves the die rolls through equal distances towards and from the work axis, means for tilting the'dies relative to the work axis, mechanism including a movable cam and a follower connected to oscillate the ring in a predetermined cycle, said cam having an inclined surface which causes the dies to penetrate progressively the entire thread length of the work during a plurality of work revolutions, and power driven change speed mechanism connected to rotate the dies positively and to move the cam in a predetermined but variable relationship of rate of die and work rotation to the rate of work penetration.

13. A thread rolling machine comprising a casing having an annular support, an outer stress ring holder mounted for rotative oscillation on said support, two spaced inner stress rings, the upper one of which is mounted on and located by the outer ring, a plurality of thread rolling dies, a support for a die, means for clamping the support and the outer stress ring together and means for adjustably supporting the lower ring on the upper one and clamping it to said support, said die support having upper and lower locating surfaces engaging said inner rings which accurately position the die roll relative to a horizontal plane.

14. A thread rolling machine comprising three die rolls arranged to roll a thread on a work piece therebetween, means for rotating the rolls positively and in synchronism, a stress ring having a cam surface and a cylindrical surface on its inner periphery, a toggle having one arm positioning a die roll and a second arm adjustably secured to said cam surface, means including a movable support for another die roll having a follower engaging said cylindrical surface which holds the die roll axis in a fixed position as the ring oscillates, said stress ring receiving the thrusts of the thread rolling operation through said toggle and movable support, and means for oscillating the stress ring and causing the toggle to move its associated die roll towards and from the work center.

ARTHUR BRADFORD REED.