US3069939A

US3069939A - Tool for rolling internal threads

Info

Publication number: US3069939A
Application number: US808845A
Authority: US
Inventors: Koehler Marian Elizabeth
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-04-24
Filing date: 1959-04-24
Publication date: 1962-12-25
Anticipated expiration: 1979-12-25

Description

Dec. 25, 1962 P. A. KOEHLER TOOL FOR ROLLING INTERNAL THREADS Original Filed Nov. 18, 1955 3 Sheets-Sheet l Dec; 25, 1962 P. A. KOEHLER 3,069,939 TOOL FOR ROLLING INTERNAL mamas Original Filed Nov. 18, 1955 s Sheets-Sheet 2 INVENTOR. PAM/4 AZ Kay/415R 1952 P. A. KOEHLER 3,069,939

TOOL FOR ROLLING INTERNAL THREADS Original Filed Nov. 18, 1955 3 Sheets-Sheet 3 INVENTOR. P40; 9. K05; 1?

United States Patent ()fiFice 3,059,939 Patented Dec. 25, 1962 3 069 939 TGDL FOR ROLLIA G INTERNAL THREADS Paul Anthony Koehler, Lyndhurst, Ohio; Marian Elizabeth Kcehler, executrix of said Paul Anthony Koehler, deceased Continuation of abandoned application Ser No. 547,732, Nov. 18, 1955. This application Apr. 24, 1959, Ser. No.

11 Claims. (Cl. 80-6) terials, like soft aluminum alloys, hard stainless steels,

titanium, and other materials are diflicult to form with cut threads Without tearing the metal but can be readily roll threaded. In such cases roll threading is also faster.

Because of the advantages that are obtainable, thread rolling has come into rather wide spread use as far as external threads are concerned. However, even though the same advantages pertain to internal threads, there is a very limited application of this principle for internal threads due, primarily, to the lack of simple and efiicient tools for performing the thread rolling operation.

The present invention provides a tap for this purpose that is easy to make and maintain, simple to use, and which provides a high degree of accuracy and uniformity in the threads produced therewith.

Among the objects of the invention is to provide a thread rolling tap in which the thread may be completely formed with one pass of the tap into the work piece.

It is another object to provide a thread rolling tap in which the thread forming roll or rolls will automatically form a thread of predetermined pitch regardless of the rate at which the tap is fed into the work piece.

It is another object to provide a thread rolling tap in which the thread forming roll or rolls include a plurality of annular thread forming ribs.

It is another object to provide a tap of the type described in which the thread forming roll or rolls are mounted on pins which are inserted in the holder at one end thereof in holes which pass completely through the holder so as to permit access to said pins for removing the same from the holder.

It is another object to provide a thread rolling tap with a plurality of thread forming rolls which has a means for limiting deflection of the rolls toward each other at each end thereof.

It is another object to provide a thread rolling tap having a plurality of thread forming rolls, and with at least one of the rolls being adjustable in its longitudinal position relative to another of said rolls.

It is another object to provide a thread rolling tap having a plurality of thread forming rolls, each mounted on a shouldered pin, and with at least one of the pins being longitudinally positionable by an adjusting screw whereby the position of the roll on such pin is longitudinally adjustable with respect to another of said rolls.

It is another object to provide a thread rolling tap comprising a holder with pins mounted therein and carrying a thread forming rolls, and with means for retaining said pins in said holder, the circle circumscribed by said rolls upon rotation of the holder being of larger diameter than the diameter of the circles circumscribed by said holder and said pin retaining means, and with the diameter of said circumscribed circle for said pin retaining means being no larger than the diameter of said circumscribed circle for said holder whereby said pin retaining means will not interfere with either chucking of the holder or insertion of the tap within a work piece to be internally threaded.

Other objects of the invention will become apparent from the following description and from the drawings in which:

FIGURE 1 is a front view, partly in section along the lines 1il of FIGURE 2, of a preferred form.

FIGURE 2 is a bottom view of FIGURE 1;

FIGURE 3 is an end view of FIGURE 1;

FIGURE 4 is a view along lines 44 of FIGURE 2.;

FIGURE 5 is a front view, partly in section along the lines 5-5 of FIGURE 6, showing an optional form with three thread forming rolls and with means for adjusting the longitudinal position of the rolls;

FIGURE 6 is a bottom view of FIGURE 5;

FIGURE 7 is an end view of FIGURE 6;

FIGURE 8 is a view along the lines 8-8 of FIG URE 5;

FIGURE 9 is a front view partly in section along the lines 99 of FIGURE 10 of an optional form employ ing a single thread forming roll;

FIGURE 10 is a bottom view of FIGURE 9;

FIGURE 11 is an end view of FIGURE 9;

FIGURE 12 is a diagram of a typical roller showing a convex configuration.

In the form illustrated in FIGURES 1 through 4, the tap comprises a holder 11 having a pair of

holes

12 and 13 drilled therethrough from end to end thereof. lAt one end of the holder these holes are enlarged as at 14 and 15. Press fitted into the enlargements are

pins

16 and 17. The pin 16 has a collar 18 which abuts the adjacent end of the holder Ill and it also has a reduced diameter extension 19 upon which a thread forming roll 20 is rotatably mounted. By continuing the

holes

12 and 13 completely through the holder from end to end thereof, a rod may be inserted into the holes for knocking out the pins when it is desired to replace the same.

Likewise, the pin 17 has a collar 21 and a reduced diameter portion 22 upon which a second thread forming roll 23 is mounted. The rolls 2G and 23 are retained upon the

pins

16 and 17 by a plate 24 and screws 25 and Z6 threaded into the outer ends of the

pins

16 and 17. The thread forming roll 20 has a series of annular ribs 27 and the roll 23 likewise has a series of annular ribs 28. These ribs 27 and 2S engage a work piece 29 for rollforming internal threads therein. The cross sectional shape of the ribs 27 and 28 conforms with the cross sectional shape of the spaces between the threads to be formed and the cross sectional shape of the spaces between the ribs 27 and 28 conforms with the cross section-a1 shape of the threads to be formed.

The first one or more ribs on each roll are preferably of smaller diameter than the others to facilitate starting of the roll into the work piece.

The axis 32-492 of the hole 12 is parallel with the axis 33-413 of the holder as viewed in FIGURE 1 and is at an angle 35 'with the axis 3333 as viewed in FIGURE 2. In other words, the axis 3232 is parallel with the axis of the holder in one plane and is at an angle 35 in another plane at right angles to the first mentioned plane.

The end of the holder adjacent the thread rolls is formed with a surface 40 which is perpendicular to the axis 32- 32.

In like manner, the axis 4141 of the allel with the hole 13 is paraXis 33-33 of the holder as viewed in 3 FIGURE 1 and is at an angle 43 with the axis of the holder as viewed in FIGURE 2. The surface 45 is perpendicular to the axis 4141. The angles 35 and 4 3 are equal to each other and are also equal to the helix angle of the thread to be formed in the work piece 29.

The outer diameter 47 of the holder 11 is smaller than the minor diameter of the threads to be formed in the workpiece so that the holder may enter the work piece if it is so desired.

The roller 29 is rotatable on the pin extension 19 about the axis 32-32 and the roller 23 is rotatable on the extension 22 about the axis 41-41.

The annular ribs 27 and 28 on the rolls are offset longitudinally with respect to each other an amount equal to one half the pitch of the thread to be formed.

In the modification shown in FIGURES through 8 there is a work holder 66 having three

longitudinal holes

61, 62, and 63. The longitudinal axes of these holes are equidistant from the axis of the holder 60 in any transverse plane perpendicular to the axis of the holder, and the angular spacing of the holes about the axis of the holder is also equal. Mounted in the hole 63 is a pin 64 having a groove 65 adjacent its inner end and having a collar 56 abutting the adjacent end of the holder 66. Outwardly of the collar 56 is a reduced diameter 57 upon which is mounted a thread forming roll 68. Adjacent the outer end of the pin 64 is a groove 69. Mounted in the

holes

61 and 62 are pins 66 and 67 with like grooves, collars, and reduced diameters as on pin 64, and with

thread forming rolls

70 and 71 rotatably mounted on their outer ends.

The holder 69 has an annular groove 73 which intersects the

holes

61, 62, and 63. Mounted in this groove 73 is a split ring 74. The ring 74 projects into the grooves 65 formed on each of the pins 64, 66, and 67 for retaining the same within the

holes

61, 62, and 63. At the inner ends of the

holes

61, 62, and 63, there are threaded sections 75, 76, and 77 into which adjusting screws 78, 79, and 80 are threaded. interposed between the adjusting screws and the corresponding pin are balls 81', 82, and 83. The adjusting screws, acting through the balls, permit direct adjustment of the longitudinal position of the pins and hence of the rolls so that the rolls may be adjusted longitudinally of each other for precise positioning thereof with respect to each other in their proper longitudinal offset. Mounted in the grooves 69 and between the three pins 64, 66, and 67 is a circular disk 34 which supports the ends of the pins to prevent deflection toward each other during the thread forming operation.

The grooves 65 are wider than the ring 74 and the disk 84 is slightly narrower than the grooves 69 so as to permit the longitudinal adjustment of the roll carrying pins 64, 66, and 67 with respect to each other. Preferably, the pins 64, 66, and 67 are initially inserted with their respective collars 56 against the adjacent end face portion of the holder 60 and with the adjusting screws 78, 79, and 80 slightly retracted. Any inaccuracy in the longitudinal positioning of any of the

rolls

68, 70, and 71 with respect to each other is then corrected by moving the respective pin 64, 66, or 67 outwardly of the holder by means of the corresponding adjusting

screw

78, 79, or 80. In such case the collar 56 of the adjusted pin will be moved slightly away from the corresponding end face of the holder 60 and inward movement of the pin will then be limited by the corresponding ball 81, 82, or 83 and the associated adjusted screw.

It will be noted that the split ring 74 which retains the pins in the holder is no larger in diameter than the holder, or in other words, a circle circumscribed by the ring 74 as the holder rotates on its longitudinal axis has a diameter no larger than the diameter of a circle circumscribed by the holder. Likewise, the

rolls

68, 70, and 71 project radially beyond both the holder 60 and retainer ring 74 so that the circle circumscribed by said rolls as the holder rotates has a diameter greater than the diameters of circies circumscribed by said holder and said ring 74. This results in an efficient structure in which the pin retaining ring 74 does not interfere with chucking of the tool in a suitable chuck and also permits entrance of the rolls into a work piece to any depth without interference from the holder or retainer ring.

The circular disk 84 is preferably notched in three places as at 89 for receiving the reduced portions of the pins which form the bottoms of the grooves 69. Such notches 89 not only support the ends of the pins directly against deflection radially inwardly of the holder, but also angularly with respect to the axis of the holder.

The

thread forming rolls

68, 7t and 71 each have annular ribs such as shown at 85. These ribs are longitudinally offset from each other a distance equal to one third of the pitch of the thread to be formed.

As in the case of the two-roller form shown in FIG- URES 1 through 4, the longitudinal axis of each thread forming roll is parallel with the axis of the holder in one plane and is at an angle with the axis of the holder in a second plane at right angles to the first mentioned plane.

In the modification shown in FIGURES 9 through 11, there is shown a holder 90 having but a single hole 91 therethrough, this hole having an enlargement 92 at one end thereof. Press fitted within the enlargement 92 is a pin 93 having a collar 94 in engagement with the adjacent end of the holder. Beyond the collar there is a reduced diameter portion 95 upon which a work roll 96 is rotatably mounted and which is retained thereon by a screw 97 threaded into the outer end of the pin 93. The roll 96 has annular ribs 98 formed thereon.

As in the case of the previously described forms, the axis of the roller 96 is parallel with the axis of the holder in one plane and is at an angle with the axis of the holder in a second plane which is at right angles to the first men tioned plane.

In operation, the two-roller form shown in FIGURES 1 through 4 and the workpiece 29 may be mounted ina suitable machine tool (not shown) for rotation relative to each other. The holder 11 is then advanced toward the work piece. The work piece will previously be formed with a hole 30 of a diameter closely equal to the pitch diameter of the thread to be formed therein. As the holder 11 is advanced, the rolls 2t and 23 will enter the work piece and form the thread. During this part of the operation the rolls 2t) and 23 will be rotated on their own aXeS by frictional contact with the work piece 29. When the thread is formed to the proper depth within the work piece 2 9, rotation of the holder is reversed and the rolls will unthread themselves from the work piece.

Operation of the three-roller and single-roller forms is similar to that of the two-roller form and a further description of the same is not thought necessary.

The axis of the holder 11 is coincident with the axis f the work piece 29 and since the axis of the roller 20 is at an angle 35 with the holder in one plane, it will likewise be at an angle 35 with the axis of the work piece in one plane. From this it is apparent that as the roller enters the hole 30, the first and last of the ribs 28 will tend to form a deeper thread impression in the work piece than will the rib 28 in the center of the roller 20. The same is true of the other roller 23 and of the rollers shown in the other forms of the invention.

The larger the diameter of the thread to be rolled with respect to the pitch of the thread, the more insignificant will be this effect and in some instances the effect can be disregarded. When it is desired that all of the ribs in the rollers make the same impression in the Work piece, the rollers may be formed in band shape as shown in FIG- URE 12. The radius R can be approximated closely enough for practical purposes by the formula:

Rradius of roller at pitch diameter of annular ribs.

L-length of roller (vertical plane through axis of roller intersects vertical plane through axis of thread midway along length of roller).

P-pitch diameter of finished thread.

6helix angle of pitch diameter of thread.

Barrel shaping in this manner so that all, or at least a plurality of ribs on the rollers make the same impression in the work piece results in a burnishmg of threads in the work piece by the succeeding ri-bs andresults in more uniform sizing of the thread and in an improved finish thereon.

Although only single, double, and three-roller forms have been illustrated and described in detail, it is obvious that any desired number of rollers may be provided. However, in each case it is necessary that the axis of each of the rollers be parallel to the axis of the holder 111 one plane and at an angle equal to the helix angle of the thread in another plane at right angles to the first mentioned plane, and that the ribs on the rollers be longitudinally offset from each other an amount equal to that proportion of the thread pitch corresponding to the angular spacing between the rollers. Modifications may be made in various details of construction without departing from the scope of the invention as defined in the following claims.

This application is a continuation of my prior co-pending application Serial Number 547,732, now abandoned, filed November 18, 1955.

I claim:

1. A tap for rolling internal threads comprising a holder, at least two pins mounted on said holder, a thread forming roll rotatably mounted on each pin, a shoulder on at least one of said pins against which the respective roll abuts, the axes of the rolls being spaced from the axis of the holder and parallel thereto in one plane and at an angle thereto in another plane, and screw means for engaging and moving said one pin longitudinally for ad usting the longitudinal position of said one pin on said holder whereby said shoulder will adjust the longitudinal pos1t1on of the roll thereagainst with respect to another of said rolls, the circle circumscribed by the adjusting means upon rotation of the holder on its longitudinal ax1s being smaller than the circle circumscribed by the rolls upon said rotation.

2. A tap for rolling threads comprising a holder, three or more pins extending from the extreme end of the holder, a thread forming roll rotatably mounted on each pin, the axis of each roll being parallel to the axis of the holder in a first plane and at an angle thereto n another plane, each pin having an integral portion pro ect ng beyond the respective roll and having a groove in said projecting portion, the bottom of each groove constituting a reduced end portion of each pin, and a circular disk between said pins having a diameter less than the diameter of a circle which passes through the axis of the pins, said disk having arcuate notches therein to receive the reduced end portion of said pins and thus be seated in said grooves for supporting the ends of the pins against deflection toward the axis of the holder, said groove retaining the circular disk against axial displacement.

3. A tap for rolling internal threads in a bore of a workpiece comprising a holder, said holder at one end having a radially outer surface adapted to be gripped by a rotatable device whereby said holder may be rotated, a plurality of longitudinally extending openings in said holder toward the other end thereof, the longitudinal axis of each opening being spaced from the longitudinal axis of the holder and parallel thereto in one plane and at an angle thereto in another plane, a pin mounted in each opening, the inner end of each pin being housed completely within said holder and terminating short of said one end of the holder whereby each pin is inaccessible for driving connection with said rotatable device, each pin carrying a thread forming means adapted to enter the bore of said workpiece, means for retaining said pins within said openings, the diameter of the circle circumscribed by said thread forming means upon rotation of said holder being greater than the diameter of the circle circumscribed by said retaining means and also being greater than the diameter of the circle circumscribed by said other end of said holder whereby said tap may enter said workpiece without interference from said retaining means or said holder.

4. A tap for rolling internal threads in a hollow workpiece, comprising a holder adapted to enter said workpiece and to be rotated about a longitudinal axis, at least two pins mounted on the holder at one end thereof and rotatable with said holder about said longitudinal axis, a thread forming roll rotatably mounted on each pin and adapted to form an internal thread in said workpiece, the axes of the rolls being spaced from the axis of the holder and parallel thereto in a first plane and at an angle thereto in another plane, means for fixing the longitudinal position of one of said rolls with respect to said holder, means for adjusting the longitudinal position of the other of said rolls with respect to said one of said rolls, said adjusting means being located wholly within the radial confines of said holder and rotatable therewith.

5. A tap in accordance with claim 4 in which there is a means rotatable with said holder and independent of said adjusting means for retaining said pins on said holder, said retaining means likewise being contained Wholly within the radial outline of the holder.

6. A tap for rolling internal threads in a bore of a workpiece comprising a holder, said holder at one end having a surface adapted to be gripped by a rotatable device whereby said holder may be rotated, a plurality of longitudinally extending openings in said holder toward the other end thereof, the longitudinal axis of each opening being spaced from the longitudinal axis of the holder and parallel thereto in one plane and at an angle thereto in another plane, a pin mounted. in each opening, the inner end of each pin being housed within said holder for protecting the same, each pin carrying a thread forming means adapted to enter the bore of said workpiece, means for retaining said pins within said openings, the diameter of the circle circumscribed by said thread forming mean-s upon rotation of said holder being greater than the diameter of the circle circumscribed by said retaining means and also being greater than the diameter of the circle circumscribed by said other end of said holder whereby said tap may enter said workpiece without interference from said retaining means or said holder, said retaining means comprising a ring carried within an annular groove in said holder and encircling said pins.

7. A tap for rolling internal threads in :a hollow workpiece comprising a holder, at least two pins journaled in the holder and projecting from one end thereof, a thread forming roll rotatably mounted on each pin and adapted to enter a hollow workpiece, means on at least one pin fixing the longitudinal position of the roll thereon, the axes of the rolls Ibeing spaced from the axis of the holder and parallel thereto in a first plane and at an angle thereto in another plane, and means carried by said holder for moving said one of the pins axially in its journal with respect to another of said pins for adjusting the longitudinal spacing of the roll on said one pin with respect to the other rolls, means independent of the adjusting means for retaining the pins within the holder, said retaining means comprising a split ring carried within a groove in said holder and fitting loosely Within a groove in said one of said pins for permitting said axial movement of said one pin by said adjusting means.

8. A tap for rolling internal threads comprising a holder, at least two pins mounted on said holder, a thread forming roll rotatably mounted on each pin, a shoulder on at least one of said pins against which the respective roll abuts, the axis of each roll being spaced from the axis of the holder and parallel thereto in one plane and at an angle thereto in another plane, adjusting means for engaging and moving said one pin longitudinally for adjusting the longitudinal position of said one pin on said holder whereby said shoulder will adjust the longitudinal position of the roll thereagainst with respect to another of said rolls, the circle circumscribed by the adjusting means upon rotation of the holder on its longitudinal axis being smaller than the circle circumscribed by the rolls upon said rotation.

9. A tap for rolling internal threads comprising a holder adapted to be rotated about a longitudinal axis, a bore in said holder extending longitudinally thereof, a pin having one end extending into said bore, the axis of said pin being spaced from said longitudinal axis and parallel thereto in a first plane and at an angle thereto in another plane, a thread forming roll rotatably mounted on the other end of said pin, said holder having an annular groove in its outer periphery intersecting said bore, said pin having an annular groove therein in register with said annular groove in said holder, and a ring mounted within the annular groove in said holder and projecting into the annular groove in said pin and serving to retain said pin within said holder.

10. A tap for rolling internal threads in a bore of a workpiece comprising a holder, said holder at one end having a surface adapted to be gripped by a rotatable device whereby said holder may be rotated, a plurality of longitudinally extending openings in said holder toward the other end thereof, the longitudinal axis of each opening being spaced from the longitudinal axis of the holder and parallel thereto in one plane and at an angle thereto in another plane, a pin mounted in each opening, the inner end of each pin being housed within said holder for protecting the same, each pin carrying a thread forming means adapted to enter the bore of said workpiece, means for retaining said pins within said openings, the diameter of the circle circumscribed by said thread forming means upon rotation of said holder being greater than the diameter of the circle circumscribed by said retaining means and also being greater than the diameter of the circle circumscribed by said other end of said holder whereby said tap may enter said workpiece without interference from said retaining means or said holder, said retaining means being located between said rolls and said one end of the holder.

11. A tap for rolling internal threads comprising a holder adapted to be rotated about a longitudinal axis, an opening in said holder extending longitudinally thereof, a pin having one end extending into said opening, the axis of said pin being spaced from said longitudinal axis and parallel thereto in a =first plane and at an angle thereto in another plane, a thread forming roll associated with said pin, said holder having an annular groove in its outer periphery intersecting said bore, said pin having an annular groove therein in register with said annular groove in said holder, and a ring mounted within the annular groove in said holder and projecting into the annular groove in said pin and serving to retain said pin within said holder.

References Cited in the file of this patent UNITED STATES PATENTS 885,068 Moy Apr. 21, 1908 2,145,587 Draper Ian. 31, 1939 2,349,863 Hallberg May 30, 1944 2,645,954 Pfingston July 21, 1953 2,720,801 Erdelyi Oct. 18, 1955