US3800585A - Die for forming lobed threads - Google Patents
Die for forming lobed threads Download PDFInfo
- Publication number
- US3800585A US3800585A US00313845A US3800585DA US3800585A US 3800585 A US3800585 A US 3800585A US 00313845 A US00313845 A US 00313845A US 3800585D A US3800585D A US 3800585DA US 3800585 A US3800585 A US 3800585A
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- United States
- Prior art keywords
- thread
- ridges
- grooves
- die
- screw
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21H—MAKING PARTICULAR METAL OBJECTS BY ROLLING, e.g. SCREWS, WHEELS, RINGS, BARRELS, BALLS
- B21H3/00—Making helical bodies or bodies having parts of helical shape
- B21H3/02—Making helical bodies or bodies having parts of helical shape external screw-threads ; Making dies for thread rolling
- B21H3/027—Rolling of self-tapping screws
Definitions
- ABSTRACT Thread rolling die having grooves and ridges which are undulated with respect to the place of die movement with the spacing of the undulations in the direction of die movement being related mathematically to the pitch and major diameters of a screw formed by the die.
- the thread rolling die for producing, from blanks having circular cross section, screws with lobed thread configurations.
- the thread rolling die comprises a block of hardened metal having a working face thereof formed with alternate grooves and ridges.
- the cross section of these grooves and ridges corresponds to the cross section of screw threads produced by a pair of the dies when a blank is rolled between them.
- the threads are given a lobular formation by means of pressings in the dies. These pressings are undulations along the length of the grooves and ridges with respect to the plane of the working face of the die.
- the undulations are produced along a length corresponding to the circumference of the screw blank being formed so that a trilobular thread will be produced. Different numbers of lobes may be produced, however, by changing the shape and spacing of the undulations or pressings. Also, the undulations, as shown, may be arranged with respect to each other in adjacent grooves and ridges such that when impressed into the screw being rolled, the resulting lobes on the screw will spiral around its circumference from one end of the screw to the other.
- the present invention is directed to novel thread roll- I ing die arrangements which are capable of impressing accurately contoured lobular formations on threaded screws with minimal distortion of the thread spiral and with minimal distortion of the thread cross section.
- the present invention is based in part on the discovery that even though lobe spacing on a .screw is normally measured along the screw thread, the critical dimensional component of corresponding undulation spacing along a thread rolling die is not in 'a direction along the grooves and ridges of the die but rather it is in the direction of relative movement of the die, i.e., perpendicular to the axis of the thread being rolled.
- the present invention is based in further part on the discovery that when lobular threads are rolled into a cylindrical member by means of a die having lobe forming pressings or undulations, the undulation spacing on the die does not correspond to any one of the blank diameter, the pitch diameter or the major diameter of the threaded member.
- the die undulation or pressing spacing corresponds to a cylindrical surface having a diameter somewhere intermediate the pitch and majordiarnetersof the threaded member More specifically, it has been found that the spacing between successive lobe forming pressings on a die, measured in the direction of die rolling movement, i.e., perpendicular to the axis of the screw being rolled, will be found on the screw where it intersects a cylindrical surface coaxial therewith, the cylindrical surface having a diameter approximately half way between the screw pitch diameter and the screw major diameter.
- the significance of the foregoing discoveries lies in the fact that they make possible the design of a lobe forming die which will roll lobular threads into a member without danger of thread distortion, waviness or thelike.
- This is done, according to the present invention, by spacing the lobe forming undulations along a die, in the direction of die movement, such that the distance between the corresponding portions of successive lobe forming undulations or pressings is related to the major diameter and pitch diameter of the screw being formed.
- the lobe spacing equals the circumferential distance about a cylinder having a diameter equal to the pitch diameter plus 55 percent of the difference between the pitch and major diameters when that distance is divided by the member of lobes to be formed in one revolution about the cylinder.
- FIG. 1 is a side view of a lobed, threaded screw of the type which may be rolled using the present inventron;
- FIG. 2 is a perspective view showing a thread rolling arrangement in which the present invention is embodied
- FIG. 3 is an enlarged elevational view of a die used in the arrangement of FIG. 2;
- FIG. 4 is an enlarged fragmentary perspective view showing an undulated portion of the die of FIG. 3;
- FIG. 5 is an enlarged fragmentary section view taken along line 55 of FIG. 3;
- FIG. 6 is an enlarged stylized view illustrating a rolling operation according to the present invention.
- the screw shown in FIG. 1 comprises a hexagonal head 10 and a threaded shank 12.
- the shank 12 is formed with threads 14 which as shown in the drawing are of standard 60 V contour.
- threads 14 which as shown in the drawing are of standard 60 V contour.
- the specific form of thread is not especially important to the present invention, although it is contemplated that the invention will find greatest application to the formation of threads corresponding to the Unified Screw Thread Standard or to the American National screw thread system.
- the threads 14 in the machine screw of FIG. 1 do not extend smoothly about the screw at a fixed distance from the screw axis, but instead they undulate up and down with respect to the pitch circumference of the screw. These undulations form lobes cross sectionally of the screw and in the present case three such lobes occur for each revolution of the thread 14.
- the lobes moreover, are arranged spirally about the screw and this spiral, which is indicated by lines 16 separating adjacent lobes, extends in a direction opposite to that of the thread helix and has a pitch or lead considerably greater than that of the thread helix.
- the lobed thread 14 is the same as described in copending US. Pat. application Ser. No. 54,716, filed July 14, 1970, and assigned to the assignee of the present invention.
- the lobed thread 14 is formed, according to the present invention, by rolling a cylindrical or slightly conical blank 18 between a pair of special rolling dies 20 and 21.
- the dies 20 and 21 are mounted in a machine 22 which holds them in parallel alignment a fixed distance apart and causes one or both of the dies to undergo movement with respect to each other along parallel paths as indicated by arrows A and B.
- the blank 18, which may have been previously headed, is inserted in the space between the dies.
- the blank 18 is inserted in the space between the dies.
- Continued relative movement of the dies in the direction of the arrows A and B causes the blank 18 to roll between them as indicated by an arrow C.
- the dies 20 have mutually facing thread forming surfaces 24 which are formed with ridges 26 and grooves 28 having cross sectional con tours corresponding to those of screw threads to be formed. Also, the ridges and grooves are angled slightly downwardly with respect to the paths of relative die movement. With this arrangement, the grooves and ridges operate to press against the outer surface of the blank 18 and to impress into that surface a screw thread formation.
- the thread rolling arrangement as thus far described is similar to conventional thread rolling arrangements well known in the art.
- the thread forming surface 24 ofthe die 20 has ridges and grooves 26 and 28 which extend continuously toward the right or entrance end of the die. Toward the left or finishing end of the die, however, the ridges and grooves making up the thread forming surface 24 are interrupted or undulated with respect to the plane of the die working surface. These undulations are arranged in slanted columns as indicated by interruption lines 30. It will be noted that the columns extend at a column angle B with respect to the upper and lower surfaces of the die and with respect to the path of die movement as indicated by the arrow B. This angle B is the same as the helix angle of the lobe spiral shown by the lines 16 in FIG. 1.
- the ridges and grooves 26 and 28 extend at a helix angle a with respect to the upper and lower die surfaces and path of die movement.
- This angle a which is in a direction opposite to that of the angle B is the same as the helix angle of the thread 14 in FIG. 1.
- the undulations in the forming surface 24 of the dies are actually a series of pressings 32 whereby the ridges and grooves 26 and 28 are actually tilted or slanted slightly with respect to the plane ofthe forming surface without appreciable change in cross section, contour or helix angle a.
- the depth of the pressings 32 i.e., the distance from the highest to the lowest point on the ridge or on the groove of each pressing measured in a direction perpendicular to the plane of the working surface 24, may vary according to thread size. In general, the pressing depth extends from 0.003 inches for a No. 2-64 fine thread screw to 0.0l inches for a 36-16 coarse thread screw.
- each pressing 32 is asymmetrical. That is, it rises gradually outwardly with respect to the plane of the working surface over most of its length in a leftward direction and then returns rather abruptly back inwardly with respect to the working surface plane.
- This configuration produces an asymmetrically lobed thread which has been found to be of particular significance in the manufacture of thread forming screws.
- the die 21 has thread forming ridges and grooves and lobe forming undulations or pressings identical in size and shape to those of the die 20, but reversed as to column and helix angle B and a so as to complement the die 20.
- the formations on the working surface of the die 21 appear to be continuations of the formations on the die 20 to the surface of a blank after it has rolled from one die surface to the other.
- the helix angle a of the two dies 20 and 21 be identical. Also, the relative vertical positioning, i.e., along the axis of the rolled blank, of the two dies must be precisely controlled. Otherwise, the ridges and grooves in one die will not appear, to the blank being rolled, as continuations of the ridges and grooves of the other die; and each die then will attempt to form its own set of threads.
- the undulations on one die must complement those of the other die so that the lobe formations produced in the blank by the pressings of one die will register properly with pressings of the other die.
- the spacing of the pressings 32 must be properly controlled in order to produce a properly formed screw with lobed threads.
- the spacings between the pressings 32 are too short, the lobes will be distorted and in fact double lobes or extra lobes will result.
- the spacings are too long, the thread contour will be affected and a wavy or drunken thread will result.
- the spacing of the pressings as used herein means the distance between corresponding points on successive die pressings along the direction of relative die movement.
- the pressing spacing should not be related in direct proportion to the size, i.e., the circumference, of the screw to be rolled. Rather, it should be related to both the pitch diameter and the thread depth of the screw, according to a particular function.
- the function which relates the pressing spacing to these two parameters of pitch diameter and thread depth is as follows:
- R a multiplication factor. It has been found that optimum results are obtained when R is equal to 0.55. However, acceptable results may be expected when R is within the range of 0.30 to 1.00;
- N the number of lobes to be formed in one revolution of the thread being rolled.
- pressing spacing along a die is not necessarily equal to pressing length.
- Pressing length as used herein means the actual length of a pressing measured along the ridge or groove on which the pressing occurs. Since the ridges and grooves are at an angle a with respect to the direction of relative die movement, it will be appreciated that it is possible for the pressings individually to have a length greater than their pressing spacing.” On the other hand, the pressing length may be shorter, for example, where it is desired to form lobes which are not immediately adjacent to each other. Also, where the lobes are to be spiralled around the screw to be rolled, the columns of pressings are slanted at an angle B which effectively increases the length of the pressings beyond the pressing spacing distance.
- each pressing on the die must be spaced from a corresponding second pressing, in the direction of relative die movement, by an amount such that a lobe formed on a screw by the first pressing will thereafter register with the corresponding second pressing when the screw has been rolled 360.
- the second or corresponding pressing will be located along a ridge and groove which is adjacent, i.e., either above or below, the ridge and groove on which the first pressing is formed.
- pressings on the die must be spaced such that corresponding points of successive pressings located along the direction of relative die movement and in mutually adjacent grooves and ridges are displaced from each other by an amount equal to: 4
- R a range from 0.30 to 1.00
- FIG. 6 shows a trilobular threaded blank 40 is rolled between two threaded dies 42 and 43. It should be understood that FIG. 6 does not accurately represent actual conditions. It will be seen in the drawing that the threaded blank is shown as having a thread crest 44 and a thread root 46, both represented in solid outline. Similarly, the drawing shows the dies 42 and 43 as having thread forming ridges 48 and grooves 50, also represented in solid outline. In a true cross section the thread roots 46 of the blank 40 and the grooves 50 of the dies 42 and 43 would be shown in dotted outline.
- the upper die 42 moves rightwardly as indicated by an arrow D while the lower die 43 remains stationary. This, of course, corresponds to relative leftward movement of the lower die 43 with respect to the upper die 42, as indicated by the arrow E.
- This relative die movement causes the blank 40 to roll clockwise about an axis 0 as indicated by an arrow F.
- the blank thread crest 44 contacts the die grooves 50 and the blank thread root 46 contacts the die ridges 48.
- the dies 42 and 43 remain a fixed distance apart and the axis 0 of the blank 40 remains centered between them.
- the rolling of the blank thread on either die resembles the rolling of a flanged wheel on a track.
- the distance between successive lobe forming pressings along a die is chosen to be equal to the circumferential distance between successive lobes to be formed on the screw measured along a cylindrical plane having a diameter approximately half way between the pitch diameter and the crest or major diameter of the screw.
- the pitch diameter (PD) to which a 'plane perpendicular to said given line together estabparticular die will roll can be calculated by the followlishing a pitch diameter and a major diameter of a ing formula: thread to be formed by rolling a cylindrical blank over said one surface in the direction of said given line with PD cot 01/77 T the axis of said blank parallel to said second line, said where: ridges and grooves being undulated with respect to the a the angle of the grooves and ridges with respect 10 plane of said one surface over at least a portion of their to the direction of rolling of relative (he move extent to produce a lobular thread on said cylindrical men!
- a thread lobe rolling die comprising a bioglg havbottoms of the die grooves.
- r PD said pitch diameter of a thread to be formed
- i MD said major diameter of a thread to be formed; where: I 5 i5tch diameter of said screw; v 77 p (11416); and M d N 32 any number of lobes to be formed in one thread;
- a thread lobe rolling die comprising a block havig g gi g formmg accordmg clam ⁇ 1 ing a working surface formed with adjacent parallel r r grooves and ridges corresponding in cross section to A thread lobe fofmlhg dle aeeol'dlhg 111 3 wherein said undulations are arranged in columns the cross sectional configuration of screw threads, said block having mounting arrangements for confining rel- 3 g d W rking ia. 7 i ative movement of said working surface in its plane 6.
- a thread lobe forming die according to claim 6 1 wherein the direction of slant of said columns is opposite to that of said grooves and ridges with respect to said given line thereby to form a lobe arrangement which spirals in a direction opposite to the threads of a screw formed by said die.
- said die is configured to form a standard screw having a size between No. 2-64 and %l 6 and wherein the overall depth of said undulations along a given ridge is between 0.003 and 0.010 inches.
- a fhraaioseramfig die comprising a block hav'-" ing a working surface formed with adjacent parallel grooves and ridges corresponding in cross section to the cross sectional configuration of screw threads, said block having mounting arrangements for confining relative movement of said working surface in its plane along a given line with respect to a corresponding working surface of an associated block, the relative depths of the grooves with respect to the ridges, their angle with respect to said given line and the number of said ridges and grooves along a second line in said where:
- MD said major diameter of a thread to be formed
- Tr pi(3.14l6); and N any number of lobes to be formed in one thread revolution.
- a thread lobe forming die according to claim 10 wherein R 0.55. v 1 g 12. A thread lobe forming die according to claim 10 wherein N 3.
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Abstract
Description
Claims (12)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US31384572A | 1972-12-11 | 1972-12-11 |
Publications (1)
Publication Number | Publication Date |
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US3800585A true US3800585A (en) | 1974-04-02 |
Family
ID=23217391
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US00313845A Expired - Lifetime US3800585A (en) | 1972-12-11 | 1972-12-11 | Die for forming lobed threads |
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Country | Link |
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US (1) | US3800585A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4353233A (en) * | 1981-01-29 | 1982-10-12 | Amca International Corporation | Dies for making thread-forming fasteners |
US5242253A (en) * | 1992-10-08 | 1993-09-07 | Semblex Corporation | Thread-forming screw |
US9643237B1 (en) * | 2013-03-18 | 2017-05-09 | Mark Doll | Compound die for dual thread forming |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2352982A (en) * | 1942-06-25 | 1944-07-04 | American Screw Co | Screw for plastics |
US2484645A (en) * | 1946-10-23 | 1949-10-11 | Illinois Tool Works | Screw fastener |
US3163196A (en) * | 1961-04-03 | 1964-12-29 | Illinois Tool Works | Preassembled fastener unit with elliptical threads |
-
1972
- 1972-12-11 US US00313845A patent/US3800585A/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2352982A (en) * | 1942-06-25 | 1944-07-04 | American Screw Co | Screw for plastics |
US2484645A (en) * | 1946-10-23 | 1949-10-11 | Illinois Tool Works | Screw fastener |
US3163196A (en) * | 1961-04-03 | 1964-12-29 | Illinois Tool Works | Preassembled fastener unit with elliptical threads |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4353233A (en) * | 1981-01-29 | 1982-10-12 | Amca International Corporation | Dies for making thread-forming fasteners |
US5242253A (en) * | 1992-10-08 | 1993-09-07 | Semblex Corporation | Thread-forming screw |
US5395195A (en) * | 1992-10-08 | 1995-03-07 | James Fulmer | Thread-forming screw with tri-roundular, tapered end |
DE4333791C2 (en) * | 1992-10-08 | 2003-06-18 | Semblex Corp | Tapping screw |
US9643237B1 (en) * | 2013-03-18 | 2017-05-09 | Mark Doll | Compound die for dual thread forming |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: NATWEST USA CREDIT CORP. Free format text: SECURITY INTEREST;ASSIGNOR:FARLEY METALS, INC.,;REEL/FRAME:004739/0041 Effective date: 19870729 |
|
AS | Assignment |
Owner name: BANK OF NEW YORK, THE Free format text: SECURITY INTEREST;ASSIGNOR:FARLEY INC.;REEL/FRAME:005221/0038 Effective date: 19890404 |
|
AS | Assignment |
Owner name: FARLEY, INC. Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:NATWEST USA CREDIT CORP.;REEL/FRAME:005221/0044 Effective date: 19890331 |
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AS | Assignment |
Owner name: SIMONS, LEON, 303 EAST 57TH STREET, APARTMENT 47E, Free format text: ASSIGNS THE ENTIRE INTEREST, JOINTLY;ASSIGNOR:FARLEY, INC., A DE CORP.;REEL/FRAME:005544/0519 Effective date: 19900813 Owner name: SIMONS, LEON Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:BANK OF NEW YORK, THE;REEL/FRAME:005544/0514 Effective date: 19900413 |
|
AS | Assignment |
Owner name: SEMBLEX CORPORATION, A CORP. OF DELAWARE, ILLINOIS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SIMONS, LEON;REEL/FRAME:005491/0588 Effective date: 19901016 |
|
AS | Assignment |
Owner name: CONTINENTAL BANK N.A., F/K/A/ CONTINENTAL ILLINOIS Free format text: SECURITY INTEREST;ASSIGNOR:SEMBLEX CORPORATION, A C ORP. OF DE;REEL/FRAME:005828/0841 Effective date: 19910611 |
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AS | Assignment |
Owner name: FARLEY INC., ILLINOIS Free format text: RELEASE OF PATENT SECURITY AGREEMENT;ASSIGNOR:BANK OF NEW YORK, THE;REEL/FRAME:007815/0822 Effective date: 19960119 |