US3538739A - Thread rolling die with cylindrical slug forming and removal surface - Google Patents

Description

Nov- 1 9 R. w. ORLOMOSKI THREAD ROLLING DIE WITH CYLINDRICAL SLUG FORMING AND REMOVAL SURFACE Filed April 1, 1968 2 Sheets-Sheet 1 &

8/ 2 XQM WM [MW mm/ by M, 62M; 62M flii'owugs R.-w.- ORLOMOSKI THREAD ROLLING DIE WITH CYLINDRICAL SLUG Nov. 10, 1970 FORMING AND REMOVAL SURFACE 2 Sheets-Sheet 2 Filed April 1, 1968 Roger 4. 08 30272018351; 2 I Mae y W United States Patent 3,538,739 THREAD ROLLING DIE WITH CYLINDRICAL SLUG FORMING AND REMOVAL SURFACE Roger W. Orlomoski, Paxton, Mass, assignor to Reed Rolled Thread Die C0., Holden, Mass., a corporation of Massachusetts Filed Apr. 1, 1968, Ser. No. 717,699 Int. Cl. B21d 13/04 U.S. Cl. 72-469 7 Claims ABSTRACT OF THE DISCLOSURE The disclosure comprises a pair of matched thread rolling dies capable of producing a gimlet pointed screw from a cylindrical blank of which the lower portion (the slug) is gradually forced away and finally severed from the screw as the point is being created. The disclosure feature is the configuration of that surface of the die which acts to produce the slug. This surface is in a preferred form part of a cylinder which intersects the point producing surface along a diagonal line at a changing angle.

BACKGROUND OF THE INVENTION Production of screws by rolling the threads therein through the use of a pair of properly grooved dies which are moved past each other with a cylindrical blank squeezed and rotated therebetween is an old and well known art which does not need to be explained to those who are skilled in this field.

However, the production of so-called gimlet pointed screws has presented certain problems posed by the creation of the pointed portion of the screw which must have thereon a thread which is a continuation of the main body thread and is in the form of a decreasing spiral running to the point. If the blank from which the screw is formed has been initially pointed prior to rolling the threads therein, the problem is somewhat simplified; but this solution calls for a more expensive blank. Such blank must be not only pointed but also exactly the right length. On the other hand, if the blank has not first been pointed, then as the threaded point is generated during the rolling of the blank between the dies, means must be provided for removing the surplus material that will be present at the lower end of the blank below the threaded point. This surplus portion is known in the trade as a slug.

Accordingly, the problem of designing a suitable configuration for dies which are capable of rolling a perfect screw thread throughout the length of the body portion as well as on the tapered gimlet point, while at the same time effectively removing the surplus material below the point, has been difficult of solution. United States Pat. No. 3,176,491 to W. L. Mau et al., issued Apr. 6, 1965, for Thread and Other Form Rolling Dies, is illustrative of some of the work that has been done along these lines.

SUMMARY The present invention discloses a new and novel structure with respect to that portion of the die which causes the gradual reduction in diameter and simultaneous pointing of the blank. As the threaded point is formed, the dies also create a slug below the point which separates from the screw just prior to completion of the threading operation. The configuration of the die surfaces that produce this result is unique in three major respects. First the slug forming surface that engages the blank below the point is curved and in a preferred form will be part of the surface of a cylinder of appropriate diameter. Secondly, the arc of the cylindrical surface that progressively engages the blank shifts progressively clockwise as viewed from the starting end of the die. Thus since the grooved 3,538,739 Patented Nov. 10, 1970 plane pointing surface is at a constant angle (usually about 20) to the blank axis, the effective wedging angle between the pointing surface and the slug forming sur face decreases continuously from the neighborhood of 150 at the start of the pointing operation to about by the time of separation of the slug from the blank.

Thirdly, the width of the cylindrical arc that engages the blank continuously decreases as the wedge angle decreases. This produces sharp and clean separation of the slug at a position shortly before the pointing operation has been completed but leaves enough metal at the still incomplete point to enable the dies to complete a finished full point of commercially acceptable quality.

The concept of having the slug forming surface curved and making a decreasing wedging angle with the grooved pointing surface runs counter to heretofore known practices in this field. The decreasing width of the curved surface up to the position of slug separation eases the force requirement as the cross section of the blank is reduced while the pointed portion is being threaded and lengthened.

It is to be understood, however, that while the preferred form of curved surface is a portion of a cylinder, it could be otherwise as, for example, a portion of a surface oval in section. Furthermore, the radius of curvature of the surface may be more or less. The radius could be so large as to produce a surface substantially flat at each section but twisted clockwise from the starting end toward the slug cut off position. In all cases, however, the wedge angel between the plane sloping grooved pointing surface and the slug forming surface constantly but not necessarily uniformly decreases as the diagonal wedge edge approaches the axis of the blank as the pointing and threading operation nears completion.

These and other objects of the invention will become more apparent as the description proceeds with the aid of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical elevation of one of the dies.

FIG. 2 is a top plan view of FIG. 1.

FIG. 3 is an end elevation to double scale of FIGS. 1 and 2 looking from the left.

FIGS. 4, 5, 6, 7 and 8 are a succession of vertical sectional views taken through a pair of dies showing the progressive character of the threading and pointing operation and the production and separation of the slug from the point. For purposes of illustration, the thread producing grooves present in the dies both on the vertical surfaces and on the sloping pointing surfaces have been omitted for clarity. Such grooves and the threads produced thereby constitute no part of the invention, as such structures are old and well known.

FIG. 9 is a perspective view, somewhat foreshortened, of the die shown in FIGS. 1, 2 and 3 looking upwardly and to the right. This shows the curved cylindrical surface meeting the diagonal wedge edge at a continually decreasing angle to the sloping grooved pointing surface.

FIG. 10 shows a finished gimlet pointed screw of the type produced by the dies of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1, 2, 3 and 9, the general structure of the dies will be readily recognized. It is to be understood that the operative portions of the two dies are identical. In practice, the moving die is made somewhat longer than the stationary die for the purpose of facilitating entry of the blank to initial rolling position between the blanks and final discharge. The thread forming grooves on both the flat and sloping surfaces and the slug forming and removal surfaces are identical. Accord- 3 ingly, it will be understood that a description of the single die shown herein is a description of both dies of a pair of dies.

In FIGS. 1, 2, 3 and 9 the die 2 has a vertical surface generally referred to as A. This surface contains a plurality of parallel V-shaped grooves 4- cut to an angularity and depth capable of producing the required thread when the blank is rolled between the dies in conventional manner.

The lower edge of the flat grooved surface A terminates in a heel line 6 which is the line of intersection between the grooved surface A and a sloping grooved pointing surface B. The grooves 4 run continuously across vertical surface A and then into sloping surface B, maintaining the correct depth to produce the required thread on the screw body and point. The surface B terminates in part at a lower edge 8 which is parallel to the heel line 6. Another edge 10 runs from the point 11 on heel line 6 of grooved surface A downwardly and away from surface A to the point 12 where it meets the edge 8. Edge 10 may be referred to hereinafter as the diagonal edge, while edge 8 running from the point 12 to the end of the die at point 14- may be referred to as the parallel edge (being parallel to heel line 6). The sloping grooved plane surface B is thus bounded by heel line 6, diagonal edge 10, parallel edge 8, and at the right end by sloping edge 16. All of these boundaries lie in the plane of surface B. For reasons that will be explained in more detail hereinafter, the diagonal line 10 is not a straight line. It is slightly curved because it constitutes the intersection of a plane surface with a cylindrical surface in which the axis of the cylinder is not parallel to the plane surface B.

The portion of the die immediately below parallel edge 8 is in the form of a vertical surface C which may be referred to as a bumpy or flat extrusion surface. This surface functions to limit the approach of the dies toward each other and also to remove any metal that might remain below the point of the screw after separation of the slug. The surface C has a lower edge 18, which is the line of intersection with the curved cylindrical surface hereinafter to be described.

The surface D, best seen in FIGS. 1, 3 and 9, is a portion of a cylindrical surface whose axis 20 is shown as lying in the same horizontal plane as heel line 6. Axis 20 at the left end of the die is at a distance X from the surface A while at the right end of the die is at a lesser distance Y from the surface A. Thus, a cylinder having its axis on the line 20, and with a radius X, will intersect sloping surface B along the slightly curved diagonal edge 10 and will intersect the vertical extrusion surface C along a slightly curved line 18.

For reference purposes, dot-and- dash lines 22, 24, 26, 28 and have been drawn in the cylindrical surface D. These lines serve to illustrate how the surface D as it moves to the right along diagonal line 10 changes its angularity with respect to the sloping portion B. Thus, it will be seen that the included angle between surface B and curved surface D gradually decreases as the blank advances across the die from position 22 to 24 to 26 to 28 and finally to position 30.

It will also be observed that the curved surface D has been cut away to provide an undercut area B. This area has a substantially vertical wall 32 and a generally horizontal wall 34 which turns downwardly at the right hand end to terminate at the point 36. The generally horizontal upper wall 34 intersects the curved surface D along the edge 38-, which edge gradually approaches diagonal edge 10, thus creating an upper sub-area P which has a maximum width at the left end 40 and a minimum width at about position 28. Thereafter the width of sub-surface F increases until point 36 is reached. The exact position of minimum width of sub-surface F is not critical except insofar as insuring breakaway of the slug sufficiently far in advance of the point 12 so that the threaded point of the screw may be properly completed thereafter.

In FIGS. 1, 3 and 9 is shown a dash line 42 in the sub-surface F. Line 42 is referred to as the contour line since it lies in the same plane as the surface A. That portion of sub-surface F above contour line 42 acts on the blank as it rolls along the die. Contour line 42 ends at point 44 where it meets the edge 38 which is rising toward but never meets diagonal edge 10. i

From the foregoing, it can be seen that that portion of sub-surface F forming the reversely sloping lower face of the wedge acting on the blank increases in width from point 11 to the point 44. Thereafter, it decreases in width to approximately position 28 by which time the crosssection of the blank between the point and the slug will have been reduced sufficiently to cause the slug to separate. After separation of the slug, the sub-surface F is out of action as the widening, sloping, pointing surface B completes the formation of the point and the thread thereon.

In a modified form of the invention, the cutaway area B might have its upper edge 38 continue from the point 44- along an extended contour line indicated by the dot-anddash line 42'. In such case, the curved sub-surface F, of constant radius, would gradually increase in width over the entire distance that the slug was being created.

In still another modification, the cut-away area E might be eliminated entirely. This would be substantially as effective in producing and cutting off the slug since none of the cylindrical surfaces below the contour line 42 and the extension thereof 42 would come into engagement with the blank during the thread forming operation. However, the extruding effect in producing the slug varies slightly as the sub-surface F is widened beyond point 44 to follow the alternative contour line 42. The narrowed construction is preferred, but in either case it will be noted that the angularity of sub-surface F with the pointing sloping surface B decreases from the point 11 to the point 12 along diagonal edge 10.

It is intended to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

I claim:

1. A pair of dies of the type described for producing gimlet pointed screws, each said dies including a vertical body thread creating surface, a ramp for creating and threading the point, said ramp intersecting said surface along a heel line and having a diagonally extending edge leading downwardly and away from said surface, said edge being the line of intersection between said ramp and a slug creating surface sloping in the opposite direction from said ramp, said slug creating surface being a portion of a cylindrical surface whose angularity with respect to said ramp continuously decreases along the length of said diagonally extending edge.

2. A die of the type set forth in claim 1 the axis of said cylindrical surface being generally horizontal but at an angle to said vertical surface.

3. The construction as set forth in claim 2 said axis extending through said die.

4. The construction as set forth in claim 2 said axis and heel line being in a plane common to both.

5. The construction as set forth in claim 2, the angle of said axis to said vertical surface being such that it converges toward said heel line.

6. A pair of dies for producing gimlet pointed screws by the rolled thread process, each die of said pair being of identical configuration over its operative portion and comprising a vertical flat grooved surface for creating the thread on the body of the screw, a sloping plane surface having therein continuations of said grooves and extending downwardly away from said fiat grooved surface for creating the threaded pointed portion of said screw, the line of intersection of said fiat grooved surface and said sloping grooved surface forming a straight heel line, a cylindrical surface intersecting with said sloping plane surface to form a slightly curved diagonal edge, said cylindrical surface sloping in the reverse direction of said sloping plane surface, the axis of said cylindrical surface being non-parallel to said vertical flat surface so that the included angle between said plane sloping surface and said cylindrical surface along said diagonal edge continuously decreases from the beginning of said diagonal edge to the end thereof, whereby the angle of the said reversely sloping cylindrical surface will continuously increase with respect to the axis of the screw and said sloping and cylindrical surfaces during the forming of said screw will act to create and remove a Slug from the lower end of the said screw.

7. The construction set forth in claim 6 in which said axis of said cylindrical surface is horizontal but runs at a constantly decreasing distance from said vertical surface over the length of said die.

References Cited UNITED STATES PATENTS MILTON S. MEHR, Primary Examiner

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