US2066372A

US2066372A - Method of making dies or punches

Info

Publication number: US2066372A
Application number: US43399A
Authority: US
Inventors: Joseph J Tomalis
Original assignee: AMERICAN SCREW CO
Current assignee: AMERICAN SCREW CO
Priority date: 1935-10-03
Filing date: 1935-10-03
Publication date: 1937-01-05
Anticipated expiration: 1954-01-05
Also published as: GB465712A; BE417609A

Description

Jan. 5, 1937. J TOMALIS 2,066,372 METHOD OF MAKING DIES OR P NCH to the operations forming the punch;

Patented Jan. 5, 1937 PATEN IQFFIICE amnion or MAKING mas on PUNCHES Joseph J. Tomalis, Providence, It. I., assignor to American Screw Company, Providence, R. 1.,

a co p ration of Rhode Island Application October 3,1985, Serial No. 43,399

.8Claims.

This invention relates to punches and to the method of making the same, and more particularly to punches of the type used in forming recesses in the heads of screws.

It is a general object of the present invention to provide a novel and improved punch and method of making the same.

, An important feature of the invention resides in the construction of. a punch comprising a projection or nub extending integrally from a shoulder on the end of a metal bar, wherein the metal of the punch is compressed and upset as a. result of cold pressing into a matrix and wherein simultaneously a fillet is formed at the junction of all of the surfaces of the projection and the said shoulder.

Another important feature of the invention resides in the method of forming a punch by first roughing it out by conventional tool-room methods using rotating tools and then forcing the punch projection cold into a matrix which changes the-heretofore machined surfaces and I the shape of the projection, compresses the metal and forms a fillet of short radius at the junctionr of the machined surfaces and the shoulder on the bar from which the punch projection is formed.

A further important feature of the invention resides in the forming of the punch proper first with arcuate surfaces and then reducing these surfaces to true planes in a cold forming operation using a matrix.

Other and further features and objects of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawing and following specification, wherein is disclosed a single exemplary embodiment of both the article and method, with the understanding however, that such changes and deviations may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawing:

Figure 1 represents a bar or rod of metal prior Figure 2 shows the same rod afterturning in a lathe to form the punch nub thereon;

Figure 3 illustrates the operation of end milling the grooves;

Figure 4 is an end view of theincompletely formed punch resulting from the operation of Figure 5 and the following figures are all on an enlarged scale and Figure 5 shows the incompletely formed punch about to'be driven into the matrix which is illustrated in verticaii central section;

Figure 6 is a 'plan view of the matrix;

Figure 7 is a side elevation of the completed punch; and j Figure 8 is an end view thereof.

It has long been proposed to form screws with some form of screw driver receiving recesses other than the conventional transverse kerf. From among these suggestions a recess of cruciform 10 cross-section has been successfully adapted and commercialized. It is substantially shown in the patent to Fearson, No. 308,246, granted November 18, 1884 for Screw, although substantial improvements have subsequently been made.

" The form of recess now manufactured in such screws may be considered substantially like that from a central opening. The wing slots taper 20 in length from a maximum at the head of the screw to substantially the size of the opening at I the bottom of the recess but remain substantially uniform in width at their edges, thickening however on' merging with the center. The walls of 25 the wing slots and the walls of the connecting surface comprise a series-of flat or plane surfaces, rather than arcuate ones, and it has been demonstrated that these are highly desirable and in fact essential in holding the screw driver in the slot when considerable resistance to the entrance of the screw is exerted. I

Recesses of the type just described are formed in the crudely up-set screw heads at a certain stage in their process of manufacture by holding the screw in a suitable anvil and forcing a properly shaped punch to the desired depth into the metal of the head whfle it is cold. This operation is an extremely severe one both on the metal of the screw and on the metal of the punch. The 40 punch must be formed to the reverse of the recess in the screw, and because of the severeness of the operation and the small size the punches are consumed rapidly. They must be exact in size and shape so that the fit of the recess on the screw driver is such that the screw can be held in place on the end of the driver for insertion into difficult places. This means that no substantial variation in the size of the recess, and hence the punch, is permitted.

. With the rapid wear on the punches, some method is required for making them easily, cheaply and rapidly. Unfortunately, the usual toolroom methods are not applicable to finish the punch because of the plane surfaces heretofore 66 also v so

for each succeeding out until there is formed the .referred to existing within the concavities be-- tween the wings and because thesesurfaces have a general splay or'fiare from tip'to base of the punch.

In accordance with the present invention, th conventional tool-room practices are first to form a developed punch shapewhich is mine}- quently and by an additional operation changed to the exact desired final form while also being improved in strengthand texture of the metal.

A suitable metal stock is used from which to form the punches, preferably tool steel cut into short lengths of rod Ill such as shown in Figure 1. It is preferably circular and of a convenientdiameter'to be .held in the punching machine head. By turning in a lathe there is provided a the tool is presented along an axis at a slight. angleto thevertical axis of the rod and the nub. The axis of the tool lies betweemthe axis of the j rod and theinclinedsurfaceof the nub. wltha the proper displacement from theflcenter of the "nub, this end mill is moved axially to out each inclined groove 15 substantially to the depth of the shoulder H. The rod is indexed through90 semi-finished punch shown in Figures 3 and 4, all surfacesof which are curved and those of ,jlthe-groovej- Iiiibeing arcuate. The surfaces It 1140* i curved in vertical section in accordance with the predeterminedshape of-the wings. Because of the; angle atfwhich the milling cutter is advanced,

of "the wings an arcuate in horizontal section and the edges ofthe' wings of the ineornplete punch increase in width from tip .to baseJas seen ,in Figures 3, 4-and 5, although L'feiring to Figures 5 and 6, it will be seen that *the' matrix is formed in a block Ilijof suitable metal which is hollowed out to provide the wing recesses 2|, having the fiat surfaces 22 tapering as shown at 23 and the intermediate fiat surfaces and 25 also tapering as shown. ,Axially of the v matrix is an opening126' to permit tip clearance and for'thepassage of a knock-out bar if required. 1

The amount .of metal in the crudely'finished nub of the punch lis slightlygreater would be I normally accepted in thelf c fiof-the causing aflsinallamount of compressionan'dfup set of the metalasw'ell as achange of-its shape i as the is forced into thematrix. Any accidental considerable excess; of the metal will be forced downinto the-opening 18. The crude nub 1 is thus. formed to exactly the size and shape de -j sired and the working-and compresslngjof ,metal' thereof strengthens, densifiesand harden's n it, although as afinal operation before. use the. punch is hardenedbyfa suitable. heat treatment. i It has been found highly desirable -='for various reasons that the iunotion'of" the: surfaces joi' the recess in a screw head -with.tlie outerzsurfaceof.

v thisistnot desired f inthe finished punch. J

I 1 To produce the final shape. of the. punch, it-is' ",forced bly hydraulic pressure or otherwise driven into a matrix,"*the recess in which is the exact I counter-part of that desired in the screws. Re-

thehead-be on aradius'ofsmall curvature and since it' is dimcult'to forrn such a radius. after the recess is punched and the screw head shaved.

the fillet-like radii areput onthe pimch-at the Junction of eachfof'its surfaces withthe fiatshoulder. l l.- Bucha radius can be seen crudely at 2am Figure 2 where it will be effective onlyon the ,basesof' the outer faces of the .In Figures 3,}, and 5,will be seen that the junctions of the concave or, arcuate-groove's with the shoulder are almost sharpmrlthough a slight radius can be given by properlyshaping the milling cutfer. The final radius, however, at all thesejun'ctions-is formed by'the matrix which has a suitable rounding oil! of all of the iunctionswhere any surface of the recess intersects the top surface of the block 20, as can be seen at 29.

Thematrix recess is formed by the usual die sinking methods which-are of course more expensive than tool-room practice, but the matrix is not exceedingly difllcult to form since the flat surfaces therein are on generally convex rather than concave surfaces as in the punch.

Thecurvature of the junction of the surfaces of the punch and its shoulder may be likened to fillets strengthening the punch at the .point of app ication of the stresses thereon where they are transferred to .the larger section of the rod.

' Thus they have the added function of strength ening the punch as well as producing in the screw a greatimprov'ement in appearance, function and ease .of manufacture;

Althoughthe' operation of forming the punch by driving it into a matrix has been described as a cold. typingfoperation, it neverthelessmay be desirable forlargersizes of punches to flrstheat the crudely formed punch to assist in its shaping in. the matrix,- thereby lessening the wear'on the .matrix andygreatly increasing its life. .Since a final hardening by heat treatment is necessary for the punch anyhow, thisheating does no harm although it does-introduce difiiculty in the way of scale. which might change the very close dimensions of the punch surfaces;

Havingflthus I described the. invention. what is claimed jas newv and desired to be secured by -1 Letters Patent 15:

l. The method offorming a punch for making screw head of cruciform plan comprising turning-the end of-a bar of steel to provide a fiat shoulder and aprojecting nub, grooving the nub substantially longitudinally with an end-mill to form alternate wings and grooves-and then coinpressing and upsetting the nub in a matrix to change the shapes of the surfaces formed by the milling operations. 1 1

2. 'Ihemethod of forming japunch for making I screwheadrecesses of cruciform plan comprising .turning'the endof a bar of steel to provide. a'fiat shoulder and 'a projecting nub, grooving the sides of the nub with an endmill having its axis nearly fparallel to the axis of the nub to form thereon alternat'e'grooves and wings and then compressing and upsetting the nub in ja-matrix to change I by pressure only at least the shapes of the arouate surfaces formed by the milling operations.

-34 :ms emsd of forming a punch for making screw I head recesses ofcruciform plan comprisingjturn'ing the end of a bar of metal to provide a} flat. shoulder withfa. nub projecting therefrom having: in longitudinal section substantially. the ffdrmof section through the-wings of Y a" finished gpunch; grooving the. sides of the hub usub tfi tially longitudinally-with a rotary tool to formalternate grooves, extending to said shoul-n 78 der, and wings and then forcing the nub into a matrix to change by pressure only the shapes of all arcuate surfaces formed by the rotary tool.

4. The method of forming a punch for making screw head recesses of cruciform plan comprising turning the end of a bar of metal to provide a flat shoulder with a tapering nub projecting therefrom having in longitudinal section substantially the form of a similar section through the wings of a finished punch, grooving the sides of the nub substantially longitudinally with a rotary tool having an axis nearly parallel to the axis of the nub to form alternate grooves, extending to said shoulder, and wings and then forcing the nub into a matrix to change by pressure only the shapes of all arcuate surfaces formed by the rotary tool to surfaces fiat transversely of the nub.

5. The method of forming a punch for making screw head recesses of cruciform plan comprising turning the end of a bar of metal to provide a flat shoulder with a nub projecting therefrom having in longitudinal section substantially the form of a similar section through the wings of a finished punch, grooving the sides of the nub substantially longitudinally with a rotary tool to form alternate grooves, extending to said shoulder, and wings, reshaping said grooves and wings and forming a rounded fillet at the junction of each nub surface with the said shoulder solely by pressure on said surfaces.

6. The method of forming a punch for making screw head recesses of cruciform plan comprising turning the end of a bar of tool steel to provide a shoulder and a tapering nub projecting therefrom, grooving the sides of the nub at a slight inclination to the nub axis with an end mill to form alternate grooves and wings each extending to the shoulder, forcing the nub cold into a matrix to change the shape of all surfaces formed by the mill and to compress the metal of the nub and thereafter hardening the nub.

7. The method of forming a punch for making screw head recesses of cruciform plan comprising turning thejend of a bar of steel to provide asubstantially flat shoulder with a tapering nub projecting therefrom, grooving the nub with an end mill rotating on an axis extending between the nub axis and nub surface to thus form alternate grooves and wings each extending to the shoulder, forcing the nub into a matrix to change all arcuate surfaces formed by the mill to flat surfaces and simultaneously forming a rounded fillet at the junction of each changed surface and the said shoulder.

8. The method of forming a punch for making screw head recesses of cruciform plan comprising turning the end of a bar of steel to provide a substantially fiat shoulder with a tapering nub projecting therefrom, grooving the nub with an end mill rotating on an axis extending between the nub axis and nub surface to thus form alternate grooves and wings each extending to the shoulder, said wings because of said angled mill axis being broader at the base than tip, forcing the nub into a matrix to change all arcuate surfaces formed by the mill to flat surfaces and reducing the wings to uniform edge thickness and simultaneously forming a rounded fillet at the junction of each changed surface and the said shoulder.

JOSEPH J. 'IOMALIS.