Punch And Die Retainers

Abstract

A punch, die or like retainer distinguished by a uniquely formed plug having the dual function of a force dissipating backup means and a precise centering device.

Description

The invention has particular relation to improvements in retainers for punch and die units and will be so described, though not so limited. In a preferred embodiment it features a uniquely advantageous triangular configuration and a specially formed centering plug. The plug has the added and most important capability of serving as a simple but effective medium for backing critically positioned punch and die components.

The invention concepts enable a simplified and more efficient punch or die installation characterized by ease of handling and economy and efficiency in use. In use thereof the cutting or blanking components of die assemblies may be quickly and precisely positioned and with a minimum of effort. Once positioned, the retainers may be quickly and readily removed and replaced without altering the precisely referenced position of the related punch or die element.

In prior art practice, the nature, character and detail of available retainers has made the precise fit and location of punch and die components a tedious and difficult task. For precision installations, punch retainers have heretofore required the use of a compensating backup plate having several variables as to form and dimension, the nature and character of which has been such to produce inherent problems. For example, unless related surfaces are critically formed and the abutting surfaces are precisely complementary, the position of the retainer and the operating component which it mounts is misaligned. In view of the fact that in the conventional installation there are so many surfaces which must be relatively abutted and so many passages which must be aligned, it has been difficult to install punches and die components with any great degree of precision or with any speed. In most cases, the required precise positioning of the punch and die components have been effected by slow and tedious adjustments of the related parts.

Further problems in installing and replacing prior art retainers, even those which mount round punches, have stemmed from the fact that the conventional retainer requires at least two dowel-locating pins which must project through the backup plate and into the related die shoe. Moreover, since retainers and backup plates have variables in dimension which are multiplied in their combination and since the retainer and the backup plate must be abutted, this has necessitated that there be enlarged openings in the backup plate to insure the projection therethrough of the dowel pins. Considering the nature and the character of the installation so provided, in operation of the punch retained thereby, there are transmitted binding and shear stresses to the dowel pins, particularly in the areas thereof at the limits of the enlarged apertures in the backup plate. There is resultant fatigue, breakage and attendant maintenance problems.

Apart from the above mentioned problems, to realize the advantages of the present invention, one must understand the set up procedure. The normal procedure in setting up a die assembly is first to set up the lower die plate on the lower die shoe so as to properly orient the contained die button. The punch to be coaxially aligned with this die button is then inserted in its retainer and centered in respect to the opening in the die button. The retainer which has at least two passages for dowel-type locator pins to be inserted in the upper die shoe is then applied to the upper die shoe with a backup plate interposed between. The backup plate has relatively enlarged openings therein for passage therethrough of the locator pins. The enlargement insures ability to adjust the plate to enable the transfer of the openings in the retainer to the upper die shoe, following which the dowel pins must be inserted. It must be understood that in conventional retainers the dimensioning between the centerline of the punch or die passage in the retainer and the passages for the dowel pins is quite rough and variable. The cost factor for doing otherwise has been prohibitive. Thus, this itself has complicated set up procedures and, due in part to this, once a retainer unit is set, it is not readily interchangeable. Moreover, as has been mentioned previously, once the conventional retainer is installed, in operation of the assembled punch there is a force pattern reactant on the backup plate and the die shoe that produces resultant shearing and bending stresses on the applied screws or locating pins at the limits of the thickness of the backup plate. Not only is there resultant fatigue, possible breakage and attendant maintenance problems, but the retainer itself may be damaged and for practical purposes it has proven exceedingly difficult to find a conventional retainer which would be readily interchangeable.

Also, in applying the conventional retainer and backup plate to a die shoe, in procedures where it is attempted to transfer the dowel pin passages in the retainer to the die shoe, many times the sloppy character of the openings in the backplate through which the drill must pass has resulted in wobble in the drilling procedure and drill breakage. Apart from this, the chips resulting in the transfer process normally fill the clearance in the openings through the backup plate. These can become lodged between the backup plate and abutted surfaces to misalign the related punch component. In some cases, the packing of the chips resulting in the transfer process have produced a shift of the backup plate to a slight degree and this also can throw the mounted punch out of line.

In addition in use of backup plates, which, as required have sloppy openings for dowel pins to pass therethrough, one produces an inherent infirmity in the retainer mount. Hence the problem of shifting and misalignment often occurs based on this alone.

In summary, considering the preceding discussion of the conventional retainer installation, it may be seen that not only can much time be wasted in the process of installation but replacement and maintenance problems are inherent in use thereof. Even more serious, the slight misalignment of a punch either in installation or during operation can produce poor quality workmanship and a large amount of rejects in the work material. The disadvantage of this is readily apparent.

The present invention obviates the above problems, insuring a simpler, a firmer and a more precise installation which enables removal and replacement of a retainer without fear of displacement of the respective axes of the related punch and die components of an installation. The invention thus insures more effective die cutting operations with considerably less malfunction potential and correspondingly a maximum work output from a minimum of material.

It is therefore a primary object of the invention to produce punch and die assemblies which may be more economically fabricated, more efficient and satisfactory in use, adaptable to a wide variety of applications and unlikely to malfunction.

Another object of the invention is to provide a unique plug element for punch and die assemblies serving both as a precise positioning device and a force-dissipating backup medium.

A further object of the invention is to provide a punch assembly which obviates the need for a backup plate.

An additional object of the invention is to provide punch and die assemblies which may be readily interchanged without affecting the precise positioning of the related punch or die components.

Another object of the invention is to provide punch and die installations with unique means for their precise reference.

A further object of the invention is to provide an improved retainer for punch, die and like elements having a configuration rendering it more versatile in use and application.

An additional object of the invention is to provide an improved retainer unit for punch, die and like elements possessing the advantageous structural features, the inherent meritorious characteristics and the means and mode of use herein described.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the drawings wherein are shown some but obviously not the only forms of embodiment of the invention,

FIG. 1 illustrates a fragment of a punch assembly embodying the concepts of the present invention;

FIG. 2 illustrates the related die assembly in fragmentary form, which die assembly embodies the invention concepts;

FIGS. 3 and 4 are fragmentary views referenced to the structure of FIG. 1 illustrating how the invention concept facilitates the transfer of holes from a punch retainer to the related die shoe; and

FIGS. 5 and 6 illustrate the unique punch retainer in accordance with the invention in both plan and elevation and with the centering and force dissipating plug removed.

Like parts are indicated by similar characters of reference throughout the several views.

The invention can be best understood with particular reference to the accompanying drawings. FIGS. 5 and 6 show a punch retainer 10 which in plan view has the unique form of a isosceles triangle the corners of which are arcuately rounded. Its apex is identified as 11 and its base corners as 12. The retainer body is relatively thick in depth between its upper and lower surfaces 13 and 14 which are respectively parallel.

The retainer 10 has a cylindrical through passage 15, perpendicular to its surfaces 13 and 14 and, while not necessarily so, in the example shown, concentric to its apex 11. One end portion 16 of the passage 15 is conically expanded. The expanded portion is relatively short in length and has its maximum cross-sectional area at the surface 13.

The retainer 10 has two additional through passages 17, both of stepped cylindrical form, which are paralleled to and triangularly and symmetrically positioned in respect to the through passage 15. The single step in each passage 17 produces a shoulder 18 adjacent to and facing outwardly of the parallel surface 14. The passages 17 provide for application therethrough of capscrews for mount of the retainer body 10 to a die shoe in a manner to be further described.

The retainer 10 has a further passage 19. In this instance the passage is relatively inclined. It opens at one end from the surface 13 and at one side of its other end to the passage 15, adjacent but spaced from the surface 14.

In FIG. 1 of the drawings the retainer 10 is installed with its surface 13 fixed in contacting and coextensive abutting relation to an upper die shoe 20. As there seen, contained in the innermost end of the passage 19 is a ball-type lock element 21. This is biased inwardly of the passage 15 by a coil spring 22. The latter is contained within the passage 19 which is capped by the die shoe 20. The ball 21 is so biased to wedge in an arcuate pocket or groove 25 formed in one side of the head 23 of a round punch 24 inserted in the lower end of the passage 15. As described, the ball 21 locks the punch 24 to depend in projected relation to the body of the retainer 10.

Attention is now directed to the plug 26 in the uppermost end of the passage 15. The plug is an integral structure but it has two distinct portions. The outer periphery of its inner portion 27 has a cylindrical configuration while the outer periphery of its outer portion 28 is conical. The portion 27 is inserted to abut and back the head of the punch and is so formed to frictionally but releasably fit in the uppermost portion of the passage 15, to the point of its conical expansion at 16. The upper or outer plug portion 28 is cut back immediately adjacent the upper end of the portion 27 and then conically expanded. Particular note must be taken of the fact that the outer peripheral surface of the portion 28 disposes concentric to and in a generally spaced parallel relation to the adjacent conically expanded surface portion 16 of the wall defining the passage 15.

Thus, the depth of the plug 26 is such that it is set inwardly of the retainer surface 13 to have one end define an abutted reference surface for the punch and its other expanded end lie in flush abutment to the die shoe 20, with the surface 13.

It will be seen that the plug 26 is tubular in nature, having a through passage 29 which is slightly larger in diameter than the cylindrical recess 30 formed in the die shoe 20 in a manner to be further described. Tightly fit in the passage 29, generally coextensive therewith, is the expanded end of a pin 31. The other end of pin 31 has a slip fit to fix it in the passage 30 of the die shoe 20. The pin 31, through the medium of the plug 26, constitutes a single centering pin for the punch 24 and the retainer body 10. The plug 26 not only serves a centering function but provides a force dissipating medium for accommodating and disseminating the stress and shock incident to a repeated operation of the punch 24. By reason of the normal spaced relation of the conically expanded surface of plug portion 28 from the adjacent retainer surface 16 undue amounts of stress on the retainer body per se is clearly avoided.

Capscrews are projected through the retainer passages 17 to engage in the die shoe 20. The shoulders 18 provide limiting surfaces for the heads of the screws. Thus there are only two hold down screws and only one locating or centering pin, which does a precision job.

Attention is directed to the fact the retainer unit can be readily replaced by a similar unit. On removal of the screws and the punch, the retainer assembly and the press fit pin 31 can be pulled from the shoe as an integrated unit. The pin 31 stays with the retainer, in the preferred embodiment illustrated, due to the nature of its press fit in the plug 26. A similar retainer unit can be quickly applied in an obvious manner. Having received thereon a pin 31 it can be fixed to the die shoe as described. The pin 31 and the plug 26 again precisely define the same punch location with no requirement for adjustment or manipulation. Passages 17 for the screws are not and need not be critically dimensioned.

The simplicity of the structure and its application and its interchangeability is readily apparent. As an alternative the retainer unit may be pulled from its plug 26 which may be left to per se provide a precision reference for slip fit of a new retainer unit as described, absent its plug.

FIG. 2 of the drawings shows the inventive plug concept applied in a slightly different form. Here it is embodied in respect to the assembly of a die button to a lower die shoe and for use in an operative relation to the punch 23--24. In this case fixed on the lower die shoe 32 is a retainer 10'. The latter is similar to the retainer 10 in all respects and like parts are identified by like numbers. Since the retainer 10' has an identical configuration and passages, the details thereof need not be further described except in reference to the improvements.

Referring to FIG. 2, it is there seen that as compared to retainer 10 the body of retainer 10' is inverted so its surface 13' abuts the lower die shoe 32. Inserted in the end of the passage 15' remote from the surface 13' is a tubular die button 33. The side of this die button is provided with an arcuate pocket or groove 25 to accommodate the wedging therein of the ball-type lock element 21' which is backed in the passage 19' by a coil spring 22'. Thus, die button 33 is locked to the retainer 10' in the manner that the punch 23--24 is locked in the retainer 10. In this case the die button is backed by one end portion 36 of a tubular plug 35. The plug portion 36 is formed to have a releasable friction fit in the passage 15' in the space therein between the die button which it abuts and the conically expanded portion of the passage which opens to its maximum cross-sectional area at the die shoe 32. In this conically expanded portion of the passage there is a plug portion 37 the outer peripheral surface of which is conically expanded. From plug portion 36 the outer surface of the plug 35 is first cut back and then conically expanded to provide a conically formed solid skirt in adjacent but spaced parallel relation to the conically expanding surface portion 16' of the passage 15'. The conical skirt on the outer surface of the plug provides a shoulder which abuts the adjacent surface of the die shoe 32 about an opening therein which receives a tubular extension 38 of the plug 35. It should be noted that while the inner diameter of the tube type plug 35 is uniform throughout its length, the outer diameter of the portion 38 is relatively reduced in respect to that of the plug portion 36. The portion 38 has a tight but releasable fit in the passage 39 provided therefor in the die shoe 32.

With the above in mind, let us now consider the procedure of an installation using the inventive concepts which would involve a composite of the punch retainer of FIG. 1 and the die retainer of FIG. 2. It is to be noted that they are precisely referenced in the drawings as they would be in a proper installation.

As has been indicated previously, the setup would normally be commenced at the lower die shoe to properly position the die button at a specific work station. In utilizing the concept of the invention as presented in FIG. 2, the plug 35 can be applied to the retainer 10' so the conical portion 37 thereof is spaced from the conically expanded surface of the passage 15'. Under such circumstances the base of the conically expanded peripheral portion 37 will lie flush with the surface 13' of the retainer body 10'. The station for the die button can be readily located as to its center on the uppermost surface of the die shoe 32 whereupon the passage 39 may be drilled. At this point the retainer 10' including the plug 35 can be precisely applied through the medium of the tubular extension 38 on the plug. The extension 38 is inserted in the passage 39 to have a relatively tight but releasable friction fit to the wall of the passage. This establishes the passage 15' in a precise orientation required for the particular work station. On insertion of the die button 33 it will be precisely positioned and backed in a stable relation in such position by the end of the plug portion 36. It will be noted that the inner diameter of the plug 35 is slightly greater than that of the die button to provide clear passage of blanks that might be punched and projected through the die button. Thus, it may be seen that the retainer 10' may be quickly and readily applied to the lower die shoe by means of a ready insertion of the plug 35 in the die shoe which immediately defines the required position for the die button.

Of course, the passages 17' of the retainer which are illustrated in FIGS. 5 and 6 are not critically related to the position of the retainer and the passages may be simply and quickly transferred to the die shoe and capscrews applied in a manner believed obvious. Accordingly, there is only required a single positioning as defined by a single plug unit such as 35. The installation of the retainer 10' and the precise positioning of the die button 33 is speedily and precisely effected.

Turning now to the retainer 10 as applied to the upper die shoe 20, the punch 24 is first inserted and locked in the retainer body 10 and brought down to position precisely and coaxially in reference to the die button 33. With the punch 24 so positioned the retainer 10 can be quickly clamped directly to the upper die shoe 20 which has already been positioned for use in the required die set. This is only possible because there is only a single locating device for the punch 24 and there are no critical aspects of positioning the passages 17 for the cap-type holddown screws. It is contemplated at this point that the plug 26 is inserted in the passage 15 as shown in FIG. 1 as an abutting backup device for the punch 24. With the retainer body 10 then clamped in place, reference is made to FIG. 3 of the drawings for the procedure whereby the passage 29 in the plug 24 may be directly transferred to the upper die shoe. With the assembly inverted as shown, there can be a direct drilling through the passage 29 of the plug and into the die shoe to effect a precision extension of the passage 29 and thereby fix the precision centering position of the plug 26 in reference to the punch to be applied to the retainer 10. It is to be understood of course, that for this procedure the punch 24 is removed. The passage 30 is then drilled through the plug and the pin 31 thereafter may be tightly inserted in the plug bore and slip fit in the passage 30 of the die shoe 20. Again, the positioning of the passages 17 are not critical. Moreover, with the retainer 10 clamped into the position as shown in FIG. 3 there can be a similar transfer of the passages 17 to the die shoe and tapping as required prior tp completing the assembly. The details thereof are of course conventional and need not be further described. Here again it may be seen that there is a single device that needs be precisely positioned in only one hole to establish the precision orientation of the punch 24.

FIG. 4 of the drawings illustrates the alternative use in transferring the plug bore 29 to the shoe 20 of a drill bushing. In insertion of the drill bushing in the passage 15, it will be seen there is thus provided a firmly backed drill bushing through the medium of the plug 26 and the transfer of the plug bore may be effected with a precision balanced condition of the drill 40. In this case the bushing also conducts the drilled chips clear of the retainer. Whether the procedure of FIG. 3 or FIG. 4 of the drawings is used is optional and would depend on the particular circumstances.

Having regard to the retainer 10 and the assembly involved in respect to the retainer 10, it may be seen that the nature of the plug 26 is such that it is extremely simple to grind its remote end surfaces parallel. The procedure in this respect involves simple fabricating procedures. By the same token the surfaces 13 and 14 are just as easily ground parallel. This means there is no difficulty in establishing a retainer assembly which can be simply and directly abutted to a die shoe and a single locating pin used in respect to the critical positioning of the inserted punch. These remarks apply equally, of course, to the substance of the die installation in FIG. 2 of the drawings.

In operation, it will be seen that the shock of impact and vibration attendant a punching process will flow in a direct axial line and due to the spacing between the conically expanded portion of the plug and the adjacent wall structure of the retainer there is a directed path for the shock effects. The shock instead of being disseminated into the retainer body with attendant problems of fatigue and deterioration of components is instead dissipated in the die shoe which has a much greater capacity to accommodate the same. Further, by the very form of the plug one finds that the unit force transmitted from one end of the plug to the other is substantially diminished due to the configuration of the surfaces which abut. Thus, whether we consider the plug in the form 26 or in the form 35, the plug will similarly serve to disseminate and dissipate the shock of punch operation, whether in respect to the punch or the die, so as to preclude deleterious effects on the retainer body and its associated components.

It will be seen that not only is the installation of the retainer simplified but also there has been an elimination of the need for conventional backup plates and the attendant problems and the complicated procedure of attempting to precisely reference pluralities of dowel pins to center a punch or die element has been completely eliminated.

An inherent advantage of the present invention is further found in the particular configuration of the retainer such as 10. This enables a more versatile placement and arrangement and rearrangement of punch and die assemblies for various application. It will be seen that the triangularlike configuration of the retainer body enables it to be positioned in clusters of abutted units, which clusters can be quickly varied and adapted for changing circumstances as and when need requires. This is a far more advantageous situation than having complicated single units which have no flexibility.

To repeat and to emphasize, the whole invention retainer unit enables that it be keyed by a single conventional dowel pin which predetermines the precise punch or die position by a tight fit of the invention plug in the retainer and to the dowel pin. Of course, as has been previously described, the positioning of the dowel pin alone is predetermined by the positioning of the retainer body per se including the plug, and either the retainer unit including the plug may be removed and replaced or the retainer unit separated from the plug, which may serve to precision position a replacement retainer body. In either event, the advantages of the invention become self-evident. The fact that the locating dowel pin is on a common centerline with the punch or die button is very advantageous in the placement of several retainer bodies on a die shoe in versatile fashion as just mentioned. The plurality of retainers may be commonly set and the holes thereof quickly transferred to a die shoe in the simple fashion described.

A further and inherent point of advantage in the use of the one dowel pin is that it avoids the potential problems of internal stress within a retainer body when a plurality of locating and orienting pins are used in parts which normally do not have a precision alignment.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

In the claims, the term "tool element" is used to describe a tool part or tool unit installed in or associated with a retainer body. This term is intended generically to define punch elements, die elements, drill bushings and like parts as disclosed herein.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Claims

I claim:

1. For use in combination with a retainer, including a passage for insertion therein of a tool element and providing means for connection thereof to a die shoe, a stress transfer means for the tool element including a pluglike insert portion, the outer peripheral surface of which is adapted to have a friction fit to the wall of said passage, and an expanded head portion, the extremity of said pluglike insert portion remote from said head portion providing an abutting backup surface for the head of the tool element and the remote extremity of said head portion providing a surface portion for engagement to the die shoe to provide for a direct transmission therethrough of the load and shock applied to the tool element, the head of said transfer means being so formed that in application to the retainer, the surface portion thereof adjacent the retainer is normally spaced therefrom.

2. Apparatus as in claim 1 characterized by means for establishing a required position of said stress transfer means in reference to the die shoe, whereby to establish per se the required position of the tool element which it backs.

3. Apparatus as in claim 1 characterized by said transfer means having a through passage which may be transferred to the related die shoe and said through passage providing means for centering thereof and the abutted tool element.

4. Apparatus as in claim 1 characterized by said stress transfer means being a centering device and the head portion thereof having an expanding generally conical peripheral configuration.

5. Apparatus as in claim 4 characterized by said transfer means having a central through passage and means defining an extension for supporting said transfer means in a precisely positioned relation to a die shoe.

6. Apparatus as set forth in claim 1 characterized by said stress transfer means being an integral structure having two distinct portions, one being cylindrically formed in its outer periphery and the other being conically formed at its outer periphery and the remote ends of said portions being parallel.

7. Retainer apparatus for a tool element comprising a retainer body including means defining a through passage for insertion in one end thereof of the head of a tool element and means for retention of the inserted element characterized by a backing means for the inserted element adapted for the precise alignment thereof with an axis of reference, said backing means being adapted for a surface contact with a die shoe to which one surface of said retainer body directly abuts, a portion of said backing means having a plug fit in said passage to have one end thereof abut and back the inserted element to orient said retainer body and the inserted element in the proper frame of reference, the fit of said backing means and the centering produced thereby of the inserted element enabling a removal and replacement of the retainer body whereby on replacement the proper frame of reference for the inserted element will be maintained.

8. Apparatus as set forth in claim 7 characterized by said backing means having a plug form for a frictional and releasable fit in said passage in backing relation to the inserted element and having a portion adapted for flush abutment with the die shoe and adjacent said die shoe a peripheral portion which is free of contact with the retainer body.

9. A retainer unit including a passage for insertion therein of a tool element characterized by a backup device a portion of which is inserted in and generally conforms in cross section to the cross section of said passage and a remote portion of which is expanded, one end of said passage being expanded in adjacent and complementary fashion to accommodate an expanded portion of said backup device, the end of said backup device remote from its expanded end providing a surface serving as an abutment for the tool element.

10. A retainer unit as set forth in claim 9 characterized by said passage being formed to accommodate said backup device for insertion therein to have its outermost surface flush with a surface of the body of the retainer unit and said backup device being centrally apertured to accommodate the insertion therethrough of a single locating pin to provide a precise orientation of an inserted tool element irrespective of other holding devices applied for securing the retainer unit to a die shoe.

11. Apparatus as set forth in claim 9 characterized by said backup device being a plug, said passage being conically expanded to the end thereof remote from that receiving a tool element, and the outer periphery of said plug conforming to the expansion of said passage and having at least an outermost peripheral portion thereof relatively spaced from adjacent expanded surface portions of the wall defining said passage, whereby on application of a tool element it will be insured that the substantial portion of shock and vibration force attendant the operation thereof will be transmitted through said plug while inhibiting significant transmission of the applied shock and vibration to the body of the retainer unit per se.

12. Apparatus as set forth in claim 11 characterized by said plug having a cylindrical extension projected beyond the retainer unit, said cylindrical extension having a lesser cross-sectional area than the relatively expanded portion of said plug and being adapted to be inserted in a die shoe to thereby center said plug without the need for a dowel or other locating-type pins.

13. Apparatus as set forth in claim 9 characterized by said retainer unit having a generally triangular configuration and being relatively thick in depth and provided with upper and lower surfaces which are parallel.

14. Apparatus as set forth in claim 13 characterized by said retainer unit having two through apertures which triangularly position in respect to said passage and provide means for insertion therethrough of the sole hold down means required for applying the retainer unit to a die shoe.

15. A retainer unit including a retainer body having plural through passages at least one of which is adapted to receive therein a tool element, and at least another passage spaced from said one through passage to receive therethrough holding means for the retainer unit on application thereof to a backing die shoe or the like, said body being distinguished by a peripheral outline of generally triangular configuration to provide that a plurality thereof may be arranged on a backing die shoe or the like in a nested closely fit relation, said retainer body including three through passages triangularly arranged, one of which positions generally concentric to one corner of the said generally triangular configuration of said body to receive therein the tool element and the other of said three through passages being located toward other respective corners of said triangular configuration, the latter passages being for receiving therethrough holding screws for fixing the retainer unit to a backing die shoe or the like, said other passages having a stepped configuration to accommodate the heads of said holding screws within said retainer body.

16. A retainer unit as in claim 15 characterized by said one through passage providing means for centering and locating the punch, die or like element received therein in reference to the backing die shoe or the like and said other of said passages being variably positionable in reference to the die shoe or the like for receipt therethrough of holding means.

17. A retainer unit as in claim 15 characterized by said retainer body having three through passages including one which positions generally concentric to one corner of the said generally triangular configuration of said body to receive therein the punch, die or like element and the other of said three through passages being triangularly positioned in reference to said one through passage for receipt therethrough of the holding screws for application of the retainer unit to a backing die shoe or the like.

18. A retainer unit as in claim 15 characterized by said one through passage generally concentric to one corner of said generally triangular configuration which receives therein the tool element providing means serving as a precise center or locating device for the retainer body on the die shoe or the like and the other of said through passages being adapted to be variably positioned in reference thereto.

19. A retainer unit including a retainer body having plural through passages at least one of which is adapted to receive therein a tool element, and at least another passage spaced from said one through passage to receive therethrough holding means for the retainer unit on application thereof to a backing die shoe or the like, said body being distinguished by a peripheral outline of generally triangular configuration to provide that a plurality thereof may be arranged on a backing die shoe or the like in a nested closely fit relation, said retainer body including three through passages one of which positions generally concentric to one corner of the said generally triangular configuration of said body to receive therein the tool element and the other of said three through passages being triangularly positioned in reference to said one through passage for receiving therethrough of the holding screws for application of the retainer unit to a backing die shoe or the like, opposed surfaces of said retainer unit at the respective ends of said concentric through passage being generally parallel and there being a plug insert in one of said surfaces to project inwardly of said concentric passage in frictional engagement with a wall portion thereof, said plug serving as a backing and force disseminating medium for an inserted tool element.

20. A retainer unit as set forth in claim 15 characterized by the opposed surfaces of said retainer unit at the respective ends of said through passages being parallel to provide a precise frame of reference for the tool element which is applied to said retainer body, the stepped configuration of said other passages including counter bores opening through one of said opposed surfaces.

21. A retainer unit including a retainer body having approximately parallel end surfaces and convergent-divergent sides providing an apex and a base portion, a through opening in the apex portion to receive a tool element, a pair of through openings longitudinally spaced apart in the base portion to receive holding screws whereby to fix the retaining unit to a backing member, said openings defining a triangular pattern of holes extending to and through opposite end surfaces, and another hole in said body opening at one end through one of said end surfaces in said triangular pattern and inclining in said body to terminate at its other end in the said through opening in said apex portion, said other hole accommodating tool element retaining means.

22. A retainer unit according to claim 21 wherein said pair of through openings in said body have counterbores opening through the other one of said end surfaces.

23. A retainer unit according to claim 21 characterized by a plug-type insert member installed in said opening in said apex portion at the said one end surface of said body, said insert member acting as a backing for the tool member and being constructed for mounting of a dowel pin therein to dispose in the axis of said apex portion opening and to project relatively to said retainer body to be received in said backing member.