US3504576A - Method for making precision die sets - Google Patents

Description

April 7, 1970 R. L. SlLBERMAN ET AL 3,504,576

METHOD FOR MAKING PRECISION DIE SETS Filed July 12, 1968 [NVEVTORS ROBE/Q7 L. S/LBERMA/V LESTER L. LOG/4N Z M mww/qrromwsys United States Patent O METHOD FOR MAKING PRECISION DIE SETS Robert L. Silberman, Highland Park, Ill., and Lester L.

Logan, Berea, Ohio, assignors to Die Supply Corporation, a corporation of Ohio Filed July 12, 1968, Ser. No. 744,420 Int. Cl. B21k /20; B21d 53/10; B23q 3/00 US. Cl. 76-107 4 Claims ABSTRACT OF THE DISCLOSURE A precision die set comprising a punchholder and a die holder and a method of making a precision die set. The punchholder and die holder are guided for precise movement relative to one another by guide posts secured at one end to the die holder and cooperating with bushings which are affixed to the punchholder. The guide posts and bushings are loosely received in non-precision made openings in the punchholder and die holder and are retained in place by epoxy adhesive. Epoxy adhesive is applied between the bushings and punchholder and between the guide posts and die holder and before the epoxy adhesive is cured, the guide posts are disposed perpendicular to the die holder and parallel to one another, with the guide posts engaging with their associated bushings so as to properly position the bushings in the punchholder. Then, the epoxy adhesive is cured to retain the components in precise assembled relationship.

BACKGROUND OF THE INVENTION This invention relates to an improved die set and to an improved method of making a die set.

A die set is an assembly consisting of an upper member called a punchholder and lower member called a die holder. The lower surface of the punchholder and the upper surface of the die holder are those on which the punch and die details of a finished punch press tool are mounted. In use, the die holder is clamped to the bed or bolster plate of the punch press, while the punchholder shank is clamped in a clamping hole in the punch press ram, or, otherwise, secured to the ram face. The tool is actuated by the reciprocating motion of the ram. The mating guide posts and bushings of the assembled die set assist in maintaining tool alignment during die setting and the operation of the tool in the punch press.

Heretofore, the guide posts and bushings have been finished with precision and to close tolerances. After precision grinding, the exterior surfaces of the guide posts and the interior surfaces of the bushings have had further treatment, as, for example, honing, polishing or plating. Further, the holes in the die holder for receiving the guide posts and the holes in the punchholder for receiving the bushings have been first drilled and then precision finished by boring and reaming or other fine finishing to a total tolerance for size and roundness of .0002 inch. The center-to-center distance between guide posts must be held to close tolerances on the order of .0005 inch in order to enable the die sets to be assembled in the field.

There are a number of standard designs for punch press tool die sets including two, three and four post arrangements. The substantial precision machining and finishing of the interfitting components of the die sets results in substantial fabrication costs. A further disadvantage of prior arrangements is that large inventories of components must be maintained in field locations.

An object of the present invention is to provide an improved precision die set and an improved method for making precision die sets by forming openings in the punchholder and die holder by inexpensive non-precision 3,504,576 Patented Apr. 7, 1970 means and bonding the guide posts and bushings in place in the desired openings by an epoxy adhesive, whereby after curing of the epoxy adhesive, the posts are retained in precise assembled relationship.

Another object of this invention is to provide an improved die set comprising a punchholder and a die holder that are readily assembled in a simplified manner through use of non-precision interengaging of certain components and use of epoxy adhesive.

Yet another object of this invention is to provide an improved method of fabricating a precision die set which includes non-precision drilling of die holder and punchholder plates and securing of guide posts and bushings respectively, in said die holder and punchholder, respectively, in a precise fashion by means of an epoxy or like adhesive to obtain a precision die set.

Other objects and advantages of the present invention will be made more apparent hereinafter.

BRIEF DESCRIPTION OF THE DRAWING Presently preferred forms of the present invention are shown in the attached drawing in which:

FIG. 1 is a perspective view of an assembled die set made in accordance with the present invention;

FIG. 2 is a top view of the assembled die set of FIG. 1, with portions of the die holder being omitted;

FIG. 3 is a cross-sectional view of the assembled die set taken generally along the line 33 of FIG. 1;

FIG. 4 is a cross-sectional view of a modified punchholder;

FIG. 5 is a view of an assembly fixture for fabricating a modified die set incorporating the punchholder of FIG. 4; and

FIG. 6 is a detail sectional view of a modified die holder.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1-3, there is illustrated a die set 10 made in accordance with the present invention. The die set 10 is comprised basically of two parts, a die shoe or die holder 12, which is adapted to be secured to the bed or bolster of a punch press by bolts or like fastening means secured to flanges 13, and a punchholder 14 that includes a shank 16 which is adapted to be connected to a ram in the punch press. Punchholders for small die sets generally have a cylindrical shank which is an integral part of the punchholder. If desired, a removable shank may be screwed into a threaded hole in the punchholder and after assembly the shank may be keyed in place to prevent turning. The punchholder 14 is adapted to be guided for precise movement toward and away from the die shoe 12 by guide means. The guide means are shown in the illustrated form of the invention include a pair of like upright cylindrical guide posts 18 that are secured at their lower ends to the die shoe 12 and extend upwardly at right angles to the surface of the die shoe. Connected to the punchholder 14 and depending therefrom are guide bushings 20 which are adapted to cooperate with and slidingly receive the guide posts 18. The lower surface 15 of the punchholder 14 and the upper surface 17 of the die shoe or die holder 12 are those on which the punch and die details of a finished punch press tool are adapted to be mounted.

The upper and lower planar surfaces 17 and 15 of the die holder 12 and of the punchholder 14, respectively, are parallel. The metal guide posts 18 which are commonly made from hardened steel, are set at right angles to the upper surface 17 of the die holder 12 and are located so as to precisely fit the guide post bushings 20 of the mating punchholder 14, so as to allow the punchholder 14 to move up and down without binding. The

bushings are commonly made from steel, bronze or a bronze plated material and are provided with oil grooves on the inside surfaces for lubrication.

The guide posts 18 are generally cylindrical in shape and after finish grinding are generally further processed to a precise measurement, for example, by polishing and plating. The guide post bushings 20 are annular and each has an opening therethrough complementary to the exterior of the guide posts for receiving an associated guide post.

Heretofore, it was necessary to precisely bore the holes in the punchholder 14 and die shoe 12 for receiving the bushings 20 and the end of the guide posts 18, respectively. The initial drilling, which was non-precision, was then followed by subsequent precise finishing operations, such as boring, reaming, honing and polishing. Precision in locating the respective openings in the punchholder and die shoe 12 was important in order to enable the desired movement of the guide posts within the bushings without binding while maintaining the desired tolerances between the guide posts and bushings. For example, when using carbide dies, lamination dies and dies for very thin materials where clearances between the punch and die will be no more than .0007 inch per side, the guide posts are designed to fit in the bushings with a gauge fit, for example, for guide post diameters on the order of 74 inch to 2 inches, the clearance will be .0001 inch between a. guide post and an associated bushing.

The present invention provides a unique Way of assembling in a precise manner the die set components which may be fabricated in a non-precision manner. Initially, the surfaces of the punchholder 14 and the die shoe 12 are machined parallel in a normal precise fashion to the desired tolerances, normally at present, .001 inch per linear foot in length and width for American Standard commercial grade and .0005 inch per linear foot in length and width in American Standard precision grade. A hole 22 is drilled into the top of the punchholder and then tapped for reception of the lower portion of the shank 16. The shank 16 may be later secured to the punchholder in the manner set forth in more detail in the copending patent application of Robert L. Silberman and Lester L. Logan, Ser. No. 710,794 filed Mar. 6, 1968. Holes 26 are then drilled into the die holder for later reception of the guide posts 18. The holes 26 are drilled in a single operation to the final desired size without any subsequent finishing operations and are substantially at right angles to the top surface of the die holder. It will be understood that there may be two, three or four holes drilled for guide posts depending upon the type of die set. In the illustrated embodiment of the invention, a two guide post die set is illustrated.

Holes 28 are drilled into the punchholder 14 at substantially right angles to the upper and lower surfaces of the punchholder for reception of the bushings 20. The holes 28 are similarly formed in a non-precision manner by drilling (without subsequent precision finishing such as boring) in a single operation to the final desired size. The configuration of the lower portion of the guide posts 18 is complementary to that of the hole 26 in the punchholder and is of a diameter slightly less than the diameter of the opening 26, so as to be received loosely therein. Similarly, the exterior of each bushing 20 is comple mentary to its associated hole 28 and is substantially less in diameter than that of the hole 28 so as to permit the bushing to be slid easily into the opening without forcing same. The clearance between the bushing exterior and Wall of the opening is on the order of .Ol5 inch. The same clearance would apply between the guide post and die shoe.

The components are then cleaned to remove all oil, chips and the like foreign contaminants from the surfaces thereof. An epoxy adhesive is applied to the holes in the die holder 12 and to the lower end of each of the guide posts 18. Similarly, an epoxy is applied to the holes in the punchholder 14 and to the exterior surface of the bushings 20. Th bushings 20 are assembled on the guide posts or memb s 18 and then the bushings 20 are inserted into the openings 28 in the punchholder and the lower ends of the guide posts 18 are inserted into the openings 26 in the punchholder 14. Since the bushings 20 fit loosely in the openings 28 and the lower ends of the pins or guide posts 18 fit loosely within the openings 26 in the die holder 12, there is relative movement permitted between the die holder 12 and the punchholder 14. The die holder and punchholder are positioned such that the guide posts are in parallel relationship to one another and perpendicular to the die holder and the punchholder before the epoxy adhesive is cured. The components of the die set are maintained in position with the top surface of the die holder 12 parallel to the bottom surface of the punchholder, and with the guide posts or pins 18 perpendicular to the parallel surfaces of the punchholder and die holder and parallel to one another. The epoxy adhesive is then cured to fix the components in precise assembled relationship.

Referring to FIGS. 4 and 5, there is illustrated a modified form of die set which is very much like that shown in FIGS. l-3 except that liners are provided in the nonprecision openings formed in the die holder or die shoe and the punchholder for receiving the guide posts and bushings, respectively. The holes 28 and 26 in the punchholder 14' and the die holder 12 may be simultaneously drilled or separately drilled as desired. Liners 40 and 42 are positioned over the opposed projections 52 and 54 extending from assembly fixture 50. An epoxy adhesive is applied to the exterior of the liners 40, 42 and the openings or holes 28 and 26 and the liners are positioned in the holes in the die holder 12' and punchholder 14' as shown in FIG. 5 with the annular surfaces 56 and 58 of fixture 50 engaging against the die holder and punchholder. The annular surfaces 56 and 58 are parallel to one another and are perpendicular to the axis through projections 52, 54 of the fixture 50. Since surfaces 15 and 17 are planar, and are abutting planar parallel surfaces 56, 58, surfaces 15' and 17 will be parallel to one another and the axes of the openings in the liners 40 and 42 will be perpendicular to the surfaces 15' and 17' of the punchholder 14' and die holder 12.

Heater means are provided in the fixture 50 to aid in curing the epoxy adhesive. Such heater means may comprise resistance elements 60 that are suitably connected to a source of power.

After the liners 40 and 42 are secured to the punchholder and die holder, respectively, the die holder 12 and the punchholder 14' are removed from the fixture 50. A bushing 20' may be secured within liner 40 and a guide post (not shown) may be secured within liner 42. The bushing and guide post may be secured to the respective liners by use of an epoxy. Alternatively, the guide post may be press fit into a respective liner to facilitate replacement, or it may be slip fit into a liner and toe-clamped in place.

As will be understood from FIG. 5, the holes 28 and 26 are of the same diameter and may be simultaneously made by drilling through clamped together die holder and punchholder. Liners of different internal diameters can be used to accommodate the different cooperating diameters of the guide post and bushing. By clamping the plates together and drilling the holes in the die holder and punch holder, any desired center-to-center distance between guide posts can be obtained. Thus, the basic die set components, namely, the die holder and punchholder blanks, the guide posts, bushings and liners can be shipped to a local warehouse. When an order is received for a specified die set, the components may be selected from inventory. The die holder and punchholder blanks are held together and drilled for a given center-to-center distance between guide posts. The liners are positioned in the respective openings in the die holder and punchholder and epoxy bonded in place such that the axes of the liners are perpendicular to the planar surfaces of the die holder and punchholder, respectively. The bushing is fixed to the liner in the punchholder and the guide post is secured to the liner in the die holder.

In FIG. 6, there is shown a portion of a modified die holder 12' having a guide post 18 detachably secured therein. Liner 42 is epoxy bonded into the opening 26' in such manner that space is provided both above and below the liner 42'. Insert 70 is placed into liner 42' with the shoulder 72 on the insert 70 abutting the top surface of liner 42'. The guide post 18 is positioned in the insert 70 and is retained in place by fastening means including washer 74 and screw 76. The screw 76 is threaded into a tapped opening in the bottom of guide post 18' and is received in a countersunk opening in the washer 74. It is seen that by this construction, the guide post is removably secured in the die holder 12 and the top of the insert 70 is flush with the top surface 17' of the die holder 12' and the washer 74 is flush with the bottom surface of the die holder 12'.

it will be noted that the guide posts may extend upwardly from the die holder for cooperation with bushings in the punchholder, or, alternatively, the guide posts may depend from the punchholder and cooperate with bushings in the die holder.

There has been provided by the present invention an improved precision die set and improved method for mailing a precision die set utilizing components that are not entirely precision finished as has been customary in the past. The bushings 20 and the guide posts 18 are machined, so that they engage one another in a precise predetermined sliding relationship, on the order of .0001 inch to .0002 inch clearance for a Class 1 fit between guide pin and bushings where the nominal outside diameter of the guide pin is /1; inch to 3 inches. However, the method of fabricating the holes 28 for the bushings 20 in the punchholder 14 and the holes 26 for the lower end of the guide posts 18 in the die shoe 12 as shown in FIGS. 1-3 is by non-precision means, namely, a single drilling of the holes to their final form in a single operation. There is no necessity for fine machining or finishing f the holes, as, for example, by boring, reaming or honing. A similar arrangement is shown in FIGS. 4 and 5 except that liners are provided in the drilled holes in the punchholder and die holder and the bushing and guide posts are secured within the liners. It will be understood that prior to epoxy bonding, all surfaces to be bonded must be cleaned to remove foreign contaminants. The present invention results in an improved construction at a materially reduced fabrication cost. Field inventories may be materially reduced as precision die sets can be fabricated in the field from standardized components.

While we have shown and described presently preferred forms of the invention, it will be understood that the invention is not limited thereto, since it may be otherwise embodied within the scope of the following claims.

We claim:

1. A method of making a precision die set comprising a punchholder having a bushing secured thereto and a die holder having elongated guide members secured thereto, the punchholder and die holder having parallel facing surfaces comprising the steps of (1) forming at least two holes in the die holder by n0n-precision means in a single operation to their final form, (2) forming a like number of holes in the punchholder by non-precision means in a single operation to their final form, said holes in the punchholder being of a size to loosely receive said bushings therein, the bushings being sized to slidably receive the elongated guide members, (3) cleaning the punchholder, die holder, guide members and bushings, (4) applying an epoxy adhesive to the holes in the die holder and to an end of each of the guide members, (5) applying an epoxy adhesive to the holes in the punchholder and to the bushings, (6) assembling the bushings on the guide members to form a subassembly, (7) inserting the subassembly into the punchholder and die holder, (8) positioning the guide members in parallel relationship to one another and perpendicular to the die holder and punchholder before curing the epoxy adhesive; and (9) curing the epoxy adhesive to fix the components in precise assembled relationship.

2. The method of claim 1 wherein the elongated guide members each have an external configuration complementary to said holes.

3. The method of claim 1 wherein the holes are simultaneously formed in the punchholder and die holder, and including the steps of bonding annular liners into said holes for receiving guide members and the bushings, respectively, applying an epoxy adhesive to the openings in the liners and to the bushings and guide members, curing the epoxy adhesive to fix the components in precise assembled relationship and assembling the bushings and guide members in respective openings in liners in the punchholder and die holder.

4. The method of claim 1 including the steps of epoxy bonding liners into the holes in the punchholder and die holder and assembling the bushings and guide posts into said liners.

References Cited UNITED STATES PATENTS 3,228,262 1/1966 Bennett 76l07 3,404,055 10/1968 Wieland et al. 15633O XR BERNARD STICKNEY, Primary Examiner US. Cl. X.R.

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