US3566513A - Metal punching - Google Patents

Abstract

A PUNCH PRODUCES AN INDENTATION IN THE METAL WITH SOME OF THE METAL BEING DISPLACED OUTWARDLY ON THE OPPOSITE SIDE. THIS DISPLACED METAL IS REMOVED AND A PUNCH IS INSERTED INTO THE IDENTATION AND FORCED THROUGH THE METAL.

D R A W I N G

Description

' Marc 2, 1971 J. E. FULLI E R 3,566,513

' 'METAL PUNCHING I Filed March 5, 1969 JucZs'OTQEQu /Zr r Patented Mar. 2, 1971 3,566,513 METAL PUNCHING Judson E. Fuller, River Forest, 111., assignor to The Harrington & King Perforating Co., Inc., Chicago, Ill. Filed Mar. 5, 1969, Ser. No. 804,390 Int. Cl. B23p 13/04 US. Cl. 29-557 4 Claims ABSTRACT OF THE DISCLOSURE A punch produces an indentation in the metal with some of the metal being displaced outwardly on the opposite side. This displaced metal is removed and a punch is inserted into the indentation and forced through the metal.

BACKGROUND OF THE INVENTION It is not diflicult to punch a relatively small hole, e.g., one-sixteenth of an inch, in sheets of comparatively soft metal, provided that the thickness of the metal is no more than about the diameter of the punch. However, some metals, e.g., stainless steel, ofier such a high resistance to a punching operation that it is exceedingly diflicult to consistently form holes by punching in such metals. For example, some companies that commercially form perforate metal by punching will limit their operations on stainless steel to holes which are no smaller than twice the thickness of the metal. For example, they would not consider perforating metal with one-sixteenth inch diameter holes in a sheet of stainless steel of greater thickness.

The difficulty is that there is so much resistance to the movement of the punch through the metal that the punches tend to break. Even though a few holes might be formed, the punches will break before very many are completed and it is uneconomical to have to keep replacing punches.

In certain industries there is a demand for perforate metal, e.g., filtration screens, with the requirements, for example, calling for one-sixteenth inch holes in a sheet of stainless steel approximately three-sixteenths of an inch thick. Since the companies which form perforate metal by punching refuse to undertake such an operation, the metal must be formed by an operation such as drilling or milling (where slots are acceptable). These are extremely expensive procedures as compared to punching.

The principal object of the present invention is to provide a novel method for punching of metals which can be performed Without the extreme danger of breaking punches.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view illustrating diagrammatically the first step of the disclosed method;

FIG. 2 is an elevational view illustrating diagrammatically the second step of the disclosed method; and

FIG. 3 is a sectional elevational view illustrating the third step of the disclosed method.

DESCRIPTION OF SPECIFIC EMBODIMENT The following disclosure is offered for public dissemination in return for the grant of a patent. Although it is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end hereof are intended as the chief aid toward this purpose; as it is these that meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found.

FIG. 1 illustrates a sheet of stainless steel in which holes are to be made to form a perforate sheet. It is, for example, three-sixteenths of an inch thick. The sheet is run through a punching machine of which only the punches and their associated dies are illustrated. The punches 11 are each aligned with an opening 12 in a platen or die 13. The punches 11 have a comparatively round nose with the sides of the punch having a slight taper. The openings 12 are substantially larger in diameter than is the cross-sectional diameter of punches 11. Thus, for example, the punches 11 have a nominal cross-sectional diameter of one-sixteenth of an inch, while the cross-sectional diameter of holes 12 is three-sixteenths of an inch. The nose of each punch 11 is, of course, in juxtaposition to one face 10a of the sheet 10, while the other face 10b is placed against die 13.

The punches 11 are forced (by other portions, not shown, of the punch press) against and into the sheet 10 at face 10a so as to produce indentations 15. The depth of the indentation will vary with the conditions encountered, e.g., the diameter of the hole to be formed, the thickness of the sheet, the resistance that the sheet offers, etc. In the illustration given, the depth of the indentation 15 is in the range of approximately one-half to two-thirds the thickness of the sheet 10 between faces 10a and 10b. In any event, it should be sufliciently deep so that some of the material of the sheet is forced downwardly into openings 12 to form significant protrusions 16. Under the specific conditions given, these protrusions 16 extend approximately one-sixteenth of an inch beyond face 10b of the sheet.

The second step of the process is to remove the protrusion 16. This can easily be done with a surface grinder. FIG. 2 illustrates the removal of the protrusion 16 by a rotating grinding wheel 17, with the protrusion to the left of the wheel having been removed.

Following the removal of the protrusion 16, a second punching operation is performed as illustrated in FIG. 3. Here there is a punch 19 which is aligned with opening 20 in a die 21. The sheet 10 is positioned so that the indentations 15 are successively aligned with punch 19 and opening 20. Punch 19 is then inserted into the indentation 15 and forced on through the sheet 10 so as to eject a slug of metal 22 to leave a finished hole 23 in the metal at the point at which the indentation 15 was first formed.

In the drawings the punches 19 are illustrated as being substantially longer than are the punches 11. This may be desirable in some instances inasmuch as the shorter punches are in less danger of breakage. Thus, the punches 11 need be no longer than substantially the desired depth of the indanta-tions 15. The cleanout punches 19, however, must of necessity be sufiiciently long to insure the removal of slug 22 from the metal. However, some practitioners of the present method may desire not to use two sets of punches and will use punches 19 for the first step as well as for the third step.

Another modification that some perforators may desire to use, particularly when the sheet 10 is of a metal that is very tough and the holes 23 are to be of a relatively small diameter in relation to the thickness of the sheet 10, is to repeat the first two steps several times before carrying out the third step. That is, a small indentation is made with a correspondingly small amount of metal being extruded on the back side in the form of a protrusion 16. This protrusion is ground off. Thereafter the indentation 15 is deepened by a second punching operation, followed by a second grinding operation to remove the resulting protrusions. Only thereafter is the final punching operation of FIG. 3 carried out. Also in the illustrated embodiment the opening 20 in die 21 are substantially equal in diameter to the punch diameter, with only a small clearance for the punch 19 and slug 22 being provided in the opening 20. Larger diameter openings 20 can be employed if the ultimate user of the sheet 10 can stand for (or desires) some deforming of the face 1% about the finished openings,

I claim:

1. In the method of punching a hole in a metal sheet using a punch on one side of the metal and a die having a punch opening aligned with the punch on the other side of the sheet, the improvement comprising the steps of:

first, pressing said punch into the sheet sufliciently far to form an indentation in said one side and displace some metal from the sheet outwardly from said other side of the sheet, but not sufliciently far to extend through the sheet nor to remove a slug of metal from the sheet;

thereafter, removing said displaced metal down to about the level of said other side; and

thereafter, continuing to press the punch against the sheet in said indentation to force a hole in the metal.

2. In the method of claim 1, performed on a sheet of stainless steel, wherein at the end of the first step the punch has penetrated into the sheet in the range of ap- References Cited UNITED STATES PATENTS 2,182,067 12/1939 Bruecker 72379X 2,540,852 2/ 1951 Wilcox 29557X 3,232,156 2/1966 Fuller 8339 JOHN F. CAMPBELL, Primary Examiner V. A. DI PALMA, Assistant Examiner US. Cl. X.R. 8339, 52

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