US3909984A

US3909984A - Punch pin flat grinding machine

Info

Publication number: US3909984A
Application number: US477104A
Authority: US
Inventors: Thomas W Mclean
Original assignee: Federal Mogul LLC
Current assignee: CARBIDE INTERNATIONAL Corp; BankBoston NA
Priority date: 1972-05-05
Filing date: 1974-06-06
Publication date: 1975-10-07
Anticipated expiration: 1992-10-07

Abstract

Precise and rapid grinding of punch pins made of extremely hard material is obtained by a process and apparatus wherein a cylindrical punch pin is securely held by a work holder means and moved linearly between grinding means to simultaneously form a plurality of ''''flats'''' in the plane of a chord of the pin cross section and to cut the cutting end of the pin. The grinding means may be rotatable wheels positioned in predetermined relationship so that when the punch is moved therebetween, the flats and end will be precisely ground. The work holder means may include a pair of spaced, generally parallel arms clamping the punch pin at spaced points along its length so that opposite sides of the pin may be simultaneously ground and so that one of the grinding wheels may pass between the arms to form a flat. A fluid cylinder operator pivots the arm to effect the clamping action.

Description

United States Patent 1191 McLean Oct. 7, 1975 PUNCH PIN FLAT GRINDING MACHINE [75] Inventor: Thomas W. McLean, Chicago, Ill.

[73] Assignee: Federal-Mogul Corporation,

Southfield, Mich.

[22] Filed: June 6, 1974 [21] Appl. No.: 477,104

Related U.S. Application Data [63] Continuation of Ser. No. 250,755, May 5, 1972,

abandoned.

[52] U.S. Cl. 51/82 R; 51/92 R [51] Int. CL B24B 7/02 [58] Field of Search 51/80 R, 80 A, 82 R, 83 R, 51/84 R, 92 R; 269/32 Primary Examiner-Donald G. Kelly Assistant ExaminerNicholas P. Godici Attorney, Agent, or FirmRobert F. Hess [57] ABSTRACT Precise and rapid grinding of punch pins made of extremely hard material is obtained by a process and apparatus wherein a cylindrical punch pin is securely held by a workholder means and moved linearly between grinding means to simultaneously form a plurality of flats in the plane of a chord of the pin cross section and to cut the cutting end of the pin. The grinding means may be rotatable wheels positioned in predetermined relationship so that when the punch is moved therebetween, the flats and end will be precisely ground. The work holder means may include a pair of spaced, generally parallel arms clamping the punch pin at spaced points along its length so that opposite sides of the pin may be simultaneously ground and so that one of the grinding wheels may pass between the arms to form a fla't. A fluid cylinder operator pivots the arm to effect the clamping action.

8 Claims, 5 Drawing Figures US. amm 0m. 7,1975 Sheet 10f2 3,909,984

US, Patent Oct. 7,1975

Sheet 2 of 2 3,909 984 PUNCH PIN FLAT GRINDING MACHINE CROSS REFERENCE TO RELATED APPLICATION This application is a continuation of application Ser. No. 250,755, filed May 5, 1972 now abandoned.

BACKGROUND OF THE INVENTION This invention generally relates to metal working and more particularly concerns an apparatus and method for simultaneously grinding a punch pin cutting end and a plurality of flat areas along the length of the punch pin wherein the pin is securely held by a work holder means and moved between a grinding means po sitioned in predetermined relationship to the pin.

The cylindrically shaped punch pin is designed to be used for the high speed punching of holes in a tape on a Telex machine and therefore must be made of an extremely hard metallic material such as tungsten carbide. In practice a plurality of punch pins are supported in a punch block with each pin having an enlarged head projecting above the punch block. Each of the punch pins is connected to a link member which has a hooked member that engages the pin above and below its head and reciprocates it at the rate of many thousands of times per minute.

In the past, these punch pins have included a circumferential recess below the enlarged head, which recess received the hooked portion of the link member therein. Recently it has been discovered that grinding a flat spot in the plane of a chord of the pin cross section provided many advantages over the circumferential recess. Thus, it was found that not only was the strength of the pin improved but also that this flat surface prevented rotation of the pin and thereby greatly increased the useful life of the pins. In addition it was found that the provision ofa second flat area on the pin made possible the inclusion of a verifier means that comprises a photoelectric cell which is beamed along a row of the punch pins in the area of the second flat spot to verify the positioning of the pin and its functionmg.

A third flat area is provided on the pin, preferably op posite to the first flat spot below the enlarged head of the pin, to receive a shipping block means therein, which block will keep the pins in the punch block prior to installation of the assembly.

While the provision of flat areas provides many advantages over the prior art, its use has been considerably limited by the inapplicability of the methods and apparatuses of grinding the circumferential recesses. As a result, the prior art means of grinding the flats has been very expensive and slow. For example, it is important that all of the flat areas on all of the pins be in exact, predetermined relationship to each other. However, this requirement presents many problems with the prior art methods and apparatuses wherein the flats are separately and individually ground and polished. Not only does this require time consuming alignment and handling, but it provides many opportunities to commit errors. The expensive material, the difficulty of working the hard material, and the high degree of accuracy required for the pins, further compounds the problems. Many rejects are extremely expensive.

SUMMARY OF THE INVENTION The problems of the prior art are overcome by the punch pin grinding machine and method, wherein a plurality of chordally extending flats are ground simultaneously with a pin cutting end. According to the method of the invention, the flats and end are formed on the punches quickly, precisely, and economically by clamping the pin along its length in a work holder means and moving the work holder with the clamped punch pin in a predetermined path between a plurality of grinding means positioned. in predetermined relationship to each other and to the pin whereby the grinding means substantially simultaneously contacts the pin to form the flat areas and the cutting end.

The flattened areas are formed in opposite sides of the pin just below the head by the positioning of the pins so that its enlarged head and adjacent neck extend beyond the workpiece holder and many therefore be simultaneously contacted by a first grinding means below the pin and a second grinding means above the pin. The pin holder means includes a clamping arm means having a first pin engaging end and a second end connected to an operator means with a pivot point between the first and second ends. The pivot arm may include a pair of spaced prongs adjacent the first end, which prongs engage the pin at spaced points along the length of the pin in order to clamp it securely. Also, the spaced prongs allow a grinding means to move therebetween and contact the pin in at least one point between the prongs to form a flat area. The operator means for the clamping arm means advantageously may take the form of a piston movable in a cylinder by changing fluid pressure. Suitable fluid supply is provided to the cylinder on opposite sides of the piston to operate the clamping arm by moving it about its pivot point. Other equivalent operating means may also be used.

In the preferred embodiment of my invention, the grinding means may be rotating wheels having an abrasive material on their circumferential edge. A plurality of wheels may be arranged to rotate about the same axis. Where the pin includes three flattened areas and a configured cutting end, I have found that three separate grinding wheels arranged in predetermined relationship are efficient and provide excellent results. In this case, the axes of the grinding wheels may all lie in generally the same plane. A first flat grinding means may be positioned below the pin adjacent the holder means and a second grinding means including a pair of grinding wheels may be positioned on an opposite side of the pin with one of the prongs extending between the pair of grinding wheels. Each of the first and second grinding means have surfaces parallel to the axis of the pin whereby a flat area is ground when the pin is moved linearly between the rotating wheels. A third grinding means for grinding the cutting end of the pin may have a configured grinding edge which forms a configured cutting end for the pin. Each of the first, second and third grinding means may be provided with suitable power means as required to perform its function. The speeds, directions of rotation, and the particular abrasive material of each of the grinding means, may be varied as required to effect optimum production.

The method of my invention includes the steps of removably mounting the punch pin on a movable holder, arranging first, second and third grinding means in spaced, predetermined relationship to each other, and moving the holder with the punch pin linearly into range of the grinding means to simultaneously grind a plurality of flats and the cutting end of the pin. These steps may also include holding the pin at a plurality of points so that one portion of the pin may be simultaneously ground at a pair of opposite points and so that a flat may be ground on the pin between the points at which it is held. A further step includes rotating the wheels of the first and second grinding means in counter rotation to minimize the amount of force tending to rotate the pin while it is being ground by the first and second grinding means.

By means of the apparatus and method of my invention, the many problems in the prior art have been effectively overcome. Thus, with the generally simultaneous grinding of the pin each of the ground areas on a pin are in exact, predetermined relationship to each other, and each pin in turn is identical with the other pins. Moreover, this high degree of accuracy is obtained quickly, economically and with a minimum of labor.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

FIG. 1 is a perspective view with parts in section showing the relationship between the linearly movable holder means and the first second and third grinding means;

FIG. 2 is a side elevational view of the holder means of FIG. 1 with parts in section to show the operation of the clamping arm operator means;

FIG. 3 is a plan view of the holder means of FIG. 2, showing the parallel prongs of the clamping arm;

FIG. 4 is a schematic elevational view of the apparatus of FIG. I, seen from the opposite direction to more clearly show the action of the grinding means on the punch pin; and

FIG. 5 is an enlarged view of a punch pin produced according to the preferred embodiment of my invention. 4

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there may be seen a punch pin grinding apparatus generally indicated at in FIG. 1

wherein a first grinding means 12, a second grinding I means 14 and a third grinding means 16 are positioned in predetermined relationship to each other and to a Work holder means 18. A clamping arm means 20 pivotally mounted on the work holder means 18 may be operated to securely hold a punch pin means 22 as shown in FIG. 2. With the punch pin 22 thus held in po sition, the holder means 18 may then be moved in a straight line along a table base 24 through the grinding means 12, 14 and 16 to form the flats and end as may be best seen in FIG. 5.

- The first grinding means '12 includes a grinding wheel 30 which rotates about an axle means 32 that is journalled in a suitable support means 34. The grinding means 12 is connected through the axle means 32 to a power source 36 by a suitable power transmission means 38. A guard and deflector means 31 may be provided about the grinding wheel 30 adjacent to its ex pected point of contact with the punch pin 22.

The grinding means 12 along with the power-source 36 may be movably mounted on a support 40, which support may rest on a base or foundation 42. Movement and adjustment of the grinding means 12 on the support 40 may be quickly and accurately provided by an adjustment means 44 which comprises a rotatable handle having threaded means engaging the support 40 to move it therealong.

The grinding wheel 30 has an abrasive circumferential edge 30a of a material suitable to grind the very hard pin punch material. Mounting of the grinding wheel 30 on the axle means 32 may be in accordance with conventional means. As shown in FIG. 4, the wheel 30 is mounted vertically with its edge 30a generally horizontal to form flat area 22a.

The second grinding means 14 is positioned above the first grinding means 12 and includes a pair of grinding

wheels

50,52 as shown in FIG. 4 mounted in spaced relationship on the same mounting means 54. The

wheels

50,52 are connected to an axle means 56 which is rotated by a motor means 58 to provide the grinding power. The second grinding means 14 may also be mounted for vertical movement by a means not shown, but which may be similar to that'illustrated with respect to the first grinding means 12.

The grinding

wheels

50 and 52 may have a circumferential abrasive grinding edge 50a, 52a respectively, which surfaces may be aligned with the axis of the pin 22 to provide the flat spots 22!) and 22c respectively as the pin 22 is moved through the grinding means. A spacer 54a separates the generally

parallel wheels

50 and 52 to provide the precise spacing between the flats 22b and 22c. As is shown, the

wheels

50 and 52 are of the same diameter and of different width. However, their respective diameters and widths may be varied to suit the pin specifications.

The third grinding means 16 may include a grinding wheel suitably mounted by a mounting means 62. An axle, generally indicated at 64, is journalled in a support 66 and connects the wheel 60 and mounting means 62 with a belt driven power source 68 to provide the grinding force required. Whereas the grinding

wheels

30, 50 and 52 lie in parallel vertical planes with their axes of

rotation

32 and 56 respectively perpendicular thereto, the grinding wheel 60 lies in a plane inclined to the horizontal and rotates on an axle 64 perpendicular thereto and inclined from the vertical. Nevertheless, the axes of rotation represented by the

axles

32,56 and 64 may all lie in the same plane whereby the grinding of the pin 22 by the first, second and third grinding means 12,14 and 16 respectively, will be simultaneous.

The grinding wheel 60 has a circumferential abrasive grinding edge 60a which is configured to shape the pin cutting end 22d with a pair of angularly related cutting surfaces. While this represents a preferred embodiment, it will be understood that other shapes and configurations of the cutting end 22d may be provided and that, accordingly, the third grinding means 16 may be adjusted to various positions by an adjustment means not shown, but which will be understood by those skilled in the art. These adjustment means may also provide for movement of the third grinding means to accommodate variations in the size of the pin 22 and the grinding wheel 60.

Referring to the holder means 18 as shown in FIGS. 1 through 4, it may be seen to comprise a lower support plate member 70 having a planar, lower surface 70a that engages an upper planar surface 24a of the table means 24 whereby the surfaces 70a and 240 may slide over each other. The support plate 70 includes a linear groove 7017 which receives a fitted linear guide means 70c therein as shown in FIG. 4. The key or guide means is connected to the support 70 by a pair of fastening means 70d extending through the holes 70e into the guide means 70c. The guide means 70c extends below the surface 70a of the support member 70 into a mating linear groove 24b in the table means 24.

Accordingly, it will be understood that the support member 70 may be moved linearly on the surface 24a in an exact predetermined path. The moving force for the holder means 18 may be provided by hand or other suitable power source capable of reciprocating action.

A support block 72 may be suitably fixedly mounted on the supporting base 70 by means such as the machine screws 73 illustrated.

The support block 72 has'a clamping arm 20 pivotally mounted thereon by means of a pivot pin 74. The clamping arm 20 has a first pin engaging end 20a and a second end 20b operatively connected to an operator means generally indicated at 80.

The support block 72 includes a clamping bed means 76 having a support surface 78 therein which supporting surface has a groove or suitable configuration therein to provide a seat for the pin 22. Thus, the pin engaging end 200 clamps the pin 22 against the surface 78 and the conforming groove in the surface 78 serves to hold it securely in position. The bed 76 may be removably secured to the support block body 72 by suitable means such as the machine screw members 75 illustrated. Spacer members 77 of various thicknesses may be interposed between the bed 76 and the support block 72 to provide for vertical adjustability of the surface 78. Where required, a key 77a may be provided between the bed 76 and the spacer member 77 to prevent relative movement therebetween. The surface 78 may be of a different metal than the bed member 76 and may be secured thereto by suitable means known in the art of metalworking.

Referring to FIG. 3, it will be seen that the clamping arm means 20 comprises a pair of generally

parallel prongs

20c, 20d, held in spaced relationship by a spacer block 21 at the pivot point. The pivot pin 74 extends from one side through the prong 20c, through the spacer block 21 and through the prong 20d to the opposite side where it may have suitable nut means 21a attached thereto. While the clamping arm need only comprise spaced prongs in the area of its pin-engaging end 20a, to allow the grinding wheel 52 to pass therebetween as is shown in FIG. 4, I have found it advantageous to make the prongs of separate pieces extending along the length of the clamping arm 20.

The operator means 80 as shown in cross section in FIG. 2 comprises a cylinder 84 having a piston 86 movably received therein. A connecting rod 88 is suitably attached to the piston 86 on one end and is pivotably connected to the clamping arm 20 on its opposite end. With the clamping arm 20 comprised of a pair of separate prongs 200, 200', the connection with the rod 88 may be effected by extending the rod between the prongs and passing a pivot pin means 82 through the prongs and the rod. As a result, movement of the piston 86 will be transmitted to the clamping arm 20 so that where the force is in a clockwise direction, as shown in FIG. 2, the end 20a will securely clamp a pin 22 against the surface 78.

A pair of fluid

pressure supplying means

90 and 92 are connected through the support block 72 to the cyl inder means 84 at points on opposite ends of the expected path of travel of the piston 86. As shown, movement of the piston is limited at its lower end by an adjustable stop member 94 extending into the cylinder 84 from the lower end where it is in threaded engagement with the support plate 70. This assures that the end 20b of the clamping arm 20 will not hit the upper edge of the support block 72. The fluid supply means 90 is connected below the upper end of the stop member 94. Upward movement of the piston 86 and the lower portion 84a of the cylinder is limited by a shoulder 84b in the cylinder 84 adjacent to the upper portion 840 of the cylinder through which the connecting rod 88 passes. The inlet of the fluid supply means 92 is just above the shoulder 84. A fluid pressure sealing member 96 seals off the cylinder about the connecting rod 88 to make the cylinder 84 pressuretight.

As is well-known, movement of the piston 86 takes place when a difference of pressure occurs on opposite sides of the piston 86 so that adding or removing fluid pressure by the

means

94,96 moves the piston 86 and pivots the clamping arm 20 toward and away from the pin receiving surface 78.

The holder means 18 has a pin positioning means 100 connected therewith, whereby the pin 22 may be exactly positioned on the surface 78. As best seen in FIGS. 1 and 4, the positioning means 100 includes a support portion 102 suitably connected to the supporting block 72, such as by means 104. An adjustable stop member 106 arranged with its axis generally parallel to that of the pin member 22 extends through the support member 102 and is adjustably held by a tightening screw 108 so that its inner end 106a provides a stop against which the enlarged head of the pin 22 may rest.

Operation of the apparatus according to the method of my invention includes the steps of arranging the first, second and third grinding means 12,14 and 16 in spaced, predetermined relationship to each other in accordance with the design of the pin 22. Thus, the grinding

wheels

30,50,52and 60 must be adjusted in accordance with the pin size to provide the predetermined flat and end configuration. A pin blank is set on the surface 78 with its enlarged head abutting the adjustable stop 106a so that the neck portion of the pin, that is, the portion just below the head, extends beyond the surface 78 a distance sufficient to allow the wheel 30 to form the flat portion 22a from the bottom. At the same time, this also allows the formation by the grinding wheel 50 of the flat surface 2217. With the pin blank thus positioned, the piston operator means is actuated by suitable control means to the fluid conduits and 92 to move the piston 86 upwardly in the cylinder 84 and rotate the clamping arm 20 about the pivot point 74 to bring the first pin. engaging end 20a into contact with the pin blank 22 to clamp it securely against the surface 78.

At this point, the holder means 18 is resting on the table 24 outside the range of the grinding means 12,14 and 16. It will be understood that the table 24 with its planar surface 24a will be fixed in relationship to the grinding means and their supports so that with the exception of the aforementioned adjusting means, there will be no relative movement therebetween. After the grinding means have been caused to rotate by the respective power sources, the holder means 18 with the pin firmly clamped in position, may be caused to move along the table surface 24a by suitable means to and through a point of contact with the grinding means 12,14 and 16 whereby flat areas 22a 22b and 220 will be formed in the pin 22. The pin 22 is a cylindrical member and hence the flats will lie in a plane passing through a chord of the pin cross section. While this flat arrangement is preferred, I contemplate the application of my invention to other flat arrangements and configurations within the scope of my contribution to the art.

The cutting end surface 22d is similarly formed by movement of the pin 22 past the edge 60a of the grinding wheel 60. After the pin has been moved past the grinding means 12,14 and 16 to the point where thegrinding operation has been completed, the holder means 18 may be reciprocated back past the grinding means again to a point where the clamping arm 20 may be safely pivoted in a counter-clockwise direction about the pivot point 74 to unclamp the pin 22 from the surface 78. At this point, the completed pin may be removed and a blank substituted in its place.

The specific grinding wheel abrasive material, the speed of rotation of the grinding wheel, the speed of feed of the pin into the grinding means all depend on the particular size and hardness of the pin and hence, will vary widely to suit the particular conditions. With regard to the direction of rotation of the grinding wheels, I have found that closing of the wheel 30 and the

wheels

50,52 to counter-rotate about the

axes

32 and 56 respectively, tends to minimize the amount of force tending to rotate the pin while it is being ground.

From the foregoing description of the apparatus and method of my invention, it may be seen that a very accurate, quick and economical production of ground punch pins is now possible. The problems of the prior art are overcome by the simultaneous grinding f the flat spots and ends of the pins so that they are in exact, predetermined relationship to each other and each pin in turn is identical with other pins.

Although I have herein set forth my invention with respect to certain specific principles and details thereof, it will be understood that these may be varied without departing from the spirit and scope of the invention as set forth in the hereunto appended claims.

I claim:

1. An apparatus for grinding a plurality of predetermined portions of a generally cylindrical shaped pin to produce a punch pin having a generally cylindrical portion with at least two flat surfaces provided thereon with one of the flat surfaces being disposed opposite the remaining flat surfaces, the apparatus comprising:

at least a first and a second grinding means for grinding the generally cylindrical portion of the pin with each of said grinding means having a grinding surface;

means for supporting said grinding means with the grinding surface of the first grinding means facing the grinding surface of the second grinding means and being spaced therefrom;

pin holder means for gripping the generally cylindrical portion of the pin including a supporting surface having a generally cylindrical groove therein conforming with the generally cylindrical portion of the pin disposed on said supporting surface, a clamping arm having at least one end to engage a pin disposed on said supporting surface, and operator means for moving the arm to clamp a pin on said surface, said holder means being moveable along a linear path on a plane surface from a position withdrawn from the grinding means to a position passing the pin clamped on the supporting surface between the spaced grinding surfaces to simultaneously form flat surfaces on opposite sides of the generally cylindrical portion; said clamping arm having a second end connected to i the operator means, and a pivot point intermediate said ends, said pin engaging end of said clamping arm including a pair of spaced prongs engaging said pin at spaced points along the length of the pin, and said second grinding means being positioned to grind a flat surface in said pin in at least one point between said prongs. 2. An apparatus for grinding a plurality of predetermined portions of a generally cylindrical shaped pin to produce a punch pin having a generally cylindrical portion with at least two flat surfaces provided thereon with one of the flat surfaces being disposed opposite the remaining flat surfaces, the apparatus comprising:

at least a first and a second grinding means for grinding the pin with each of said grinding means having a grinding surface;

means for supporting said grinding means with the grinding surface of the first grinding means facing the grinding surface of the second grinding means and being spaced thereform;

pin holder means for gripping the pin including a supporting surface configured to mate with a portion of the cylindrical portion of the pin disposed on said supporting surface, a clamping arm having at least one end to engage a pin disposed on said supporting surface, and operator means for moving the arm to clamp a pin on said surface, said holder means being moveable along a linear path on a plane surface from a position withdrawn from the grinding means to a position passing the pin clamped on the supporting surface between the spaced grinding surfaces to simultaneously form flat surfaces on opposite sides of the generally cylindrical portion;

said clamping arm having a second end connected to the operatormeans, and a pivot point intermediate said ends, said pin engaging end of said clamping arm including a pair of spaced prongs engaging said pin at spaced points along the length of the pin, and said second grinding means being positioned to grind a flat surface in said pin in at least one point between said prongs.

3. An apparatus according to claim 2, wherein said operator means is a piston movable in a cylinder under fluid pressure, said cylinder being integrally formed in said holder means, and said piston means bieng connected to the second end of said clamping arm to rotate said clamping arm about its pivot point and to cause said pin engaging end to clamp said pin against movement on said supporting surface.

4. An apparatus according to claim 2, wherein said first grinding means comprises a grinding wheel having an abrasive surface on its peripheral edge and means to rotate said wheel, said second grinding means compris ing a pair of grinding wheels mounted in spaced positions on the same axis with each wheel having an abrasive surface on their peripheral edge to form a pair of axially spaced flat surfaces on the pin, and means to rotate both wheels of the second grinding means, said grinding wheels being rotated in generally parallel planes, said grinding wheels of the first and second grinding means bieng aligned with the linear path of the pin holder means so that one of the pair of wheels of the second grinding means forms a flat surface in the pin between the pair of spaced prongs and the other wheel of the second grinding means and the wheel of the first grinding means form the remaining flat sur faces adjacent to one of the pair of prongs.

5. An apparatus according to claim 2, wherein said pin holder means includes positioning means attached to said holder means to provide an abutment for a head end of the pin, said postionirlg means being adjustably movable along an axis generally parallel to the central axis of said pin so that a pin having its head engaging said adjustable positioning means is axially positioned on the supporting surface in a desired position.

6. An apparatus for grinding a plurality of predetermined portions of a generally cylindrical shaped pin to produce a punch pin having a generally cylindrical portion with at least two flat surfaces provided thereon with one of the flat surfaces being disposed opposite the remaining flat surfaces, the apparatus comprising:

said first grinding means comprising a grinding wheel having an abrasive surface on its peripheral edge and means for rotating the grinding wheel, and said second grinding means comprising a pair of spaced grinding wheels mounted for rotation on the same axis with each wheel having an abrasive surface on their peripheral edge to form a pair of axially spaced flat surfaces on the pin and means for rotating the grinding wheels of the second grinding means in spaced planes generally parallel to the plane of the wheel of the first grinding means, and wherein said clamping arm grips said pin at a position between the positions of the spaced flat surfaces formed by the grinding wheels of said second grinding means.

7. An apparatus in accordance with claim 6, which includes third grinding means arranged to grind a cutting edge on an end of said pin simultaneously with the grinding of the flat surfaces on said opposite sides of said pin.

8. An apparatus according to claim 7, wherein said third grinding means comprises a grinding wheel having an abrasive surface on its peripheral edge and means for rotating the grinding wheel in a plane inclined to the

Claims

1. An apparatus for grinding a plurality of predetermined portions of a generally cylindrical shaped pin to produce a punch pin having a generally cylindrical portion with at least two flat surfaces provided thereon with one of the flat surfaces being disposed opposite the remaining flat surfaces, the apparatus comprising: at least a first and a second grinding means for grinding the generally cylindrical portion of the pin with each of said grinding means having a grinding surface; means for supporting said grinding means with the grinding surface of the first grinding means facing the grinding surface of the second grinding means and being spaced therefrom; pin holder means for gripping the generally cylindrical portion of the pin including a supporting surface having a generally cylindrical groove therein conforming with the generally cylindrical portion of the pin disposed on said supporting surface, a clamping arm having at least one end to engage a pin disposed on said supporting surface, and operator means for moving the arm to clamp a pin on said surface, said holder means being moveable along a linear path on a plane surface from a position withdrawn from the grinding means to a position passing the pin clamped on the supporting surface between the spaced grinding surfaces to simultaneously form flat surfaces on opposite sides of the generally cylindrical portion; said clamping arm having a second end connected to the operator means, and a pivot point intermediate said ends, said pin engaging end of said clamping arm including a pair of spaced prongs engaging said pin at spaced points along the length of the pin, and said second grinding means being positioned to grind a flat surface in said pin in at least one point between said prongs.

2. An apparatus for grinding a plurality of predetermined portions of a generally cylindrical shaped pin to produce a punch pin having a generally cylindrical portion with at least two flat surfaces provided thereon with one of the flat surfaces being disposed opposite the remaining flat surfaces, the apparatus comprising: at least a first and a second grinding means for grinding the pin with each of said grinding means having a grinding surface; means for supporting said grinding means with the grinding surface of the first grinding means facing the grinding surface of the second grinding means and being spaced thereform; pin holder means for gripping the pin including a supporting surface configured to mate with a portion of the cylindrical portion of the pin disposed on said supporting surface, a clamping arm having at least one end to engage a pin disposed on said supporting surface, and operator means for moving the arm to clamp a pin on said surface, said holder means being moveable along a linear path on a plane surface from a position withdrawn from the grinding means to a position passing the pin clamped on the supporting surface between the spaced grinding surfaces to simultaneously form flat surfaces on opposite sides of the generally cylindrical portion; said clamping arm having a second end connected to the operator means, and a pivot point intermediate said ends, said pin engaging end of said clamping arm including a pair of spaced prongs engaging said pin at spaced points along the length of the pin, and said second grinding means being positioned to grind a flat surface in said pin in at least one pOint between said prongs.

4. An apparatus according to claim 2, wherein said first grinding means comprises a grinding wheel having an abrasive surface on its peripheral edge and means to rotate said wheel, said second grinding means comprising a pair of grinding wheels mounted in spaced positions on the same axis with each wheel having an abrasive surface on their peripheral edge to form a pair of axially spaced flat surfaces on the pin, and means to rotate both wheels of the second grinding means, said grinding wheels being rotated in generally parallel planes, said grinding wheels of the first and second grinding means bieng aligned with the linear path of the pin holder means so that one of the pair of wheels of the second grinding means forms a flat surface in the pin between the pair of spaced prongs and the other wheel of the second grinding means and the wheel of the first grinding means form the remaining flat surfaces adjacent to one of the pair of prongs.

5. An apparatus according to claim 2, wherein said pin holder means includes positioning means attached to said holder means to provide an abutment for a head end of the pin, said postioning means being adjustably movable along an axis generally parallel to the central axis of said pin so that a pin having its head engaging said adjustable positioning means is axially positioned on the supporting surface in a desired position.

6. An apparatus for grinding a plurality of predetermined portions of a generally cylindrical shaped pin to produce a punch pin having a generally cylindrical portion with at least two flat surfaces provided thereon with one of the flat surfaces being disposed opposite the remaining flat surfaces, the apparatus comprising: at least a first and a second grinding means for grinding the pin with each of said grinding means having a grinding surface; means for supporting said grinding means with the grinding surface of the first grinding means facing the grinding surface of the second grinding means and being spaced therefrom; pin holder means for gripping the pin including a supporting surface configured to mate with a portion of the cylindrical portion of the pin disposed on said supporting surface, a clamping arm having at least one end to engage a pin disposed on said supporting surface, and operator means for moving the arm to clamp a pin on said surface, said holder means being moveable along a linear path on a plane surface from a position withdrawn from the grinding means to a position passing the pin clamped on the supporting surface between the spaced grinding surfaces to simultaneously form flat surfaces on opposite sides of the generally cylindrical portion; said first grinding means comprising a grinding wheel having an abrasive surface on its peripheral edge and means for rotating the grinding wheel, and said second grinding means comprising a pair of spaced grinding wheels mounted for rotation on the same axis with each wheel having an abrasive surface on their peripheral edge to form a pair of axially spaced flat surfaces on the pin and means for rotating the grinding wheels of the second grinding means in spaced planes generally parallel to the plane of the wheel of the first grinding means, and wherein said clamping arm grips said pin at a position between the positions of the spaced flat surfaces formed by the grinding wheels of said second grinding means.

8. An apparatus according to claim 7, wherein said third grinding means comprises a grinding wheel having an abrasive surface on its peripheral edge and means for rotating the grinding wheel in a plane inclined to the axis of said pin.