JP2008087011A - Die for press-formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain one pair of dies for press-formation constituted so that in the press-formation processing at high speed, mutual collision of the formation processing surfaces of one pair of dies is canceled. <P>SOLUTION: In the dies for press-formation forming a drilling part 4, a forming edge 24 capable of forming a cutting edge 8 is arranged in the peripheral edge 23 at one side of a formed recessed surface 21, a projecting surface 22 is formed in the peripheral edge 23 of the formed recessing surface 21 at the reversed side, and a formed processing surfaces 20 of the dies 10 are formed by shaping clearance grooves 12 along the projecting surface 22 from the peripheral edge 23 so that the tip edge part of the forming edge 24 is inserted into the faced clearance groove 12 when the dies 10 are joined together. According to this invention, burr protruded to the periphery from the screw-basic material is sharply pressed and the screw can be formed and the sharp cutting-edge can be formed in the drilling part and further, since useless hitting of the dies is not needed, the breakage is reduced. Furthermore, the adjustment of the most approaching position of the dies is made to easy and the preparing time is shortened and also, the strength of the cutting-edge in the drilling part is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a die for forging and forming a drill portion in the manufacture of a drill tapping screw that can be screwed while forming a pilot hole for screwing the workpiece into the workpiece, and in particular, has a relatively high strength for the workpiece. The present invention relates to a die for forming a cutting edge of a drill part for drilling a sufficiently screwable pilot hole.

  Generally, a so-called drill tapping screw having a cutting edge-shaped drill portion formed at the tip is often used as a screw to be screwed in while making a pilot hole in a workpiece. Conventionally, the drill part of these drill tapping screws has been manufactured by cutting, but recently, this drill part is processed by cold heading. The dies for processing the drill part by such forging process are face-to-face dies with a forming surface provided at the front end on the opposite side, and the tip of the leg portion of the screw material is forged into a drill shape. It is like that. In such dies, forging is performed on the screw material supplied in large quantities and a drill part is formed at the tip of the screw material. Will not be supplied to the butting position of the die, but will be abutted with each other in a state where no screw material is inserted between the dies, the molding surface will collide (so-called empty shot), and the molding surface of the die will be damaged There was a problem to do.

In order to solve this problem, a contact surface that prevents the molding surfaces from colliding with each other when the dies are brought into contact with each other recently is provided at the corner of the molding surface of each die so that no blanking occurs. I have to. This is shown in Japanese Utility Model Publication No. 6-66837. This is formed by forming contact surfaces slightly higher than the periphery of the molding surface on both upper sides of the molding surface and on the lower side of the molding surface. However, in order to eliminate such a phenomenon, it is necessary to provide the contact surface. However, if this contact surface is provided on the molding surface of the die, many irregularities are formed on the molding surface of a limited size. In particular, in a die for forging a part such as a comparatively small drill screw, if the contact surface is formed by cutting or polishing, it takes time to work due to the balance with the forming surface. Cost, which has led to an increase in cost. In addition, when the drill part is formed with a die having such a contact surface, while the screw material of the drill tapping screw is continuously supplied in accordance with the die that is facing and forging, the die Although the drill part of a predetermined shape is obtained without being damaged, since this forging process is performed at a high speed, when the above-mentioned phenomenon of punching occurs without the screw material being supplied in accordance with this forging process, Due to the inertia of the dies, the molding surfaces of the dies still collide and are damaged. This is because in order to obtain the cutting edge of the drill part, it is necessary to adjust the dies so that they are as close as possible, and it takes a lot of time to adjust the gap for uniform production of the drill part. . In addition, the drill part obtained from the forging process is formed by compressing and deforming the cylindrical material by hitting the screw material, so that the excess material generated during the forging process protrudes from the molding process surface. The structure of the outer periphery of the drill that becomes the cutting edge is rough, and the drill is not strong and the cutting edge is crushed if the drill is weak and relatively thick. There is also. In order to solve this problem, as shown in FIG. 7 and FIG. 8, a streak-like groove 112 is formed at a position slightly away from the peripheral edge 123 of the molding surface 121 that forms the body portion of the drill portion 104, and forging. In some cases, burrs generated during processing are prevented from jumping out of the molding surface 121.
Japanese Utility Model Publication No. 6-66837 JP-A-60-121031

However, even if a groove that prevents the burr from jumping outward is formed along the peripheral edge at a position slightly away from the molding surface in this way, the burr is not sufficiently prevented from jumping out. Has not improved sufficiently. In addition, since the screw material is positioned between the dies and is forged on the opposing forming surfaces, if the screw material is not positioned between these dies for some reason, The molding process surfaces of these dies collide and are damaged. For this reason, the exchange of dies frequently occurs, and the cost still increases. Furthermore, even if the contact surface is formed, much time and labor are required for adjusting the closest dimension in the abutting of the molding surfaces of the dies. In addition, when the contact surface is formed only on the lower side of the die so that the processing of the molding surface is facilitated, this theoretically avoids collision, but in high speed forging processing, Inertia works, and there are still problems such as inability to resolve the collision between the dies.

  An object of the present invention is to obtain a forging die that eliminates such problems and eliminates the mutual collision of the forming surfaces of the die during high-speed forging.

  It is an object of the present invention to form a cutting edge-shaped drill portion 4 that forms a pilot hole for screwing the screw thread 5 into a work piece at the tip of the leg portion 3 where the screw thread 5 is formed, so that they can be forged. In a pair of forging dies for forging and forming the drill portion 4 by abutting the oppositely arranged forming surfaces 20, screws are formed on one peripheral edge 23 of the concave concave surface 21 constituting the forming surface 20. A forming blade 24 capable of forming a cutting blade 8 for cutting and drilling a pilot hole when rotating in the screwing direction is provided, and the center of the forming concave surface 21 on the side opposite to the forming blade 24 is continuously directed toward the tip. A substantially triangular projecting surface 22 inclined to the side is formed, and a relief groove 12 having a predetermined depth is formed from the peripheral edge 23 of the molding concave surface 21 along the peripheral edge of the projecting surface 22 to mold one die 10. Machined surface 20 This is achieved by providing a die for forging forming in which the leading edge of the forming blade 24 enters the counterpart clearance groove 12 when the processing surfaces 20 of the die 10 face each other. .

  In addition to the above-described structure, this object is also achieved because the escape groove is provided at least along the peripheral edge 23 of the molding concave surface 21 that forms the body portion of the drill portion 4. Since the bottom side is formed so as to be narrowed widely, it is possible to avoid the collision of the peripheral edges of the molding concave surfaces of the dies facing each other.

  According to the present invention, the tip of the screw material of the drill tapping screw is positioned between the dies, and the forming blade for forming the cutting blade of the drill portion when the forging process is performed by abutting the pair of dies against each other. Because it is in the position to enter the relief groove of the die, the burr that protrudes from the screw material to the periphery is pressed sharply to form an extremely thin shape, and it becomes possible to form a sharp cutting edge on the drill part . Also, in the repeated forging of the die, each time the dies are brought into contact with each other in a state where the supplied screw material is not positioned at a predetermined position between the opposing die forming surfaces, the die forming blade is Since the die enters the escape groove without colliding with the molding surface of one of the dies, the die is not blown and its breakage is reduced, and the life of the die is extended. Further, in the adjustment adjustment of the dies, adjustment of the closest approach position of the dies becomes easy, and the setup time is shortened. Further, since the forming blade forming the tip of the drill portion is inclined downward and rearwardly downward from the projecting surface of the counterpart die, there is no collision even when the dies are brought into contact with each other. In addition, unlike the prior art, a contact surface is not necessary, and the forming work is facilitated in forming the die forming surface. In addition, the relief groove can restrict the burr from popping out when a burr is generated during the forging process of the material, thereby preventing the free flow of the material structure and pressing the burr with the forming blade. Since it is formed into an extremely thin shape, the structure of this portion becomes dense, and a specific effect such as an improvement in the strength of the cutting edge of the drill portion can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In FIG. 6, reference numeral 1 denotes a drill tapping screw in which a drill portion 4 is formed at a tip portion of a leg portion 3 integral with the head portion 2 and a screw thread 5 is formed from the drill portion 4 to the head portion 2. The head 2 is formed with a cross groove 6 that can be engaged with a driver bit (not shown). The shape may be a polygonal shape such as a hexagon or a square. The drill portion 4 of the drill tapping screw 1 has a rake face 7 formed on the screw rotation direction side of the screw, and a cutting edge 8 is formed on the outer periphery of this face. The cutting blade 8 is configured to drill while cutting the workpiece when making a prepared hole in a workpiece (not shown). Thereafter, the cutting blade 8 is formed in the leg portion 3 in the prepared hole formed by the drill portion 4. The thread 5 is screwed while forming a female screw (not shown).

  As shown in FIGS. 1 and 3, the drill portion 4 of the drill tapping screw 1 is formed by forging at the tip end portion of the leg portion 31 of the screw material 30 by facing a pair of dies 10 and 10 to face each other. The forming surfaces 20 are respectively formed on the opposing surfaces of the front ends of the dies 10 and 10 facing each other. The forming surface 20 has a forming concave surface 21 having a sectoral cross section so that the outer peripheral surface of the body portion of the drill portion 4 is formed on the center line thereof, and the forming concave surface 21 is as shown in FIGS. 1 and 2. Moreover, it is formed in a substantially conical shape so as to form the tip of the drill portion 4 and becomes shallower as it reaches the tip. A protruding surface 22 that forms the rake face 7 of the drill portion 4 is provided on the left side in FIG. 1 on the front end side of the forming concave surface 21, and the protruding surface 22 constitutes the forming concave surface 21. In the peripheral edge 23, it is a substantially triangular flat surface that is inclined toward the center as it goes to the tip continuously from the peripheral edge 23, with a middle point slightly lowering from the upper end of the die 10. Around the molding surface 20 formed by the molding concave surface 21 and the projecting surface 22, there are inclined surfaces 11 that incline backward and downward from the peripheral edge 23 and the projecting surface 22 toward the outside of the die 10. It has a formed shape, and the molding surface 20 protrudes in front of the die 10.

  Further, on the side of the molding surface 20 where the projecting surface 22 is located, along the peripheral edge 23 of the molding concave surface 21 and the outer peripheral edge of the projecting surface 22, a distance as close as possible to these is given a predetermined depth. A relief groove 12 is formed. Further, the clearance groove 12 is formed by cutting and drilling a prepared hole 24 formed on the side without the projecting surface 22 across the center line of the molding concave surface 21, that is, when the drill portion 4 rotates in the screwing direction. As shown in FIGS. 4 and 5, when the forming blade 24 capable of forming the cutting blade 8 dies 10 and 10 face each other, the forming blade 24 of one die 10 and the relief groove of the other die 10 are disposed. 12 are positions along each other. Specifically, the interval (S) between the forming blade 24 and the side wall 13 of the relief groove 12 is set to be 0.02 mm to 0.03 mm. As a result, when the dies 10 and 10 face each other at high speed, the tip edge of the forming blade 24 slightly enters the escape groove 12 so that the forming blade 24 does not collide with the other die 10. .

  The escape groove 12 has, for example, a trapezoidal cross section in which the opposite entrance sides of the dies 10 and 10 are wide and the bottom side behind the dice 10 and 10 is narrow. It may be a circular or triangular cross section. In addition, the side wall 13 of the escape groove 12 located on the center side of the molding surface 20 is set to an angle that becomes a parallel surface along the inside of the molding blade 24 of the mating die 10, so that the molding blade 24 is connected to the escape groove 12. Contact is more reliably removed.

  In the pair of dies 10, 10 having such a configuration, the leg portions 31 of the screw material 30 shown in FIG. 3 are positioned at a predetermined position between the dies 10, 10 facing each other, and then the dies 10, 10 of each other are positioned. When the front surfaces are brought into contact with each other and the high-speed forging process is performed, plastic deformation is applied to the distal end portion of the leg portion 31. At this time, a burr (not shown) as an extra material jumps outward from the molding surface 20, that is, on the inclined surface 11, and a part of the burr fits into the escape groove 12 at the time of the jump, Bali popping out is restricted. At almost the same time, the forming blades 24 of the dies 10 and 10 reach the position of the clearance groove 12, the burrs are pressed and formed into an ultrathin streak shape, and the shape of the outer periphery of the drill portion of the drill tapping screw 1 is can get. By fitting the burr into the relief groove 12 in this way, the flow of the material is restricted, and a fine structure is obtained without roughening the material structure, and the outer periphery of the drill part 4 has a uniform shape and relatively high strength. A cutting blade 8 is formed.

  As described above, when the screw material 30 is reliably supplied to a predetermined position for each high-speed forging process of the drill portion 4, the drill portion 4 is formed accurately. On the other hand, the screw material 30 is supplied for some reason. When the dies 10 and 10 are brought into contact with each other in a state where they are not, so-called blanking occurs, the molding surfaces 20 collide with each other. Since the dies 10 and 10 at this time are subjected to an inertial force, as shown in FIG. 5, the tips of the forming blades 24 of the forming surface 20 slightly enter the clearance grooves 12. At this time, the forming blade 24 of the forming surface 20 that forms the tip cutting edge 8 of the drill portion 4 protrudes slightly forward from the protruding surface 22, and the lower side of the protruding surface 22 faces rearward and downward. The inclined surface 11 is inclined, and the molding blade 24 of the mating die 10 is adjusted so as not to contact the tilted surface 11 when the molding surface 20 of the mating die 10 approaches again. . Thereby, the shaping blade 24 is not damaged, and the lifetime of the dies 10 and 10 is extended.

  Next, the screw blank 30 in which the drill portion 4 is formed in this way is then supplied to a rolling die (not shown) for rolling the thread 5 to the leg portion 31, and all burrs are removed. Thus, the drill tapping screw 1 having the thread 5 on the leg 31 and the drill 4 at the tip thereof is obtained. The screw tapping times of the drill tapping screw 1 thus obtained and the drill tapping screw 1 obtained by the prior art were measured and compared, and the results are shown in Table 1. The workpiece used in this measurement is a stack of 2 mm cold rolled steel plates (SPCC plates), the nominal diameter of the drill tapping screw 1 is 4.8 mm, the length is 19 mm, the screwing thrust is 245 N, The rotation time was 2500 rpm, and when 10 drill tapping screw samples were each screwed in, the time from the start of screwing to the seating of the screw head seat on the workpiece was measured.

  As a result, the conventional drill tapping screw 1 has an average screwing time of 2.95 seconds, and the drill tapping screw 1 obtained by the present invention has an average screwing time of 2.44 seconds. It was. From this result, it was found that the drill tapping screw 1 obtained according to the present invention was screwed in 0.51 second earlier. This is obtained by quick pilot hole formation due to the difference in accuracy of the drill portion 4 obtained by the forging process with the same nominal diameter and length of the screw, and the difference in the shape of the molding surface 20 of the dies 10 and 10. It was brought about by.

It is an enlarged front view of the shaping | molding process surface of the die | dye in this invention. FIG. 2 is a partial plan view of FIG. 1. It is a perspective view which shows embodiment of the dice | dies by this invention. It is an enlarged principal part top view which shows the matching state of a pair of dice | dies. It is a principal part expanded sectional view of this invention. It is a front view of a drill tapping screw. It is a front view which shows the drill part molding state of the prior art example of this invention. It is a top view except the screw raw material in alignment with the AA of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill tapping screw 2 Head 3 Leg 4 Drill part 5 Thread 6 Cross groove 7 Rake face 8 Cutting blade 10 Die 11 Inclined surface 12 Relief groove 13 Side wall 20 Molding surface 21 Molding concave surface 22 Projection surface 23 Peripheral 24 Molding Blade 30 Screw material 31 Leg

Claims (3)

Opposite to each other so that a cutting edge-shaped drill portion (4) for forming a pilot hole for screwing the screw thread into the workpiece at the tip of the leg portion (3) where the screw thread (5) is formed can be forged. In a pair of forging dies for forging the drill part by butting the molding surfaces (20) arranged in the
A forming blade (24) capable of forming a cutting blade (8) for cutting and drilling a pilot hole when rotating the screw in the screwing direction on one peripheral edge (23) of the forming concave surface (21) having a concave cross section constituting the forming surface. A substantially triangular projecting surface (22) inclined continuously toward the tip is formed on the periphery of the molding concave surface opposite to the molding blade, and projects from the periphery of the molding concave surface. A relief groove (12) having a predetermined depth is formed along the peripheral edge of the surface to form a molding surface of one die (10), and when the molding surfaces of the die are opposed to each other, A die for forging forming characterized in that the tip edge of the forming blade enters into the other escape groove.   2. The die for forging forming according to claim 1, wherein the relief groove is provided at least along a peripheral edge of a forming concave surface forming a body portion of the drill portion. 3. The die for forging forming according to claim 1, wherein the relief groove is formed so that the inlet side is wide and the bottom side is narrow.

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