JPS58205637A - Die for cold forging - Google Patents

Abstract

PURPOSE:To prevent occurrence of cracks in forming members at the time of forging and simplify the constitution of the die, by constituting the forming hole in the die body with plural forming members and, at the same time, by installing a hole through which a knockout pin is inserted, to the lower part of the forming hole. CONSTITUTION:A forming member 12 is fitted to the upper half part 2a of a reception hole 2 in a die body 1 and a forming hole 4 having a nearly hexagonal cross section and a knockout pin inserting hole 6 communicating with a concaved part 7 and the forming hole 4 are formed on the center line of the forming member 12. Moreover, the forming member 12 is equally divided into six parts by three planes containing the central axis of the hole 6 and two angular parts of the forming hole 4 which are opposed to each other, respectively, and each split piece 12a is closely contacted with each other. Since each split piece 12a can be deformed individually against elastic force when a nut is forged by placing a metallic material having a nearly cylindrical shape in the forming hole 4 and by pressing the metallic material with a pressure pin, the breakage of the forming member 12 by the angular part of the forming hole 4 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a mold for cold forging bolts, nuts, etc.

BACKGROUND OF THE INVENTION Conventionally, in this type of cold forging die, a housing hole 2 with a circular cross section extending vertically is formed in the center of a main body 1, as shown in FIG. 1-2. The housing hole 2 has an upper half portion 2a whose inner circumferential surface is sloped in the direction of extrusion of the nut, that is, from the bottom to the top.
and a lower half 2b that is continuous to the upper half 2a. A first molded member 3 is fitted into the L half portion 2a, and a molded hole 4 having a hexagonal cross section is provided in the center thereof. Below the first molded member 3, a second molded member 5 having substantially the same external shape as the inner circumferential surface of the upper half 2a is press-fitted into the upper half 2a. A knockout pin insertion hole 6 communicating with the molding hole 4 is provided in the center of the second molded member 5, and a recess 7 is provided in the upper surface of the second molded member 5 to form a round end face. formed). Further, the molded hole 4, the recess 7, and the insertion hole 6 are arranged on the same axis. A notch 8 for air venting is formed on the outer peripheral edge of the upper surface of the second molded member 5, and a narrow groove 9 is formed in the main body 1 so as to communicate with this notch 8. Further, a support member 10 is press-fitted into the lower half 2b of the housing portion 2, and an insertion hole 11 for a knockout pin is formed in the center of the support member 10, which communicates with the insertion hole 6 of the second molded member 5. has been done.

In this conventional structure, a substantially cylindrical metal material is press-fitted into the molded hole 4, and a nut is forged to match the inner surface shape of the molded hole 4 and the shape of the recess 7.

When the nut is forged in the forming hole 4, the air between the forming hole 4 and the metal material M is removed by a knockout pin (not shown) that is moved back and forth in the insertion holes 6 and 11. Joint surface and notch 8 of the same molded member
It is discharged outward from the narrow groove 9 through. However, in this conventional configuration, since a large pressure is applied to the recess 7 during nut forging, the second molded member 5 tends to break more quickly than the first molded member 3. Therefore, although the first molding member 3 can be used, there is a drawback that the entire mold body 1 becomes unusable due to damage to the second molding member 5.

In addition, in this conventional configuration, since the first molded member 3 and the second molded member 5 are formed separately, it is necessary to assemble the molded hole 4 and the insertion hole 6 so that their central axes coincide with each other. It is necessary to form a notch 8 for air venting, and this requires high processing precision, resulting in an increase in the manufacturing cost of each component.

Furthermore, during nut forging, large pressure is applied to the inner peripheral surface of the molding hole 4, so there is a risk that the first molding member 3 will break at the corner of the molding hole 4 and its pieces will scatter outside the main body 1. there were.

Purpose This invention was made in order to eliminate the above-mentioned defects, and its purpose is to simplify the configuration and to
Another object of the present invention is to provide a cold forging die that can prevent damage to a second molded member and is easy to assemble.

EXAMPLE An example embodying this invention is shown in FIGS. 3 to 6.
This will be explained according to the diagram. In this embodiment, the configurations of the main body 1, the accommodation hole 2, the insertion hole 11 of the support member 10, etc. are the same as those of the conventional configuration, and therefore will be described using the same reference numerals.

Now, a molded member 12 having approximately the same external shape as the inner peripheral surface of the upper flat part 2a is fitted into the -L half part 2a of the accommodation hole 2, and a cross section of approximately A hexagonal molded hole 4 and a knockout pin insertion hole 6 communicating with the molded hole 4 are formed. Further, a recess 7 is formed in the molded member 12 at the boundary between the molded hole 4 and the insertion hole 6. The molded member 12 is divided into six pieces along a plane including the central axes of the molded hole 4 and the insertion hole 6 and the inside of the molded hole 40, and each divided piece 12 is in close contact with the upper half of the accommodation hole 2. It is housed in the section 2a.

Therefore, when forging a nut in this embodiment, the tip protrusion of the knockout pin is placed in the molding hole 4 as shown in FIG. The metal material is pressed toward the recess 7 from above the mold body 1 by the pressing bottle 13, and a nut is forged according to the inner surface shape of the recess 7 and the molding hole 4. After a recess 14 is formed at the center of both upper and lower surfaces of the metal material M by the tip protrusion of the knockout pin and the tip protrusion of the suppressing pin 13, the knockout pin is moved upward to tighten the nut. is pushed upwards. Note that this recess 14 is provided to facilitate the formation of a screw hole after the nut is forged.

In addition, in this embodiment, when a large pressure is applied to the inner circumferential surface of the forming hole 4 during nut forging, each divided piece 12a resists its own elastic force, as shown by the dashed line in FIG. Therefore, the molding member 12 can be prevented from being damaged from the corners of the molding hole 4. Further, based on the deformation, a gap is formed between each divided piece 12a and the metal material M, and air is discharged from the gap. Therefore, unlike the conventional structure, there is no need to form the notch 8 and narrow groove 9 for air venting in the molded member 12 and the main body 1, and the structure can be simplified.

Further, since the molded member 12 is not divided in the vertical direction, there is no need to align the central axes of the molded hole 4 and the insertion hole 6 when assembling the molded member 12, and the assembly can be easily performed.

Effects As detailed above, the present invention has a molding hole for forging a raw material according to the inner shape of the raw material and a molding hole connected to the molding hole on one axis of the molding member fitted into the accommodation hole of the mold body. In addition, by providing a knockout pin insertion hole having an inner diameter at least smaller than the molding hole, and dividing the molded member into a plurality of pieces along a plane including the -axis line, cracking of the molded member during forging can be prevented. This has excellent effects in that it can be prevented, the structure can be simplified, and it can be easily assembled.

[Brief explanation of drawings]

1 and 2 show a conventional example of the present invention, in which FIG. 1 is a plan view of the mold, and FIG. 2 is a sectional view. Third
The figures k""'e show one embodiment of the present invention, in which Fig. 8 is a plan view of the mold, Fig. 4 is a sectional view, and Fig. 5 is a sectional view of the mold.
The figure is a perspective view of the molded member, and FIG. 6 is a sectional view of the main part during forging. Mold body 1, accommodation hole 2, molding hole 4, insertion hole 6, molding member 1
2. Knockout pin K, metal material M. Patent Applicant Masu Ogawa, Attorney On, Patent Attorney 1) Hiroshi Nobuo, Figure 8, Figure 41!1

Claims (1)

[Claims] l. On the -axis of the molding member (12) fitted into the accommodation hole (2) of the mold body (1), there is a molding member for forging the raw material (M) according to its inner shape. a hole (4), and an insertion hole (K) for a knockout pin (K) that communicates with the molded hole (4) and has an inner diameter at least smaller than that of the molded hole (4);
6), and the molding member (12) is divided into a plurality of pieces along a plane including the -axis. 2. The inner circumferential surface of the accommodation hole (2) and the outer circumferential surface of the molded member (12) are characterized in that they form an oblique shape that is inclined toward the extrusion direction of the forged product forged in the molded hole (4). A mold for cold forging according to claim 1.