JPH08267166A - Roll forming method for shaftlike metallic parts - Google Patents

Abstract

PURPOSE: To produce rolled thread, which has less deformation through thread cutting with roll dies, by performing thread rolling on the outer diameter of a base material machined slightly smaller in the outer diameter in the center of a shaftlike metallic part than that of both ends before roll forming. CONSTITUTION: A shaftlike metallic part, i.e., round bar like object 3 to be worked is held in roll dies consisting of a fixed die 6 and a movable die 7, so that threading is performed on the outer diameter of the object 3 by operating roll dies. Before this threading, the size of the outer diameter D1 in the center 10 of those 11, 10, 12 of the object 3 to be threaded is formed with a reduced size slightly smaller than the outer diameter D2 of both ends 11, 12, 13. The reason is that the diameter is reduced in the equivalent to an excess thickness produced at the time of thread rolling of the object 3 by the roll dies, so that uneven thickness and pressure are absorbed which are due to plastic deformation caused by roll forming and that the deformation of the object is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a flat-rolling method for processing a highly accurate screw on the outer diameter of a shaft-shaped metal part.

[0002]

2. Description of the Related Art Screws generally obtained by rolling are
The precision is low, so it is limited to applications that do not require precision such as fastening. For this reason, if you need highly accurate screws,
Expensive screws manufactured by cutting with an automatic lathe are used. Usually, when a screw is rolled to the outer diameter of a straight round bar, it is common to perform rolling by using the raw material of the straight round bar as in the case of the product. When rolling a workpiece made of straight round bar material,
As shown in FIG. 2, since the rolling work is performed in a free state only by sandwiching the workpiece with the rolling dies, bending or deformation occurs due to plastic deformation during the working. In addition, when the shape of a straight round bar, especially a small-diameter round bar, is rolled, the outer diameter of the threaded portion after rolling will vary due to distortion such as plastic deformation. To produce
Not only can a uniform screw shape not be obtained, but these distortions also cause the bending of the entire screw to be further increased. For this reason, conventionally, it is necessary to correct the bend after the rolling process, and since the deformation such as the bend is irregular, there is the troublesomeness of having to correct it manually. It is also becoming.

[0003]

By the way, the deformation such as the bending of the rolling screw that occurs during the conventional rolling process described above is caused by the pressure applied from the rolling die to the thread portion of the workpiece during the rolling process of the screw. Since it is generated by the plastic deformation stress caused by, it has been found that the problem can be solved by forming the shape in which the stress concentration is dispersed and forming a work that requires as little force as possible, and then performing the rolling process. did. Therefore, before rolling, the outer diameter of the intermediate part of the thread rolling part of the workpiece, that is, the round bar material is formed to be slightly smaller than the outer diameter of both ends to form a sudden diameter due to plastic deformation. A shape for relieving stress concentration is provided in advance on a workpiece to perform thread rolling. Also,
When performing thread rolling, the workpiece is held at three or more points including both end surfaces and the outer diameter of the workpiece, and the bending of the workpiece is corrected simultaneously with the thread rolling. are doing. Further, the center for holding both ends of the work piece is configured to apply the pressure of the elastic or fluid pressure cylinder to the work piece from both ends to hold the work piece.

[0004]

According to the method for rolling a shaft-shaped metal component of the present invention, the outer diameter of the central portion of the round bar material of the workpiece to be screwed is set before the rolling. Formed by reducing the diameter slightly smaller than the outer diameter of both ends, so that the amount of plastic deformation generated by the pressure applied to the workpiece from the rolling die is absorbed by the reduced diameter portion, and rolling with less deformation is performed. It is characterized in that it is configured in. In addition, when rolling is performed, both ends of the work piece are held by the center, and one or two or more locations of the outer diameter of the unrolled portion outside the rolling die are held by the guide portion. The present invention is characterized in that the bending of the workpiece is corrected simultaneously with the thread rolling process. Furthermore, a center that holds both end surfaces of the work piece
Is characterized in that one end face is supported by the pressure of the elastic body, and the other end face is supported by the pressure of the fluid pressure cylinder.

[0005]

According to the rolling method described above, the thread rolling process is performed on the workpiece in which the outer diameter of the central portion of the workpiece before thread rolling is reduced to be slightly smaller than the outer diameter of both ends. By doing so, the plastic deformation stress generated at the time of rolling is absorbed by the reduced diameter portion, so that it is possible to manufacture a rolled screw with little deformation even if the screw is processed using a rolling die.

[0006]

Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 shows an embodiment of a method for rolling a shaft-shaped metal part according to the present invention. That is, the work piece 3 in the shape of a round bar is sandwiched by a rolling die composed of a fixed die 6 and a moving die 7, and the rolling die is operated to form a screw W on the outer diameter of the work piece 3. Prior to this processing, the outer diameter dimension D of the central portion 10 of the outer diameter portions 11, 10 and 12 of the workpiece on which the screw W is processed
1 is formed to have a diameter slightly smaller than the outer diameter D2 of both ends 11, 12, and 13. This reduces the diameter by an amount corresponding to the surplus wall generated when the screw is rolled on the workpiece 3 by the rolling die, absorbs uneven thickness and pressure due to plastic deformation generated during rolling, and It is provided so that the amount of deformation of is reduced as much as possible. Also, the workpiece 3
Is a guide portion 4 or 5 which supports both end surfaces thereof at the centers -1 and 2 and holds necessary portions of the outer diameter portion of the unrolled portion 13 at one point or at two or more points. It is provided to correct the bending that occurs during thread rolling. The centers-1 and 2 for supporting both end surfaces of the workpiece are configured such that one is supported by the pressure of an elastic body such as a spring and the other side is supported by fluid pressure such as air pressure or hydraulic pressure. At the time of thread rolling, the support pressure balance of the center that supports both ends of the work piece can be balanced on the average while responding to the stretching stress in the axial direction due to the plastic deformation that occurs in the work piece. The bending stress applied to the work piece is provided to be as small as possible to prevent the work piece from bending.

[0007]

As described above, according to the method for rolling a shaft-shaped metal component of the present invention, the outer diameter of the central portion of the shaft-shaped metal component is made slightly smaller than the outer diameter of both ends before rolling. In addition to performing thread rolling on the machined product, both ends of the shaft-shaped metal part are supported by elastic bodies and a center held by fluid pressure when rolling, and the outer diameter of the part that is not rolled Since the guide portions 4 and 5 that hold one or more portions are provided to correct the bending that occurs during thread rolling, the plastic deformation stress generated during rolling processing is reduced in diameter. Since both centers that support both ends of the shaft-shaped metal part are supported by the elastic body and fluid pressure, there is little deformation even when performing rolling using a rolling die. A screw can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a rolling processing method for processing a rolled screw according to the present invention.

FIG. 2 is a perspective view showing a state where a rolling screw is processed by a conventional rolling die.

[Explanation of symbols]

 1 center 2 center 3 work piece 4 guide part 5 guide part 6 fixed die 7 moving die 8 elastic body 9 fluid pressure cylinder-10 central part of work piece 11.12.13 both ends of work piece

Claims (3)

[Claims] 1. A method for rolling an external thread on a shaft-shaped metal part, wherein the outer diameter of the central part of the shaft-shaped metal part is machined to be slightly smaller than the outer diameter of both ends before rolling. A thread rolling method characterized by performing thread rolling on the outer diameter of a material. 2. Thread rolling by holding both end surfaces of a shaft-shaped metal part at the center during rolling and holding the outer diameter portion of the portion not subjected to rolling processing at one place or at two or more places. The rolling method according to claim 1, wherein the rolling is performed. 3. A means for holding both end faces of a shaft-shaped metal part by a center when performing a rolling process, wherein one center is configured to be supported by the pressure of an elastic body and the other center is supported. 2. The rolling processing method according to claim 1, wherein is supported by fluid pressure-cylinder pressure.