JPH0462813B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a bolt for manufacturing a cotter pin hole for fitting a cotter pin for preventing rotation of a nut into a threaded portion of a bolt used in a mechanical part of an automobile, etc. This article relates to methods for machining cotter pin holes.

(Prior Art) As a conventional method of machining split pin holes in bolts, there is a method as shown in FIG. 8, for example.

Figure 8 shows a ball stud used in an automobile ball joint.The lower diameter portion 2 of the ball stud shaft 1 before thread processing is shown.
As shown in enlarged view as part A, a split pin hole 3 is drilled by drilling, and both sides of the drilled hole are chamfered for finishing.

Furthermore, punching out split pin holes using a punch has been proposed instead of drilling using a drill.

(Problems to be Solved by the Invention) However, in the case of drilling using such a conventional drill, since it is a cutting process, processing time is required, and two chamfering processes are required after drilling. Therefore, there was a problem that the number of processing steps increased.

In addition, punching with a punch requires less processing time, but since it is punching into a curved surface, if the bolt axis is not aligned accurately so that the punch axis passes through it, the screws may be damaged. When the punch is driven into the diameter portion, the bolt side moves and bending stress is applied to the punch, which causes the punch to be easily damaged, resulting in a short life span and a lack of economic efficiency.

(Means for Solving the Problems) The present invention has been made in view of these conventional problems, and aims to shorten the processing time by punching, and to reduce bending stress during punching. The purpose of the present invention is to provide a method for machining split pin holes for bolts, which prevents the occurrence of split pin holes and ensures the durability of the punch.

In order to achieve this object, the present invention provides a method for forming split pin holes for bolts used in mechanical parts of automobiles and the like from a direction perpendicular to the shaft. A first step of forming a shallow recess with a diameter approximately the same as or slightly larger than the split pin hole on opposite sides of the pin hole machining position or on one side that will be the punch driving side while restraining the lower diameter portion of the screw; This method includes a second step of punching a split pin hole by driving a punch into the recess formed in the first step.

(Example) FIG. 1 is a cross-sectional explanatory diagram showing the first step in the split pin hole processing method of the present invention.
A cross section is shown in FIG.

In the first step shown in FIGS. 1 and 2, the threaded lower diameter portion 13 of the tip of the bolt 12 to be machined is inserted into the bolt set hole 11 formed in the restraint jig 10.
The outer circumferential portion of the threaded lower diameter portion 13, which will be the processing position, is held down by the restraining jig 10, and the threaded lower diameter portion 13 is split into the threaded lower diameter portion 13 in a fixed state by the illustrated restraining jig 10. Through holes 14 and 15 are provided above and below the machining position of the pin hole, and in the first step, through holes 14 and 15 are provided.
The punches 16a, 16b are pressed against the screw lower diameter portion 13 from above and below through the
By causing plastic deformation that causes the tip portion of the screw to bite into the lower diameter portion 13 of the screw, a shallow recess 18a,
18b are formed at opposite positions. this punch 1
In forming the recesses 18a and 18b by pressurizing the screws 6a and 16b, the screw lower diameter portion 13 is
Since the outer peripheral part is restrained by
The flow of material due to deformation when pressurized by 6a and 16b occurs only in the axial direction, and does not deform the threaded lower diameter portion 13, which has been created to a specified size by rolling or the like.

In addition, the size of the depressions 18a and 18b formed in the lower diameter portion of the thread 13 by pressurizing the punch in the first step is such that the diameter of the depression is the same as or slightly larger than that of the split pin processing hole. .
Further, the shapes of the depressions 18a and 18b are determined depending on the shapes of the tips of the punches 16a and 16b. In this embodiment, since the tip of the punch is spherical, spherical depressions 18a and 18b are formed in the outer peripheral portions of the threaded lower diameter portion 13 on opposite sides in the first step.

FIG. 3 is a cross-sectional explanatory view showing the second step of punching out the split pin hole by driving a punch into the lower diameter portion of the screw where the recess was formed in the first step shown in FIGS. 1 and 2; -The cross section is shown in FIG.

In the second step shown in FIGS. 3 and 4, the depression 1
The bolt 12 formed with 8a and 18b is held in the restraining jig 2.
A punch guide hole 22 is formed on the recess 18a side of the threaded lower diameter portion 13 in the assembled state by inserting it into the bolt set hole 21 of No.
Further, a scrap removal hole 23 is opened on the side of the depression 18b, and the entrance side of the scrap removal hole 23 is opened in the depression 1.
The small diameter hole 23a corresponds to the diameter of 8b,
With the bolt 12 set on the restraint jig 20, the punch 24 is driven into the recess 18a through the punch guide hole 22, and the lower diameter portion 13 of the screw is punched out from the recess 18a toward the recess 18b as shown in the figure. A split pin hole 25 is punched out. The scrap 26 generated by punching out the split pin hole 25 with the punch 24 is
The scraps are discharged to the outside from the lower scrap removal hole 23.

In the punching process of split pin holes using the punch 24, since the recess 18a is previously formed in the first step on the outer peripheral surface of the lower diameter portion 13 of the screw into which the punch 24 is driven, the punch 24 is However, punch 24
Hollow 18 with the same or slightly larger diameter
By stabilizing the tip of the punch, bending of the punch that occurs during punching can be reliably prevented. Furthermore, punch 2
In the first step, a recess 18b that is the same as or slightly larger than the punch 24 is also formed in the lower diameter portion 13 of the thread, which is the punching side of the punch. Deformation is absorbed and burrs on the punching side can be prevented.

Figures 5 and 6 show other shapes of the recesses formed in the first step shown in Figures 1 and 2. Figure 5 shows that the tip of the punch is shaped like a truncated cone so that the hole can be screwed in the first step. Trapezoid-shaped depressions 26a and 26b are formed on opposite sides of the lower diameter portion 13, and FIG. 6 shows that by using a punch with a conical tip in the first step, the opposite sides of the lower diameter portion 13 are Conical depressions 27a and 27b are formed on both sides.

When the trapezoidal conical or conical depressions shown in FIGS. 5 and 6 are formed in the first step, the third and fourth
The punch used for punching split pin holes in the second step shown in the figure has a shape opposite to the depression formed in the first step, for example, in the case of FIG. 5, it has a truncated conical tip. In the case of FIG. 6, it is preferable to use a punch with a conical tip.

FIG. 7 shows a more specific example of the first step of the split pin hole machining method of the present invention for automobile ball studs, in which the ball stud 30 is housed in a socket via a bearing. It has a ball portion 30a and a shaft portion 30b integrally formed with the ball portion 30a, and the tip of the shaft portion 30b becomes a threaded lower diameter portion 13.
Drill a split pin hole in 3. Therefore, as the bolt set hole 11 of the restraining jig 10 used in the first step, the lower diameter portion 13 of the screw where the split pin hole is to be machined is restrained and fixed in a hole shape that matches the shaft portion 30b of the ball stud 30. Punches 16a and 16b for forming a depression are pressurized from both sides of the portion 13. When pressurizing the punches 16a and 16b to form a recess, since the outer periphery of the lower diameter portion of the screw is tightened by the restraining jig 10, the direction toward the tip of the shaft portion and the ball portion 3
The material flows toward the 0a side, causing deformation in the axial direction on both sides. However, since the length from the center of the ball part 30a to the split pin hole processing position must be a specified dimension, the axial restraint jig 32 is brought into contact with the tip of the ball part 30a in the axial direction.
When a depression is formed with the punches 16a and 16b, the axial deformation occurs only in the direction of the tip of the shaft portion 30b, and even if the depression is formed by the pressure of the punches 16a and 16b, the cotter pin hole is removed from the center of the ball portion 30a. The specified dimensions up to the center remain unchanged.

The use of such an axial restraint jig 32 is
It is also used in the second step in which a punch is driven into the recess formed in the process, and even if axial deformation occurs during the punching process, it will not affect the specified dimensional relationship required for the ball stud 30. I try not to let it affect me.

In the above embodiment, the depressions were formed on both the driving side and the punching side in the first step, but the depressions may be formed only on the driving side.

(Effect of the invention) As explained above, according to the present invention, the first
In the process, while restraining the lower diameter portion of the screw before drilling the threaded hole of the bolt, a shallow recess with approximately the same or slightly larger diameter as the split pin hole is formed on either side of the split pin hole processing position or on one side that will be the punch driving side. death,
In the second step, a punch is driven into the recess formed in the first step to punch out the cotter pin hole, so a recess is pre-formed in the processing area where the punch will be inserted in the pre-punching step. Since a punch with the same diameter or slightly smaller diameter is driven into the recess, the stability of the punch tip during driving is ensured, the bending of the punch due to driving is reliably prevented, and the durability of the punch used for punching is increased. In addition, the cotter pin hole can be drilled almost perpendicular to the shaft, and if the size and depth of the recess to be formed in the first step are determined appropriately, the recess can be formed on both sides of the cotter pin hole. The same processed shape as chamfering can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the first step in the processing method of the present invention, Fig. 2 is a - sectional view of Fig. 1,
Figure 3 is a sectional view showing the second step in the processing method of the present invention, Figure 4 is a cross-sectional view of Figure 3, and Figures 5 and 6 show the types of depressions formed in the first step. FIG. 7 is an explanatory cross-sectional view showing a first step of a specific example of machining a split pin hole for an automobile ball stud, and FIG. 8 is an explanatory view showing a conventional method. 10, 20: Restriction jig, 11, 21: Bolt set hole, 12: Bolt, 13: Lower diameter portion of screw, 1
4, 15: Through hole, 16a, 16b: Punch, 1
8a, 18b: depression, 23: scrap removal hole,
24: Punch, 25: Cotter pin hole, 26:
Scrap, 30: Ball stud, 30a: Ball portion, 30b: Shaft portion, 32: Axial restraint jig.

Claims (1)

[Scope of Claims] 1. In a method of machining split pin holes for bolts used in mechanical parts of automobiles, etc., in which a split pin hole is formed through the bolt from a direction perpendicular to the axis of the bolt, A first step of forming a shallow recess with a diameter approximately the same as or slightly larger than the split pin hole while constraining the diameter portion on opposite sides of the split pin hole processing position or on one side that will be the punch driving side; A method for machining cotter pin holes for bolts, comprising a second step of punching a cotter pin hole by driving a punch into the formed recess.