JPH0457411B2 - - 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, it takes time because it is a cutting process, and it requires two steps of drilling and chamfering after drilling. There was a problem in that the number of man-hours required for processing 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 a cotter pin hole for bolts used in mechanical parts such as automobiles, in which a cotter pin hole is formed through the bolt from a direction perpendicular to the axis of the bolt. The lower diameter part of the screw is wrapped in a restraint jig and fixed, and the inner diameter is about the same as a split pin hole and the outer diameter is the same as that of a cotter pin hole by passing through the restraint jig into the lower diameter part of the screw that has been restrained and fixed. Press a cylindrical holding jig whose diameter is 1.5 to 2 times the diameter of the split pin hole to pressurize and deform the split pin hole machining area at the lower diameter of the bolt, and then insert a punch through the holding jig into the lower diameter of the screw. The split pin hole is punched out by driving into the part.

(Example) FIG. 1 is a cross-sectional view showing the configuration of an apparatus for realizing the processing method of the present invention, and FIG. 2 is a cross-sectional view thereof.

In FIGS. 1 and 2, reference numeral 10 denotes a restraining jig for restraining and fixing the lower diameter portion 12 of the bolt 11 at the hole drilling position. Diameter portion 12
As shown in the figure, press fit and secure in a wrapped state. A through hole 15 is penetrated above the bolt set hole 13 in the restraining jig 10 from a direction perpendicular to the axis 14 of the bolt 11, and a holding jig 16 is mounted in the through hole 15. This presser jig 1
6 is the presser jig 16 when the diameter of the split pin hole 20 shown by the imaginary line to be machined in the lower diameter portion 12 of the screw is d.
The inner diameter d1 of the holding jig 16 is approximately the same as the diameter d of the split pin hole 20, and the outer diameter d2 of the presser jig 16 is an outer diameter that is 1.5 to 2 times that of the split pin hole 20, that is, d2=1.5.
The size is ~2×d.

A punch 18 is passed through the presser jig 16, which has such a dimensional relationship between the inner and outer diameters with respect to the split pin hole, as shown in the figure, to punch out the split pin hole 20 in the threaded lower diameter portion 12.

A scrap removal hole 19 is formed at a lower position opposite to the through hole 15 into which the presser jig 16 is attached, and the entrance portion of the scrap removal hole 19 is connected to the small diameter hole 1.
9a, and the scrap punched out from the lower diameter portion 12 of the thread by driving the punch 18 is discharged to the outside.

Figures 3, 4, and 5 show a presser jig 16 used in the apparatus configuration for realizing the processing of the present invention shown in Figures 1 and 2.
Fig. 3 shows a flat pressing surface 21 with the pressing surface on the lower diameter portion of the bolt thread being a flat surface, and the holding jig shown in Fig. 4 has a pressing surface 21 with the pressing surface on a circular arc. It has a notched curved pressing surface 22, and the radius R of this curved pressing surface 22 is the radius of the lower diameter portion of the thread of the bolt 11 in FIGS. 1 and 2. Furthermore, the fifth
The holding jig 16 shown in the figure has a V shape on the pressing surface to the lower diameter portion of the screw.
It is characterized by the provision of a V-shaped circumferential protrusion 23, which allows for easy biting into the machined surface.

Next, a split pin hole machining method of the present invention realized by the above-described apparatus configuration will be explained.

First, as shown in FIG. 1, the threaded lower diameter portion 12 of the bolt 11, which will be the part to be machined with the split pin hole, is press-fitted into the bolt set hole 13 of the restraint jig 10, and the lower threaded part, which will be the machined part, is wrapped around it. In this restraint fixing, bolt 11
Movement around the axis and in the axial direction is restricted.

Next, as shown in FIG. 6, pressure is applied from the direction shown by the arrow to the holding jig 16 attached to the through hole 15 of the restraint jig 10, and the tip of the holding jig 16 is pressed against the threaded lower diameter portion 12 of the bolt 11. The pressing jig 16 tightens the threaded lower diameter portion 12 to be processed, and also connects the bolt set hole 13 of the restraining jig 10 with the threaded lower diameter portion 1.
2, and furthermore, a bulge 24 of extra thickness is formed by pressurized deformation in the inner diameter hole of the holding jig 16 which becomes a punch guide hole.

While maintaining the pressurized state of the presser jig 16 shown in FIG. 6, the punch 18 is driven into the lower diameter portion 12 of the thread through the inner diameter hole of the presser jig 16, which serves as a punch guide hole, as shown in FIG. A split pin hole 20 is formed by punching as shown in the figure, and the scrap 25 produced by this punching is discharged to the outside from the lower scrap shaft hole 19.

According to the cotter pin hole machining method of the present invention, the bolt 11 is first set in the bolt set hole 13 of the restraint jig 10 and restrained and fixed, so that the axial center line of the punch 18 is uniquely aligned with the axis of the bolt 11. Correct machining positioning that passes through the center line from a direction perpendicular to the center line can be performed, and in this state, the stress caused by driving the punch 18 is directed in the direction of the center axis of the bolt 11, so that the bolt 11 rotates around the axis when receiving the driving stress. It does not move, and bending stress applied to the punch 18 due to movement around the axis can be reliably prevented.

In addition, when punching with the punch 18, the presser jig 16 is pressed against the threaded lower diameter portion 12, which is the processed portion, and excess thickness 24 is formed inside due to processing deformation.
The movement of the bolt 11 during the punching process is further restricted in order to tighten it to the extent that it can be tightened, and since the punch 18 is driven into the bulge 24 caused by pressing the presser jig 16, the impact of the punch 18 is The breaking stress concentrates on the bulge 24, and as a result, the split pin hole 2 formed by punching
The machined surface of the 0 becomes clean, and unnecessary build-up and burrs on the driving side can be reliably prevented.

The properties of the bulge 24 due to excess thickness when pressurized with this presser jig 16 vary depending on the shape of the tip surface of the presser jig 16, as shown in FIGS. 3, 4, and 5. Rather than the flat pressing surface 21 shown in FIG. 3, the curved pressing surface 22 shown in FIG. According to the pressing surface equipped with the V-shaped circumferential protrusion 23, the cutting on the driving side of pin hole machining by punching is performed by the biting of the V-shaped circumferential protrusion 23, so that the punching process using a punch can be performed more appropriately. becomes possible.

(Effects of the Invention) As described above, according to the present invention, the lower diameter portion of the bolt before thread processing is wrapped and restrained with a restraint jig, and the lower diameter portion of the screw that is restrained and fixed is Penetrate the restraining jig and press a cylindrical holding jig whose inner diameter is about the size of a cotter pin hole and an outer diameter of 1.5 to 2 times that of the cotter pin hole from a direction perpendicular to the bolt axis to remove the lower diameter of the bolt. The part to be machined for the cotter pin hole is deformed under pressure, and then a punch is driven into the lower diameter part of the screw through the inner diameter hole of the holding jig to punch out the cotter pin hole, so the processing is performed prior to the punching process. Since the lower diameter part of the screw is pressurized with a holding jig, the strength of restraint and fixation of the lower diameter part of the screw to be machined is more reliable, and the build-up that occurs due to pressure deformation by the holding jig is further improved. Since the punch is driven into the part, the necessary stress concentration for the driving process can be obtained more appropriately.Furthermore, by tightening and fixing the lower diameter part of the screw with the holding jig and guiding the punch with the holding jig, the appropriate processing position can be achieved. is held, so no bending stress is applied to the punch during driving, and even if the driving punch tries to bend due to the reaction force caused by driving, the punch is held through the holding jig, so the holding jig does not bend the punch. The guiding action reliably prevents the punch from being bent due to the reaction force, which reduces the processing time for punching and also improves the durability of the punch by reliably preventing the punch from bending. Guaranteed and highly economical split pin hole machining is possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of an apparatus for carrying out the processing method of the present invention, and FIG. 2 is a -
3, 4 and 5 are explanatory diagrams showing the presser jig used in the first and second device configurations, FIGS. 6 and 7 are explanatory diagrams showing the processing method of the present invention, and FIG. FIG. 2 is an explanatory diagram showing a conventional method. 10...Restraint jig, 11...Bolt, 12...
Lower diameter part of screw, 13... Bolt set hole, 14...
...Center axis, 15...Through hole, 16...Press jig, 18...Punch, 19...Scrap removal hole, 19a...Small diameter hole, 20...Cotter pin hole, 2
1... Flat pressing surface, 22... Curved pressing surface, 2
3... V-shaped circumferential projection, 24... swell, 25...
... Scrap.

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, The diameter portion is wrapped and restrained with a restraint jig, and the lower diameter portion of the screw that is restrained and fixed is penetrated through the restraint jig and the inner diameter is about the same as a split pin hole and the outer diameter is Press a cylindrical holding jig whose diameter is 1.5 to 2 times the diameter of the split pin hole to pressurize and deform the split pin hole machining area at the lower diameter of the bolt, and then pass the punch through the holding jig and insert a punch into the lower diameter of the screw. A method of machining split pin holes for bolts, which is characterized by punching the split pin holes by driving them into the parts.