JPS61242740A - Cold forging method for split pin hole of bolt and the like - Google Patents

Abstract

PURPOSE:To form a split pin hole with high efficiency and at low cost by forming a recessed groove with cold forging at the end part of the thread of a bolt and by pressing with contraining the forming end part thereof with nearly globular punch in the split pin hole working of the bolt for automobile, etc. CONSTITUTION:The bolt blank with recessed groove at its tip is made by subjecting the thread end part 5a of a bolt to cold forging with the forming die 7 with projection part. The tip thereof is fitted a backing die 9 and pressed with the punch 8 having nearly globular recessed part 10 on its tip. The bolt tip is drawn to form a split pin hole. This method is highly efficient compared with the conventional punching machining method and the cost is reduced as well.

Description

DETAILED DESCRIPTION OF THE INVENTION 7. Field of Industrial Application The present invention relates to a method for cold forging split pin holes for bolts and the like for automobiles.

Conventional Method As a conventional method for machining split pin holes, there is a method as shown in FIG. 4, for example.

In the figure, the end of a ball stud A is drilled to form a drill hole B, and both ends of the drill hole B are chamfered C.

Problems to be Solved by the Invention However, in this conventional split pin hole drilling method, a narrow and deep hole is machined at right angles to the shaft-shaped portion, so it is difficult to machine the hole during cutting. This method requires a large amount of time, is not economical, and has the problem that the drill is easily broken, increasing the cost of cutting tools.

Means for Solving the Problems The present invention has been made in view of these conventional problems, and is intended to solve the above problems by forming split pin holes by cold forging.

Example The present invention will be explained below based on the drawings.

FIG. 1 is a diagram illustrating an embodiment of the present invention.

First, the configuration will be explained as shown in Fig. 1a (a).

(B) is a side view and an end view of a bolt (ball stud) l completed according to the present invention, in which 2 is a split pin hole, 3 is a drawn portion on the end surface, and 4 is a threaded portion.

The processing procedure is shown in Figure 1, c and d.

First, as shown in b, in the first step, the threaded end of the pole is formed by cold brewing so as to form a concave groove 5.0Then, in the second step, the formed end is shaped into a spherical shape, as shown in c. The split bottle hole 2 is formed by drawing with a punch die 6 or the like having a shape. However, as shown in d above, the threaded portion 4 is formed by thread rolling (or machining is also possible).

That is, the present invention includes the first step of preforming (concave grooves) and the second step of drawing (sweet forming) the forming process of the holes of split bottles of bolts, etc. in the cold brewing process of bolts, etc. By incorporating two processes, the split bottle hole forming is performed at the same time as the pole stud cold brewing process, and thread processing is performed in the subsequent process to complete bolts with split pin holes that do not require cutting.

Figures 2 and 3 each show other embodiments of the present invention, and in each figure, a represents the first step (cold brewing), and b represents the second step (drawing). In each of a and b, (a) is a side view.

(b) is an end view.

The one in Fig. 2 has a thinner side wall 5a of the recessed groove than the one in Fig. 1 to facilitate punching, and Fig. 3 shows a case where the split bottle holes are formed in a cross shape. show.

In Fig. 2.3, 7 is a mold, 8 is a punch mold, and 9 is a mold.
1 indicates a type, and 10 indicates a substantially spherical portion.

As detailed in the description of the invention, the present invention is a ball-studded split pin hole configuration that is performed by press working instead of relying on machining as in the past, reducing machining time and machining costs, and has great practical effects. be.

[Brief explanation of drawings]

FIGS. 1 to 3 each explain the present invention in detail, and in FIG. 1, (a). (b) is a side view and an end view of the finished product; b. c and d are diagrams explaining the order of the processing steps. In FIGS. 2 and 3, a and b are explanatory views of the first and second steps, respectively, and in each figure (a) is a side view and (0') is an end view. FIG. 4 is an explanatory diagram of a conventional example, in which (a) is a side view and (b) is an enlarged cross-sectional view of the part. l...Bolt, 2...Split bottle hole, 3...Drawing part, 4...Threaded part, 5...Concave groove part, 6...
Punch mold, 7... Molding mold, 8... Punch mold, 9...
・The receiver is a type, 10...approximately spherical shaped part. After and

Claims (1)

[Claims] In the method of machining split pin holes for bolts, etc. for automobiles, the first step is to form a concave groove in the threaded end of the bolt by cold forging, and the second step is to form the formed end with a substantially spherical punch die. A method for cold forging split pin holes for bolts, which involves two steps.