JPH0742971B2 - Blank and bolt manufacturing method using the blank - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blank for manufacturing a bolt in which a thread of an internal thread can be easily spread, and a method for manufacturing a bolt using the blank.

(Prior Art) For example, a stud bolt, which is formed on a base material and screwed into a screw hole, is provided with a small-diameter guide portion at the tip to improve the biteability into the female screw hole. Has been.

Conventionally, in order to manufacture such a bolt by a rolling method, as shown in FIG. 4, a portion between a large diameter portion (1) on which a screw is rolled and a small diameter portion (2) at its tip is formed. A method of manufacturing a blank (4) having a tapered boundary surface (3) and rolling the blank (4) with a die has been used.

However, in the conventional bolt manufactured in this way, the tip thread applied to the tapered boundary surface (3) among the threads rolled on the large diameter portion (1) is an incomplete thread. ,
As shown in the data to be described later, there is a drawback that the screw is not sharp. Therefore, when the bolt is screwed in, the tip screw thread enters a portion other than the regular female screw of the female screw hole, and if it is forcibly tightened as it is by an automatic machine, seizure may occur.

(Problems to be Solved by the Invention) The present invention solves the conventional problems as described above, and manufactures a bolt in which the tip of the thread is well raised and the bite into the female screw hole is good. It has been completed to provide a new blank that can be manufactured and a method for manufacturing a bolt using this blank.

(Means for Solving the Problem) The above problem is that the boundary surface between the large diameter portion on which the screw is rolled and the small diameter portion at the tip thereof is slightly different from the plane perpendicular to the axis of the blank. Solved by a blank that features a sloping.

Further, the above problem is to manufacture a blank in which a boundary surface between a large-diameter portion on which a screw is rolled and a small-diameter portion at its tip is slightly inclined with respect to a plane perpendicular to the axis of the blank, This is solved by a method of manufacturing a bolt, which is characterized in that a screw is rolled on this blank by a die.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(Embodiment) FIG. 1 shows a blank (4) for manufacturing a stud bolt, which is an embodiment of the present invention. (1) is a large-diameter portion where a screw is rolled, and (2) is The small-diameter portions (2) and (3), which are guide portions formed at the tip thereof, are substantially tapered boundary surfaces formed between the large-diameter portion (1) and the small-diameter portion (2). . In the blank (4) of the invention, this interface (3) is slightly inclined with respect to the plane (5) perpendicular to the axis of the blank (4) as shown in FIG. The size of this inclination angle α is 0.5 to 0.5 of the lead angle β of the screw (6).
It is preferably about 1.5 times.

Such a blank (4) is rolled using a normal die, and a screw (6) is formed on the large diameter portion (1) as shown in FIG.

(Operation) In the bolt of the present invention manufactured as described above, the tip thread thread rolled on the large diameter portion (1) is slightly inclined with respect to the plane (5) perpendicular to the axis of the blank (4). Since it is begun to cut from the boundary surface (3) thus prepared, as shown in FIG. 1, in the portion where the inclination angle α of the boundary surface (3) is opposite to the lead angle β of the screw (6), the threads are It rises rapidly and, conversely, the inclination angle α of the boundary surface (3) on the back side is screwed (6).
In the portion inclined in the same direction as the lead angle β of, the rising edge of the screw thread becomes gentle.

Fig. 3 is a graph showing such a change in thread height for a threaded bolt with a lead angle β of 2.27 °, when the inclination angle α of the boundary surface (3) is 0 ( If the inclination angle α is 1.4 °, which is half the lead angle β,
When the inclination angle α is 2.27 °, which is equal to the lead angle β, and the inclination angle α is 3.4 times, which is 1.5 times the lead angle β, the results of the actual measurement of the change in the thread height in the circumferential direction are shown.

As can be seen from this graph, the bolt manufactured by the method of the present invention rises the screw thread up to 1/2 turn about 50% faster than the conventional product.

Further, the bolt manufactured by the method of the present invention shows a gradual change in the height of the screw thread from 1/2 rotation to 1 rotation, but it does not reach 100% in the graph. It can be seen that the required rotation speed is 5/4, which is smaller than the rotation speed required for the conventional product to reach the complete thread, which is 6/4.

As a result, the bolt manufactured by the method of the present invention can be accurately screwed into the female screw of the female screw hole with a slight rotation, and the biteability to the female screw hole becomes good.

(Effects of the Invention) As described above, the bolt manufactured using the blank of the present invention has a better start-up of the tip thread compared to the conventional product, and reaches a complete thread with less rotation. Therefore, it has good bite into the female screw hole. Further, such a blank can be manufactured without requiring any special technique, and since the thread can be rolled by a conventional die, there is no difficulty in manufacturing.

Therefore, the present invention has an extremely great contribution to the industry as a blank and a bolt manufacturing method using the blank that solves the conventional problems.

[Brief description of drawings]

1 is a front view showing a blank of an embodiment of the present invention, FIG.
The figure is a front view showing the state of rolling the screws on this blank,
FIG. 3 is a graph showing changes in the height of the screw thread in the circumferential direction, and FIG. 4 is a front view showing a conventional blank. (1): Large diameter part, (2): Small diameter part, (3): Boundary surface,
(4): Blank, (6): Screw.

Claims (2)

[Claims] 1. A boundary surface (3) between a large-diameter portion (1) on which a screw (6) is rolled and a small-diameter portion (2) at its tip is a plane (5) perpendicular to the axis of the blank. ) Is slightly inclined to the blank. 2. A boundary surface (3) between a large diameter portion (1) on which a screw (6) is rolled and a small diameter portion (2) at its tip is a plane (5) perpendicular to the axis of the blank. The manufacturing method of the bolt characterized by manufacturing the blank (4) slightly inclining with respect to this, and rolling the screw (6) by a die to this blank (4).