JPH0211946Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is for bolt rolling, which can economically roll bolts with threads formed right below the bearing surface of the bolt head. It's about dice.

(Prior art) Rolled bolts are manufactured by a method in which a blank is sandwiched between a movable die and a fixed die that have threads with a constant lead angle, and the threaded portion is formed by rolling the bolt. If the lower surface of the head of the blank comes into contact with the die during the process, the die may be damaged or the lower surface of the blank's head may be damaged, so it is necessary to provide sufficient space between the upper end of the threaded part and the lower surface of the head. . This interval is called the x dimension in the industry, and when bolt rolling is performed using conventional bolt rolling dies, it is difficult to make this x dimension less than 1.0 times the bolt pitch. was. However, in recent years, steel plates for automobiles have become thinner in order to save fuel, reduce weight, improve formability, etc., and the bolts used to fasten them are also threaded to the part directly below the bearing surface of the bolt head. There is a strong need to form a

In order to meet these demands, we have developed methods such as eliminating the chamfering of the die and firmly pressing the head of the blank to perform bolt rolling, and using wedge-shaped dies to gradually reduce the x dimension of the chamfered part. , Bolt rolling methods such as reducing the pitch to 0.5 or less in the final finished part have been attempted. However, with these methods, it was difficult to adjust the setup, and the dies were frequently chipped and worn, resulting in economical problems.Furthermore, the bearing surface side of the bolt was easily damaged, resulting in quality problems.

(Problems to be solved by the invention) The present invention solves the above-mentioned problems of the conventional technology, and economically transfers bolts whose threads are formed directly below the bearing surface of the bolt head. It was developed with the aim of creating bolt rolling dies that can be used to form bolts.

(Means for solving the problem) The present invention has a lead angle β of the terminal thread formed at the end of the die surface which is larger than the lead angle α of the normal thread. This is a characteristic feature.

(Embodiment) Next, the present invention will be explained in detail with reference to the illustrated embodiment. 1 is a fixed die, 2 is a movable die, and both the fixed die 1 and the movable die 2 are used to roll a bolt to be rolled. In addition to being carved with a threaded portion 3 and a biting portion 4 with a normal lead angle α calculated from the pitch P and its effective diameter D using the formula α=tan ^-1 (P/π・D). , each terminal end is provided with a terminal thread 5 having a lead angle β larger than the normal lead angle α over a length of at least one revolution of the blank 10. The length of the terminal thread portion 5 may be longer than one rotation of the blank 10, but in order to form a thread around the entire circumference of the blank 10, it is sufficient to have a length of one rotation. Therefore, in order to shorten the length of the die, it is most economical to make it the length of one rotation as in the embodiment. The deviation A of the thread due to a change in the lead angle at the terminal end is determined by the distance x between the head 11 of the blank 10 and the end face of the die when rolling is performed using the thread 3 with the lead angle α. shall be set. Further, as shown in FIG. 2, a V-groove 6 is recessed in the starting position of the biting portion 4 of the movable die 2 for reliably feeding the blank 10. In the embodiment, the lead angle of the terminal thread part 5 was set to β over its entire length, but a part with another lead angle γ was provided in the middle of the lead angle α of the normal thread part 3 to create a stepwise shape. It may also be changed from α to γ to β.

(Function) As shown in FIG.
A screw is rolled on the shaft portion 12 of the blank 10 by supplying the blank 10 with the blank 1 and moving the movable die 2 in the direction of the arrow. This thread rolling is first carried out by the conventional method using the thread portion 3 of each die with a normal lead angle α, and as shown in FIG. Since the blank 10 is supplied to the biting part 4 of the die with a small distance x between it and the end face of x from the head 11 of the shaft portion 12
The screw is rolled to a position that is 100 mm apart. Next, if the movable die 2 is further moved in the direction of the arrow from this state, the lead angle β formed at the end of each die over a length of at least one rotation of the blank 10 is larger than the normal lead angle α. The blank 10 is moved toward the die side by the terminal thread portion 5, and the thread is rolled up to the vicinity of the head 11. At this time, the movement of the blank 10 is performed by engaging the thread already carved on the blank 10 by the threaded portion 3 with the terminal threaded portion 5, so the amount of movement must be strictly controlled. In addition, since the blank 10 is only slightly rotated during this time to perform thread rolling at the distance of x, the head 11 can be rotated without making the bearing surface of the head 11 come into contact with the end surface of the die. The thread can be rolled to the position just before the seat surface of the part 11, and as a result, the threaded part 13 is formed up to the vicinity of the head 11, as shown in FIG. 5, making the bolt advantageous for tightening thin plates, etc. can be obtained by the rolling method.

(Effects of the invention) As is clear from the above explanation, the present invention allows the blank to be moved toward the die side using the end screw thread with a large lead angle provided at the end of the die, and the screw can be rotated to the vicinity of the head. This method solves the problems of the conventional method, as it is possible to easily and economically manufacture a bolt with a threaded part near the head without damaging the die or the lower surface of the bolt head. As a bolt rolling die, its practical value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a plan view of a fixed die according to an embodiment of the present invention, FIG. 2 is a bottom view of the movable die, FIG. 3 is a side view showing the state at the start of rolling, and FIG. 4 is a plan view thereof. FIG. 5 is a front view of a bolt manufactured using the die of the present invention. 3... Normal thread part, 5... Final thread part,
10...Blank.

Claims (1)

[Scope of utility model registration request] The lead angle of the terminal thread part 5 formed at the end part of the die surface is set to the lead angle α of the normal thread part 3.
A bolt rolling die characterized by having a lead angle β larger than .