JP2552890B2 - Screw rolling die - Google Patents

Description

TECHNICAL FIELD The present invention relates to a die for rolling a thread on a shaft portion of a screw material having a head portion formed on a base end side. .

(Prior Art) In this type of rolling die, as shown in FIG. 5, a thread forming groove 2 having a width and a depth adapted to the thread is provided side by side at a constant lead angle on the surface of the die 1. Has been done. The die 1
As shown in FIG. 6, one having the same shape is used as the fixed die 1A and the other as the moving die 1B, and the head 3 preliminarily held by the starting end side of each die is formed and the washer 4 is assembled as necessary. The threaded part 7 having a predetermined thread is rolled on the shank 6 of the screw material 5 that has been inserted.

(Problems to be Solved by the Invention) However, in the case of the above-described conventional die, as shown in FIG. 6, the die is pressed and pinched on the terminal end side of the die where the rolling process is completed. When it is plastically deformed, the thread forming groove on the upper end side of the die as shown in FIG.
The screw material in 2a is pressed upwards and the thread forming groove 2a
The thread 7a rolled with is the regular thread 7b as shown in Fig. 8.
Formed into smaller diameter imperfect threads.

For this reason, for example, in the case of a screw 7 with a washer incorporated as shown in FIG.
Play occurs, and the washer 4 of another screw is caught in this gap during plating or the like, causing a defective product.

Further, as shown in FIG. 10, for example, when the fastened members 9 and 10 having a small plate thickness are fixed by the tapping screw 8 having a short length without a washer, the fastening force is reduced because the number of screw threads is substantially reduced. There were problems such as.

Therefore, in the present invention, in order to improve the above problems,
The purpose of the present invention is to provide a rolling die that can eliminate incomplete threads under the neck.

(Means for Solving Problems) The gist of the present invention is to provide a screw on the upper end side of a rolling die for forming a screw thread adjacent to the seat surface of the screw head and on the terminal end side where the rolling is completed. This is a thread rolling die in which a flat portion having no thread forming groove is provided, and the width and depth gradually increase from the flat portion to the regular thread forming groove.

(Example) Below, this invention is demonstrated based on the Example shown in figure. As shown in FIGS. 1 and 2, the die 11 is provided with the thread forming groove 12 on the surface similarly to the conventional die, but at the upper end portion of the die and the end portion side where the rolling is completed ( In the embodiment, a flat portion 13 having no thread forming groove is provided with a width of 0.2 to 0.3 on the extension line of the thread forming groove 12 which is about ½ of the die length. Between the flat portion 13 and the thread forming groove 12, there is provided a taper groove 14 formed so that the width and the depth gradually increase toward the thread forming groove. The tapered groove 14 has an arcuate inner bottom portion as shown in FIG. 3, and is formed at the same time when the thread forming groove 12 is formed by the cutter 15.

When the thread is rolled using the die 11 having the above-described structure, the screw material 16 that is about to be pushed upward as shown in FIG. 4 is blocked by the flat portion 13 and the thread forming groove is formed by the taper groove 14. It is moved to the direction of 12, and finally the thread forming groove 12 forms a regular thread.

(Effects of the Invention) As is apparent from the above-described embodiment, according to the rolling die of the present invention, the thread under the neck is rolled into a regular thread, and the incomplete thread as in the conventional example is obtained. It is possible to solve the problems such as the connection of the washer built-in screws and the reduction of the fastening force of the short tapping screws.

Also, the die itself can be easily manufactured almost like a conventional die.

[Brief description of drawings]

FIG. 1 is an overall front view of a die according to an embodiment of the present invention, FIG. 2 is an enlarged front view of an essential part of the die, FIG. 3 is a sectional view of an essential part along a lead angle of the die, and FIG. FIG. 5 is a side view of the main part of the die, FIG. 5 is a front view of the die according to the conventional example, FIG. 6 is a vertical sectional view for explaining a thread rolling process state of the die, and FIG. 7 is an enlarged view of the main part of the die. Sectional drawing, FIG. 8 is an enlarged sectional view of the main part of the screw rolled by the die, and FIG. 9 is an explanatory view of a connection accident of the washer-incorporated screw rolled by the die,
FIG. 10 is an explanatory view of a state where a thin plate is fastened with a short tapping screw rolled by the die. [Explanation of symbols] 11 …… Die, 12 …… Thread forming groove 13 …… Flat part, 14 …… Taper groove 15 …… Cutter, 16 …… Screw material

Claims (1)

(57) [Claims] 1. A flat portion having no thread forming groove is provided on an upper end side of a rolling die for forming a screw thread adjacent to a seat surface of a screw head and on a terminal end side where rolling is completed, A screw rolling die in which the width and the depth are gradually increased from the flat portion to shift to a regular thread forming groove.