JPH04157035A - Manufacture of tapping screw and roll forming tool for tapping screw - Google Patents

Abstract

PURPOSE:To manufacture the tapping thread of top end cut without requiring an other process and lowering the manufacturing accuracy by setting a blade part to cut the top end part of the thread blank material at the section of the moving end side on one side of a pair of dies. CONSTITUTION:A pair of plate shape dies 11, 12 having a thread ridge part forming part 13, 15 and a tapered part forming part 14, 16 are provided, and when the thread blank material is roll formed by using this, the required number of the thread ridge part 14, 16 are formed, and more, the blade part 19 to cut the top end part of thread blank material is formed at the section of the moving final end side of one hand of a pair of dies. Therefore, the top end part is cut, and the top end of tapping thread s not formed to a sharp point.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Field of Application) The present invention provides a tapered tip by sandwiching a screw material between a pair of plate-shaped dies and moving the two dies relatively. The present invention relates to a self-tapping screw rolling tool for rolling self-tapping screws and a self-tapping screw manufacturing method.

(Prior Art) Conventionally, when manufacturing a tapping screw, as shown in FIGS. 6 and 7, a plate-shaped die 1 on the fixed side having a thread forming part 1a and a tapered part forming part 1b, A screw material 3 having a round bar-shaped lower neck is sandwiched between plate-shaped dies 2 on the movable side that also have a thread forming part 2a and a tapered part forming part 2b, and the die 2 is moved in the direction of arrow Q in FIG. The screw material 3 is caused to roll. In this way, the tapping screw 4 is manufactured. In this case, the diameter of the tip of the tapping screw 4 is gradually reduced by the "cutting" performed by the tapered portion forming portions 1b and 2b during the above-mentioned transfer, and the tip excess material 3a is naturally cut off.

However, in such cutting by "massaging", the tip of the tapping screw 4 becomes sharp, as shown in FIG. 8, and there is a risk of injury when handling the screw.

As a countermeasure to this problem, it is conceivable to cut the tip of the tapping screw 4, but it requires a great deal of effort to perform the cutting operation on each screw.

As another countermeasure, as shown in FIG. 9, the thread material 5 is formed with a tapered part 5a whose tip is cut in advance to prevent the above-mentioned "cutting". Rolling is considered to be possible.

However, even in this case, in addition to the rolling process, a tapered part machining process is required for the thread material, which increases production costs. Furthermore, if the tip diameter dimension d of the screw material 5 is small, as shown in FIG. If d is large, as shown in FIG. 11, the required number of threads will be formed on the tapered portion 6a, but a burr 6b will be formed at the tip, which may cause injury, and the length under the neck g will be too large. There is also the problem that dimensional accuracy deteriorates due to variations.

(Problems to be Solved by the Invention) As can be seen from the above, when manufacturing a self-tapping screw by rolling a screw material with a round bar-shaped neck portion using a conventional self-tapping screw rolling tool, Although it is possible to roll a self-tapping screw with the required number of threads, there is a problem in that the tip of the self-tapping screw becomes sharp.
When manufacturing self-tapping screws by rolling the screw material with a conventional self-tapping screw rolling tool, the number of manufacturing steps increases, production costs increase, and the necessary threads may not be obtained or burrs may occur. There is a problem that manufacturing accuracy is reduced, such as occurrence of cracks or variations in length under the neck.

The present invention has been made in view of the above circumstances, and its purpose is to use a round bar-shaped screw material that does not form a tapered part as a screw material, but to produce a tapping screw with a cut tip without requiring a separate process. Moreover, it is an object of the present invention to provide a tapping screw rolling tool and a tapping screw manufacturing method that can be manufactured without reducing manufacturing accuracy.

[Structure of the Invention] Means for Solving Cap 1) The self-tapping screw rolling tool of the present invention includes a pair of plate-shaped dies each having a thread forming portion and a tapered portion forming portion. In the device for rolling a tapping screw with a tapered tip by sandwiching a screw material and moving the two dies relatively, the tip of the screw material is placed at a portion of one of the pair of dies at the end of movement. It is characterized by the provision of a cutting blade.

Further, in the tapping screw manufacturing method of the present invention, a screw material is sandwiched between a pair of dies, and the dies are relatively rolled from a movement start end side to a movement end side, thereby forming a screw thread portion of both dies. The thread forming part and the tapered part forming part form a threaded part and a tapered part in the thread material, and the tip of the tapered part is cut by a blade part provided on one of the dies.

(Function) The self-tapping screw rolling tool of the present invention includes a pair of plate-shaped dies having a thread forming part and a tapered part forming part. By rolling this material using this tool, not only can the necessary number of threads be formed, but also because a blade part for cutting the tip of the thread material is formed at the end of the movement of one of the dies. Unlike the case where the tip is cut and the tip of the screw is cut by "mass cutting", the tip of the tapping screw does not have a sharp shape.

Also, in the tapping screw manufacturing method of the present invention, by sandwiching a screw material between a pair of dies and relatively moving both dies from the movement start end side to the movement end side, the thread portions of the two dies are formed. Since a threaded part and a tapered part are formed in the screw material at the part and tapered part forming part, by using a threaded material with a round bar-shaped neck part as the threaded material and rolling this, the required number of threaded parts can be formed. Since the tip of the tapered portion is cut by the blade provided on one of the dies, a tapping screw with a cut tip can be manufactured by the -th rolling process.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 5.

1 and 2 show a rolling tool for self-tapping screws. Of the pair of plate-shaped dies 11 and 12, the die 11 is arranged in a fixed state, and the die 12 is moved in the direction of arrow A in FIG. 2 relative to the die 11. The die 11 has a thread forming portion 1 consisting of a groove.
3 and a tapered portion 14 consisting of an inclined surface, and the die 12 is also similarly formed with a threaded portion forming portion 15 and a tapered portion forming portion 16, respectively. and,
The die 11 on the fixed side has a portion 11a on the rolling end side.
A recessed part 17 is formed in the recessed part 17, and a cutting blade block 18 is attached to this recessed part 17 by screwing. A blade portion 19 is formed in this cutting blade block 18. As shown in FIG. 3, this blade portion 19 is shaped to stand out from the end 14g of the tapered portion 14.

Now, a case will be described in which a tapping screw 21 (see FIG. 5) having a shape in which the tip of the tapered portion 21b is cut is manufactured from the screw material 20.

The head of the screw material 20 is preformed, and the lower neck portion is shaped like a straight round bar. However, this screw material 2
As shown in FIG. 2, the movable die 12 is placed on the movement start end side of the fixed die 11 and moved in the direction of arrow A while being pressed against the screw material 20. As a result, the thread material 20 is rolled between both dies 11 and 12, and the thread forming parts 13 and 15 of the dies 11 and 12 form a thread 21a, and the tapered parts 14 and 16 form a threaded part 21a. A portion 21b is formed. In this case, since the thread material is formed from the round bar-shaped thread material 20, the necessary number of threads 21a are formed also in the tapered portion 21b by the movement of the die 1.1.12. When the thread material 20 reaches the end of its movement, the tip of the thread material 20, that is, the tip of the tapered portion 21b, is cut by the blade 19 together with the remaining material 20a, as shown in FIG. In this way, the self-tapping screw 21 is manufactured. As a result, the tapping screw 2
The tip of 1 does not have a sharp shape. Further, since the cutting position with respect to the screw material 20 is constant, there is no variation in the length under the neck of the tapping screw 21, and the required number of threads 21a can be obtained, resulting in good manufacturing accuracy.

In the above embodiment, the blade portion 19 is provided separately on the die 11, but it may be formed integrally.

[Effects of the Invention] As is clear from the above, according to the present invention, the following effects can be obtained.

According to the self-tapping screw rolling tool and self-tapping screw manufacturing method of the present invention, a self-tapping screw having a cut-off tip can be manufactured so that it has the required number of threads and there is no variation in the dimensions under the neck. Unlike conventional tapping screws in which the tips of the screws are sharpened by "mass cutting", there is no risk of injury and no deterioration in manufacturing accuracy can be obtained.

According to the self-tapping screw manufacturing method of the present invention, a self-tapping screw having a cut-off tip can be manufactured in a single rolling process without deteriorating manufacturing accuracy.

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention,
Fig. 1 is a vertical side view of the die stacked, Fig. 2 is a plan view of the same, Fig. 3 is a cutaway view of the main part of the rolling tool, Fig. 4
The figure is a vertical cross-sectional side view showing the state of self-tapping screw manufacturing.
The figure is a side view showing a manufactured self-tapping screw. 6 to 8 show conventional examples, where FIG. 6 is a diagram equivalent to FIG. 2, FIG. 7 is a diagram equivalent to FIG. 4, FIG. 8 is a diagram equivalent to FIG. The figure shows a different conventional example.
The figure is a side view of the screw material, FIG. 10 is a side view of the tip of the tapping screw, and FIG. 11 is a side view of the tip of the tapping screw with a different finish from FIG. 10. In the drawing, 11.12 is a die, 13.15 is a thread forming part, 14.16 is a thread part, 18 is a cutting blade block, 1
9 is a blade, 20 is a screw material, 21 is a tapping, 21a
21b represents a threaded portion, and 21b represents a tapered portion. Agent Patent Attorney Tsuyoshi Sato Figure 6 Figure 7 Figure 8 Figure 9 k Figure 10 Figure 11 Also 9ai -

Claims (1)

[Claims] 1. A pair of plate-shaped dies having a thread forming part and a tapered part forming part are provided, and by sandwiching a thread material between the two dies and moving the two dies relatively, the tip can be formed. A device for rolling a tapping screw having a tapered portion, characterized in that a blade portion for cutting the tip of the screw material is provided at a portion on the movement end side of one of the pair of dies. Ingredients. 2. By sandwiching the thread material between a pair of dies and moving both dies relatively from the movement start end side to the movement end side, the thread material is formed at the thread forming part and the tapered part forming part of both dies. A method for manufacturing a tapping screw, characterized in that a threaded portion and a tapered portion are formed in the screw, and the tip of the tapered portion is cut by a blade provided on one of the dies.