JPS6048648B2 - Tapping screws for thin plates and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuft pin screw, particularly for thick plates, and a method for manufacturing the same.

Some conventional tuft pin screws have threads provided at fine pitches on a shaft portion of a circular cross section in order to stabilize the attachment and holding force of a member.

This type of tatsupin screw has a large holding force after tightening, so it is suitable for attaching thin plates. However, if the component is thick, the tightening time will be longer, so the influence of screwing torque cannot be ignored, and the screwing will be difficult. Reducing the screwing torque has become a problem in order to improve workability. SUMMARY OF THE INVENTION The object of the present invention is to provide a tuft pin screw particularly suitable for thick plates, which is improved in such a way that the screwing torque is reduced when tightening the plates.

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a tuft pin screw 10 according to the invention.

The tuft pin screw 10 includes a head 12, a shaft 14 with an oval cross section extending from the head, and a tapered tip 16 with an oval cross section extending gradually from the shaft. Become. A thread having a substantially elliptical outer diameter is formed on the shaft portion 14 having an elliptical cross section, and when threaded by a threading machine having a thread with a normal machined surface,
It has a tall, complete thread 18 on its major diameter, while it has a low, incomplete thread 19 on its minor diameter. Similarly,
The tapered tip 20 has a relatively tall, complete thread 20 formed along its long diameter, and a low, incomplete thread 22 formed along its short diameter. Next, an example of a method for manufacturing a tuft pin screw according to the present invention will be described.

FIGS. 3 and 4 show a heading dozen 30 for heading blanks. This heading die has a large oval hole 32 for forming the shaft portion 14 of the screw, an oval taper hole 34 for forming the tapered tip 16, and a small oval hole 36. is provided. A blank is forged from the wire by this forging die 30 and a forging die (not shown) for forming a screw head. The pressed blank 40 is shown in FIGS. 7 and 8. The same reference numerals have been used for corresponding parts of the tuft pin screws shown in FIGS. 1 and 2. Next, as shown in FIGS. 9 and 10, this blank 40 is supplied between the rear end of the fixed rolling pin 44 and the front end of the movable rolling die 42, and the movable rolling die 42 is moved in the direction of the arrow. By moving the head 12 in the direction
Threads are rolled on the shaft portion 14 and the tapered tip portion 16 other than the above. When thread rolling is carried out using an ordinary thread rolling tool, the tuft pin screws shown in FIGS. 1 and 2 are rolled. In addition, in order to ensure that a complete thread is rolled on the shaft along its entire circumference by both dies while the axis of the shaft of the blank having an elliptical cross section moves along the center line between the two dies. , the threads on the machined surfaces of both dies can be formed by elliptical development curves. When the tuft pin screw according to the present invention is screwed in, first the high thread 20 of the long diameter part of the elliptical cross section of the tapered tip part 16 is screwed in, and then the shank part 14
The thread 18 on the long diameter portion contacts the pilot hole of the mating material at two points and forms a thread while plastically deforming the mating material.

Since the taper tip is screwed in while making two-point contact with the pilot hole, the screw-in is sharp, and since there are few contact points between the taper tip and the screw on the shaft, the frictional force is extremely small, and the screwing torque is significantly reduced. Ru. moreover,
After the tightening is completed, the inner diameter of the female thread of the mating member is made smaller than the diameter of the pilot hole due to plastic deformation, so there is an advantage that the contact area with the male thread of the long diameter portion of the shaft portion increases.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the tut pin screw according to the present invention, FIG. 2 is an end view of the tut pin screw shown in FIG. Fig. 4 is an end view thereof, Fig. 5 is a cross-sectional view taken along line A-A' in Fig. 3, and Fig. 6 is a cross-sectional view taken along line B-B' in Fig. 3. A cross-sectional view, Fig. 7 is a side view of a tuft pin screw blank formed by a heading tool, Fig. 8 is an end view thereof, and Figs. 9 and 10 show the blank being thread-rolled by a rolling die. It is an explanatory view of a rolling process.

Claims (1)

[Scope of Claims] 1. Consisting of a head, a shaft with an elliptical cross section extending from the head, and a tapered tip with an elliptical cross section extending gradually from the shaft, A tuft pin screw for a thick plate, characterized in that the shaft portion and the tapered tip portion are formed with a thread having a substantially elliptical outer diameter. 2 Consisting of a head, a shaft with an elliptical cross section extending from the head, and a tapered tip with an elliptical cross section extending gradually from the shaft, the shaft and the tapered tip In a method for manufacturing a tatsupin screw for a thick plate, in which a screw thread having an approximately oval outer diameter is formed in the part,
A blank consisting of an axis of an elliptical cross section with a head and a tapered tip is forged from a wire rod using a forging die, and then the axis of the blank is formed using a rolling die having threads on the machined surface formed by an elliptical development curve. A method characterized in that a thread having a substantially elliptical outer diameter is simultaneously rolled at the end portion and the tapered tip end portion.