JPH08226424A - Tapping screw and manufacture thereof - Google Patents

Abstract

PURPOSE: To attain sufficient holding power without giving any burring process on the thin board side by forming a protrusion which protrudes out in the normal line of the flank of a thread respectively at the proper positions of the high and low threads. CONSTITUTION: A tapping screw is provided with a shank 2 and a head 3 which is formed at one end of the shank 2. The shank 2 is formed with a double-start thread of a high thread 4 and a low thread 24, and the high thread 4 and the low thread 24 are in the same direction. At the rear end of the shank 2, protrusions 5, 25 protruding out in the direction of the normal line of the flank of the thread 4, 24 and in the diametrical direction of the shank 2 respectively are formed per one pitch at respective threads. This tapping screw 1 has the low thread 24, so even when it is screwed into a thin board, it can be screwed to a little initial screwing torque without destroying the thin board, even if the diameter of the lower hole formed at the thin board is made smaller than an ordinary tapping screw with the same outside diameter as the high thread 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw which can be tapped by itself, that is, a tapping screw and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventional conventional tapping screws are single-threaded screws, and the heights of their threads are all the same except for the tips of screws and incomplete threads.

[0003]

In the conventional tapping screw described above, when screwing into a thin plate, sufficient retaining force cannot be obtained unless burring is performed on the prepared hole of the thin plate. However, there is a problem that the cost of preparing the pilot hole becomes high.

In many cases, after the tapping screw is tightened, it is necessary to prevent the loosening by applying an adhesive to the fastening portion. However, if the adhesive is attached in this way,
There is a problem that the tapping screw cannot be removed and the work cost of attaching the adhesive agent is higher than the work cost of screwing the tapping screw itself.

Even when burring is performed,
In order to obtain a sufficient holding force, it is necessary to make the lead of the tapping screw small to some extent, which causes a problem that the screwing cannot be performed quickly.

The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to provide a sufficient holding force even when screwing into a thin plate or without burring on the thin plate side. To provide a self-tapping screw and a method for manufacturing the same.

Another object of the present invention is to provide a tapping screw which can prevent loosening without applying an adhesive and can reduce initial screwing torque, and a manufacturing method thereof.

Another object of the present invention is to provide a tapping screw and a method for manufacturing the tapping screw, which can perform a screwing operation quickly and can obtain a sufficient holding force.

Another object of the present invention is to provide a method for producing a tapping screw, which can produce the tapping screw of the present invention by rolling similarly to a normal tapping screw.

Further objects of the present invention will be apparent from the following description.

[0011]

A tapping screw according to the present invention has two threads, a high thread and a low thread, at least in place of said high thread and / or low thread. The protrusion is provided so as to protrude in the direction normal to the flank of the screw thread.

In the tapping screw manufacturing method according to the present invention, a blank is supplied between a plurality of rolling dies, and the plurality of rolling dies are relatively moved to roll the blank between the plurality of rolling dies. By the tapping screw manufacturing method for manufacturing the tapping screw by thread rolling, by increasing the rolling pressure in the region corresponding to the portion to be provided with the convex portion higher than the normal rolling pressure, the plurality of At least one of the rolling dies has a blank contact surface in the vicinity of a terminal end portion of the blank, and the convex portion is formed by biting the corresponding portion of the blank outward.

[0013]

Since the tapping screw of the present invention has a low thread, even when it is screwed into a thin plate, the diameter of the prepared hole provided in the thin plate is smaller than that of a normal tapping screw having the same outer diameter as the high thread. Even if is made small, the thin plate can be screwed in with a small initial screwing torque without breaking. By reducing the diameter of the prepared hole in this way, the catch rate can be increased, so the holding force can be increased without performing burring on the prepared hole side. The processing cost can be reduced.

In addition, since the convex portion projecting at least in the normal direction of the flank of the thread is provided at a suitable position of the high thread and / or the low thread, the thread is on the side of the threaded material such as a thin plate. It is crimped to the female screw formed on the base plate to prevent loosening. Therefore, the work of attaching an adhesive to the fastening portion, which has been conventionally required, is not required, and the work cost can be significantly reduced, and the tapping screw once fastened can be removed.

Further, since it has two threads, even if the pitch is the same as that of a conventional tapping screw of the related art, the lead can be made larger, so that the screwing can be carried out quickly, and thereby Can reduce the work cost.

Further, according to the method for manufacturing the tapping screw of the present invention, the tapping screw having the convex portion can be manufactured by rolling similarly to the ordinary tapping screw, so that the tapping screw of the present invention can be manufactured at low cost. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in the drawings. FIG. 1 shows a front view of an embodiment of a tapping screw according to the present invention. The tapping screw 1 comprises a shaft portion 2 and a head 3 provided at one end of the shaft portion 2. The shaft portion 2 is provided with two threads of a high thread 4 and a low thread 24, and the high thread 4 and the low thread 24 are oriented in the same direction (right-handed). There is. On the rear end side (head 3 side) of the shaft portion 2, the screw threads 4, 2
4, the protrusions 5 and 25 protruding in the normal direction of the flanks of the screw threads 4 and 24 and in the radial direction of the shaft portion 2 are provided on the screw threads 4 and 2 respectively.
4 is provided for each pitch. 2 and 3 show the convex portion 5,
2 is a view of the protrusions 5 and 25 seen from a direction different from that of FIG. 1 in order to clarify the shape of 25, and FIG.
FIG. 3 is a sectional view taken along the line A, and FIG.
On the tip side of the shaft portion 2, the protrusions 5 and 25 are not provided on the screw threads 4 and 24. The head 3 is provided with a hole or groove 6 for fitting a driver.

For reference, one of concrete examples of dimensions and angles of each part of the screw in this embodiment is shown below (of course,
It goes without saying that the present invention is not limited to such specific dimensions).

Outer diameter d ₁ = 4.0 at high thread 4
mm ・ Outer diameter d ₂ = 3.3 mm at low thread 24 ・ Valve diameter d ₃ = 2.6 mm ・ Lead l ₁ = l _{2 of} high thread 4 and low thread 24
= 1.4 mm, -Pitch P = 0.7 mm-High thread 4 and low thread 24 with respect to lead angle
Of the flanks on the front end side of α ₁ , β ₁ = 30 degrees (Fig. 4
High thread 4 and low thread 24 for lead angle
The flank flank inclination angles α ₂ and β ₂ = 10 degrees (Fig. 4)
Reference) Specific dimensions and angles of the respective parts of the ordinary tapping screw corresponding to the above specific example are as follows.

-Outer diameter = 4.0 mm -Valley diameter = 3.0 mm -Lead and pitch = 0.7 mm -Frank angle (corresponding to α ₁ + α ₂ ) = 60 degrees In this tapping screw 1, low thread Since it has 24, even when screwed into a thin plate (for example, a thickness of 0.3 to 0.6 mm), the diameter of the prepared hole provided in the thin plate is larger than that of a normal tapping screw having the same outer diameter as the high thread 4. Even if the thickness is small, the thin plate can be screwed in with a small initial screwing torque without breaking. By reducing the diameter of the prepared hole, the catching rate can be increased, so the holding force can be increased without burring on the prepared hole side, reducing the prepared hole processing cost. can do. In the case of the tapping screw 1, it is preferable that the diameter of the prepared hole is about the same as the root diameter. For example, in the case of the specific size and angle example, the diameter of the prepared hole is preferably about 2.7 mm. (In the case of the corresponding normal tapping screw, the prepared hole has a diameter of about 3.7 mm).

Further, since each of the threads 4 and 24 is provided with the projections 5 and 25 protruding in the normal direction of the flanks of the threads, the threads 4 and 24 are on the material to be screwed in such as a thin plate. It is crimped to the female screw formed on the base plate to prevent loosening. Therefore, the work of attaching an adhesive to the fastening portion, which has been conventionally required, is unnecessary, and the work cost can be significantly reduced by this as well (in the present embodiment, the high thread 4 and the low thread 24 are used). However, in the present invention, only one of the high thread 4 and the low thread 24 may be provided with a projection).

Further, since it has the two threads 4 and 24, even if the pitch is the same as that of a conventional tapping screw of the related art, the lead can be enlarged and the screwing can be performed quickly. The work cost can be reduced also by this.

Next, an embodiment of a method for manufacturing the tapping screw 11 shown in FIGS. 1 to 4 by thread rolling will be described. FIG. 5 shows a blank (material) 1'in this embodiment, which is provided with a shaft portion 2'having a circular cross section and a head portion 3. Of the shaft portion 2 ', the portion (tip side) where the convex portions 5, 25 are not provided when the tapping screw 1 is formed is a small diameter portion 2a', and the convex portions 5, 2 are formed.
The part (rear end side) where 5 will be provided is the small diameter part 2
The large diameter portion 2b 'is thicker than a'by an appropriate size. The head 3 is provided with a hole or groove 6 for fitting a driver.

FIG. 6 is a plan view showing a rolling operation in this embodiment, wherein 7 is a rolling fixed flat die (hereinafter, fixed die), 8 is a rolling movable flat die (hereinafter, moving die). is there. FIG. 7 is a front view of the fixed die 7, FIG. 8 is an enlarged side view of the fixed die 7, and FIG. 9 is an enlarged plan view of a main part of the fixed die 7. As shown in FIG. 10, the blank contact surface 9 of the fixed die 7 has a thread forming groove 10 having a cross-sectional shape corresponding to the thread 4 of the tapping screw 1.
Is provided. In FIGS. 6, 8 and 9, the top of the thread forming groove 10 in the relief portion 12 to be described later is indicated by a line 10b (solid line in FIG. 8, broken line in FIG. 9) and the thread forming groove 10 in other portions. 10 on top
a, the bottom of the thread forming groove 10 corresponding to the top of the high thread 4 in the relief portion 12 described later is indicated by a broken line 10d, and the bottom of the thread forming groove 10 corresponding to the top of the high thread 4 in the other portions is shown. Each is indicated by a broken line 10c (in FIGS. 6, 8 and 9, the bottom portion of the thread forming groove 10 corresponding to the top portion of the low thread 24 is not shown in order to keep the drawings from becoming complicated. This bottom is also formed in the same manner as the bottom of the thread forming groove 10 corresponding to the top of the tall thread 4).

A region 9b of the blank contact surface 9 of the fixed die 7 to which the large diameter portion 2b 'of the blank 1'is contacted.
As shown in FIGS. 6 and 8, the end portion (upper region in FIG. 7) is provided with a slope 11 inclined in a direction away from the opposing moving die 8. In addition, in this embodiment, the slope 11 is slightly curved in an arc shape as shown in FIG. 9, but it may be flat.

On the other hand, in the area 9a (the lower area in FIG. 7) of the fixed die 7 where the small diameter portion 2a 'of the blank 1'abuts, it is the same as the die for ordinary thread rolling. A relief portion 12 is provided. As shown in FIG. 9, in the relief portion 12, the top portion 10b and the bottom portion 10d of the thread forming groove 10 are both inclined in a direction in which the top portion 10b and the bottom portion 10d gradually move away from the opposing moving die 8. Here, the inclination angle of the escape portion 12 is smaller than the inclination angle of the slope 11. In this embodiment, in the inclined surface 11, the bottom portion 10c of the thread forming groove 10 is inclined in the direction away from the moving die 8 as in the case of the bottom portion 10d of the thread forming groove 10 in the relief portion 12. Although not provided, the bottom portion 10c of the thread forming groove 10 at the slope 11 is not covered by the bottom portion 10 at the escape portion 12.
Similar to d, it may be inclined in a direction away from the moving die 8.

As shown in FIG. 6, the moving die 8 is
Has a structure similar to that of a normal rolling flat die, and the blank contact surface 13 has a slope 1 in the fixed die 7.
The slope and the relief portion corresponding to 1 and the relief portion 12 are not provided. In addition, 14a shows the top of the thread forming groove of this moving die, and 14b shows the bottom.

In this embodiment, as shown in FIGS. 6 and 7, the large diameter portion 2b 'of the shaft portion 2'of the blank 1'abuts the area 9b of the blank abutment surface 9 of the fixed die 7. The small diameter portion 2a 'is set so as to abut on the region 9a of the blank abutment surface of the fixed die 7, and the moving die 8 is moved in the same manner as in the case of ordinary thread rolling. B
Moving in the direction and rolling the blank 1'between the moving die 8 and the fixed die 7, the threads 1 and 24 are formed on the blank 1 '.
Is formed.

Here, the small diameter portion 2 of the blank 1 '
When the rolling pressure is set to a normal magnitude at the contact portion between a'and the blank contact surface 9 of the fixed die 7, the large diameter portion 2b 'of the blank 1'and the blank contact surface of the fixed die 7 are contacted. The rolling pressure at the contact portion of the contact surface 9 with the region 9b becomes higher than usual (in other words, the diameter of the large diameter portion 2b 'of the blank 1'is equal to that of the large diameter portion 2b' and the fixed die). The rolling pressure is set to be higher than the normal rolling pressure by an appropriate amount at the contact portion of the region 7 with the region 9b). When the blank 1 ′ reaches the start end of the slope 11 at the end of the region 9b of the blank contact surface 9 of the fixed die 7, the contact area between the fixed die 7 and the blank 1 ′ becomes small in this portion, Since the contact pressure between the fixed die 7 and the blank 1'becomes high, the slope 1 of the fixed die 7
At the same time that the vicinity of the beginning of 1 bites deeply into the blank 1 ',
The corresponding portion of the blank 1 ′ is extruded to the outside to form convex portions 5 and 25 that swell in the normal direction of the flanks of the threads 4 and 24 and in the radial direction of the shaft portion 2.

On the other hand, at the contact portion between the small diameter portion 2a 'of the blank 1'and the area 9a of the blank contact surface 9 of the fixed die 7, the rolling pressure has a normal magnitude, and the clearance portion 12 has a clearance. Since the inclination angle is small and the distance from the moving die 8 is gradually increased, the convex portions 5 and 25 are not formed in this region 9a, and the normal threads 4 and 24 are obtained.

In the tapping screw 1 shown in FIG. 1, only in a partial section (rear end side) of the shaft portion 2,
Although the projections 5 and 25 are formed on the threads 4 and 24, the projections 5 and 25 may be provided on the threads 4 and 24 in the entire section of the shaft 2. In that case, the inclined surface 11 may be provided at the end portion of the entire area of the blank contact surface 9 of the fixed die 7. However, if the projections 5 and 25 are provided on the threads 4 and 24 in the entire section of the shaft portion 2, the initial screwing torque may increase, but like the tapping screw 1 shown in FIG. Only on the rear end side, the protrusions 5, 2 on the threads 4, 24
5 is formed, and the convex portions 5 and 25 are not formed on the tip side of the shaft portion 2, the initial screwing torque can be reduced, and the loosening preventing function can be exerted when the tapping screw 1 is tightened to some extent. The advantage of being able to do is obtained (usually, the locking function is required only when the tapping screw 1 is screwed in to some extent).

FIG. 11 shows another embodiment of the fixed die 7 according to the present invention. In this embodiment, the slope 11 is inclined with respect to the direction perpendicular to the traveling direction of the blank 1 '. When the inclined surface 11 is perpendicular to the traveling direction of the blank 1'as in the fixed die 7 of FIGS. 6 to 9, the convex portions 5 and 25 are arranged in the axial direction of the shaft portion 2 as shown in FIG. It is formed by arranging in a parallel direction, but when the slope 11 is inclined obliquely to the direction perpendicular to the traveling direction of the blank 1'as shown in FIG. 11, the convex portions 5, 25 are formed as shown in FIG.
Are formed in a spiral arrangement on the shaft portion 2.

Further, in each of the above-described embodiments, since the slope 11 is provided only on the fixed die 7 side, the threads 4, 24 are formed.
One convex portion 5 and 25 is formed for each pitch of
If the movable die 8 is also provided with the inclined surface 11, it is possible to form two convex portions 5 and 25 for each pitch of the threads 4 and 24 as shown in FIG. In the case where the blank 1'is inclined with respect to the traveling direction or in the case of a multi-thread screw, the number of convex portions 5 and 25 per pitch is different from this.

FIGS. 14 and 15 show still another embodiment of the fixed die 7 of the present invention. In this embodiment, the slope 11 and the relief portion are also provided at the end of the region 9b of the blank contact surface 9. Is not provided. When thread rolling is performed in the same manner as described above using such a fixed die 7, the convex portions 5 and 25 are formed to rise substantially in the radial direction of the shaft portion 2 as shown in FIG. Even when the convex portions 5 and 25 having such a shape are formed, the loosening preventing function can be obtained. However, in this case, when the tapping screw 1 is intentionally rotated in the loosening direction, the projections 5 and 25 may destroy a screwed object such as a thin plate. If the sloped surface 11 is provided at the end of the region 9b of the blank contact surface 9, the convex portion rises while being inclined with respect to the radial direction of the shaft portion 2 of the tapping screw 1, and the tapping screw 1 is loosened intentionally. When trying to rotate in the direction
It is possible to reduce the risk that the threaded material will be broken.

FIG. 17 shows still another embodiment of the fixed die 7 according to the present invention. In this embodiment, the shaft 2'of the blank 1'has a step like the blank 1'of FIG. By making the region 9b of the blank contact surface 9 of the fixed die 7 protrude from the region 9a, the rolling pressure in the region 9b is increased more than usual. Also by this, the same effect as in the case of the above-mentioned embodiment can be obtained.

In each of the above-mentioned embodiments, the threads of the threads 4 and 24 are triangular, but in the present invention, the threads of the threads 4 and 24 may be other kinds of threads. Good.

Further, in each of the above-mentioned embodiments, the convex portion 5,
Although 25 projects in the normal direction of the flanks of the threads 4 and 24 and in the radial direction of the shaft portion 2, it does not have to project in the radial direction of the shaft portion 2 (even in such a case, the loosening stopper). Function is obtained).

Further, although a flat die is used in each of the above-mentioned embodiments, a die having another shape such as a round die may be used in the tapping screw manufacturing method of the present invention. However,
When a round die is used, it is necessary to determine the end portion of the blank contact surface of the round die and set such that the rolling operation for each blank is always completed at this end portion.

[0039]

As described above, the tapping screw according to the present invention provides (a) a sufficient holding force even when it is screwed into a thin plate without burring on the thin plate side. It is possible to prevent loosening without attaching an adhesive, and to reduce the initial screwing torque. Therefore, the work of attaching an adhesive to the fastening portion, which has been conventionally required, is not required, and the work cost can be significantly reduced, and the tapping screw once fastened can be removed.

(C) It is possible to obtain an excellent effect that the screwing operation can be carried out quickly and a sufficient holding force can be obtained.

Further, the method for manufacturing a tapping screw according to the present invention has an excellent effect such that the tapping screw according to the present invention can be manufactured by a rolling process like a normal tapping screw.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a tapping screw according to the present invention.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is a view in the direction of arrow A in FIG. 2;

FIG. 4 is an enlarged cross-sectional view showing the threads of the tapping screw of the above embodiment.

FIG. 5 is a front view of a blank in an embodiment of a method for manufacturing a tapping screw according to the present invention.

FIG. 6 is a plan view showing a thread rolling operation in the embodiment of the method for manufacturing the tapping screw.

FIG. 7 is a front view showing a fixed die in an embodiment of the method for manufacturing the tapping screw.

FIG. 8 is a side view showing the fixed die.

FIG. 9 is an enlarged plan view showing a main part of the fixed die.

FIG. 10 is an enlarged cross-sectional view showing a thread forming groove of the fixed die.

FIG. 11 is a front view showing another embodiment of the fixed die in the method for manufacturing a tapping screw according to the present invention.

12 is a front view showing another embodiment of the tapping screw of the present invention manufactured by using the fixed die of FIG.

FIG. 13 is an enlarged cross-sectional view showing still another embodiment of the tapping screw of the present invention.

FIG. 14 is a front view showing still another embodiment of the fixed die in the method for manufacturing a tapping screw according to the present invention.

FIG. 15 is a plan view showing a main part of the fixed die shown in FIG.

16 is an enlarged sectional view showing still another embodiment of the tapping screw of the present invention manufactured by using the fixed die of FIGS. 14 and 15. FIG.

FIG. 17 is a side view showing still another embodiment of the fixed die in the method for manufacturing the tapping screw of the present invention.

[Explanation of symbols]

1 Tapping screw 1'Blank 2 Shaft part 2a 'Small diameter part 2b' Large diameter part 4 High screw thread 5 High screw thread convex part 7 Fixed die 8 Moving die 9 Blank contact surface of fixed die 9a Blank contact surface 9 , Small diameter part 2 of blank 1 '
Area a'abutting 9b Large diameter portion 2 of blank 1'of blank abutting surface 9
Area where b'abuts 11 Slope 24 High screw thread 25 High screw thread protrusion

Claims (3)

[Claims] 1. A thread having two threads, a high thread and a low thread, protruding at a proper position of the high thread and / or the low thread at least in a normal direction of a flank of the thread. A tapping screw characterized by having a convex portion. 2. The tapping screw according to claim 1, wherein the convex portion rises while being inclined with respect to a radial direction of a shaft portion of the tapping screw. 3. The blank according to claim 1, wherein a blank is supplied between the plurality of rolling dies, and the plurality of rolling dies are relatively moved to roll the blank between the plurality of rolling dies. A tapping screw manufacturing method for manufacturing a tapping screw by thread rolling, wherein a rolling pressure in a region corresponding to a portion where the convex portion is to be provided is higher than a rolling pressure in a normal case, and the plurality of rolling dies are provided. A method for manufacturing a tapping screw, wherein at least one of the dies has a blank contact surface in the vicinity of a terminal end portion thereof bite into the blank and the meat of a corresponding portion of the blank is extruded to form the convex portion.