JP3130658U - Tapping screw - Google Patents

Abstract

Provided is a tapping screw with good screw accuracy and which can be easily formed.
A kerf 8 is formed simultaneously with thread rolling. The cross section of the cut groove 8 has a substantially trapezoidal shape having a flat portion 10 at the groove bottom. The second inner wall surface 12 on the downstream side in the screw rotation direction A is inclined with respect to the radial direction B of the screw shaft 2 at an inclination angle G (0 ° <G ≦ 10 °). The second inner wall surface 12 and the peripheral surface 3 of the screw shaft 2 intersect to constitute a cutting blade 13. Since the wide space secured near the groove bottom of the cut groove 8 functions as a fledgling space at the end of rolling, the screw diameter does not increase by restoration.
[Selection] Figure 2

Description

  The present invention relates to a tapping screw that can be cut into the inner surface of a hole in a metal plate by screwing it into the hole in the metal plate.

Conventionally, in this type of tapping screw, after a screw shaft is manufactured by rolling, a kerf extending across the thread from the tip of the screw shaft is cut. Typically, the kerf has, for example, a V-shaped cross section, and a cutting blade for tapping is configured by a corner portion formed by intersecting one inner wall surface of the kerf with the peripheral surface of the screw shaft (for example, Patent Document 1).
However, since the cutting process of the kerf is performed, the number of processes is increased and the manufacturing cost is increased accordingly.

Further, in the case of cutting, incision can be made only perpendicular to the tangent line of the screw peripheral surface, and therefore, burrs are likely to occur. In such a case, there is a possibility that the tapping resistance increases and the hole cannot be cut. On the other hand, when deburring is performed by barrel polishing or the like, screw accuracy is not achieved.
Japanese Patent Laid-Open No. 11-151546

Therefore, the inventor of the present application considered that the above-described kerf is formed at the same time as thread rolling. Therefore, for example, it is conceivable to provide a protrusion for forming the above-mentioned kerf at the screw rolling end position of a flat rolling vise.
However, in this case, the thread formed by rolling is distorted by the effect of forming a kerf at the thread rolling end position, resulting in a new problem that the screw accuracy is deteriorated.

  The present invention has been made in view of the above problems, and an object thereof is to provide an inexpensive tapping screw that can be easily formed with good screw accuracy.

  In order to achieve the above object, the present invention is the only cutting formed on the circumferential surface (3) of the screw shaft (2) during thread rolling and extending across the thread (5) from the screw tip (4). A groove (8), and the cross-section of the cut groove (8) has a flat groove bottom (10) along the thread root (9) and a first inner wall surface upstream of the screw rotation direction (A). (11) and a second inner wall surface (12) on the downstream side in the screw rotation direction (A). The second inner wall surface (12) has a screw shaft (2 ) In the radial direction (B) at an inclination angle G satisfying 0 ° <G ≦ 10 ° so that the entrance of the kerf (8) expands, and the second inner wall surface (12) And the peripheral surface (3) of the screw shaft (2) intersect to form a tapping cutting blade (13). Inclined in the same direction with respect to the axis (C) of the shaft (2).

Meat that moves in the vicinity of the root of the screw at the time of thread rolling tries to recover by escaping into the space near the groove bottom in the cut groove at the end of rolling. However, in a conventional groove having a V-shaped cross section, the space near the groove bottom is narrow and cannot escape into the space near the groove bottom, so there is no escape space for meat, and the screw diameter inevitably increases.
In contrast, in the present invention, a flat portion is provided at the bottom of the groove to secure a relatively large space near the bottom of the groove, so that meat that has moved near the bottom of the screw during thread rolling can be removed. As a result of being able to escape to the space near the groove bottom at the end of rolling, the screw diameter does not increase and the screw accuracy is easily obtained.

Since the inclination angle G of the second inner wall surface with respect to the radial direction of the screw shaft is set in a range of 0 ° <G ≦ 10 °, high cutting performance can be achieved as a cutting blade.
In order to improve the cutting performance of the cutting blade, the inclination angle G is preferably as small as possible, but it is not preferable that the inclination angle G is too small in consideration of tapping resistance. Therefore, when emphasizing the cutting performance, it is preferable to set the inclination angle G in a range of 0 ° <G ≦ 5 °. When importance is attached to the reduction of tapping resistance, the inclination angle G is set to 5 ° <G. It is practical to set a range of ≦ 10 °.

If a plurality of grooves are provided as the cut grooves, the material flesh is easily brought up and raised during rolling, which may deteriorate the screw accuracy. On the other hand, in the present invention, since only one kerf is provided, it is possible to ensure the screw accuracy without unnecessarily drawing a large amount of material during rolling.
If the cutting blade is inclined in the direction opposite to the helical line with respect to the axis of the screw shaft, the meat is pushed up along the helical line during rolling and moved downward (to the tip of the screw shaft). The meat will not escape. For this reason, since the amount of meat restored at the end of screw rolling increases, the screw outer diameter increases. As a result, there is a concern that the screw accuracy is not obtained and the biting into the hole of the metal plate is deteriorated. On the other hand, according to the present invention, the cutting blade and the helical winding line of the thread are inclined in the same direction, so that the meat can be smoothly released during rolling, so that the screw accuracy can be increased.

The kerf preferably extends beyond the tapered portion of the tip of the screw shaft. Further, if the tapered portion is formed at the same time as the rolling, the manufacturing cost can be remarkably reduced.
In a tapping screw with a relatively fine screw pitch, the kerf may traverse all the threads on the screw shaft. Further, in the case of a tapping screw having a relatively coarse thread pitch, the kerf may cross a plurality of screw threads so as to slightly exceed the tapered portion.

  The cutting blade is preferably inclined at an angle of 10 to 30 ° with respect to the axis of the screw shaft. The reason is that if the angle is less than 10 °, the resistance of the cutting blade decreases, and there is a risk of slipping. On the other hand, if the angle exceeds 30 °, the cross-section of the cutting blade becomes substantially round and the cutting becomes worse. This is because the performance of the cutting blade deteriorates. Note that, in the above range of 10 to 30 °, the long screw length is preferably in the range of 10 to 20 °, and the short screw length is preferably in the range of 20 to 30 °. This is because the kerf needs to cross the required number of threads. In consideration of the screw length and the performance of the cutting blade, it is most realistic to set the angle within the range of 15 to 20 °.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic perspective view of a tapping screw according to an embodiment of the present invention. Referring to FIG. 1, the present tapping screw 1 is formed by rolling, and a thread 5 having a predetermined number of turns is provided on a peripheral surface 3 of a screw shaft 2 from a screw tip portion 4. A taper portion 6 having a tapered shape is provided on the peripheral surface of the screw tip portion 4. The peripheral surface 3 of the screw shaft 2 is provided with a single kerf 8 extending from the screw tip 4 to the screw head 7 side across the plurality of screw threads 5.

As shown in FIG. 1, in the tapping screw 1 having a relatively small screw pitch, the kerf 8 preferably crosses all the screw threads 5 from the screw tip 4 to the screw head 7. However, the kerf 8 does not necessarily have to reach the screw head 7.
Further, as shown in FIG. 3, in the tapping screw 1 having a relatively coarse screw pitch, the kerf 8 only needs to cross the thread 5 so as to slightly exceed the tapered portion 6 of the screw tip 4.

The kerf 8 is formed at the same time as thread rolling with a die. As the material of the present tapping screw 1, steel can be used.
Referring to FIGS. 1 and 2, the cross-section of the kerf 8 includes a flat portion 10 provided at the groove bottom and substantially along the thread bottom 9, and a first inner wall surface 11 on the downstream side in the screw rotation direction A. And a second trapezoidal shape having a second inner wall surface 12 on the upstream side in the screw rotation direction A.

The first inner wall surface 11 is inclined with respect to the radial direction B of the screw shaft 2 so that the entrance of the kerf 8 expands, and the inclination angle F is set in a range of 50 to 80 °, for example.
The second inner wall surface 12 is inclined so that the entrance of the kerf 8 expands with respect to the radial direction B of the screw shaft 2, and the inclination angle G is set in a range of 0 ° <G ≦ 10 °. ing. The second inner wall surface 12 and the peripheral surface 3 of the screw shaft 2 intersect with each other to form a tapping cutting blade 13.

  The reason why the inclination angle G of the second inner wall surface 12 is set in the range of 0 ° <G ≦ 10 ° is to achieve high cutting performance as the cutting blade 13. In order to improve the cutting performance of the cutting blade, it is preferable that the cutting edge is as small as possible. However, if the cutting edge is too small, the tapping resistance is increased. Is practically preferable, and when importance is placed on the reduction of tapping resistance, it is practically preferable to set the inclination angle G in a range of 5 ° <G ≦ 10 °.

  Further, the above-described cutting blade 13 and the helical line of the screw thread 5 are inclined in the same direction with respect to the axis C of the screw shaft 2. This is to smoothly escape the meat brought in during rolling and increase the screw accuracy. In particular, the inclination angle H of the cutting blade 13 with respect to the axis C of the screw shaft 2 is preferably set in the range of 10 to 30 °. The reason is that if the angle is less than 10 °, the cutting resistance of the cutting blade 13 decreases, and there is a risk of slipping. On the other hand, if the angle exceeds 30 °, the cross-section of the cutting blade 13 becomes substantially round and the cutting becomes worse. is there. Among the above ranges, a long screw length is preferably in the range of 10 to 20 °, and a short screw length is preferably in the range of 20 to 25 °. This is because the kerf 8 needs to traverse the required number of threads 5. In consideration of the screw length and cutting blade performance, the range of 10 to 15 ° is the most realistic.

According to the present embodiment, since the kerf 8 is formed at the same time as thread rolling, the number of steps can be reduced, and a tapping screw can be manufactured inexpensively and easily.
Moreover, since the flat portion 10 is provided at the groove bottom of the kerf 8 to secure a relatively large space near the groove bottom, the meat that has moved near the bottom 9 of the screw during thread rolling As a result of being able to escape to the space near the groove bottom at the end of rolling, the screw diameter does not increase and the screw accuracy is easily obtained.

In particular, since only the kerf 8 is provided, there is no need to unnecessarily increase the thickness of the raw material during rolling, and screw accuracy can be ensured from this point as well.
The present invention is not limited to the above embodiment. For example, as shown in FIG. 3, in the tapping screw 1 having a relatively coarse screw pitch, the kerf 8 extends from the screw tip 4 to the tapered portion 6. It suffices if the plurality of screw threads 5 are crossed by a little over.

The kerf 8 having a long screw length is sufficient if it extends over, for example, about 4 to 7 threads from the tip of the screw shaft. In addition, in the case of a short screw length, for example, it is sufficient to straddle about two or three threads.
In addition, examples of the material of the mating member to which the present tapping screw can be applied include steel and aluminum alloys. In addition, various modifications can be made within the scope of the present invention.

It is a side view of the tapping screw of one embodiment of the present invention. It is sectional drawing of a tapping screw. It is a side view of the tapping screw of another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tapping screw 2 Screw shaft 3 Circumferential surface 4 Screw tip part 5 Screw thread 6 Tapered part 7 Screw head part 8 Groove 9 Valley bottom 10 Flat part 11 1st inner wall surface 12 2nd inner wall surface 13 Cutting edge A Screw rotation direction B Radial direction C Axis G Inclination angle of second inner wall surface with respect to radial direction of screw shaft

Claims (3)

It is formed on the peripheral surface (3) of the screw shaft (2) during thread rolling, and has a single groove (8) extending from the screw tip (4) across the screw thread (5),
The cross section of the cut groove (8) includes a flat groove bottom (10) along the thread root (9), a first inner wall surface (11) upstream of the screw rotation direction (A), and screw rotation. A substantially trapezoidal shape having a second inner wall surface (12) on the downstream side in the direction (A),
The second inner wall surface (12) has an angle of inclination G satisfying 0 ° <G ≦ 10 ° with respect to the radial direction (B) of the screw shaft (2) so that the inlet of the kerf (8) expands. Is inclined to
The second inner wall surface (12) and the peripheral surface (3) of the screw shaft (2) intersect to form a tapping cutting blade (13),
A tapping screw characterized in that the helical line of the cutting blade (13) and the screw thread (5) is inclined in the same direction with respect to the axis (C) of the screw shaft (2).   2. The tapping screw according to claim 1, wherein the inclination angle G is set so as to satisfy 0 ° <G ≦ 5 °.   The tapping screw according to claim 1, wherein the inclination angle G is set so as to satisfy 5 ° <G ≦ 10 °.

Images