JP4512991B2 - Tapping screw - Google Patents

Description

The present invention relates to Flip It tapping, and in particular to the structure of the self-tapping screws that are suitable for fastening to the metallic thin plate.

  FIG. 8 is a cross-sectional view showing a pilot hole (burring hole) shape by a conventional extrusion process. In the conventional fastening material 24 having a plate thickness of 1.2 mm to 0.8 mm, the material is squeezed by extrusion processing to ensure an extrusion height 25. When a normal JIS tapping screw type 3 forming type is used for such a fastening material 24, when the plate thickness of the fastening material 24 is thin, the protruding portion tip 26 spreads as shown by a dotted line 27 during thread rolling. In other words, an effective screw length cannot be ensured, and a phenomenon that the internal thread breaking torque is reduced may occur. In addition, the fastening performance is greatly affected by variations in the sag portion 28 of the screwed portion in the extrusion process. Moreover, a large pressing pressure is required for burring.

  However, conventionally, with JIS tapping type 3 screws, even if burring is performed on the fastening material 24 side, it is said that screws cannot be fastened particularly with a thin sheet metal material such as a sheet thickness of 0.6 mm. In other words, the internal thread breaking torque is small on the internal thread side, making it impractical. Conventionally, when a type 3 screw is repeatedly fastened to a burring-shaped female screw having a plate thickness of 0.8 mm, the female screw is broken when the number of repeated fastenings is less than 10 times.

  In the type 1 screw, there is a method of screw fastening to a thin plate without burring, but the axial force, that is, the force for pressing the material to be fastened against the fastening material is small, and repeated fastening is impossible. In other words, the OA equipment cannot be used in places where it is required to ensure axial force (contact pressure), prevent loosening, etc. from the safety standard surface applied to all screw tightening places.

  On the other hand, the reuse of equipment is increasing due to environmental considerations. In such a case, it is required that the screw can be fastened a plurality of times. Moreover, the energy saving effect by weight reduction is also anticipated.

  Therefore, as a screw that can be repeatedly fastened to a thin plate without burring, a tapping screw for forming type metal thin plate in which the number of threads of the effective thread is twice the number of threads of the lead Is considered.

  However, the above-mentioned type of tapping screw has a drawback that the axial force is small. If the tightening torque (driver torque) is increased to improve the axial force, the material to be fastened, especially the plate thickness is 0.6 mm. Female screw breakage may occur when the screw hole is large and a thin plate material is used.

It is an object of the present invention to provide a tapping screw that is not limited to a thin plate material or the like, can be used for various plate materials without burring, can be repeatedly fastened, and can secure the axial force of the screw .

It is another object of the present invention to provide a tapping screw that satisfies the basic characteristics required for screw fastening, that is, a screwing torque, a loosening torque, and a female screw breaking torque, and that can improve repeated fastening performance.

In order to achieve the above object, the tapping screw according to claim 1 of the present invention is smaller than the outer diameter of the screw head lower surface recessed in the screwing direction around the female screw side lower hole portion into which the tapping screw is screwed . And a concave portion larger than the outer diameter of the screw is provided,
Concave shaped portion, compared screwing direction of the tapping screw, Ru used for fastening to the metal thin plate is formed by a shallower refine than the female thread side lower bore peripheral thickness at threaded root side is wide trapezoidal section shape A tapping screw,
To the thread count of the lead portion, Ru der those for forming the type of sheet metal threads number of effective thread portion is the number of 2 times,

It is characterized by that.

Those according to the second aspect, in order to achieve the above object, the peripheral internal thread lower hole portion which tapping screw is screwed, smaller than the screw head lower outer diameter which is recessed with respect to the screwing direction, and it Flip Provide a concave part larger than the outer diameter,
Concave shaped portion, said relative screwing direction of the tapping screw, Ru used for fastening to the metal thin plate by screwing source side is wider shape is formed by half blanking shallower than the female thread side lower bore peripheral thickness tapping A screw,
To the thread count of the lead portion, Ru der those for forming the type of sheet metal threads number of effective thread portion is the number of 2 times,
It is characterized by that.

According to the third aspect of the present invention, in order to achieve the above object, in the tapping screw according to the first or second aspect, the maximum outer diameter of the screw portion of the tapping screw is 5 to 20 % of the concave shape portion of the thin metal plate. It is large .

The Flip I tapping according to the present invention, As has been described, even when the fastened thickness of the metal sheet to be fastened object thin, reduces the bite of the external thread incomplete thread portion, burring the female screw portion processing also enables fastening by securing the axial force of the screw is not provided, there is an effect that Ru Hakare on preventing loosening of NoMuko by taking advantage of characteristics of the tapping screw for forming the type of sheet metal.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a side view showing an example of a thin plate tapping screw 1 (hereinafter simply referred to as a tapping screw 1) used in an embodiment of the present invention. The head 5 has a hexagonal shape with a cross-recessed seat, and the threaded portion is constituted by a lead portion 6 having three threads and an effective screw portion 7 having six threads. The 6-thread thread of the effective thread portion 7 has thread threads 9 and 10 symmetrical with respect to the thread center axis 8. Therefore, when initially tightened obliquely with respect to the material to be fastened, the direction is corrected so as to be perpendicular to the fastened location by the resistance of the three screw threads that increase from the effective screw portion 7, and the center axis 8 is corrected so as to be more perpendicular to the fastened location by acting so that the resistance difference between the opposing threads 9 and 10 is also reduced. Further, at the time of re-fastening, since the number of screw threads of the lead portion is previously formed with respect to the number of screw threads of the lead portion, it is considered that it is easy to trace and acts very effectively on repeated fastening.

  FIG. 2 is a cross-sectional view of an embodiment of the present invention in a state of being fastened using the screw shown in FIG. In this embodiment, the material to be fastened 2 is fastened to the fastening material 3 with a tapping screw 1 shown in FIG. The recessed portion 4 of the fastening material 3 is in a state in which a pressurizing force is applied due to a slight deformation due to the axial force of the tapping screw 1 in the fastened state.

  FIG. 3 is a sectional view of a recess around the pilot hole in the fastening material 11 having a thickness of 0.6 mm and 0.8 mm. In the vicinity of the female screw pilot hole 12 of the fastening material 11, a recessed portion 14 is formed by narrowing down the trapezoidal cross-sectional shape with a wider screwing source side with respect to the screwing direction 13 of the tapping screw 1. The diameter 15 of the bottom part of the concave shaped part 14 is 0.5 to 0.2 mm larger than the maximum outer diameter of the threaded part of the tapping screw 1 to be fastened, the angle 16 of the inclined surface part is about 45 ° ± 15 °, The depth 17 is set to 1/4 to 1/2 of the plate thickness of the fastening material 11.

  FIG. 4 is a cross-sectional view of a recess around a prepared hole in the fastening material 18 having a plate thickness of 1.0 mm. Around the female screw pilot hole 19 of the fastening material 18, a concave portion 21 formed by half-cutting in the screwing direction 20 of the tapping screw 1 is formed. Similar to the example of FIG. 3, the diameter 22 of the concave portion 21 is 0.5 to 0.2 mm larger than the maximum outer diameter of the tapping screw 1 to be fastened, and the half punching depth 23 is the thickness of the fastening material 18. 1/4 to 1/2.

  In both examples of FIGS. 3 and 4, the diameter and depth of the bottoms and the like of the concave portions 14 and 21 are set from the viewpoint of ensuring bending strength due to the shape effect around the pilot hole and facilitating processing. . Further, the difference between the drawing process and the half-punching process was selected from the viewpoint of ease of processing due to the plate thickness of the fastening materials 11 and 18 and securing the strength. In the drawing and half punching processes, the press pressure is smaller than that of the burring.

FIG. 5 is a cross-sectional view of an example in which a flat thin plate fastening material 29 not provided with a recess is fastened as a comparative example. Around the female screw hole 30 of the fastening material 29, a bending moment with the screw hole end portion 33 of the fastened material 32 as a fulcrum acts by the axial force of the screw 31, and deformation occurs. Deformation due to this bending stress is a major factor of internal thread failure. On the other hand, in both examples of FIGS. 3 and 4, the periphery of the female screw pilot holes 12 and 19 has a shape that is strong against bending stress, and the female screw breakage is well prevented.
(Experimental example)
FIG. 6 is a diagram of the effect of female screw breaking torque by the presence or absence of a recess as in the embodiment of the present invention described above, and shows the result of measuring the female screw breaking torque when using a screw having a nominal diameter of 3 (not shown). Show. In the figure, 34 indicates the internal thread breaking torque characteristic of the fastening material having a plate thickness of 0.6 mm and having a recess. The female screw breaking torque of the fastening material with a plate thickness of 0.6 mm and no recess is 1.1 N · m or less because the female screw breaks when tightened with a tightening torque of 11 kgf · cm (1.078 N · m). it is conceivable that. As an effect of the presence of the concave portion, the performance improved by about 87 to 62% in the prepared hole diameter measured this time.

  In the figure, 35 indicates a female screw breaking torque characteristic of a fastening material having a plate thickness of 0.8 mm with a recess, and 36 in the figure indicates a female screw breaking torque characteristic of the fastening material having a thickness of 0.8 mm without a recess. . Each pilot hole diameter is improved by about 50%.

  The internal thread breakage is caused by insufficient bending stress due to an increase in the distance between the end of the internal thread and the holding part on the side to be fastened. When the hole was 3.5 mm × 5 mm, the tightening torque was 1.1 N · m, the female thread was frequently broken without the recess, and the female thread was not broken with the recess.

  FIG. 7 is a diagram showing the effect of the loosening torque by the presence or absence of a recess as in the above-described embodiment of the present invention, and shows the result of measuring the loosening torque when using a screw having a nominal diameter 3 (not shown). In the figure, 37 indicates a loose torque characteristic with a plate thickness of 0.6 mm and a recess. With the same plate thickness and without a recess, measurement was impossible due to the occurrence of internal thread failure (loosening torque = 0). In the figure, 38 indicates a loose torque characteristic with a plate thickness of 0.8 mm and a recess, and 39 in the figure indicates a loose torque characteristic with a plate thickness and no recess.

  As can be seen from the result, the performance of the prepared hole diameter measured this time is about 30%. This is considered that the distortion in the concave portions 14 and 21 functions as a loosening prevention as in the case where the dish washer is inserted.

  When the thickness of the female screw plate was 0.8 mm, the female screw breaking torque averaged 1.42 N · m without recess and the female screw breaking torque average with recess was 2.14 N · m, and the loosening torque was improved by about 30%. When the plate thickness was 0.8 mm, the average loose torque was 0.58 N · m when there was no recess, and the average loose torque was 0.77 N · m when there was a recess.

  In other words, steel plates with a thickness of 0.6 mm, which could not be used because screws cannot be fastened, can be used in places where axial force is required in the past, and switching from a plate material with a thickness of 0.8 mm to a thinner plate material. Can be achieved, and the cost can be greatly reduced and the energy can be saved. In addition, even if the plate thickness of the material used is 0.6 mm, compared to the conventional plate thickness of 0.8 mm and the fastening performance in the burring process, the female screw breaking torque is improved, the repeated fastening performance is greatly improved, and the reusability is improved. .

  Furthermore, even when switching from conventional burring processed parts with a plate thickness of 0.8 mm, burring processing is changed to half-pressing processing, the processing press pressure is reduced, workability is improved, and repeated fastening performance is also greatly improved. To improve. Even if the plate thickness of the material used is 1.0 mm, it can be fastened by mere drilling instead of burring as in the past, or if larger internal thread breaking torque is required, it can be processed by half blanking Improves.

That is, even when the fastened thickness is thin, and bite the reduction of the external thread incomplete thread portion, also enables fastening without providing a burring the female screw portion, three in the number of threads in the read unit , it is possible to utilize the characteristics of the tapping screw for forming the type of sheet metal that the number of threads in the useful thread portion is a six. Of course, the same effect can be achieved with other tapping screws having different numbers of threads.

It is a side view which shows an example of the tapping screw for thin plates used by embodiment of this invention. It is sectional drawing of one Embodiment of this invention. It is a recessed part sectional view of a pilot hole periphery with the fastening material of board thickness 0.6mm and 0.8mm in one Embodiment of this invention. It is a recessed part sectional view of a pilot hole periphery with the fastening material of board thickness 1.0mm in one Embodiment of this invention. It is sectional drawing of the comparative example which fastened the fastening material of the flat thin plate which does not provide the recessed part. It is a figure of the internal thread destruction torque effect by the presence or absence of a recessed part like embodiment of this invention. It is a figure of the loosening torque effect by the presence or absence of a recessed part like embodiment of this invention. It is sectional drawing which shows the pilot hole shape by the conventional protrusion process.

Explanation of symbols

1: Tapping screw for thin plate 2: Fastened material 3: Fastening material 4: Recessed portion 5: Head portion 6: Lead portion 7: Effective screw portion 8: Screw center shaft 9, 10: Screw thread 11, 18: Fastening material 12, 19: Female screw pilot hole 13, 20: Screwing direction of tapping screw 14: Concave shape part of trapezoidal cross section 21: Concave shape part of half punching process

Claims (3)

Surrounding under internal thread side bore the tapping screw is screwed, the screw head smaller than lower surface outer diameter, and the large concave portion than thread diameter provided recessed with respect to the screwing direction,
Concave shaped portion, compared screwing direction of the tapping screw, Ru used for fastening to the metal thin plate is formed by a shallower refine than the female thread side lower bore peripheral thickness at threaded root side is wide trapezoidal section shape A tapping screw,
To the thread count of the lead portion, Ru der those for forming the type of sheet metal threads number of effective thread portion is the number of 2 times,
A tapping screw characterized by that. Surrounding under internal thread side bore the tapping screw is screwed, the screw head smaller than lower surface outer diameter, and the large concave portion than thread diameter provided recessed with respect to the screwing direction,
Concave shaped portion, said relative screwing direction of the tapping screw, Ru used for fastening to the metal thin plate by screwing source side is wider shape is formed by half blanking shallower than the female thread side lower bore peripheral thickness tapping A screw,
To the thread count of the lead portion, Ru der those for forming the type of sheet metal threads number of effective thread portion is the number of 2 times,
A tapping screw characterized by that. In tapping screws according to claim 1 or 2, tapping screws maximum outer diameter of the threaded portion of the tapping screw, characterized in that 5-20% larger than the concave portion of the metals sheet.