JPH1047324A - Drill screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dimensions of a hole before threading so as to heighten connecting strength and reduce bouncing of a tip part of drill part so as to be able to connect positively and efficiently at a fastening point by making the diameter of a peripheral part cutting edge smaller toward the tip of the drill part. SOLUTION: In a drill part 30, a peripheral part cutting edge 34 is formed along the internal wall surface 32 of a drill groove 31 and the peripheral surface of the drill part 30, and a tip part cutting edge 35 is formed along an intersecting line between the internal wall surface 32 and a tip part 36 of the drill part 30. The diameter of the peripheral part cutting edge 34 is made smaller toward the tip of the drill part 30. Accordingly, even though a hole- before-threading cut by the tip part 36 is of irregular shape, the hole-before- threading is shaped toward the root of the drill part 30 so as to be formed into regular dimensions. A sufficient thread groove can thereby be formed at the time of tapping by a following thread part 20 so as to be able to obtain larger fastening torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill screw in which cutting of a pilot hole and tapping are performed continuously, and the screw can be tightened as it is.

[0002]

2. Description of the Related Art For example, when joining thin metal sheets with screws, a screw tapping process is usually performed after drilling a screw hole in both thin metal sheets, and then a screw having a predetermined outer diameter is formed. To join the two. However, according to such a method, the steps of drilling and tapping a screw, and the step of fastening with a screw are performed separately from each other, so that the working efficiency is very poor.

[0003] Therefore, a method of using a drill screw having a drill portion formed at the tip end of the screw, and performing a single screwing operation to simultaneously perform the steps of drilling a hole, tapping, and tightening the screw is becoming widespread. . FIG. 6 shows a conventional drill screw 1
It is a front view which shows the shape of 00. As shown in the figure, the drill screw 100 is a shank 10 having a head 110.
1, a screw part 120 and a drill part 130 are formed.

The head 110 is formed integrally with the shank 101, and has an engaging recess 111 on the upper surface for engaging with the tip of a rotary tool such as a driver. Further, a predetermined thread is formed on the threaded portion 120 by rolling. Further, two vertical grooves (hereinafter referred to as “drill grooves”) 131 are formed in the drill portion 130 by die molding.

[0005] The drill portion 130 includes the above-described drill groove 1.
An outer peripheral cutting edge 132 having a predetermined rake angle is formed along an intersection line between the inner wall surface 134 of the drill 31 and the outer peripheral surface of the drill portion 130, and the intersection between the inner wall surface 134 and the distal end surface of the drill portion 130 is formed. A tip cutting edge 133 having a predetermined rake angle is formed along the line, and these cutting edges cut a threaded hole in an object to be mounted such as a thin metal plate.

The diameters of the outer peripheral cutting edges 132 are all equal in the axial direction.
Is set between 118 ° and 120 °. When two metal thin plates (thickness: 0.6 mm to 1.2 mm) are overlapped and joined using the conventional drill screw 100 having such a shape, the tip of the drill screw 100 is attached to the metal surface. Press and tighten with a rotating tool such as a screwdriver while applying a load. Then, first, a small hole is opened in the surface of the metal plate by the cutting force of the distal end cutting edge 133, which is enlarged, and then the screw hole is gradually deepened while being cut by the outer peripheral cutting edge 132.

When the first pitch of the thread 121 of the thread portion 120 reaches the screw hole, the screw is further screwed into the screw hole while cutting a screw groove. The operation of forming the prepared screw hole and tapping is also performed on the lower metal sheet, and by further tightening the drill screw 100, the two metal sheets are joined. As described above, according to the drill screw 100, the fixing by screw tightening can be performed at a stroke without performing the screw hole and tapping step in advance, so that the efficiency of the assembling operation can be improved. .

[0008]

However, the conventional drill screw 100 has the following problems. (1) That is, when drilling a screw hole in a thin metal plate with the drill portion 130, the dimensional accuracy of the screw hole is not very good, and an elliptical shape or, in some cases, a square screw hole is opened. It can even get lost.

Such a situation occurs when a hole is formed by cutting with the tip cutting edge 133 of the drill portion 130, or when shifting from the tip cutting edge 133 to cutting with the outer peripheral cutting edge 132. It is considered that this is caused by the cutting edge shaving the inner peripheral surface of the thin screw hole of the thin plate more than necessary. As shown in FIG.
Since the outer diameter of the screw 21 is not so large as compared with the outer diameter of the drill portion 130, if the dimensional accuracy of the prepared screw hole is not good as described above, the thread groove will not be sufficiently formed when the next screw portion 120 is tapped. Not being formed, the screwing property between the screw portion 120 and the screw hole is deteriorated, the tightening torque is reduced, and the bonding strength between the metal thin plates may be reduced.

(2) Also, cutting chips (cutting powder) generated at the time of screw tightening enter between the stacked metal thin plates, and are fixed in a state where they are separated from each other (a state in which one of the metal thin plates is floating). May not be possible. (3) Further, at the time of drilling a screw hole, "dancing" occurs at the tip of the drill portion on the metal surface, and it is difficult to determine the point of the fastening point (position of the screw hole).

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has improved dimensional accuracy of a prepared screw hole to increase the bonding strength. It is possible to reduce the fluctuation of the tip of the part and to reliably and efficiently join at the positioned fastening point,
It is intended to provide a drill screw.

[0012]

In order to achieve the above object, the present invention provides a shank provided with a head, wherein a drill portion is formed at the tip of the shank, and a screw portion is formed between the head and the drill portion. A drill screw, wherein the drill portion is provided with an outer peripheral cutting edge and a distal end cutting edge at an outer peripheral portion and a distal end, respectively, and the diameter of the outer peripheral cutting edge is smaller as it is closer to the distal end of the drill portion. It is characterized by becoming.

Further, the present invention is characterized in that a screw thread for at least one pitch of the screw portion extends to the drill portion. Further, in the present invention, the tip angle of the tip cutting edge of the drill portion is 100 ° to 115 °, and the width of the chisel edge is set to approximately 10% of the minimum diameter of the drill portion. It is characterized by being.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a drill screw 1 according to the present invention will be described.
An embodiment will be described with reference to the drawings. FIG. 1 is a front view showing the shape of the drill screw 1, and FIG. 2 is a plan view thereof. As shown in the figure, a drill screw 1 is provided on a shank 2 in which a head 10 is integrally formed.
And the drill part 30 is formed.

An upper surface of the head 10 has an engaging recess 11 for engaging with a tip of a rotary tool such as a driver.
In the present embodiment, the cross section of the engagement recess 11 is
It has a rectangular shape as shown in the plan view of FIG. 2, and a rotating tool having the same rectangular cross section is inserted into the rectangular shape so that it can be rotated while applying a load. When the cross section of the head 10 is a regular hexagon or the like, it can be tightened with a hexagonal screwdriver. In this case, the engaging recess 11 may not be provided.

Further, the shape of the engaging concave portion 11 may be a normal cross hole. In this case, it is possible to tighten with a driver bit having a cross-shaped cross section. Threads 21 are formed at equal pitches in the screw portion 20, the outer diameter of which is larger than the maximum diameter of the drill portion 30, and the diameter of the thread groove portion 22 (the inner diameter of the screw) is the maximum diameter of the drill portion 30. It is set slightly smaller. Further, one pitch 21 a of the thread 21 extends to the outer periphery of the drill portion 30.
As a result, the operation can be smoothly shifted from the drilling operation by the drill unit 30 to the screwing operation, and the screw groove can be reliably cut and the screwing time can be reduced.

An outer peripheral cutting edge 34 having a predetermined rake angle is formed in the drill portion 30 along a line of intersection between the inner wall surface 32 of the drill groove 31 and the outer peripheral surface of the drill portion 30. A tip cutting edge 35 having a predetermined rake angle is formed along a line of intersection between the inner wall surface 32 and the tip surface 36 of the drill portion 30. The diameter of the outer peripheral cutting edge 34 becomes smaller toward the tip, and the present drill screw 1 forms a taper angle of about 1.5 ° as shown in FIG.
When the length is 0 mm and the length is 5.5 mm, a difference between the maximum diameter and the minimum diameter of the drill portion 30 is about 0.2 mm. This taper is formed in order to adjust the shape of the irregular pilot hole at the tip of the drill portion 30 as described later and to finally finish it into a perfect circle of a specified size. In order to achieve the object, an optimal value is set in consideration of conditions such as the axial length of the drill portion 30 and the outer diameter of the thread portion.

However, the magnitude of the taper angle greatly affects the amount of cut into the object and the torque required for screwing (screwing torque), and this point must be taken into consideration. For example, if the taper angle is set to 2 °, the amount of cutting of the outer peripheral cutting edge 34 into the object increases, and the time required for screwing the drill screw 1 (hereinafter referred to as “screwing time”). Can be shortened, but the screwing torque also increases,
The burden on the screw tightening device increases. Conversely, if the taper angle is reduced to 1 °, the amount of cut can be reduced and the screwing torque can be reduced, but the rate of reduction in screwing time is correspondingly reduced. As a harmony point of these conditions, the taper angle is desirably set to about 1.5 ° as in the present embodiment.

The tip angle A of the tip cutting edge 35 formed on the tip face 36 is set to 110 °, which is sharper than the conventional one (118 ° to 120 °). A chisel edge 37 is provided at the point of the tip surface 36.
(See FIG. 4) is formed. This chisel edge 37
First contact the surface of the object to be screwed,
It is an important cutting edge for cutting positioning holes.

FIG. 3 is a side view when the drill portion 30 of the drill screw 1 is viewed from the direction of the white arrow in FIG. As shown in the figure, the drill groove 31 has inner wall surfaces 32 and 33. As described above, the outer peripheral cutting edge 3 is provided at the intersection of the inner wall surface 32 with the outer peripheral surface and the distal end surface of the drill portion 30.
4. A tip cutting edge 35 is formed. A drill groove 31 is also formed in a part of the thread 21a for one pitch formed in the drill portion 30.

FIG. 4 is an end view of the drill portion 30 when FIG. 1 is viewed from below. As shown in the figure, two drill grooves 31 are formed axially symmetrically, and the outer peripheral cutting edge 34 is formed on the outer end surface of the inner wall surface 34. The chisel edge 37 is formed at the junction of the two tip surfaces 36, and its width W1 is approximately 10 mm of the minimum diameter W of the drill portion 30.
It is set to the size of%. Since the width of the chisel edge in the conventional drill screw is about 16% of the outer diameter of the drill portion, the cutting force can be greatly improved as compared with the conventional drill screw along with the reduction of the above-mentioned tip angle A. It has become possible.

The above-described drill portion 30 is formed by molding, and the screw portion 20 is formed by rolling. FIG.
It is a figure which shows a mode that the drill part 30 of the said drill screw 1 cuts a screw hole in a thin metal plate. In the figure, the broken line 41 indicates the minimum diameter of the drill portion 30 and the solid line 43
Indicates the maximum diameter of the drill portion 30. When the drill screw 1 is fastened to a thin metal plate, the tip of the drill portion 30 is brought into contact with the metal surface and rotated while applying a load. Then, first, a small hole for positioning is cut in the surface of the thin metal plate by the chisel edge 37, and the hole is gradually enlarged by the tip cutting edge 35, and the screw hole becomes deeper. Then, the process proceeds to cutting by the outer peripheral cutting edge 34.
At this time, as described above, the inner peripheral surface of the prepared screw hole is unnecessarily chipped by the cutting blade, resulting in an irregular inner diameter as shown by the solid line 42. However, in the present drill screw 1, the diameter of the outer peripheral cutting edge 34 of the drill portion 30 becomes smaller toward the distal end, in other words, becomes larger as it is closer to the screw portion 20, so that the inner circumference of the irregular screw hole is reduced. The surface is cut and shaped by the outer peripheral cutting edge 34 having a larger diameter, and finally, a perfect circular screw hole having a specified dimension shown by the solid line 43 is formed. Subsequently, tapping by the screw portion 20 is performed. However, as described above, the thread for one pitch is also formed on the upper portion of the drill portion 30, so that the screw is formed in parallel with the finishing of the prepared screw hole. Standing is started, and a smooth screwing function is obtained. When the screw is screwed into the screw hole having the specified size, a screw groove is formed firmly on the inner peripheral surface of the screw hole, and a sufficient tightening torque can be obtained.

Further, in the present embodiment, as described above, the taper is formed in the drill portion 30 to reduce the tip diameter, and further, the tip angle A of the drill portion 30 is reduced to 110 ° and the chisel edge 37 is formed. Is also reduced to 10% of the minimum diameter of the drill portion, so that the cutting efficiency of the drill portion 30 is improved, and the time for screwing in with the drill screw can be greatly reduced.

The following (Table 1) and (Table 2) are experimental data showing the reduction of the screwing time.

[0025]

[Table 1]

[0026]

[Table 2]

In each of the tables, the conventional shape of the drill screw has an outer diameter of 4.2 mm and a diameter of 3.2 mm.
mm, tip angle 120 °, chisel edge width O. 5m
m, the nominal length of the screw is 13 mm, and the drill screw of the present invention has the same outer diameter and nominal length of the thread part as the conventional one. The minimum diameter of the portion is set to 3.0 mm, the tip angle is set to 110 °, and the chisel edge width is set to 0.3 mm. Also, both drill screws are formed of a material having the same hardness.

Table 1 shows the hardness HRB62.
1. A load of 1 for each drill screw on a 1.6mm thick steel plate
FIG. 5 shows experimental data when screwing at a rotation speed of 2500 rpm with a load of 3.6 kg, and the screwing time was measured after 10 trials. As is clear from the same table, the screwing time of the drill screw of the present invention is shorter than that of the conventional drill screw, and the average time is
1.14 seconds, which is a time reduction of about 21% compared to the average value of 1.45 seconds for the screwing time by the conventional drill screw.

This time reduction rate becomes more remarkable as the thickness of the steel sheet increases. (Table 2) shows a load of 15.8 Kg for each drill screw on a steel plate having a hardness of HRB 47.3 and a thickness of 3.2 mm.
Shows the experimental data when screwing in at a rotation speed of 2500 rpm while loading, and as shown in the same table, a difference of 1.42 seconds occurs between the average screwing times of both, which is almost 36%. Equivalent to time saving.

As described above, the larger the thickness of the steel plate, the larger the shortening rate of the screwing time is because the outer peripheral cutting edge 34
This is largely due to the fact that the cutting efficiency of the outer peripheral cutting edge 34 is improved by providing a taper in the outer peripheral portion. That is, the cutting powder continuously cut by the tip cutting edge 35 of the drill portion and the following tapered outer peripheral cutting edge 34 is surely carried upward along the taper and the drill groove 31 and cut. The cutting efficiency is improved by being discharged from the surface, whereby the screwing time is further shortened. In particular, as the thickness of the steel plate becomes thicker, that is, the cutting force of the tapered outer peripheral cutting edge 34 is often exerted. Thus, the reduction rate of the screwing time can be improved.

The drill screw 1 has a small tip angle A, a narrow chisel edge width, and a sharp tip as described above to enhance the cutting force. "Dance" of the drill bit, which has conventionally occurred on the surface of the metal plate when opening, has been reduced, and positioning of the pilot hole has been facilitated. Such a reduction in “bounce” and a drastic reduction in the screwing time make the screw tightening process more efficient, so that the production efficiency can be improved especially when used in a production line. .

Further, the improvement of the cutting force solves the problem that, when the metal sheets are overlapped and joined together, the chips are mixed between the sheets and the sheets are joined in a floating state. You. That is, the reason that the cutting powder is mixed between the metal sheets is that the lower metal sheet having no prepared hole is bent by the load applied to the drill screw 1 at the time when the preparation of the prepared metal sheet is completed. Although it is considered that a gap is generated between the drill screws 1 of the present invention, since the cutting force at the tip of the drill portion 30 is improved,
Before a large bending force is applied to the lower metal sheet, a pilot hole is made in the metal sheet, so that there is almost no gap where chips are mixed. In addition, since the above-mentioned tapered outer peripheral cutting edge 34 improves the cutting force, continuous large chips are generated, so that the efficiency of discharging to the outside of the prepared hole is improved and more and more mixed in the gap. It became difficult to do.

This makes it possible to join a plurality of thin metal plates in a desired state in which they are in close contact with each other with a high tightening torque. It can also be used as a building material by being combined with, and the use of drill screws can be expanded. The cutting force increases as the tip angle A of the drill portion 30 decreases, but on the other hand, the rigidity decreases and the tip is easily chipped.
It is desirable that the angle be set in the range of 0 ° to 115 °. For the same reason, the width of the chisel edge is preferably about 10% of the minimum diameter of the drill portion.

[0034]

As described above, according to the present invention, the outer diameter of the outer peripheral cutting edge provided on the outer peripheral portion of the drill portion of the drill screw is formed in a tapered shape so as to become smaller as the outer peripheral portion thereof becomes closer to the tip portion. As a result, even if the threaded hole cut at the tip of the drill has an irregular shape, it will be shaped as it goes to the root of the drilled part, and it will be possible to form a threaded hole of specified dimensions . Thereby, a thread groove can be sufficiently formed at the time of tapping by the next screw portion, and a larger tightening torque can be obtained.

Further, according to the present invention, since the screw thread for at least one pitch of the screw part is formed so as to extend also to the drill part, the screw part can be smoothly screwed into the formed screw hole. Further, the tip angle of the tip cutting edge of the drill portion is 1
Since the chisel edge width is set to approximately 10% of the minimum diameter of the drill portion, the cutting force of the tip portion of the drill portion can be improved, and the outer peripheral portion can be cut. Coupled with the fact that the blade is formed in a tapered shape, the screw tightening operation can be performed in a short time.

That is, the cutting powder continuously cut by the tip cutting edge of the drill portion and the subsequent tapered outer peripheral cutting edge is surely carried upward along the taper and the drill groove and cut. Since it is discharged from the surface, the cutting speed is increased and the screwing time can be shortened.
As the thickness of the metal plate is larger, the screwing time is significantly reduced. As a result, the time required for the screw tightening process in a production line or the like can be greatly reduced, and this greatly contributes to an improvement in productivity.

In addition, the chips can be closely attached to each other without chips or the like being mixed between the members to be joined.
"Dancing" of the cutting edge of the drill portion at the start of the screw drilling operation can be reduced, and efficient screw tightening can be performed.

[Brief description of the drawings]

FIG. 1 is a front view of a drill screw according to the present invention.

FIG. 2 is a plan view of the drill screw.

FIG. 3 is a view of a drill portion of the drill screw as viewed from a direction of an arrow in FIG. 1;

FIG. 4 is a diagram showing an end face of a drill portion when the drill screw is viewed from below in FIG. 1;

FIG. 5 is a view showing a state in which a pilot hole of a drill screw is being cut by a drill portion of the drill screw.

FIG. 6 is a front view showing the shape of a conventional drill screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill screw 10 Head 20 Screw part 30 Drill part 31 Drill groove 34 Peripheral cutting edge 35 Tip cutting edge 37 Chisel edge A Tip angle W1 Chisel edge width

Claims (3)

[Claims] 1. A drill screw having a drill portion formed at a tip portion of a shank having a head portion and a screw portion formed between the head portion and the drill portion, wherein the drill portion has an outer peripheral portion. And a distal end having an outer peripheral cutting edge and a distal end cutting edge, respectively, wherein the diameter of the outer peripheral cutting edge decreases as it approaches the distal end of the drill portion. 2. The drill screw according to claim 1, wherein a screw thread of at least one pitch of the screw portion extends to the drill portion. 3. A tip angle of a tip cutting edge of the drill portion is:
The drill screw according to claim 1 or 2, wherein the chisel edge width is set to approximately 10% of a minimum diameter of the drill portion.