JPH10292809A - Self-drilling tapping screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-drilling tapping screw by which chips can be smoothly discharged and also by which the tightening operation thereof to a work can be enabled with a relative low tightening torque. SOLUTION: Since the self-drilling tapping screw is constituted in such a way that a drill part 10 having a cylindrical shape whose diameter is larger than the root diameter of the thread part 5 and smaller than the ridge diameter thereof and having a conical shape at its front end is formed at the end of the leg part 3, and double guide grooves 13 are formed from the front end of the drill part 10 up to the starting position of the thread part 5, and also a recessed groove 20 similar to the root diameter of the thread part 5 is provided between the starting position of the thread part 5 and the rear end of the drill part 10, chips are moved up to the root part of the thread part 5 from the guide grooves 13 through the recessed groove 20, so that the clogging thereof between the wall of the prepared hole of the tapping screw and the tapping screw can be entirely prevented. Further, tightening torque of the drill screw can be reduced for obtaining smooth screw tightening work, so that the load of a worker can be reduced. Furthermore, since the seating surface of the screw head part is securely brought into contact with the work, the occurrence of a screw floating condition can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-tapping screw which can be screwed into a work without forming a pre-drilled hole in the work in advance, and the self-tapping screw itself forms a prepared hole in the work. In particular, the present invention relates to a self-drilling tapping screw capable of discharging a workpiece without clogging generated when a pilot hole is formed in a drill portion.

[0002]

2. Description of the Related Art Conventionally, when a tapping screw is screwed into a metal plate, a pilot hole into which the screw is screwed is mainly drilled in a metal plate-like work in advance using a tool such as a drill. By screwing a self-tapping screw into the prepared hole, a female screw is formed and screwed into the work by itself. In such a case, as shown mainly in FIG. 5, the screw thread 105 is formed up to the tip of the leg 103, and the leg 103 has a tapered shape in which the tip 110 has a small diameter from the tip to the tip. A formed tapping screw is used, and the tapping screw is screwed into a prepared hole 131 of the work 130 having a diameter smaller than the thread diameter, for example, an effective diameter or less.

In the case where the pilot hole 131 is not formed in the work 130, for example, a 3-130
For example, those disclosed in Japanese Patent Application Laid-Open Publication No. 44-44 are used. As shown in FIG.
Is formed at the tip of the body 111.
A drill portion 110 having substantially the same diameter as the effective diameter of 05 and having a slightly larger diameter toward the distal end is integrally formed. The tip of the drill portion 110 has a tapered conical shape, and the leg 1
The guide groove 11 is formed on the outer periphery facing the center line 03.
3 is a self-drilling tapping screw formed;
Using this, a pre-drilling and screwing operation is continuously performed on a work (not shown).

[0004]

However, when such a conventional tapping screw is used, a drill hole is always drilled in the work until the screw of the work is screwed in until the screw is screwed. The work must be performed, and therefore, a separate work of forming a pilot hole in the work is required, and the work time and man-hours are increased. There is no particular problem when using only a small amount of such tapping screws in the product.However, if there are many screws to be used in the product, the operator needs to drill a prepared hole in the work with this drill to determine where the screws need to be. The number increases according to the number, and therefore, the fatigue of the worker is likely to occur, and the working environment is extremely deteriorated. Further, when using a relatively thin metal plate, the work is bent during the operation with the drill, so that the appearance of the product is impaired.

[0005] Next, in another conventional example, a pilot hole is made in the work with a drill portion at the tip of the screw, and a female screw is formed continuously with the prepared hole, and the screw is screwed. Since the guide grooves are formed only from the front end to the rear end of the drill part, the chips generated by the cutting in the drill part are used as the drill holes on the outer peripheral surface of the drill part and the prepared hole of the workpiece formed by this drill part. The drill screw is clogged with the wall surface, so that the tightening torque required for tightening the drill screw increases more than necessary. In addition, there is a problem that the drill screw is clogged during the tightening, the work cannot be completely tightened, and the screw floats.

A first object of the present invention is to provide a self-drilling tapping screw which solves the above-mentioned problem and enables a work to be tightened to a work with a relatively low tightening torque. Is to provide a self-drilling tapping screw in which clogging of chips is reduced as much as possible by smoothly discharging chips generated in a drill portion.

[0007]

SUMMARY OF THE INVENTION A first object of the present invention is to:
In a screw composed of a leg 3 on which a thread 5 is formed and a head 2 integrally formed with the leg 3, a circle having a diameter equal to or larger than the root diameter of the thread 5 and smaller than the peak diameter is formed at the tip of the leg 3. A drill portion 10 having a columnar shape and a conical tip is formed, and two guide grooves 13 are formed from the tip of the drill portion 10 to the start position of the thread 5 of the leg 3. This is achieved by providing a self-drilling tapping screw having a relief groove 20 similar to the root diameter of the thread 5 between the position and the rear end of the drill portion 10.

The second object of the present invention is achieved by providing a self-drilling tapping screw in which the rear end of the drill portion forming the relief groove is circumferentially inclined at an angle equal to the lead angle of the thread 5. .

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
4 through FIG. In FIG. 1, 1 is a head 2
And a self-drilling tapping screw including a leg 3 and a head 2 having a diameter larger than the diameter of the leg is integrally formed at one end of the leg 3. An engagement hole 4 is formed in the head 2 so that a driver bit (not shown) for applying a screwing force for screwing the screw 1 into engagement with the leg 3 and the center line of the head 2. This engaging hole 4 is formed so that the tip of the driver bit engages. If the head 2 of the screw 1 has a hexagonal outer peripheral surface, the driver bit has a hexagonal shape that fits this. The hole may be a so-called box bit (not shown).

The leg 3 has a thread 5 which is substantially parallel to the tip and has substantially the same outer diameter. The tip of the leg 3 has a thread formed on the leg 3. 5
The threadless portion 11 is formed in a cylindrical shape having a diameter not less than the valley diameter and smaller than the ridge diameter, specifically, a diameter not less than the valley diameter and not more than half the height of the ridge, and slightly tapered. A point 12 having a conical tip is formed. still,
The threadless portion 11 may be substantially parallel to the tip or may be slightly thick.

As shown in FIG. 2, two conical guide grooves 13 extend along the axis from the tip of the screw 1 to the side opposite to the center line of the tip from the conical point 12 to the threadless portion 11. The guide groove 13 is formed so that the bottom becomes gradually shallower as it goes away. A cutting edge 14 is formed on the outer edge of the guide groove 13 on the advance side in the screwing direction, and the drill portion 10 is formed. This cutting blade 14 has a sharp point 1
2 is also formed on the outer peripheral edge of the tip 1.
A chisel edge 15 is provided at the intersection of the two guide grooves 13 at the end of the second. As shown in FIG. 3, the rear end of the guide groove 13 has reached the start position of the thread 5 at the tip of the leg 3 where the thread 5 is formed. A relief groove 20 is formed in the circumferential direction between the rear end 10 and the rear end. The relief groove 20 has a bottom surface 21 having a diameter equal to the root diameter of the thread 5, and an end face 22 at the rear end of the drill portion 10 forming the relief groove 20 is inclined in parallel with the lead angle of the thread 5. The rear end of the guide groove 13 is extended to reach the escape groove 20. Although the end face 22 is inclined forward with respect to the bottom 21 of the valley, the end face 22 may be upright with respect to the bottom 21 of the valley, so that more chips 6 escape. Enter the groove 20.

When such a self-drilling tapping screw 1 is used, the screw 1 is pressed against a work 30 made of a metal plate, and the screw 1 is rotated in the screwing direction to be screwed. A guide hole (not shown) is formed in the work 30 with the cutting blade 14 of the twelve, and a prepared hole 31 larger than the guide hole is formed in the work 30 as shown in FIG.
Is gradually opened. At this time, the work 30 is connected to the drill 1
Since the zero cutting blade 14 is shaved, the cutting powder 6 is discharged along the two guide grooves 13 of the drill portion 10. This guide groove 1
The swarf 6 ejected from 3 then moves to the relief groove 20,
It will move to the valley of the screw thread 5.

In this manner, the prepared hole 3 in the drill portion 10 is formed.
When the formation of 1 is completed, the screw 1 is screwed into the work 30 while the female screw is formed by the thread 5 of the leg 3. By this series of screw tightening work, this drill screw 1
Is tightened to the work 30 with a low tightening torque.

[0014]

As described above, according to the present invention, a drill portion 10 having a cylindrical shape and a conical tip is formed at the tip of the leg 3 at the tip of the screw thread 5 at a diameter not less than the root diameter of the thread 5 and smaller than the tip diameter. Two guide grooves 13 are formed from the tip of the drill portion 10 to the start position of the thread 5 of the leg 3, and
Is a self-drilling tapping screw having a relief groove 20 similar to the root diameter of the screw thread 5 between the start position of the drill portion 10 and the rear end of the drill portion 10. The work of constantly drilling a prepared hole in the work becomes unnecessary, and the work time and man-hours are reduced. Also,
Even when many screws are used in the product, the operator does not have to drill a hole in the work, so that the fatigue of the operator is reduced and the working environment is extremely good. Furthermore,
When used for a metal plate, the screws bite into the work in a short time, so that the bending of the work due to the screwing operation is reduced, and the appearance of the product is improved. In addition, when the drill portion is slightly tapered, the work for preparing a hole in the work becomes smooth, and the thread is formed smoothly.

In addition, even if a pilot hole is drilled in the work at the drill portion at the tip of the screw and a female screw is formed continuously and the screw is screwed into the work, it is generated by cutting at the drill portion. The chips can move from the guide grooves to the escape grooves, and the chips do not become clogged between the outer peripheral surface of the drill portion and the prepared hole wall surface. In addition, the tightening torque required for tightening the drill screw is thereby reduced, a smooth screw tightening operation can be obtained, the burden on the operator is reduced, and fatigue is reduced. Further, since the head seat surface of the screw is securely brought into contact with the work, the occurrence of the floating state of the screw is eliminated. In addition, since the relief groove is formed parallel to the lead angle of the screw thread, the chip can smoothly move to the thread valley and the self-drilling tapping screw can be easily discharged. Specific effects can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is an enlarged bottom view of FIG.

FIG. 3 is an enlarged view of a main part of the present invention.

FIG. 4 is an enlarged sectional view of a main part, similar to FIG. 3, showing a use state.

FIG. 5 is a front view showing a conventional example of the present invention.

FIG. 6 is a front view showing another conventional example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Self-drilling tapping screw 2 Head 3 Leg 4 Engagement hole 5 Thread 6 Cutting powder 10 Drill part 11 No screw part 12 Sharp point 13 Guide groove 14 Cutting blade 15 Chisel edge 20 Escape groove 21 Bottom surface 22 End surface 30 Work 31 Lower hole

Claims (2)

[Claims] 1. A leg 3 having a thread 5 and a leg 3
In the screw comprising the head 2 integrally formed with the thread, a drill portion 10 having a cylindrical shape and a conical tip is formed at the tip of the leg 3 at the tip of the thread 5 with a diameter not less than the root diameter of the thread 5 and smaller than the tip diameter. A double guide groove 13 is formed from the tip of the drill portion 10 to the start position of the thread 5 of the leg 3, and furthermore, a thread is formed between the start position of the thread 5 and the rear end of the drill portion 10. A self-drilling tapping screw, wherein a relief groove 20 having the same diameter as the root diameter of No. 5 is formed. 2. The self-drilling tapping screw according to claim 1, wherein the rear end of the drill portion forming the relief groove is circumferentially inclined at an angle equal to the lead angle of the screw thread.