JPH036366B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a drill screw integrally equipped with a drill portion for drilling a pilot hole in a fastened object.
In particular, the present invention relates to an improvement of a drill screw in which the drill portion is formed by forging such as pinch pointing.

[Conventional technology]

Recently, with the increasing demand for this type of drill screw, in order to reduce the manufacturing cost of the drill screw, the drill part at the lower end of the threaded shank with the head integrally formed at the upper end has been used as a pinch point. Forming is carried out by forging such as taing.

Such forged drill screws include those in which the free end of the drill part is formed into a sharp so-called pinpoint, as disclosed in US Pat. No. 3,710,676, and Japanese Patent Publication No. 48-13139 Publication (US Patent No. 3395603), Special Publication No. 1983-45604
Publication No. 59-7046 (U.S. Patent No. 7046)
4407620) etc., there is one in which a chisel edge is formed at the free end of the drill part.

The latter drill screw with chisel edge is constructed as shown in FIGS. 10-13.

That is, the drill part 1 formed by forging has a left and right groove formed at the free end of the drill part 1 that extends diagonally upward from the longitudinal axis 2 of the shank toward the head at the upper end of the shank and outwardly with respect to the longitudinal axis 2 of the shank. A pair of inclined end surfaces 3, 3 are provided so as to intersect with each other at a position where both the inclined end surfaces 3, 3 coincide with the longitudinal axis 2 of the shank, and two longitudinal grooves extending upward from these inclined end surfaces 3, 3 are provided. 4, 4 are provided diagonally, and among the two groove surfaces constituting both the vertical grooves 4, 4, the first groove surfaces 4a, 4a and the both inclined end surfaces 3, 3 are aligned with the longitudinal axis 2. By intersecting on both sides of the virtual plane 5 including, the tip cutting edges 6, 6 are formed at the intersection, and
By locating the intersecting ridge lines of the pair of left and right inclined end surfaces 3, 3 on a line connecting the starting ends 6a, 6a of the both tip cutting edges 6, 6 closer to the longitudinal axis 2, the both tip cutting edges 6, starting point 6 at 6
A chisel edge 7 having a relatively short length L and extending in a straight line perpendicular to the longitudinal axis 2 was formed between a and 6a.

[Problem that the invention seeks to solve]

When a drill screw with a pinpoint free end like the former is pressed against an object while rotating, one point on the longitudinal axis of the screw comes into contact with the object. There is almost no so-called dancing phenomenon in which the part swings in a direction perpendicular to the longitudinal axis as it rotates, and it has the advantage of being able to be screwed into a predetermined position accurately. However, there are problems in that the sharp pinpoints are easily damaged, the initial performance of entering the object to be fastened is low, and it takes a long time for screwing.

On the other hand, the latter one in which the chisel edge 7 is formed at the free end has the advantage of being able to reduce the damage at the chisel edge 7 and having better initial entry performance into the object to be fastened than the pinpoint method. However, there is a problem in that a dancing phenomenon occurs in the drill part when it is rotated and pressed against an object to be fastened.

That is, the chisel edge 7 in the prior art described above aligns the intersecting ridge line of the pair of left and right inclined end surfaces 3, 3 formed at the free end of the drill part with the starting ends 6a, 6a of the two cutting edges 6, 6 closer to the longitudinal axis 2.
The shape of the cross section in the direction perpendicular to the longitudinal direction of the chisel edge 7 is such that the chisel edge 7 is located on a line that connects the chisel edges 7 to each other as shown in FIG. The inclined end surfaces 3, 3 have a triangular shape, and the inclined end surface 3, which is inclined diagonally upward from the chisel edge 7, exists over the entire length of the chisel edge 7 in a portion on the front side of the chisel edge 7 in the rotational direction of arrow A. I will do it.

In this way, the inclined end surface 3 located on the front side of the chisel edge 7 in the rotational direction functions as a rake surface for releasing cutting chips during cutting by the chisel edge 7, but the inclined end surface 3 on the front side in the rotational direction , and the surface 8 of the object 8 to be fastened
Naturally, the angle α formed with a is 90 as shown in Figure 13.
Since it is much smaller than the angle, it does not fully function as a rake face, and in other words, the inclined end face 3 located at the front side in the rotational direction of the chisel edge 7 prevents cutting chips from escaping into the vertical groove 4. In addition,
This chisel edge 7 is in a straight line in a direction perpendicular to the longitudinal axis 2, and the chisel edge 7 contacts the object 8 along its entire length.
Since the pressing force against the object 8 to be fastened is dispersed over a wide area, the cutting performance of the chisel edge 7 is correspondingly low.

In other words, in the forged drill screw with a chisel edge disclosed in each of the above-mentioned prior art, the chisel edge, which has low initial cutting performance against the fastened object, comes into contact with the workpiece in a line contact state. When pressed against an object 8 while rotating, the so-called dancing phenomenon in which the drill part 1 swings in a direction perpendicular to the longitudinal axis 2 becomes considerably large, and as a result, the position of the drill screw relative to the object to be fastened is shifted. In other words, not only does it have the disadvantage that it is difficult to screw it into a predetermined position accurately, but it also has the problem that it takes a long time to screw it into the object to be fastened.

Therefore, the present invention improves the cutting performance of a drill screw in which a drill portion with a chisel edge is formed by forging as in the prior art without causing a decrease in the strength of the chisel edge. In addition, it is an object of the present invention to solve the problems of the prior art by adding the above-mentioned pinpoint advantages.

[Means for solving problems]

To achieve this object, the present invention includes a shank having a thread formed on its outer periphery, a head integrally formed at the upper end of the shank, and a drill portion formed by forging at the lower end of the shank. ,
The drill part is provided with a pair of left and right inclined end surfaces, each of which is inclined upwardly from the longitudinal axis of the shank toward the head and outwardly with respect to the longitudinal axis, at a free terminal end of the drill part. Two longitudinal grooves constituted by a first groove surface and a second groove surface are provided so as to extend from both the inclined end surfaces toward the head, and a first groove forming a part of each of the two longitudinal grooves is provided.
The groove surface and the both inclined end surfaces intersect each other on both sides of a virtual plane including the longitudinal axis, and a tip cutting edge is formed at each of the intersection points, and the both inclined end surfaces are made to intersect with the both tip cutting edges. In a drill screw in which the starting ends of the portions of the blades closer to the longitudinal axis intersect in a ridge shape on a line connecting each other, and this intersecting ridge line is formed as a chisel edge, the chisel edge is downwardly moved to a portion on the longitudinal axis. The first groove surface of both vertical grooves is formed into a mountain-shaped shape that has an apex that projects and slopes obliquely upward from the apex at a relatively gentle inclination angle toward the starting end of the cutting edge at both ends. A concave cutting surface inclined with respect to the longitudinal axis is provided at least in a portion connected to the cutting edges at both ends thereof, in order to form a rake angle on the cutting edges at both ends; A pair of left and right flat rake faces extending parallel to the longitudinal axis from the chisel edge toward the first groove surfaces in both longitudinal grooves, such that both rake faces extend along the chisel edge to a portion adjacent to each other at the apex thereof. The configuration was set up so that

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A drill screw 10 shown in FIG. It consists of a drill part 13 formed by forging such as pinch pointing at the lower end part of the shank 11, and the head part 12 has a tool for rotating the screw,
For example, it has a groove or recess 14 for engaging a screwdriver (in which case the head 12 may be formed with a square or hexagonal head for engaging a wrench therein); A spiral thread 15 is integrally formed on the outer peripheral surface of the shank 11 by means such as rolling.

The maximum diameter D of the drill portion 13 (more specifically, the distance between the side cutting edges 25 and 25 formed on the side surface of the drill portion 13 as described later) is smaller than the diameter of the thread 15. It is configured to have a dimension larger than the valley diameter.

As is well known in the art, the drill portion 13 is formed by sandwiching the lower end portion of the blank after forming the head 12 and before forming the thread 15 from both sides between a pair of opposing left and right forging dies. By attaching the drill part 13, the drill part 13 is forged into the shape described below.

The drill portion 13 formed by forging has a shape that extends obliquely upward from the longitudinal axis 16 of the shank 11 toward the head 12 at the upper end of the shank 11 at the free end of the drill portion 13, and the longitudinal axis 16
A pair of left and right inclined end surfaces 17, 17 which are inclined outward by an appropriate angle θ with respect to the both inclined end surfaces 1
7 and 17 are provided so as to cross each other in a ridgeline at a position that coincides with the longitudinal axis 16, and two vertical grooves 18 and 18 extending upward from these inclined end surfaces 17 and 17 are provided at diagonal portions. .

Both the vertical grooves 18, 18 are formed on the first groove surface 1, respectively.
9, and a second groove surface 20 that intersects with the first groove surface 19.

The first groove surface 19 and the inclined end surfaces 17, 17, which constitute a part of each of the vertical grooves 18, 18, are connected to the virtual plane 21 on both sides of the virtual plane 21 including the longitudinal axis 16. By intersecting along substantially parallel lines, tip cutting edges 22, 22 are respectively formed at the intersection points. Further, in order to form a rake angle in the both end cutting edges 22, 22, at least in a portion of the first groove surface 19 of the both longitudinal grooves 18, 18 that is connected to the both end cutting edges 22, 22, the longitudinal grooves 18, 18 are A concave cutting surface 19a that is inclined with respect to the axis 16 is provided. However, the drawings of the embodiment show a pair of left and right side cutting edges 25 in the drill part 13,
25 (This side cutting edge 25 will be described later)
Also, a case is shown in which the first groove surface 19 is entirely recessed so that a concave cut surface 19b is provided to form a rake angle.

Then, by positioning the intersecting ridge lines of the pair of left and right inclined end surfaces 17, 17 on a line connecting the starting ends 23, 23 of the both tip cutting edges 22, 22 closer to the longitudinal axis 16, both tip cutting edges can be cut. Between the starting ends 23, 23 of the blades 22, 22,
A chisel edge 24 of relatively short length L is formed which extends in a straight line perpendicular to the longitudinal axis 16.

In addition, on the side surface of the drill part 13, a pair of left and right side cutting edges 25, 25 are formed by the first groove surfaces 19 of the longitudinal grooves 18, 18, and a pair of side cutting edges 25, 25 are formed at the ends of the tip cutting edges 22, 22 near the outer periphery. 26, 26
It is formed to extend upward from. Therefore, the distance between the two side cutting edges 25, 25 becomes the maximum diameter D in the drill part 13, and the distance between the two side cutting edges 25, 25 becomes the maximum diameter D in the drill part
A hole with the same inner diameter as this maximum diameter D is bored in the
Next, the thread 15 of the shank 11 enters this hole while forming an internal thread on the inner surface of the hole. In addition, these both side cutting blades 25, 25
As shown in FIG. 4, the tip cutting edge 22,
It is inclined with respect to the longitudinal axis 16 so as to gradually extend rearward in the direction of rotation of the drill screw 10 as it approaches the shank 11 from 22 . Further, counter-chamfered surfaces 27, 27 are formed on the rear sides of the both side cutting blades 25, 25 in the rotational direction.

The chisel edge 24 has an apex 24a projecting downward at a portion on the longitudinal axis 16, and is directed diagonally upward at a relatively gentle angle β from the apex 24a toward the starting end 23 of the cutting edges 22, 22 at both ends. It is formed into a mountain-shaped shape that slopes downward.

Further, among both inclined end surfaces 17, 17 forming the chisel edge 23 in the drill portion 13, second groove surfaces 20, 20 in both the vertical grooves 18, 18
In the part facing the chisel edge 24 and adjacent to the chisel edge 24, both vertical grooves 1 are formed from the chisel edge 24.
A pair of left and right flat rake surfaces 28, 28 extending parallel to the longitudinal axis 19 toward the first groove surface 19 in the grooves 8, 18 are formed at the apex 24a thereof along the chisel edge 24. The structure is such that they extend to mutually adjacent parts.

Note that the reference numeral 29 indicates both the rake faces 28, 28.
In order to form the inclined end surface 17 and the second groove surface 20
Although the inclined surface 29 is provided at the intersection with the slanted surface 29, this inclined surface 29 is not necessarily required.

Both the rake faces 28, 28 are formed on both inclined end faces 1 when forming the drill part 13 by forging.
7, 17, first groove surface 1 in both vertical grooves 18, 18
9 and the second groove surface 20, and both counter-challenged surfaces 27, 2
While the chisel edge 24 can be easily formed by forging at the same time as forming the chisel edge 24,
It is also possible to form a chevron shape having a shape at the same time as the above-mentioned forging.

In this way, from the chisel edge 24 to both longitudinal grooves 1
The chisel edge 24 extends parallel to the longitudinal axis 19 toward the first groove surface 19 at 8 , 18 .
A pair of left and right flat rake faces 28, 28 provided adjacent to each other at the apex 24a of
is located on the front side in the rotational direction of the chisel edge 24 of the drill portion 13 when the drill screw 10 is rotated in the direction of arrow A around the longitudinal axis 16 and the drill portion 13 is pressed against the fastened object 30. On the other hand, both rake faces 28, 28
As shown in FIGS. 8 and 9, the object to be fastened 30
is substantially perpendicular to the surface 30a of
Chisel edge 2 to ensure smooth release to 8 and 18.
4, the cutting performance at the chisel edge 24 can be greatly improved.

On the other hand, the chisel edge 24 is placed at the apex 24 at a position on the longitudinal axis 16, which is the center of rotation of the screw.
Since the chisel edge 24 is formed into a chevron-shaped shape having an angle a, the apex 24a of the chisel edge 24 first comes into contact with the surface 30a of the object 30 as a so-called pinpoint, but in this case, the rotation of the chevron-shaped chisel edge 24 On the front side in the direction, there are both rake faces 2 as described above.
8, 28 to improve the cutting performance of the chisel edge 24, and the chisel edge 24 contacts the object 30 as a so-called pinpoint as described above.
The dancing phenomenon when the drill screw 10 is pressed against the fastened object 30 while rotating is as follows.
It can be significantly reduced compared to the case of the prior art.

Moreover, with respect to the pair of left and right cutting edges 22, 22 in the drill portion 13, the cutting edges 2 are
Although a rake angle is formed by the concave cutting surface 19a that is inclined with respect to the longitudinal axis 16 in order to improve the cutting performance at the chisel edge 24, the pair of left and right rake surfaces 28, 2
8 to the concave cutting surface 19 relative to the longitudinal axis 16.
Since the chisel edge 24 is formed into a flat surface that is parallel to the longitudinal axis 16 without being inclined as in case a, the strength of the chisel edge 24 is reduced by providing both rake faces 28, 28. 28, 28 are inclined with respect to the longitudinal axis 16 in the same way as the concave cutting surface 19a, the strength of the chisel edge 24 is significantly reduced), therefore,
This makes it possible to reliably reduce the occurrence of damage to the chisel edge 24.

According to experiments, the upward inclination angle β from the apex 24a of the chisel edge 24 is 5.
It was found that a temperature of ~25 degrees was appropriate.

That is, if the upward inclination angle β of the chevron-shaped chisel edge 24 exceeds 25 degrees, the apex 24a of the chisel edge 24 will become too sharp, and a chip will occur at the apex 24a. If the upward inclination angle β was less than 5 degrees, the pinpoint dancing prevention effect could not be obtained. Furthermore, according to experiments, even when the upward inclination angle β of the chisel edge 24 is set to 5 to 25 degrees, the pair of left and right rake faces 28, 28 are formed on the chisel edge 24 as described above. Otherwise, the initial penetration performance for the object to be fastened 30 would be lower than in the case of the chisel edge in the prior art. Additionally, experiments have shown that it is appropriate for the length L of the chisel edge 24 to be 10 to 30% of the diameter of the thread 15 (this is the nominal diameter of the drill thread).

[Action/effect of the invention]

As described above, the present invention achieves the following operations and effects by having the configuration described in the claims.

The chisel edge 24 in the drill part 13,
The shank 11 has an apex 24a on the longitudinal axis 16, and is formed in a mountain shape that slopes diagonally upward from the apex 24a at a relatively gentle inclination angle β, thereby providing a so-called pin to the object to be fastened. A pair of left and right flat rake faces 28, 2 extend parallel to the longitudinal axis 16 from the chisel edge 24 toward the first groove surface 19 in both longitudinal grooves 18, 18.
8 so that both rake faces 28, 28 extend along the chisel edge 24 to a portion adjacent to each other at the apex 24a, the cutting performance of the chisel edge 24 can be improved, and the strength of the chisel edge 24 can be reduced to a small extent. In other words, the chisel edge 24
The combination of these two factors, together with the ability to significantly improve the process without causing frequent breakage, makes it possible to reliably reduce the dancing phenomenon that occurs when a drill screw is rotated and pressed against an object to be fastened. Therefore, the drill screw can be easily screwed into a predetermined position in the object to be fastened accurately.

Both vertical grooves 18, 18 from the chisel edge 24
The longitudinal axis 1 toward the first groove surface 19 at
A pair of left and right flat rake faces 2 extending parallel to 6
By providing the rake surfaces 28, 28 so that they extend along the chisel edge 24 to the portion adjacent to each other at the apex 24a, the initial approach performance of the chisel edge 24 to the object to be fastened can be improved. 2
The decrease in strength in 4 is small, in other words,
In addition to being able to significantly improve the chisel edge 24 without causing frequent breakage, at least the portions of the first groove surfaces 19 of the longitudinal grooves 18, 18 that are connected to the tip cutting edges 22, 22, A concave cutting surface 19a inclined with respect to the longitudinal axis 16 is provided, and the cutting edge 2 at both ends is
By forming a rake angle on 2 and 22 and improving the cutting performance of both tip cutting edges 22 and 22,
The time required for screwing into objects to be fastened can be significantly shortened, and the pressing force on objects to be fastened can be reduced, so the workability of screwing into objects to be fastened can be significantly improved. In this case, it is possible to reliably reduce the possibility that the thin metal plate will be dented and deformed by the pressure of the drill screw.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the whole drill screw according to the first embodiment of the present invention, FIG. 2 is a bottom view of FIG. 1, and FIG.
The figure is a 3-3 side view of Figure 2, Figure 4 is a 4-4 side view of Figure 3, and Figure 5 is an enlarged view of the main parts of Figure 1.
Figure 6 is a bottom view of Figure 5, an enlarged view of Figure 2, and Figure 7.
The figure is a side view taken from 7-7 of FIG. 5, FIG. 8 is a sectional view taken from 8-8 of FIG. 5, FIG. 9 is a sectional view taken from 9-9 of FIG. 5, and FIGS. 10 to 13. 10 shows a conventional example, FIG. 10 is an enlarged view of the drill part, FIG. 11 is a bottom view of FIG. 10, and FIG. 12 is 12-1 in FIG. 10.
13 is a sectional view taken along line 13-13 in FIG. 10. 10...Drill screw, 11...Shank, 12
...Head, 13...Drill part, 15...Screw thread,
16...Longitudinal axis of shank, 17... Inclined end surface, 18... Vertical groove, 19... First groove surface of vertical groove, 2
0...Second groove surface of vertical groove, 21...Virtual plane, 22
... Tip cutting edge, 19a... Concave cutting surface of tip cutting edge, 23... Starting end of tip cutting edge, 24... Chisel edge, 24a... Apex of chisel edge, 25...
Side cutting edge, 26... End of tip cutting edge, 27...
Second cut face, 28... rake face, β... upward inclination angle of chisel edge.

Claims (1)

[Claims] 1. A shank 11 having a thread 15 formed on its outer periphery.
, a head 12 integrally formed at the upper end of the shank 11 , and a drill part 13 formed by forging at the lower end of the shank 11 . At the terminal end thereof, the longitudinal axis 16 is diagonally upward from the longitudinal axis 16 of the shank 11 toward the head 12.
A pair of left and right inclined end surfaces 1 which are inclined outwardly relative to the
7 and 17 are provided, and the first groove surface 19 is provided, respectively.
and a second groove surface 20, two vertical grooves 18,
18 from the both inclined end surfaces 17, 17 to the head 1
2, and both vertical grooves 18, 1
The first groove surface 19 and the both inclined end surfaces 17, 17, which constitute a part of each of the grooves 8,
intersect on both sides of the virtual plane 21 containing
Tip cutting edges 22, 22 are formed at the intersection points, respectively, and the inclined end surfaces 17, 17 are formed with starting ends 23, 23 at the portions of the tip cutting edges 22, 22 closer to the longitudinal axis 16. In a drill screw in which the chisel edge 24 intersects in a ridge shape on lines connecting each other and the intersecting ridge line is formed on the chisel edge 24, the chisel edge 24 is connected to the longitudinal axis 16.
The upper part has an apex 24a projecting downward, and a relatively gentle inclination angle β from the apex 24a toward the starting ends 23, 23 of the cutting edges 22, 22 at both ends.
While forming a mountain-shaped shape that slopes diagonally upward,
At least the portions of the first groove surfaces 19 of the longitudinal grooves 18, 18 that are connected to the cutting edges 22, 22 at both ends are provided with the longitudinal axis 16 in order to form a rake angle in the cutting edges 22, 22 at both ends. Further, the drill portion 13 is provided with a concave cutting surface 19a that is inclined with respect to the chisel edge 24.
A pair of left and right flat rake surfaces 28, 28 extending parallel to the longitudinal axis 16 toward the first groove surface 19 in the grooves 8, 18 are formed at the apex 24a thereof along the chisel edge 24. A drill screw characterized by being provided so as to extend to mutually adjacent parts. 2. The drill screw according to claim 1, wherein the inclination angle β of the chisel edge 24 diagonally upward from the apex 24a is set to 5 to 25 degrees.