JPH033083B2 - - 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 Forming is performed by forging such as pinch pointing.

Conventional drill screws made by such forging are disclosed, for example, in Japanese Patent Publication No. 48-13139 (US Patent No. 3395603), Japanese Patent Publication No. 58-4504, and Japanese Patent Publication No.
As described in Publication No. 59-7046 (U.S. Pat. No. 4,407,620), the drill portion is shown in FIGS.
The shape is as shown in FIG. 15.

That is, the drill part 1 of the conventional drill screw has a drill part 1 at the free end thereof extending obliquely upward from the longitudinal axis 2 of the shank toward the head of the upper end of the shank and outward with respect to the longitudinal axis 2 of the shank. A pair of left and right inclined end surfaces 3, 3 are provided so that the two inclined end surfaces 3, 3 intersect with each other in a ridgeline shape at a position that coincides with the longitudinal axis 2 of the shank, and a Two extending vertical grooves 4, 4 are provided diagonally, and among the two groove surfaces that constitute both vertical grooves 4, 4, the first groove surfaces 4a, 4a and the both inclined end surfaces 3, 3, respectively. By intersecting on both sides of the virtual plane 5 including the longitudinal axis 2, the cutting edge 6,
6, and the pair of left and right inclined end surfaces 3,
By positioning the intersecting ridge lines of the two tip cutting edges 6, 6 on the line connecting the starting ends 6a, 6a of the both tip cutting edges 6, 6 closer to the longitudinal axis 2, the two tip cutting edges 6, 6
Between the starting ends 6a, 6a, the longitudinal axis 2
A chisel edge 7 having a relatively short length L extending in a straight line at right angles to the cylindrical part was formed.

[Problem that the invention seeks to solve]

The drill portion 1 having the chisel edge 7 formed at the free end as described above is disclosed in, for example, US Pat.
3710676, which does not have a chisel edge and has a free end formed into a sharp so-called pinpoint, while rotating the drill screw around the longitudinal axis 2 in the direction of arrow A. When the drill part is pressed against the object to be fastened 8, the entire chisel edge 7 rotates and is pressed against the object to be fastened 8 in a line contact state, so that the initial cutting performance for the object to be fastened is improved. Has good advantages.

However, this chisel edge 7 aligns the intersecting ridgeline of the pair of left and right inclined end surfaces 3, 3 formed at the free end of the drill part with the line connecting 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 as shown in FIG. 15 over the entire length of the chisel edge 7. 3, it has a triangular shape, and the part on the front side of the chisel edge 7 in the rotation direction of arrow A has the chisel edge 7.
An 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 this way, the inclined end face 3 located on the front side of the chisel edge 7 in the rotational direction functions as a rake face for releasing cutting debris during cutting by the chisel edge 7, but the inclined end face 3 on the front side in the rotational direction Naturally, the angle α between this and the surface 8a of the object to be fastened 8 is as shown in FIG.
Because it is much smaller than 90 degrees, it does not fully function as a rake face, in other words, the inclined end face 3 located on the front side in the rotation direction of the chisel edge 7
However, since this prevents the cutting debris from escaping into the vertical groove 4, the cutting performance of the chisel edge 7 is correspondingly low.

In other words, the conventional forged drill screws disclosed in the above-mentioned prior arts do not yet have sufficient initial cutting performance for the objects to be fastened, and require a large thrust (the pressing force of the drill screw against the objects to be fastened) to screw into the objects to be fastened. ), and it also took a long time to screw in.

Moreover, the reason why the cutting performance of the chisel edge 7 is low is that the chisel edge 7 does not penetrate into the fastened object 8 poorly, and the chisel edge 7 is not cut into the fastened object 8.
Since the so-called dancing phenomenon in which the drill part 1 swings in a direction perpendicular to the longitudinal axis 2 when pressed while rotating is quite large, there is also the problem that the screwing position of the drill screw with respect to the object to be fastened is likely to shift.

The present invention aims to improve the initial cutting performance of the chisel edge in a drill screw in which the drill portion with the chisel edge is formed by forging as in the prior art.

[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 each consisting of a first groove surface and a second groove surface are provided to extend from the both inclined end surfaces toward the head, and the first groove surface and the both inclined end surfaces in the both longitudinal grooves are provided. are intersected on both sides of an imaginary plane including the longitudinal axis, and tip cutting edges are formed at the intersection points, and both inclined end surfaces are formed on the tip of the tip cutting edge closer to the longitudinal axis. In a drill screw in which the starting ends of the parts intersect in a ridgeline shape on a line connecting each other, and this intersecting ridgeline is formed as a chisel edge, the first
A concave cutting surface inclined with respect to the longitudinal axis is provided on at least a portion of the groove surface that is connected to the both tip cutting edges to form a rake angle with respect to the both tip cutting edges, while the drill portion is provided with a concave cutting surface that is inclined with respect to the longitudinal axis. is a pair of left and right flat rake surfaces that extend substantially parallel to the longitudinal axis from the chisel edge toward the first groove surface of both longitudinal grooves, and the rake surfaces flow along the chisel edge at any point on the chisel edge. The structure is such that it extends to the area adjacent to the area.

[Effect]

In this way, by providing a pair of left and right flat rake surfaces that extend substantially parallel to the longitudinal axis from the chisel edge toward the first groove surface of both longitudinal grooves, the drill screw can be rotated around the longitudinal axis of the drill part. When pressed against an object to be fastened, both rake faces are located on the front side in the rotational direction of the chisel edge and are approximately perpendicular to the surface of the object to be fastened, so that they are not cut by the chisel edge. Since the cutting waste smoothly escapes into both vertical grooves, the cutting performance of the chisel edge can be improved.

However, in the case where a pair of left and right flat rake faces are provided for the chisel edge, a rake angle is formed by a concave cutting surface that is inclined with the longitudinal axis with respect to the pair of left and right tip cutting edges of the drill part. If both of the flat rake faces are configured to be inclined with respect to the longitudinal axis like the concave cutting surfaces, the thickness of the chisel edge becomes thinner and its strength is significantly reduced, resulting in frequent chipping of the chisel edge. That's what I do.

Further, in the case where a pair of flat left and right rake faces are provided for the chisel edge, when the two rake faces are configured to extend along the chisel edge beyond an arbitrary point on the chisel edge until they overlap each other. In this case, part or all of the inclined end face of the chisel edge located on the rear side in the direction of rotation is cut off by the rake face, and the strength of the chisel edge is also significantly reduced. Due to frequent occurrence of defects, the cutting performance of the chisel edge rapidly deteriorates.

Therefore, in the present invention, when a pair of left and right flat rake faces are provided for the chisel edge, the two rake faces are directed from the chisel edge to the first groove surface of the longitudinal grooves as described above. It is configured to extend substantially parallel to the longitudinal axis and to extend along the chisel edge to a portion adjacent to any point on the chisel edge.

In this way, the left and right pair of flat rake faces are
By configuring the chisel edge to extend substantially parallel to the longitudinal axis from the chisel edge toward the first groove surface in both longitudinal grooves, the cutting performance of the pair of left and right cutting edges in the drill portion is improved. Although the rake angle is formed by a concave cutting surface that is inclined with respect to the longitudinal axis in order to improve the In addition, it is possible to prevent the rake faces from becoming thinner as shown in FIG. , by configuring the chisel edge so that it does not extend beyond any point on the chisel edge to overlap with each other, the inclined end face located on the rear side in the rotational direction of the chisel edge is cut off by both the rake faces. Because you can avoid that,
By providing the pair of left and right flat rake faces on the chisel edge, it is possible to reliably prevent the strength of the chisel edge from significantly decreasing.

〔Effect of the invention〕

Therefore, according to the present invention, the cutting performance of the chisel edge can be significantly improved without causing frequent breakage of the chisel edge, so that the thrust force when screwing the drill screw into the object to be fastened can be reduced, The time required for screwing can be shortened, and the chisel edge bites into the object to be fastened better, reducing the dancing phenomenon that occurs when the chisel edge is pressed against the object while rotating, which reduces the deviation of the screwing position and requires less force. This has the effect of allowing screws to be screwed into accurate positions in a short time.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A drill screw 10 shown in FIG. The head 12 has a groove or recess 14 for engaging a tool for rotating the screw, such as a screwdriver. (In this case, the head 12 may be formed into a square head or a hexagonal head.) A spiral thread 15 is integrally formed on the outer peripheral surface of the shank 11 by means such as rolling molding. ing.

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 section 13 is configured to cut the lower end portion of the blank after the head 12 is formed and before the thread 15 is formed using a pair of opposing left and right casting dies. By sandwiching it from both sides, it 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 diagonally.

Both vertical grooves 18, 18 have first groove surfaces 19, 19
and second groove surfaces 20, 20 that intersect with the first groove surfaces 19, 19.

The first groove surface 19 and the inclined end surfaces 17, 17, which constitute a part of each of the longitudinal grooves 18, 18, are arranged on both sides of the imaginary plane 21 including the longitudinal axis 16, on the imaginary plane 21. By intersecting along a line substantially parallel to the above, 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 locating 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.

Incidentally, on the side surface of the drill portion 13, side cutting edges 25, 25 are formed by the first groove surfaces 19 in both the vertical grooves 18, 18, and the side cutting edges 25, 25 are formed on the side cutting edges 22, 2
It is formed so as to extend upward from the terminal ends 26, 26 near the outer periphery at 2.

Therefore, the distance between the two side cutting edges 25, 25 becomes the maximum diameter D in the drill part 13, and a hole with the same inner diameter as this maximum diameter D is drilled in the object 30, and then a hole is drilled in the hole. Then, the thread 15 of the shank 11 enters the inner surface of the hole while forming a female thread. Note that the both side cutting blades 25, 2
On the rear side of 5 in the rotational direction, counterfeed surfaces 27, 27 are formed.

Of both inclined end surfaces 17, 17 forming the chisel edge 24 of the drill portion 13, a portion facing the second groove surfaces 20, 20 of the longitudinal grooves 18, 18 and adjacent to the chisel edge 24 includes: From the chisel edge 24 to both vertical grooves 18, 18
The longitudinal axis 1 toward the first groove surface 19 in
A pair of left and right flat rake faces 2 extending substantially parallel to 6.
8, 28 such that both rake faces 28, 28 overlap each other along the chisel edge 24 beyond an arbitrary point 24a on the chisel edge 24 (in the first embodiment, a point on the longitudinal axis 16). The structure is such that it does not extend to the point 24a, but extends to a portion adjacent to the arbitrary point 24a.

Note that the symbols 29, 29 are the rake faces 28,
28 is an inclined surface provided between the inclined end surface 17 and the second groove surface 20, but this inclined surface 29 is not necessarily required.

When forming the drill part 13 by forging, the two rake faces 28, 28 are formed on both inclined end faces 1.
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
It can be easily molded at the same time as No. 7 molding.

In this way, from the chisel edge 24 to both longitudinal grooves 1
A pair of left and right grooves extending substantially parallel to the longitudinal axis 16 toward the first groove surface 19 at 8 and 18, and extending along the chisel edge 24 to a portion adjacent to an arbitrary point 24a on the chisel edge 24. The flat rake faces 28, 28 of the drill screw 10 are rotated in the direction of arrow A around the longitudinal axis 16 of the drill part 13 to be fastened to the object 3.
When pressed to 0, the drill part 13
The rake faces 28, 28 are located on the front side in the rotational direction of the chisel edge 24, and the rake faces 28, 28 are located on the front side of the chisel edge 24 in the rotational direction, and the rake faces 28, 28 are located on the front side in the rotational direction of the chisel edge 24.
The chisel edge 24 is approximately perpendicular to a.
The cutting waste cut by the vertical grooves 18, 18
This can be achieved over the entire length of the chisel edge 24.

Further, with respect to the pair of left and right tip cutting edges 22, 22 in the drill portion 13, both tip cutting edges 22, 2 are provided.
Although a rake angle is formed by the concave cutting surface 19a in the region of the longitudinal axis 16 in order to improve the cutting performance in the chisel edge 24, the pair of left and right rake surfaces 28, 28 on the chisel edge 24
is formed into a flat surface that is substantially flat with the longitudinal axis 16, and further, the rake faces 28, 28 extend along the chisel edge 24 to a portion adjacent to an arbitrary point 24a on the chisel edge 24, Both rake faces 28, 28 are the chisel edge 2.
The chisel edge 2 is configured so that they do not overlap beyond an arbitrary point 24a on the surface of the chisel edge 2.
4, the decrease in strength is small (both rake faces 28,
28 is inclined with respect to the longitudinal axis 16 similarly to the concave cutting surface 19a, and both rake surfaces 2
8, 28 at any point 24 on the chisel edge 24
(If the overlap exceeds a, the strength of the chisel edge 24 will be significantly reduced.) Therefore, the strength of the chisel edge 24 is thus high, and the cutting debris cut by the chisel edge 24 is , and the ability to smoothly release the material into both vertical grooves 18, 18 over the entire length of the chisel edge 24, the cutting performance of the chisel edge 24 can be improved without causing frequent breakage of the chisel edge 24. , can be significantly improved.

Note that the embodiment shown in FIGS. 5 and 6 is as follows:
Any point 24a on the chisel edge 24
In this case, the width dimensions along the longitudinal direction of the chisel edge 24 of both the rake faces 28, 28 were made equal by aligning with the longitudinal axis 16, but the present invention is not limited to this. As shown in FIGS. 10 and 11, an arbitrary point 24a on the chisel edge 24 is decentered by an appropriate dimension e from the longitudinal axis 16, so that both rake faces 2
8 and 28, the width L1 of one of the rake faces 28 is made longer, and the width L1 of the other rake face 28 is made longer.
The purpose can be achieved even if the structure is configured so that 2 is shortened.

[Brief explanation of the drawing]

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, FIG. 3 is a side view taken from 3-3 in FIG. 2, and FIG. The figure is a 4-4 side view of Fig. 3, Fig. 5 is an enlarged view of the main part of Fig. 1, Fig. 6 is a bottom view of Fig. 5 and an enlarged view of Fig. 2,
Figure 7 is a side view from 7-7 of Figure 5, and Figure 8 is a side view of Figure 5.
FIG. 9 is a sectional view taken along line 9-9 in FIG. 5, FIG. 10 is an enlarged view of the drill part of the second embodiment of the present invention, and FIG. Figure, 12th
15 shows a conventional example, FIG. 12 is an enlarged view of the drill part, FIG. 13 is a bottom view of FIG. 12, FIG. 14 is a sectional view taken along line 14-14 of FIG. 12,
FIG. 15 is a sectional view taken along line 15-15 in FIG. 12. 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, 20...
Second groove surface, 21... Virtual plane, 22... Tip cutting edge, 19a... Concave cutting surface of tip cutting edge, 23...
Starting end of tip cutting blade, 24...Chisel edge, 24a
...Any point on the chisel edge, 25...Side cutting edge, 26...Terminal end of tip cutting edge, 27...Double face, 28...Rake face.

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
8, the first groove surface 19 and the both inclined end surfaces 17,
17 are intersected at both ends of a virtual plane 21 including the longitudinal axis 16, and tip cutting edges 22, 22 are formed at the intersection points, respectively, and both inclined end surfaces 17, 17 are made to intersect with each other at both ends of the virtual plane 21 including the longitudinal axis 16. Cutting blades 22, 22
In a drill screw, the chisel edge 24 intersects in a ridgeline shape on a line connecting the starting ends 23, 23 in a portion closer to the longitudinal axis 16, and this intersecting ridgeline is formed in the chisel edge 24.
At least the portions of the first groove surfaces 19 in the first grooves 8 and 18 that are connected to the both tip cutting edges 22 and 22 are formed with respect to the longitudinal axis 16 in order to form a rake angle with respect to the both tip cutting edges 22 and 22. The drill portion 13 is provided with a concave cutting surface 19a that is inclined at
From the chisel edge 24 to both vertical grooves 18,1
A pair of left and right flat rake surfaces 28 , 28 extending substantially parallel to the longitudinal axis 16 toward the first groove surface 19 at 8 are formed along the chisel edge 24 .
A drill screw characterized in that it is provided so as to extend to a region adjacent to an arbitrary point 24a on the top. 2 Any point 2 on the chisel edge 24
4a eccentrically from the longitudinal axis 16, the width of both the rake faces 28, 28 along the longitudinal direction of the chisel edge 24 is such that the width of one rake face is longer and the width of the other rake face is shorter. A drill screw according to claim 1, characterized in that it is configured as follows.