JPH0261642B2 - - 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, it relates to the modification of a drill screw whose drill portion is formed by forging such as pinch pointing.

[Prior Art] Recently, with the increasing demand for drill screws of this type, in order to reduce the manufacturing cost of the drill screws, the lower end portion of a threaded shank with a head integrally formed at the upper end has been developed. The drill part is formed by forging such as pinch pointing.
No. 48-13139 (U.S. Patent No. 3395603), Japanese Patent Publication No. 58-4504, and Japanese Patent Publication No. 59-7046 (U.S. Patent No. 4407620) disclose a drill formed by forging at the lower end portion of the shank. The portion is shaped as shown in FIGS. 13 to 16.

That is, the drill part 1 disclosed in each of the above-mentioned prior arts is formed by forging, and the free terminal end of the drill part 1 is diagonally upward from the longitudinal axis 2 of the shank toward the head of the upper end of the shank. A pair of left and right inclined end surfaces 3, 3 which are inclined outwardly relative to the shank 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 these inclined end surfaces 3, 3 are provided.
Two vertical grooves 4, 4 extending upward from the vertical grooves 4, 4 are provided diagonally, and among the two groove surfaces forming the vertical grooves 4, 4, the first groove surfaces 4a, 4a and the both inclined end surfaces 3, 3 By intersecting each of them on both sides of the virtual plane 5 including the longitudinal axis 2, tip cutting edges 6, 6 are formed at the intersection points, and the intersecting ridge lines of the pair of left and right inclined end surfaces 3, 3 are formed. , starting ends 6a, 6a closer to the longitudinal axis 2 of the cutting edges 6, 6 at both ends;
A chisel edge 7 with a relatively short length L extending in a straight line perpendicular to the longitudinal axis 2 is formed between the starting ends 6a, 6a of the cutting edges 6, 6 at both ends by locating it on the line connecting the two. It 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. , 3 has a triangular shape, and on the front side of the chisel edge 7 with respect to the rotational direction of arrow A, there is an inclined end surface 3 that slopes diagonally upward from the chisel edge 7 over the entire length of the chisel edge 7. Become.

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 16.
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 linear in a direction perpendicular to the longitudinal axis 2, and the chisel edge contacts the object to be fastened 8 over its entire length, so that the pressing force against the object to be fastened 8 is distributed over a wide area. Therefore, the cutting performance of the chisel edge 7 is correspondingly low.

In other words, the forged drill screw with a chisel edge disclosed in each of the above-mentioned prior arts does not have sufficient initial cutting performance for the object to be fastened, and a large thrust (the force of the drill screw against the object to be fastened) is required to screw into the object. Not only does this require a large amount of pressing force, but it also takes 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.
When pressed while rotating, the so-called dancing phenomenon in which the drill part 1 swings in a direction perpendicular to the longitudinal axis 2 becomes quite large, so 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.

Therefore, an object of the present invention is 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]

For this reason, 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 has a pair of left and right inclined end surfaces at the free end of the drill part that are inclined upwardly from the longitudinal axis of the shank toward the head of the upper end of the shank and outwardly with respect to the longitudinal axis. The end surfaces are provided so as to intersect with each other at a position that coincides with the longitudinal axis, and two vertical grooves each consisting of a first groove surface and a second groove surface are provided so as to extend upward from the both inclined end surfaces. , by intersecting the first groove surface constituting a part of each of the longitudinal grooves and the inclined end surfaces on both sides of an imaginary plane including the longitudinal axis, a tip cutting edge is formed at the intersection point. By positioning the intersecting ridge lines of the pair of left and right inclined end surfaces on a line connecting the starting ends of the cutting blades at both ends closer to the longitudinal axis, a chisel edge is formed between the starting ends of the cutting blades at both ends. In the drill screw, a portion of the both inclined end faces facing the second groove surface of both the vertical grooves and adjacent to the chisel edge has a portion extending substantially parallel to the longitudinal axis from the chisel edge. to form a rake face configured to be continuous with the first groove surface in both longitudinal grooves, and at the same time, the chisel edge is lowered at a position slightly eccentric from the longitudinal axis in a portion between both ends of the chisel edge. It is characterized by being formed into a mid-height shape with the most protruding part.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A drill screw 10 shown in FIG. and a drill part 13 formed by forging such as pinch pointing, and the head 12 has a groove or recess 14 for engagement with 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. There is.

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 the head is formed and before the thread is formed between a pair of left and right forging dies facing each other from both sides. Then, the drill part 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 intersect with each other at a position that coincides with the longitudinal axis 16, and two longitudinal grooves 18 and 18 are provided diagonally extending upward from these inclined end surfaces 17 and 17. Both vertical grooves 18,
18 is the first groove surface 19, 19 and the first groove surface 1;
9 and 19, and second groove surfaces 20 and 20 intersecting with each other.

The first groove surfaces 19 , 19 and the inclined end surfaces 17 , 17 , which constitute a part of each of the longitudinal grooves 18 , 18 , are defined by a virtual plane 21 including the longitudinal axis 16 .
By intersecting along lines substantially parallel to the imaginary plane 21 on both sides, tip cutting edges 22, 22 are formed at the intersections.

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 blades 22, 22 closer to the longitudinal axis 16, both tips A chisel edge 24 having a relatively short length L is formed between the starting ends 23, 23 of the cutting blades 22, 22, extending in a straight line at right angles to the longitudinal axis 16.

Note that, on the side surface of the drill portion 13, side cutting edges 25, 25 are formed by the first groove surfaces 19, 19 in both the vertical grooves 18, 18, and
It is formed so as to extend upward from the terminal ends 26, 26 near the outer periphery at 2, 22. Therefore,
The distance between the two side cutting edges 25, 25 is the maximum diameter D in the drill portion 13, and a hole having the same inner diameter as this maximum diameter D is bored in the object 30 to be fastened.
Further, the first groove surface 1 in both the vertical grooves 18, 18
9 and 19 are formed into concave curved surfaces so that each of the tip cutting edges 22, 22 and the side cutting edges 25, 25 have an appropriately correct rake angle. Side cutting blade 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 23 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 said longitudinal axis 16
Flat rake faces 28, 28 are formed so as to extend substantially parallel to the first groove faces 19, 19 of the longitudinal grooves 18, 18.

Further, the chisel edge 24 is tilted diagonally downward from its both ends, that is, the starting ends 23, 23 of the cutting blades 22, 22 at both ends, toward a position eccentric by a slight dimension e with respect to the longitudinal axis 16. In other words, the chisel edge 24 is formed into a medium-height shape so as to have the most protruding portion 24a that protrudes downward at a portion between both ends of the chisel edge 24 and at a position offset by a slight dimension e from the longitudinal axis 16. do.

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.

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 at the same time as the forging process described above, it is also possible to form the chisel edge 24 into a medium-height shape having the most protruding part 24a at the same time as the forging process described above.

Both rake surfaces 28, 28 formed in this manner and substantially parallel to the longitudinal axis 16 press the drill portion 13 against the object to be fastened 30 while rotating the drill screw 10 around the longitudinal axis in the direction of arrow A. In this case, the chisel edge 24 of the drill portion 13 is located on the front side in the rotational direction, while the rake faces 28, 28 are approximately at a distance from the surface 30a of the object to be fastened 30, as shown in FIGS. 8 and 9. The vertical shape allows the chips cut by the chisel edge 24 to smoothly escape into both the vertical grooves 18, 18.

On the other hand, by forming the chisel edge 24 into a medium-height shape having the most protruding portion 24a at a position eccentric to the longitudinal axis 16, which is the rotation center of the screw, the surface 30a of the object to be fastened 30 has the following features: The most protruding part 24a of the chisel edge 24 comes into contact first, and the pressing force acts concentratedly on this most protruding part 24a, and the most protruding part 24a is aligned with the longitudinal axis 16, which is the rotation center of the screw. radius e around
Since it turns with a certain amount of force, the biting performance against the object 30 to be fastened is significantly improved.

In this case, an appropriate eccentric distance e from the longitudinal axis 16 to the most protruding part 24a of the chisel edge is 5/100 to 20/100 of the maximum diameter D of the drill part 13, according to experiments. When it is small, no improvement in the biting performance is observed by making the chisel edge 24 medium-height, and when it is larger than this, the drill part 13 is improved by making the most protruding part 24a of the chisel edge 24 eccentric with respect to the longitudinal axis 16. The so-called "dancing" phenomenon, in which the wheels sway from side to side, increases. Furthermore, the shape of the chisel edge 24 is not limited to the illustrated chevron shape, but may be a circular arc or a parabolic shape. However, when the chisel edge 24 is shaped like a chevron as shown, The inclination angles β1 and β2 with respect to the line perpendicular to 16 were suitably between 6 degrees and 18 degrees.

Note that the embodiment shown in FIGS. 5 and 6 is as follows:
In the case where the width dimension along the longitudinal direction of the chisel edge 24 of both the rake faces 28, 28 was set to exactly half the length L of the chisel edge 24, Figure 10 and Figure 1
As shown in FIG. 1, the width L1 of one of the two rake faces 28, 28 is made longer and the width L2 of the other rake face 28 is made shorter. The most protruding portion 24a of the chisel edge may be located at the joint of the two. By locating the most protruding part 24a of the chisel edge at the joint between both rake faces 28, 28 in this way, the strength of the most protruding part 24a of the chisel edge is improved. It is possible to reduce the loss of.

Moreover, as shown in FIG. 12, 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.
2 and positioning the most protruding part 24a at the part of the rake face 28 with the shorter width dimension has the advantage that chipping of the chisel edge 24 and the most protruding part 24a can be further prevented.

[Action/effect of the invention]

As described above, the drill screw of the present invention has a rake face formed on the chisel edge of the drill portion formed by forging to smoothly release the cutting waste cut by the chisel edge into the vertical groove, and the chisel edge is formed into a medium-high shape with the most protruding part at a position eccentric from the longitudinal axis of the shank.When cutting with the chisel edge during cutting, cutting debris can be smoothly released by the rake face, and the most protruding part of the chisel edge is The protruding portion improves the biting into the fastened object, and the initial cutting performance of the chisel edge is improved because the chisel edge does not have a rake surface unlike the above-mentioned prior art, and the chisel edge is aligned in a straight line. Since the drill screw is significantly improved over the conventional one, it is possible to reduce the thrust when screwing the drill screw into the object to be fastened, and the time required for screwing in can be shortened.In addition, the chisel edge bites into the object to be fastened better, making it easier to rotate the chisel edge. At the same time, it is possible to reduce the dancing phenomenon when pressed against an object to be fastened, so there is little deviation in the screwing position, and the screw can be screwed into an accurate position in a short time with light force.

[Brief explanation of drawings]

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 FIG. FIG. 11 is an enlarged view of the drill part of the second embodiment, FIG. 11 is a bottom view of FIG. 10, and FIG. 12 is an enlarged view of the drill part of the third embodiment of the present invention.
Figures 3 to 16 show conventional examples;
The figure is an enlarged view of the drill part, Fig. 14 is a bottom view of Fig. 13, Fig. 15 is a cross-sectional view taken from 15-15 in Fig. 12, and Fig. 16 is a sectional view taken from 16-16 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, 23... starting end of tip cutting edge, 24... chisel edge, 25... side cutting edge, 26... terminal end of tip cutting edge, 27... ...Second cut surface, 28...Rake surface,
24a...The most protruding part of the chisel edge.

Claims (1)

[Claims] 1. 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 has a pair of left and right inclined end surfaces, which are inclined upwardly from the longitudinal axis of the shank toward the head of the upper end of the shank and outwardly with respect to the longitudinal axis, at the free end of the drill part. The inclined end surfaces are provided so as to intersect with each other at a position that coincides with the longitudinal axis, and two longitudinal grooves each consisting of a first groove surface and a second groove surface are provided so as to extend upward from both of the inclined end surfaces. a first groove provided and forming a part of each of the longitudinal grooves;
By intersecting each of the groove surface and the both inclined end surfaces on both sides of a virtual plane including the longitudinal axis, a tip cutting edge is formed at the intersection point, and an intersecting ridge line of the pair of left and right inclined end surfaces is formed. , a drill screw in which a chisel edge is formed between the starting ends of the cutting edges at both ends by being positioned on a line connecting the starting ends of the cutting edges at both ends closer to the longitudinal axis; A portion of both longitudinal grooves facing the second groove surface and adjacent to the chisel edge is configured to extend from the chisel edge substantially parallel to the longitudinal axis and to be connected to the first groove surface of both longitudinal grooves. The chisel edge is formed into a medium-height shape having a most protruding part that protrudes most downward at a portion between both ends of the chisel edge and at a position slightly eccentric from the longitudinal axis. Characteristic drill screw. 2 The width along the longitudinal direction of the chisel edges on both rake faces is configured so that the width on one rake face is long and the width on the other rake face is short, so that the chisel edge protrudes the most at the joint of both rake faces. The drill screw according to claim 1, characterized in that the drill screw has a portion located therein. 3 The width dimension along the longitudinal direction of the chisel edges of both rake faces is configured so that the width dimension of one rake face is long and the width dimension of the other rake face is short, so that the rake with the shorter width dimension of both rake faces The drill screw according to claim 1 or 2, characterized in that the most protruding portion of the chisel edge is located at a location on the surface. 4 Determine the eccentric distance from the longitudinal axis of the shank to the most protruding part of the chisel edge with respect to the maximum diameter of the drill part.
The drill screw according to claim 1, 2, or 3, characterized in that the diameter is 5/100 to 20/100.