SK155099A3 - Connecting element for connecting at least two wooden construction parts and a joint plate - Google Patents

Abstract

The invention relates to a connection between two wooden construction parts (2 and 3). According to the invention, a joint plate (4) is introduced, the base part (5) of said joint plate (4) being connected to the wooden construction part (2) so that it is flush therewith, by means of screws (7). Said joint plate (4) is pushed into a slit (8) in the wooden construction part (3) and the appropriate number of connecting elements (1) are then introduced, passing through the wooden construction part (3) and the joint plate (4). A connecting element of the type used has a boring part (11) at one end and a tool contact part (12) at the other end. The material which is worked off is taken up by a segment with a reduced cross section (14) and corresponding chucking grooves (13). The connecting element can also be secured axially after placement by means of a thread (15) at one end of said connecting element. After placement, the connecting element sits in such a way that it fits perfectly in the self-made bore as a fixing element between the joining plate (4) and the wooden construction part.

Description

Technical field

The invention relates to a fastener having a substantially rod-like shaft and is used for joining at least two wooden building elements and at least one gusset plate which is inserted into one or more notches in the wooden building elements and which is preferably made of metal.

BACKGROUND OF THE INVENTION

In the case of lattice or frame constructions, the used wooden building elements are usually joined by means of girders made of metal. The gusset plates are inserted into the notches located centric at the ends of the wooden building elements. In the wooden components and gusset plates, identical holes are arranged, in which pins are usually inserted. These metal pins secure the gusset plate in the respective wooden building element. In order to ensure that the pins can transfer the prescribed forces between the timber building elements and the gusset plate and that a rigid connection can be created which prevents mutual displacement, the holes in the timber building elements and the gusset plate must be accurately aligned and made with each other.

Since two materials are used, on the one hand, wood and on the other, metal gussets, there are particular problems in forming holes. As a rule, in order to maintain drilling tolerances, holes have now been drilled into wooden building components. Then, the gusset plate is inserted into the notches of the wooden building elements, and holes are formed in the gusset plate, the holes already formed in the wooden building elements forming a kind of drilling template. With a suitable drill, openings are made in the gusset plate and the peg required to connect the wooden components and the gusset plate together. On the one hand, this manufacturing process is very demanding and, on the other hand, it is not possible to achieve a rigid and load-bearing joint, because the fit accuracy is not optimal.

It is also known to produce holes in the gusset plate. This gusset plate is used as a template for drilling holes in wooden building elements. Since in this case the end position of the gusset plate is offset axially relative to the drilling position, there may be some inaccuracies,

-2so dimensional tolerances may not be observed. Moreover, this method of manufacture is very lengthy and time consuming.

According to a further known process (DE-C-43 15 101), a gusset plate is first inserted into a corresponding notch in a wooden building element. In this correct position, holes are made into the wooden components and the gusset using a drilling device. A step drill is used in order to take into account the unequal conditions in drilling in wood and metal. After the holes have been made, the corresponding pins can be hammered in.

Even in such a known embodiment, proper holding of the drilling device is necessary, as care must also be taken not to slide the gusset plate inserted into the corresponding notch in the wooden building element.

Particularly when working on a construction site, problems arise in such an embodiment, since the use of very large and bulky equipment on site is associated with lengthy handling. In addition, access to such a device is not available everywhere.

Furthermore, a known connection for covered joints of beams (DE-A-41 24 553) is known, in which precise metering and drilling operations can be avoided. For the connection between the wooden building element and the gusset plate, nails are hammered in without creating holes. To this end, a special construction of the gusset plate is necessary to allow nails to penetrate through it. It must therefore be taken into account that the region of the gusset plate into which the nails penetrate must be made of thin-walled sheet. In view of this special area, there is a risk of nails bending or splitting, especially when such gusset plates are used at the front of the wooden building elements.

The present invention has therefore set itself the object of providing the connecting means described above, by means of which it is possible to establish a precise connection between the timber building elements and the gusset plates, with easy handling for each type of timber building elements and gusset plates.

SUMMARY OF THE INVENTION

According to the invention, this is done so that the rod shaft has a drilling portion at one end and a tool receiving portion at the other end to screw it in, the diameter of the shaft being at least about one or more portions of its length.

The diameter of the drill portion, and the shaft has, at the opposite end of the drill portion, means for axially securing the displacement in the installed state.

By means of the invention, an opening can be formed in at least one of the gusset plates, or possibly also in the gusset plate, in a wooden building element by means of a rod-like connecting means which ultimately forms a connection of the gusset plate and the wooden building element. Since the connecting means thus creates a hole in the gusset plate in one working step and at the same time a connection between the two elements, there is always an exact match between the holes in the gusset plate and the wooden building element. This creates a precise and non-sliding connection between the gusset plate and the timber component. It does not matter whether, when a plurality of parallel connecting means are arranged, they lie exactly parallel to each other or whether they are at an acute angle between them. Each connection means forms a precisely arranged and flush joint between the wooden building elements and the gusset plate.

The coupling means holds in the opening of the gusset plate and / or the wooden building element with a force connection securing the means against axial displacement. Because of the drilling chips, an additional internal connection is established between the fastener and the gusset plate or the wood component, so that only by screwing in the fastener a positive and / or force-locking connection is achieved to secure the fastener against axial displacement. Other additional means may also be used to form the shaped and / or force-tight, leak-proof connection.

By means of the fastener according to the invention, it is also possible to insert or place the gusset plate in a wooden building element with pre-prepared openings, whereby the fastener is inserted into the pre-prepared opening and subsequently forms a hole in the gusset plate. In this way, it is possible to use the holes provided in the factory as a template for the additional drilling of the gusset plate. Even in such a method, an opening is created in the gusset plate by means of the fastener itself, which at the same time forms a connection between the wooden building element and the gusset plate. Also, a precise fit between the holes in the wooden building element and in the gusset plate is also provided so that the connecting means firmly connects the wooden building element and the gusset plate to each other.

The fastener does not have to penetrate the entire wooden building element. The fastening process of the fastener may be terminated before a through hole is formed. Thus, on one side of the wooden building element, the manner of connection to one another will not be visible at all. Thus, for aesthetic reasons, the connection on one side of the wooden building element can be made hidden or invisible. From the strength point of view, a through hole is not required for the connection, since it is sufficient if the fastener on both sides of the gusset plate only reaches a certain area of the wooden building element.

By means of these measures according to the invention, a connection means is created which is very suitable for this particular purpose of use. Screws have hitherto been used to attach joining plates or the like that are located on the surface of wooden building elements. So far, no self-drilling fasteners have been used in the timber structures when joining together wooden building elements and gussets. It is precisely in the above-mentioned solution that the formation of a rod-shaped fastener with a suitable borehole represents a significant advance. With such a fastener, the necessary opening can be made in one operation. In addition, a fastener is provided which serves in the opening for the connection between the gusset plate and the wooden building element. In addition, a precise and rigid fastening to one another is possible by means of such a connecting means. With a suitable drill part, the correct opening can be created in an optimal way, both in the wooden building element and in the metal plate.

A variety of drilling screws (among others by DE-A-38 28 446) having a drill tip and a threaded shank are known. With such drilling screws a suitably long thread is available and the hole diameter is larger than the diameter of the shank core in the thread region. However, drilling screws are generally unsuitable for this purpose, since there is already a drilling offset corresponding to the thread pitch during drilling. However, this is not possible when drilling relatively thick gusset plates.

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It is further proposed that chip grooves are or are formed on the drilling portion and optionally on the rod shaft section adjacent to the drilling portion. These chip grooves create the possibility that the material produced and removed during drilling can be conveniently transported and retained. In this case, it is not necessary for the chips to be transported outside the wooden building element, but it is sufficient if the chips produced enter the chip grooves in a compacted form. It is also not important whether or not

Some metal shavings will penetrate the wall of the hole, as this does not imply any effect on the final fit. The connecting means, which itself has formed the opening, remains ultimately in the formed opening.

In one embodiment variant, it is proposed that immediately after the drilling part there is a section which has a reduced cross-section compared to the drilling part. This creates an area immediately behind the drilling portion, which has an increased chip-absorbing capacity.

In a particular embodiment of the invention, a second drilling section is disposed on the rod shaft, which is offset axially against the drilling part and has an increased drilling diameter. As a result, the formation of the hole and the amount of chips produced can be divided into two successive bores. Especially with thicker fasteners, this is an advantage.

In order to create a particularly large capacity for trapping the resulting chips, it is proposed that one or more chip grooves run over most or all of the rod shaft length.

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A further variant of the embodiment has a thread or thread-like shape at least over a portion of the length of the rod shaft. This provides additional protection against axial displacement of the fastener so that the fastener does not come loose even after shrinking even in the event of shrinkage in the region of the wooden building element.

In other possible embodiments, it is proposed in this connection that a roughened surface, grooving or the like, or elevations or depressions, be formed at least over a certain portion of the rod shaft length. Also in this way, an additional safeguard against the rotation and displacement of the coupling means can be provided, which prevents the coupling means from escaping from the formed hole after its final sinking.

In order to optimally close the opening of the opening and to suitably compact the wood in this area, it is proposed to provide a conical extension at the opposite end of the rod shaft to the drilling part. Such a conical extension may also be used to increase the torque accordingly. In this way, it is possible to use the automatic turning off of further screwing depending on the torque.

A preferred embodiment is that the reduced-section section is adjoined by a rod-shaped section having a diameter at least approximately corresponding to the diameter of the hole and having one or more chip grooves. In this way, not only an enlarged circular chip-retaining space is created which follows the drilling part but also to it.

-6 adjacent chip grooves that are capable of retaining the drilled material without leaving the chip grooves immediately from the drilling portion. This also ensures that the torque applied to the coupling means does not increase too much in the case of a large burst of drilling chips.

In a particular method of using the fastener according to the invention, it is particularly advantageous if the tool gripping part is designed recessed. Not only a specially shaped recessed part but also a kind of groove can be considered as a certain recessed part for gripping the tool. Thus, it is possible in a simple manner to screw the driven end of the fastener below the surface of the wooden building element.

However, it is also possible within the scope of the invention that the tool gripping part is designed to be external, in which case, for example, an external hexagon can be used. Since such an external tool-receiving part, especially when the fastener has been inserted into the cross-section, must be designed with appropriately small dimensions, the possibility of using the external tool-receiving parts depends on the torque to be transferred.

In a particular embodiment of the fastener, especially when a larger fastener diameter is required, it is proposed that a further drilling section having an increased drilling diameter over the first drilling section is followed by a cylindrical section on the rod shaft with a slightly smaller diameter compared to the next. drilling section. Although this additional drilling section forms a slightly larger hole, the following rod shaft is perfectly held both in the gusset plate and in the wooden building element. Nevertheless, it is ensured that the torque does not increase too much even if there is no play. Thus, an appropriate balance is provided between the necessary torque to form the bore, to move the fastener and the necessary fit between the bores.

In one embodiment of the fastener, it is proposed that one or more chip grooves are spirally positioned. Thus, in the course of drilling, the resulting chips, like the spiral drill, are blown into the chip grooves in the direction of the driven end of the fastener. This ensures that the chip grooves are virtually completely filled with the drilling chips at the final recess of the fastener, such that a substantially cylindrical fastener with an integral surface contacting the hole is formed.

However, it is also possible within the scope of the invention that one or more chip grooves are arranged parallel to the axis. Driving chips in such chip grooves, despite the rotation of the coupling means, practically does not exist, so that the chip grooves in such an arrangement are only filled in the axial direction due to the pressure of the chips arising during the drilling in the axial direction.

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Further features and specific advantages of the invention will be explained in greater detail below with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In FIG. 1 is an exploded view of a connection between two wooden building elements by means of a gusset plate, wherein the inserted connecting means are also shown;

In FIG. 2 shows an embodiment of the joining of wooden building elements by means of a special kind of gusset plate;

FIG. 3 is a view of the special fastener of FIG. 1;

In FIG. 4 to FIG. 9 shows various ways of making joints of wooden building elements and gusset plates, whereby other constructions of fasteners are also partially used;

In FIG. 10 and FIG. 11 shows two types of embodiment of joining two face-to-face wooden building elements with correspondingly shaped gusset plates.

DETAILED DESCRIPTION OF THE INVENTION

The present invention thus relates to a method of joining and a corresponding fastener 1 for joining at least two wooden building elements 2 and 3. According to Fig. 1, a gusset 4 is used for this purpose, with a base part 5 lying perpendicular to the gusset 4. It has holes 6 into which screws 7 can be inserted. Thus, the base plate 4 is butt-bolted over the base part 5 to the wooden building element 2. Thus, the wooden building element 3 is connected with its front side, i.e. its end, to the wooden building element 2. The timber building element 3 has a notch 8 into which the gusset plate 4 can be inserted. In principle, it is possible to design the gusset plate 4 on the outside of the end of the timber building block.

However, it is advantageous, in view of better transmission and distribution of forces, to provide an approximately centric arrangement of the gusset plate 4 in the notch 8 of the wooden building element.

3. After insertion of the gusset plate 4 into the notch 8, the timber elements 2 and 3 are in the prescribed relative position so that the gusset plate 4 and the timber element 3 can be connected to each other. The connecting means itself creates a corresponding opening 9 into the gusset plate 4 and possibly also into the wooden building element 3 and then serves as the connecting means which remains in the opening 9 which it has itself created.

In this context, it is also possible that the fastener 1 does not penetrate completely through the wooden component 3, and thus that one end thereof does not completely pass through the wooden component 3. This may be advantageous for aesthetic reasons, but also makes sense if it is not to be The drill portion 11 of the fastener 1, for example using the fasteners and the method according to the invention in rooms with high humidity, can be produced from carbon steel.

According to a partially modified method, it is also possible that the wooden building element 3 has holes already made in the workshop, whereby a gusset plate 4, which does not yet have holes, is inserted into the notch 8. The prepared holes 9 then form a kind of drilling template into which the fasteners J are inserted. The fasteners 1 must thus only create holes in the gusset plate 4 and are then used as suitable fasteners between the gusset plate 4 and the wooden building element 3.

It is the use of a self-drilling fastener that great progress can be achieved in joining at least two wooden building elements by means of a gusset, which not only results in easier and faster handling, but also in that each fastener used is inserted so that it fits exactly, creates optimum power transfer without lateral displacement.

In the embodiment shown in FIG. 1 and 3 essentially consists of a rod shaft 10 having a drilling portion 11 at one end and a recessed tool receiving portion at the other end. The diameter D2 of the shank 11 is at least approximately equal to the diameter of the hole D1 of the drill portion 11 on one or more portions of its length and must be located in the final position of the fastener 1 in the region of the gusset 4 and in adjacent areas of the wooden component

3. At least where the greatest shear forces occur at the joint between the gusset plate 4 and the timber component 3, there must be good fit between

9 through a hole 9 and a shaft 11). Drilling part Π. has corresponding chip grooves. The connecting means 1 according to the invention has, at least according to the embodiment of FIG. 1 and 3, in the region of the shank 10 adjacent to the drill portion 11, one or more chip grooves 13. These chip grooves 13 extend helically in the illustrated embodiment, which facilitates the transport of the machined material in the form of chips from the drilling. The material to be processed does not necessarily have to be transported out of the opening, but can be retained in the adequately compacted form in the opening itself or in appropriate recesses of the fastener k in this context, it is also possible that one or more chip grooves extend in the axial direction. . Such chip grooves are not only continuously filled with the material to be conveyed during drilling, but also retain the chips that remain on the wall of the hole or are filled with axially pushed chips.

Suitably, the chip grooves 13 extend along a large section or along the entire length of the rod shaft 10, but at least on a length with a diameter D2. Depending on the resulting chips from the drilling process, the chip grooves can also be designed to be reasonably shorter.

In the embodiment of FIG. 1 and 3, a section 14, which has a reduced cross-section D3, is adjacent to the drilling part 11, in comparison with the drilling part. This creates an additional annular space immediately behind the drilling portion U for receiving chips during drilling. The section 14 must have a diameter D3 that can transmit the torque during the drilling process. However, this section 14 has no influence on the force transmission between the gusset plate 4 and the wooden building element 3, since it lies far from the gusset plate 4 inserted in the notch 8.

Downstream of the reduced cross-section 14 following the drill portion H is a section of a rod shaft 10 having a diameter D2 and starting at a certain distance from the drill portion H. Especially for creating an optimal fit, the drill diameter D1 of the drill portion H is approximately equal to the diameter The shaft section 1P with a diameter D2 has spirally extending chip grooves 13 over its entire length in the illustrated embodiment. In this embodiment, a relatively large space can be formed in the region of the annular space in the region of the section 14 and in the adjacent chip grooves 13. catching chips when drilling.

At the opposite end of the coupling means 1, opposite to the drilling portion 11, a thread 15 is formed which engages in the formed hole 9 at the last rotation in the drilling process.

- means i, so that even if it is not directly subjected to shear forces or if there is shrinkage in the area of the wooden component 3, it cannot spontaneously pull out of the formed hole 9. Instead of thread Γ5 other thread-like arrangements may be used and it is also possible to use a plurality of circular parallel cuts having, for example, a sawtooth-shaped cross-section. The point is simply to provide an additional possibility of securing against movement of the coupling means 1 in the direction of its axis.

In this context, another embodiment is the use of a roughened surface, scoring or the like, or other elevations or depressions are used. In all such embodiments, spontaneous rotation or spontaneous axial displacement of the coupling means is prevented.

In the embodiment of FIG. 1 and according to other embodiments shown, a corresponding notch 8 extending over the entire height or thickness of the wooden building element 3 is also shown. Naturally, it is also possible for the notch 8 not to be formed in its plane as a continuous but rectangular hole on the front Thus, it is apparent on the wooden building element 3 only according to the fasteners 1 used that the joint with the gusset plate has been used here, because the notch 8 and hence the gusset arrangement. sheet 4 is not visible from the outside.

In the construction shown in Fig. 2, the wooden building elements 17, 18 and 19 are connected by means of V-shaped gussets 4. In this way, a lattice structure can be made of wood, using gussets 4 and connecting means 1 for interconnection. here, at the ends of the wooden building elements 18 and 19, openings 8 are provided, into which the gusset plates 4 can be inserted. Also in the wooden building element 17, notches 8 are placed, into which the gussets 4 are inserted. a kind of wall part. Through the direct use of the fasteners 1, holes 9 are formed in the wooden building elements 17.18 and 19 as well as in the gussets 4 and at the same time a fitting connection is formed. Naturally, even in such an embodiment, openings 9 can be formed in the wooden building elements 17, 18 and 19 already during their manufacture, and only the openings in the gusset plates have to be formed by means of the fastening means according to the invention. In such an embodiment, the bore portion H of the fastener 1 according to the invention must penetrate two at a distance

- 11 punched plates. Therefore, it is particularly important that the connecting means and the holes correspond to each other, which can only be achieved by the present invention, i.e. if the fastener itself drills a hole in which it is to be precisely embedded and to transmit forces.

In FIG. 4 is a cross-sectional view of an embodiment that would be formed in a finished joint according to the embodiment of FIG. 1. It is clear that the length of the whole fastener I must be equal to or shorter than the thickness of the wooden building element 3 measured in the direction of the axis of the fastener 1. It is clear that by means of the reduced cross-section of section 14 and a relatively large space is created to retain chips when drilling. Should shorter fasteners 1 be used, it is to be ensured that the drill portion U penetrates through the gusset plate 4 before the thread 15 is inserted into the hole at the end of the fastener. A slow movement when drilling through the gusset plate 4 would destroy the area to be pulled out, as the wood would be completely abraded.

The embodiment of FIG. 5 shows the use of a further drilling section 20 spaced from the drilling section 11 which has an enlarged diameter compared to the first drilling section U. Thus, the hole can be drilled gradually, and such an embodiment makes sense if a larger diameter fastener D4 is to be used. Thus, another drilling section 20 is followed by a rod shaft 10 having a diameter D4, whereby the diameter D4 of the shaft W may be slightly smaller than the diameter of the drilling section of the other drilling section 20. Such a measure causes no large friction in the hole between the coupling means I and the hole 9. so that the drilling process is terminated up to the final installation of the fastener without too much torque increase. Within the scope of the invention, it is possible that more than two different diameters of the boiling sections are used, which may be dependent on the respective diameter D4 of the shank 10.

It can be seen from Figures 6 to 8 that a variety of embodiments of the fasteners can be used and that sections with a reduced cross-section 14, chip grooves 13 or other embodiments can be combined with each other. In the embodiments of FIG. 6 to 8, the opposite end of the shank 10 has a conical extension 21 further to the drill portion 11. Here, in the end region of the wall of the hole, it is still sufficiently compacted to prevent splintering of the chips on the surface of the wooden building element. gripping the tool 12, whereby such a part can be designed as a screwdriver slot.

In the embodiment of FIG. 9, the tool gripping portion 16 has the shape of an external grip, taking care that the respective torque has to be transferred and that the end with the tool gripping portion 16 has to be embedded in the wooden building element 3. Therefore, an appropriate adjustment must be made used tool.

Fig. 9 shows an embodiment of a fastener 1 having one or more elevations 22 on the surface. It is possible for these elevations 22 to remain after the final fastening of the fastener 1 in the region of the wooden building element or in the region of the gusset 4. achieves protection against rotation and displacement.

The embodiments of FIG. Figures 10 and 11 show that not only the right-angled wooden building elements or the timber building elements in the lattice structure, but also the wooden building elements 23, 24 which grip the obtuse angle with the connection of their end faces can be joined by the gusset plate 4. In this case, two gussets 4 are used, which are connected to the crossmember 25 in two opposite directions and which engage the respective slots at the ends of the wooden building elements 23.24. It is also possible for the two wooden building elements 23, 24, as shown in FIG. 11 - they connect at an obtuse angle, whereby it is also possible for the gussets 4 to form an angle with respect to each other or to the intermediate sheet 25. Here too, the connection is made by means of fasteners 1 according to the invention. 4 and which then form the connection itself.

In the foregoing description, the tool-receiving part 12 or 12 has been discussed. 16 in the form of a recessed or external engagement. Within the scope of the invention, it is possible that the fastener 1 according to the invention is designed in a manner similar to a screw with a head having a corresponding recessed or external engagement. In such a construction, however, it must be taken into account that the fastener cannot be completely embedded on the screw-in side, since the head exceeds the respective shank diameter 10.

The connecting means 1 can e.g. The drilling section is in this case made cured for the required drilling process. It is also possible to weld the drill part or use suitable drill plates, e.g. carbon steel.

It has also been assumed in the previous description that a gusset plate of metal, for example steel or aluminum, is used. With suitable material strength, it would also be possible to use a plastic gusset plate, and the method and connection means according to the invention can also be used in such a construction.

Claims (13)

Patent claims A fastener with a substantially rod-shaped shaft for connecting at least two wooden building elements and at least one gusset plate inserted into one or more notches in the wooden building elements, preferably made of metal, characterized in that the rod (10) has at least at one end, a drilling portion (11) and at the other end a gripping tool portion (12, 16) for rotating, wherein the diameter (D2) of the shank (10) corresponds to at least approximately the drilling diameter (D1) of the drilling portion (11), and at the opposite end of the shank (10) opposite the drilling portion (11) is provided means for axially securing the displacement in the installed state. The connection means according to claim 1, characterized in that the drill part (11) and optionally also the rod shaft section (10) adjacent to the drill part (11) has one or more chip grooves (13). Fastener according to claim 1, characterized in that the drilling part (11) is followed by a section (14) which has a reduced diameter (D3) compared to the drilling part (11). Fastener according to one of Claims 1 to 3, characterized in that a further drilling section (20), which has an increased drilling diameter compared to the first drilling part (11), is offset on the rod shank (10) over the drilling part (11). . Fastener according to claim 2, characterized in that a large part of the length or the entire length of the rod shaft (10) is or is provided with one or more chip grooves (13). Fastener according to one of Claims 1 to 5, characterized in that at least one part of the length of the rod shaft (10) is a thread (15) or a thread-like arrangement. Fastener according to one of Claims 1 to 5, characterized in that at least one part of the length of the rod shaft (10) has a roughened surface, a groove or the like, or an elevation or depression. Fastener according to one of Claims 1 to 7, characterized in that the opposite end of the rod shaft (10) to the drill part (11) is conically widened. Fastener according to claim 3, characterized in that there is one or more at least approximately adapted to the drilling diameter (D1) on the section of the rod shaft (10) following the reduced cross section (14) (D3) chip grooves (13). Fastener according to one of Claims 1 to 9, characterized in that the tool-receiving part is designed as a recessed (12). Fastener according to one of Claims 1 to 9, characterized in that the tool-receiving part is designed as an outer grip (16). Fastener according to claim 4, characterized in that for a further drilling section (20) which has an increased drilling diameter compared to the first drilling part (11), the rod (10) essentially has a cylindrical section which has a cylindrical section compared to the other a slightly smaller drilling diameter in the drilling section (20). Connection means according to one of Claims 1 to 12, characterized in that the one or more chip grooves (13) are arranged so that they run helically. Fastener according to one of Claims 1 to 12, characterized in that one or more chip grooves (13) are arranged to run parallel to the axis.