Wood screw

Abstract

The invention relates to a wood screw (10) with a point (12), a screw head (14), a shank (16) extending from the screw head (14) and transitioning into a convex conical point section (18), wherein the point section (18) forms the transition from the shank (16) to the point (12), and a thread (26) extending into the point section (18) through a cylindrical threaded shank section (20) adjacent to the point section (18), and wherein the thread (26) is designed as a double thread in the area of ​​the point section (18).

Description

[0001] The invention relates to a wood screw.

[0002] Wood screws are known from the prior art. Typically, wood screws have a screw head, a point, and a shank extending between them, which has a cylindrical core diameter. A thread runs along the shank towards the point, allowing the wood screw to cut a corresponding thread when driven into a workpiece and thus gain a hold in the drilled hole.

[0003] To improve the driving behavior of wood screws, differently designed threads can be provided along the shank, for example, continuous threads from the tip to the head or threads formed in sections along the shank. The addition of cutting geometries in the form of cutting ribs, chip breakers, or peeling ribs in the area of ​​the screw tip or shank is also known. These reduce resistance when driving the wood screw into a workpiece, as the aforementioned cutting geometries scrape away and remove some of the wood material during the driving process.

[0004] However, the known wood screws have room for improvement regarding their screw-in behavior.

[0005] The JP S56 160414 A is a metal screw that ensures secure insertion even into thin metal plates. For this purpose, the screw has a second thread at its tip.

[0006] DE 20 2013 101296 U1 describes a screw that has four threads in a front end section. Spaced apart from these four threads, there is an engagement thread in the shank area, which engages after these four threads.

[0007] EP 3 943 763 A1 refers to a wood screw in which a single-start or multi-start thread runs from the head end, through the shank section, to the tip. An additional opposing thread is also present.

[0008] Therefore, the object of the present invention is to provide a wood screw which is characterized by good screw-in behavior in a workpiece.

[0009] This problem is solved according to the invention by a wood screw according to claim 1.

[0010] Advantageous embodiments are described in the dependent claims, which can optionally be combined with one another.

[0011] According to the invention, the wood screw has a point, a screw head, and a shank that extends from the screw head and transitions into a convex, conical point section. The point section forms the transition from the shank to the point. Furthermore, the wood screw has a thread that extends into the point section via a cylindrical threaded shank section adjacent to the point section. The thread is double-start in the area of ​​the point section.

[0012] A cylindrically shaped threaded shank section refers to the shape of the thread core within the threaded shank section, excluding the thread itself. One thread terminates at the tip section before the transition to the threaded shank section, while the other thread continues to a milled section of the shank.

[0013] In this way, a wood screw can be provided that is only double-started in the tip section, whereas the wood screw is essentially single-started in the threaded shank section. The underlying principle is that the double-start thread is only necessary in the tip section, since the wood screw, due to its convex conical tip, only needs to be stabilized at the beginning of the screwing process. Once the wood screw according to the invention is tightened, i.e., the convex conical tip is countersunk in the workpiece, a single-start thread in the threaded shank section is sufficient for further screwing.

[0014] According to the invention, a chip breaker in the form of a rib is provided in the transition area between the tip section and the threaded shank section.

[0015] The proposed wood screw is characterized by improved insertion behavior in a workpiece. This improved insertion behavior is achieved through the combination of the convex conical tip section and the double-start thread in the tip section.

[0016] The convex, conical tip section allows for maximum wood displacement with just a few turns when screwing into a workpiece. This is due to the convex geometry of the tip section's outer contour, which, unlike conventional, purely conical tip sections, features a steeper increase in core diameter in the area immediately surrounding the tip. In longitudinal section, the cone-defining circumferential surface of the tip section is convexly curved outwards. The increase in core diameter then gradually flattens out towards the screw head. As this section moves into the drilled hole in the wood, the displaced wood is compacted. This further stabilizes the drilled hole and improves the screw's driving behavior.

[0017] Due to the rapid increase in core diameter, there is increased resistance at the beginning of the screwing process. To ensure that the wood screw according to the invention can be screwed into a workpiece stably and without wobbling despite this increased resistance, a double-start thread is provided in the area of ​​the convex conical tip section, allowing the wood screw to grip securely after just a few turns. Therefore, the double-start thread also works synergistically with the convex conical tip section to improve the screwing behavior of the wood screw according to the invention. Furthermore, the second thread also stabilizes the wood screw laterally during insertion.

[0018] According to a first aspect of the invention, the first thread and the second thread of the double-start thread terminate at a distance from each other in the direction of the tip. In particular, the first thread and the second thread terminate at the same distance from the tip to prevent the wood screw from tilting when it is first gripped.

[0019] This creates a thread-free section between the tip and the start of the double thread. This advantageously allows for precise positioning of the tip on a wooden workpiece, with the thread-free section being countersunk into the workpiece without being screwed in. This ensures that the ends of the first and second threads rest on the surface of the workpiece before insertion. The subsequent insertion of the wood screw can therefore be carried out from a supported position, thus preventing grinding and wobbling movements of the screw during insertion.

[0020] According to a further aspect of the invention, the first and second threads of the double-start thread are offset from each other by 180°. A wood screw with such a double-start thread is particularly easy to manufacture and does not wobble when screwed in.

[0021] In a further embodiment, the first thread and the second thread of the double-start thread each have screw head-side thread flanks and oppositely arranged tip-side thread flanks, wherein the tip-side thread flanks are inclined towards the tip.

[0022] The characteristic "inclined towards the tip" is understood below to mean that, viewed in a cross-sectional plane in which the center axis of rotation of the wood screw lies, the thread flanks facing the tip form an angle γ with the center axis of rotation that is less than or equal to 90°. Such a wood screw exhibits improved pull-out strength.

[0023] Another aspect of the invention provides that the first thread and the second thread of the double-start thread each terminate in a cutting wing on the tip side.

[0024] The cutting wings act as scraping sections, improving the screw's insertion into a workpiece. While the cutting wings initially increase resistance, they result in a more stable screw drive overall, without grinding or wobbling.

[0025] The cutting wings can each have the same or a lesser radial height than the thread opening into the cutting wings.

[0026] For example, the cutting wings can have a radial height of up to 1 / 8, 1 / 4 or 1 / 2 the height of the thread.

[0027] In cases where the radial height of the cutting wings is less than that of the thread, an intermediate thread section can be provided between each cutting wing and the thread it engages. The radial height of this intermediate thread section decreases continuously from the thread down to the height of the cutting wing. This prevents undercuts during manufacturing, allowing the screw to be inserted without stress concentrations.

[0028] Radial height refers to the radial extent of the cutting wing or thread in relation to the outer contour of the tip section.

[0029] If the cutting wings have the same radial height as the thread terminating in them, the cutting wings can serve as a bearing surface on the workpiece. This allows the wood screw to be driven in from a stable, supported position.

[0030] If the cutting wings have a lower radial height than the thread opening into the cutting wings, the resistance at the beginning of the screwing process is reduced compared to cutting wings that have the same radial height as the thread.

[0031] According to another aspect of the invention, each cutting wing has a cutting edge that extends at a substantially perpendicular angle to the rotational axis of the wood screw. Providing a cutting edge reduces the resistance encountered when driving in the wood screw, thus improving the overall driving behavior.

[0032] Furthermore, the convex conical tip section can have an acute angle α in a range of 15 to 30°, preferably from 25 to 30°.

[0033] The screw tip of the wood screws according to the invention is thus designed in a needle- or nail-like manner, allowing the wood screw to be inserted into the wood material before screwing it in. In this way, the wood screw can be fixed in the workpiece without the need for initial screwing.

[0034] Furthermore, the convex conical tip section, viewed in a cross-sectional plane containing the axis of rotation, can have a radius R for which the following relationship applies, based on the nominal diameter (d) of the thread of the wood screw in the threaded shank section: d / R = 0.13 - 0.18, preferably d / R = 0.145 - 0.175. For example, the nominal diameter can be 8 mm and the radius 45 to 55 mm.

[0035] Such a radius of the convex, conical tip section is particularly suitable for displacing sufficient wood at the beginning of the screwing process and then compacting it accordingly as the screwing progresses. This increases the stability of the milled bore and improves the overall driving behavior of the wood screw.

[0036] In particular, it is provided that the rib extends at least partially around the tip section or threaded shank section in a ring-like manner, with the rib preferably being continuous around the circumference.

[0037] The rib can also be designed like the additional thread in EP 3 943 763 A1, to which reference is hereby made.

[0038] It is therefore conceivable that a rib is provided which extends section by section in the area of ​​the convex conical tip section from one thread to the next in the longitudinal direction of the screw and merges into the thread at the opposite ends without crossing over any thread.

[0039] Preferably, such a rib extends over a maximum of 1 / 3 of the length of the convex conical tip section, in particular over less than 1 / 3 of the length of the convex conical tip section, so that the screw fits well when screwed in and yet scrapes sufficiently.

[0040] The transition zone refers to the area between the tip section and the threaded shank section. In this zone, the thread no longer needs to be double-started.

[0041] Such a rib reduces the resistance when screwing in the wood screw by breaking and removing the wood chip as the screw is screwed in.

[0042] In a further aspect of the invention, the thread shank section and / or the tip section has a non-circular cross-section. In particular, the cross-section of the thread circle has a trilobular shape.

[0043] A non-circular cross-section is understood to mean a non-circular circumference of the thread core, which has the thread core and also arc-shaped bulges at periodic intervals.

[0044] Firstly, this cross-sectional design improves wood compaction. Secondly, it reduces friction between the threaded shank section of the wood screw and the milled hole. In particular, the trilobular shape ensures that the thread core is in direct contact with the hole at only three points within the threaded shank section. In the inner sections, the thread is radially deeper, resulting in higher pull-out strength.

[0045] According to a further aspect of the invention, a milling section is provided on the shank immediately adjacent to the screw head end of the thread, which extends from the threaded shank section towards the screw head, wherein the milling section has several protruding cutting ribs with a higher thread pitch than that of the thread in the threaded shank area.

[0046] The milled section also reduces the screw-in resistance in the unthreaded area between the head and the milled section. In particular, the milled section with its cutting ribs reduces stress peaks when driving in the wood screw, resulting in smoother operation.

[0047] Another aspect of the invention provides that the thread core widens in the milling section in the direction of the screw head, in particular conically, and furthermore in particular wherein the thread core is conically shaped throughout the entire milling section.

[0048] The aspect mentioned above is based on the consideration that the weakest area of ​​a wood screw is usually the transition between the shank and the threaded section. By increasing the size or diameter of the thread core, stress peaks during insertion and notch effects under load are reduced, making the transition between the shank and the threaded section less susceptible to damage.

[0049] According to another aspect of the invention, an odd number of cutting ribs are provided in the milling section, in particular wherein three, five or seven cutting ribs are provided and / or that the cutting rib forms an angle β with the rotational center axis of the wood screw, which is in a range of 40 to 50°.

[0050] An odd number of cutting ribs improves the screw-in behavior of the wood screw, as it runs more smoothly when screwed in.

[0051] Another aspect of the invention provides that, viewed from the tip, the thread core transitions continuously in all radial sections over its entire length in the milling section from a non-circular, preferably trilobular, thread core cross-section to an annular thread core cross-section.

[0052] In this way, a smooth transition is achieved between the threaded shank section, which has a trilobular thread core cross-section along its entire length in all radial sections, and the unthreaded area between the head and the milled section, which is circular along its entire length up to the screw head in all radial sections. In other words, the thread core of the milled section represents a hybrid form between a non-circular, in particular a trilobular, thread core and a circular thread core cross-section.

[0053] The term "continuous" means that the non-circular, especially trilobular, thread core cross-section of the threaded shank section transitions seamlessly, without interruption, steps, or undercuts, to the annular thread core cross-section of the unthreaded section. This avoids notches that would reduce the cross-section and thus impair the screw's dimensional stability.

[0054] The invention is described in more detail below with reference to exemplary embodiments and the accompanying drawings. The drawings show... Figure 1 a side view of a wood screw according to the invention; Figure 2 in a side view a convex conical tip section of the wood screw according to the invention Figure 1 ; Figure 3 an isometric representation of the convex conical tip section of the wood screw according to the invention made of Figure 1 ; Figure 4another side view of the convex conical tip section of the wood screw according to the invention. Figure 1 ; Figure 5 in a sectional view along section line AA in Figure 4 the convex conical tip section of the wood screw according to the invention Figure 1 ; Figure 6 in a side view a convex conical tip section with a ring-shaped chip breaker; Figure 7 in a sectional view along a section line BB a trilobular cross-section of the thread core in the threaded shank section of the wood screw according to the invention. Figure 1 ; and Figure 8 in an enlarged side view a milled section of the wood screw according to the invention. Figure 1 .

[0055] Figure 1 Figure 10 shows a screw in a side view. Screw 10 is a wood screw, more precisely a self-tapping wood screw.

[0056] The screw 10 has several sections, namely a tip 12, a screw head 14, a shaft 16 and a convex conical tip section 18, which forms the transition between the shaft 16 and the tip 12.

[0057] Adjacent to the convex conical tip section 18 is a cylindrical threaded shaft section 20 with a cylindrical thread core, which extends from the convex conical tip section 18 in the direction of the screw head 14.

[0058] A milling section 22, which also extends towards the screw head 14, adjoins the screw head end of the threaded shaft section 20.

[0059] The milling section 22 is limited on the screw head side by a threadless section 24, which extends from the milling section 22 into the screw head 14 and ends there.

[0060] The sections mentioned above are explained in more detail below.

[0061] First, the threaded shank section 20 and the tip section 18 are identified based on the Figures 2 to 5 A closer look.

[0062] As in the Figure 2 As can be clearly seen, the screw 10 also has a thread 26 which extends into the tip section 18 via the cylindrical threaded shaft section 20 adjacent to the convex conical tip section 18.

[0063] In the area of ​​the tip section 18, the thread 26 is double-start. More precisely, the thread 26 is double-start only in the area of ​​the tip section 18 and single-start in the area of ​​the threaded shank section 20.

[0064] Therefore, the thread 26 has a first thread 28 and a second thread 30 in the area of ​​the convex conical tip section 18.

[0065] Both threads 28, 30 run offset by 180° from each other and end at a distance a in the direction of the tip 12. In particular, the first thread 28 and the second thread 30 end at the same distance a from the tip 12.

[0066] The first thread 28 and the second thread 30 of the thread 26 each have tip-side thread flanks 32 and screw-head-side thread flanks 34, which are arranged oppositely to each other. The tip-side thread flanks 32 are inclined towards the tip 12. This means that, viewed from the side, the tip-side thread flanks 32 and the axis of rotation Rm form an angle γ towards the tip that is less than or equal to 90°.

[0067] As in the Figures 2 and 3 As can be clearly seen, the first thread 28 and the second thread 30 of the double-start thread 26 each end in a cutting wing 36 on the tip side.

[0068] As in the Figures 2 and 3 As shown, the cutting wings 36 can have the same radial height as the thread 26 terminating in the cutting wings. However, it is also conceivable that the cutting wings 36 have a smaller radial height than the thread 26 terminating in the cutting wings 36 (not shown here). For example, the cutting wings 36 can have a radial height of up to 1 / 8, 1 / 4, or 1 / 2 the height of the thread 26.

[0069] Each tip-side cutting wing 36 has a cutting edge 38 that extends substantially at a perpendicular angle to the axis of rotation Rm of the wood screw 10. The cutting edge 38 is formed at the intersection of the head-side thread flank 34 of a thread and a clearance surface 39. In this case, the head-side thread flank 34 forms the rake face with respect to the cutting edge 38.

[0070] In the embodiment shown, the clearance surface 39 is bounded by the cutting edge 38 and the tip-side thread flank 32 and essentially corresponds to the cross-section of a thread 28, 30. In particular, the clearance surface 39 corresponds to an oblique cut through one of the threads 28, 30.

[0071] Since the thread flanks 32, 34 are convex in the embodiment shown, a clearance surface 39 in the form of an ellipse is accordingly obtained.

[0072] As in Figure 3 As can be clearly seen, the cutting edge 38 of the cutting wing 36 transitions into a cutting edge 40 perpendicular to it, which is formed at the intersection of the tip-side thread flank 32 and the head-side thread flank 34. The cutting edge 38 thus essentially corresponds to the radial height of the cutting wings 36 mentioned above.

[0073] The cutting edge 38 of the cutting wing 36 is a different cutting edge from the cutting edge 40, which forms the backbone of the thread flanks 32, 34 and is present in every known screw with a thread. In particular, cutting edge 38 is a cutting edge formed separately from the cutting edge 40 of the thread 26.

[0074] It follows that the described cutting edge 38 does not extend parallel to the axis of rotation R m of the wood screw.

[0075] Furthermore, a thread-free area 41 is given between the tip 12 and the two cutting wings 36, the length of which essentially corresponds to the distance a defined at the outset. The distance a is shown in the drawings as the distance between two radial, parallel lines that extend radially to the central axis and pass through the tip on one side and the ends of the threads 28, 30 on the other. In other words, the distance a is also defined by the distance between two parallel planes. The first plane extends radially to the central axis and includes the tip, and the second plane includes the ends of the threads 28, 30.

[0076] Starting from the point-shaped tip 12 and the adjoining threadless area 41, the cutting wings 36 begin, from which the first thread 28 and the second thread 30 extend.

[0077] In this process, one of the two threads 28, 30 ends before the transition to the thread shank section 20 at the tip section 18 and the other thread 28, 30 extends along the thread shank section 20 to the milling section 22.

[0078] In addition to the double-start thread 26 and the cutting wings 36, the convex conical tip section 18 is characterized by the convex geometry of its outer contour. This is particularly well suited to Figure 2 and 5 to recognize.

[0079] In particular, the convex conical tip section 18 has an acute angle α in a range of 15 to 30°, preferably from 25 to 30°.

[0080] Viewed in a section plane in which the axis of rotation lies, the tip section 18 has a radius R to form the convexity, for which the following relationship applies, based on the nominal diameter d of the thread of the wood screw 10 in the threaded shank section 20: d / R = 0.13 - 0.18, preferably d / R = 0.145 - 0.175.

[0081] A transition section 42 is provided between the tip section 18 and the threaded shank section 20.

[0082] More precisely, the tip section 18 transitions towards the screw head 14 in the area of ​​the transition section 42 into a conical section 44, which extends from the tip section 18 towards the threaded shank section 20 and connects both sections 18 and 20. Towards the threaded shank section 20, the diameter of the conical section 44 tapers until it corresponds to the cylindrical core diameter of the shank 16 in the area of ​​the threaded shank section 20.

[0083] Starting from the conical section 44, the threaded shank section 20 extends to the milling section 22.

[0084] At the pointed end of the threaded shank section 20, i.e., in the transition area between the pointed section 18 and the threaded shank section 20, a chip breaker 46 in the form of a rib is provided. The chip breaker 46 is arranged at a distance from the tapered section 44 and thus at a distance from the double-start thread 26.

[0085] The chipbreaker 46, for example, can have the shape of a rib, which, as in the Figure 1 and 2 shown, starting from the thread 26 and extending over the outer contour of the shaft 16.

[0086] It is also conceivable that the chip breaker 46 extends at least partially around the threaded shaft section 20 in a ring shape, with the chip breaker 46 preferably being designed to be continuous around its entire circumference.

[0087] This embodiment is in Figure 6The chip breaker 46, in this example, comprises a thread flank 48 facing the tip 12 and a thread flank 50 facing the screw head 14, which together form a cutting edge 52. In particular, the thread flank 48 facing the screw head 14 extends substantially perpendicular to the axis of rotation Rm of the wood screw 10.

[0088] Furthermore, it is also possible to arrange a rib in the area of ​​the convex conical tip section 18, which extends section by section from one thread 28, 30 to the next thread 28, 30 in the longitudinal direction of the screw 10 and transitions into the thread 26 at the opposite ends without crossing over a thread 28, 30, wherein the rib preferably extends over a maximum of 1 / 3 of the length of the convex conical tip section 18, in particular over less than 1 / 3 of the length of the convex conical tip section 18 (not shown here).

[0089] As in Figure 7 As can be seen, the thread core 54 of the shaft 16 in the threaded shaft section 20 is cylindrical. In particular, the threaded shaft section 20, i.e., the thread core 54 with the thread 26, is non-circular or has a non-circular cross-section.

[0090] Preferably, the cross-section has a trilobular shape, as shown in Figure 7 to recognize.

[0091] Due to its trilobular shape, the cross-section 56 of the shaft 16 touches the circumferential wall 58 of a borehole 60 only at three contact points 62.

[0092] The milling section 22 is explained in more detail below.

[0093] Immediately adjacent to the screw head end of the thread 26, the milling section 22 is provided on the shank 16, extending from the threaded shank section 20 towards the screw head 14, the milling section 22 having several projecting cutting ribs 64. The cutting ribs 64 have a higher thread pitch than the threads 28, 30 of the thread 26 in the threaded shank section 20.

[0094] In particular, an odd number of cutting ribs 64 are provided in the milling section 22. Preferably, three, five or seven cutting ribs 64 are provided.

[0095] Particularly preferably, a cutting rib 64 encloses an angle β with the rotational center axis of the wood screw 10, which lies in a range of 40 to 50°.

[0096] As in Figure 8As can be clearly seen, the thread core 54 widens in the milling section 22 in the direction of the screw head 14. In particular, the thread core 54 widens conically.

[0097] The thread core 54 is particularly preferably designed to be conical throughout the entire milling section 22.

[0098] Furthermore, the thread core 54, viewed from the tip, transitions continuously along its entire length in all radial sections of the milled section 22 from a non-circular, preferably trilobular, thread core cross-section to a circular thread core cross-section. Thus, the milled section 22 represents a transition zone between the non-circular or trilobular thread core 54 of the threaded shank section 20 and the annular thread core 54 of the unthreaded section 24. The transition from one cross-section to the other occurs continuously over the entire length of the milled section 22, i.e., steplessly, so that no undercuts or notches are present at the interfaces between the threaded shank section 20 and the milled section 22, nor between the unthreaded section 24 and the milled section 22.

[0099] The threadless section 24 and the screw head 14 are described in more detail below.

[0100] Adjacent to the milled section 22 is the unthreaded section 24, which extends from the milled section 22 to the screw head 14 and terminates therein. As described above, the threaded core 54 in the unthreaded section 24 is circular along its entire length in all radial sections.

[0101] The screw head 14 is conical on its underside facing the tip 12 and has grooves 66 with adjacent cutting edges 68 in this area.

[0102] Furthermore, the screw head 14 has a recess 70 which has a drive geometry 72 which is formed in a contact area with an inserted screwdriver drive geometry (not shown here) as a negative of the screwdriver drive geometry (not shown here).

Claims

1. Wood screw (10), having a tip (12), a screw head (14), a shank (16) which extends from the screw head (14) and transitions into a convex conical tip portion (18), wherein the tip portion (18) forms the transition from the shank (16) to the tip (12), and a thread (26) which extends into the tip portion (18) via a cylindrical thread-shank portion (20) adjacent to the tip portion (18), wherein the thread (26) is configured to be a double-start thread in the region of the tip portion (18), wherein one thread turn (28, 30) terminates before the transition to the thread-shank portion (20) at the tip portion (18) and the other thread turn (28, 30) runs as far as a milled portion (22) of the shank (16), and wherein a chip breaker in the form of a rib is provided in a transition region between the tip portion (18) and thread-shank portion (20).

2. Wood screw (10) according to Claim 1, characterized in that in each case a first thread turn (28) of the double-start thread (26) and a second thread turn (30) of the double-start thread (26) terminate at a distance (a) from the tip (12) in the direction of the tip (12), in particular wherein the first thread turn (28) and the second thread turn (30) terminate at the same distance (a) from the tip (12).

3. Wood screw (10) according to Claim 2, characterized in that the first thread turn (28) and the second thread turn (30) of the double-start thread (26) run offset by 180° to one another.

4. Wood screw (10) according to Claim 2 or 3, characterized in that the first thread turn (28) and the second thread turn (30) of the double-start thread (26) in each case have thread flanks (34) on the screw head side and thread flanks (32) on the tip side arranged opposite thereto, wherein the thread flanks (32) on the tip side are inclined toward the tip (12).

5. Wood screw (10) according to one of Claims 2 to 4, characterized in that the first thread turn (28) and the second thread turn (30) of the double-start thread (26) in each case terminate in a cutting blade (36) on the tip side.

6. Wood screw (10) according to Claim 5, characterized in that each cutting blade (36) has a cutting edge (38) which extends substantially at a perpendicular angle to the central axis of rotation (Rm) of the wood screw (10).

7. Wood screw (10) according to Claim 5 or 6, characterized in that the cutting blades (36) in each case have a radial height which is the same as or lower than the thread (26) leading into the cutting blades.

8. Wood screw (10) according to one of the preceding claims, characterized in that the convex conical tip portion (18) has at least one of the following features: - an acute angle α ranging from 15 - 30°, preferably from 25 - 30°; - when viewed in a cutting plane, in which the central axis of rotation (Rm) is located, the tip portion (18) has a radius (R) to which the following relationship applies, relative to the nominal diameter (d) of the thread (26) of the wood screw (10) in the thread-shank portion (20): d / R = 0.13 - 0.18, preferably d / R = 0.145 - 0.175.

9. Wood screw (10) according to one of the preceding claims, characterized in that the rib extends at least in some portions around the tip portion (18) or thread-shank portion (20) in an annular manner, wherein the rib is preferably designed continuously around the circumference, or that a rib is provided in the region of the convex conical tip portion (18), which rib extends in some portions from one thread turn (28, 30) to the next thread turn (28, 30) in the longitudinal direction of the screw (10) and transitions into the thread (26) at the opposing ends without intersecting the thread turn (28, 30), wherein the rib preferably extends over a maximum of 1 / 3 of the length of the convex conical tip portion (18), in particular over less than 1 / 3 of the length of the convex conical tip portion (18).

10. Wood screw (10) according to one of the preceding claims, characterized in that the thread-shank portion (20) and / or the tip portion (18) has a non-circular cross section, in particular wherein the cross section has a trilobular shape.

11. Wood screw (10) according to one of the preceding claims, characterized in that a milled portion (22) which extends from the thread-shank portion (20) in the direction of the screw head (14) is provided on the shank (16) immediately adjacent to the end of the thread (26) on the screw head side, wherein the milled portion (22) has a plurality of protruding cutting ribs (64) with a greater thread pitch than that of the thread (26) in the thread-shank portion (20).

12. Wood screw (10) according to Claim 11, characterized in that the thread core (54) in the milled portion (22) widens in the direction of the screw head (14), in particular conically, further in particular wherein the thread core (54) is designed to be conical in the entire milled portion (22).

13. Wood screw (10) according to Claim 11 or 12, characterized in that an uneven number of cutting ribs (64) is provided in the milled portion (22), in particular wherein three, five or seven cutting ribs (64) are provided and / or each cutting rib (64) encloses with the central axis of rotation (Rm) of the wood screw (10) an angle β which ranges from 40 - 50°.

14. Wood screw (10) according to one of Claims 11 to 13, characterized in that, when viewed from the tip, the thread core (54) in the milled portion (22) transitions continuously over its entire length in all radial portions from a non-circular, preferably a trilobular, thread core cross section, into a circular thread core cross section.

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