WOOD DRILL

Description

State of the art

[0001] The present invention relates to a wood drill bit with a clamping section for a rotationally fixed connection to a tool holder of a hand-held power tool, and a head section provided with a centering geometry, wherein the clamping section is formed at a first end facing away from the workpiece and the head section at a second end of the wood drill bit facing the workpiece, wherein the clamping section is connected to the head section via a shank section, and wherein a maximum outer radius of the head section is greater than a maximum outer radius of the shank section, wherein the head section has at least one main cutting edge with at least two steps for drilling a hole with a predetermined inner radius in a workpiece, and an outer radius of a main cutting edge base is less than 60% of an outer radius of the head section. Such a wood drill bit is known from document EP 2 217 417 A1.

[0002] Wood drill bits are available in a wide variety of designs. They allow for drilling holes with high dimensional accuracy in wood or wood-like materials. However, these materials often contain metallic objects, such as fasteners like nails, screws, or staples. If the wood drill bit comes into contact with these metallic objects during drilling, this leads to significant wear on the cutting edges and a correspondingly considerable reduction in tool life.

[0003] From EP 2 217 417 B1, an auger drill with a reamer is known. This previously known drill can cut through a large number of metal nails, at least when drilling in wood at slow speed and with high torque, without a significant decrease in drilling performance due to the dulling of the main cutting edges. Disclosure of the invention

[0004] The present invention relates to a wood drill bit with a clamping section for a rotationally fixed connection to a tool holder of a hand-held power tool, and with a head section provided with a centering geometry. The clamping section is formed at a first end facing away from the workpiece, and the head section at a second end of the wood drill bit facing the workpiece. The clamping section is connected to the head section via a shank section, and the maximum outer radius of the head section is greater than the maximum outer radius of the shank section. The head section has at least one main cutting edge with at least two steps. According to one embodiment, the head section serves to bore a hole with a predetermined inner radius into a workpiece, wherein the outer radius of a main cutting edge base is less than 60%, preferably less than 50%, of the outer radius of the head section.

[0005] Due to the preferably multi-stage, axially retracted design of the at least one main cutting edge of the wood drill bit, metal bodies located within the workpiece are cut through in sections, resulting in considerably less wear on the main cutting edge. The wood drill bit can easily cut through any metal bodies even at high speeds, and not only in the torque mode of a hand-held power tool at reduced speed and high torque. The dimensioning of the main stage also limits the required drive torque of the wood drill bit when cutting through metallic objects. The wood drill bit is preferably intended for drilling in wood and other comparably soft materials, such as plastic. The overall axial length of the wood drill bit can preferably be up to 600 mm with a diameter preferably between 6 mm and 35 mm.

[0006] Preferably, the head section has a spirally wound surface geometry with at least one chip groove and at least one secondary cutting edge.

[0007] The spirally wound surface geometry ensures the trouble-free removal of chips produced during drilling. The secondary cutting edges guarantee a virtually smooth inner wall of the hole drilled into the workpiece with the wood drill bit.

[0008] Preferably, the at least two steps of the at least one main cutting edge are axially retracted by one step height in relation to the radially inner main cutting edge base towards the second end of the wood drill.

[0009] As a result, the main cutting edge separates a metal object piece by piece into metal fragments and therefore does not have to remove the entire metal object across its transverse extent in relation to the longitudinal center axis.

[0010] In a technically advantageous further development, each of the at least two stages of the main cutting edge has a radial step width.

[0011] Due to the at least one radially outermost step of a main cutting edge, improved cutting results are achieved in wood that is interspersed with metal bodies such as nails, screws, staples, etc.

[0012] According to a favorable embodiment, the radial step width is between 1 mm and 10 mm, preferably between 2 mm and 5 mm.

[0013] This exemplary design results in improved work outcomes.

[0014] Preferably, each step base of the at least two steps is inclined by a step angle perpendicular to the longitudinal center axis in the direction of the first end of the wood drill.

[0015] This results in a simple and improved cutting of any metal components present in the workpiece. The step walls of the steps run essentially parallel to the longitudinal center axis of the wood drill bit.

[0016] Preferably the step angle is between 0° and 65°, preferably around 40°.

[0017] As a result, improved work results are easily and simply achieved when using the wood drill.

[0018] According to a further embodiment, a profile angle of between 10° and 30° exists between the at least one main cutting edge and perpendicular to the longitudinal center axis. If the shank section deviates from a cylindrical shape and has a helical geometry, the profile angle should be greater than the pitch of this helical shank geometry. The profile angle is particularly preferably between 15° and 25°.

[0019] This allows for safe and reliable improved cutting results.

[0020] Preferably, the wedge angle of at least one main cutting edge is approximately 60°.

[0021] This allows for the provision of a robust and durable cutting edge, which can preferably increase the service life of the wood drill bit.

[0022] Preferably, a rake angle exists between the at least one chip groove and the longitudinal center axis. The rake angle is preferably 15°.

[0023] This ensures improved, gradual cutting through any metallic foreign matter that may be present in a wooden workpiece. Furthermore, chips are safely and reliably removed from the borehole.

[0024] In another favorable embodiment, the centering geometry is screw-like with a spirally circumferential thread with a pitch.

[0025] This allows the wood drill bit to automatically pull itself into the workpiece after being placed against it, preferably with simultaneous precise centering.

[0026] Preferably, the thread pitch is between 1 mm and 2.5 mm.

[0027] As a result, the wood drill bit is easily and quickly drawn into the workpiece to be drilled after being positioned, enabling precise centering and dimensionally accurate drilling.

[0028] Preferably, the wood drill bit is made of high-strength carbon steel. Alternatively, at least the cutting edge can be made of high-speed steel (HSS) and / or tungsten carbide. The main cutting edge is designed to allow manufacturing using conventional machining processes and / or known hot or cold forming processes such as forging, bending, or stamping.

[0029] As a result, the wood drill bit has a comparatively long service life. Brief description of the drawings

[0030] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. The drawings show: Fig. 1 a side view of a wood drill bit, Fig. 2 a side view of the wood drill bit rotated by 90° about a longitudinal center axis Fig. 1 , Fig. 3 a top view of the wood drill of Fig. 2 , Fig. 4 a partial top view of a head section of the wood drill of Fig. 2 , Fig. 5 an enlarged partial top view of the head section of Fig. 4 , and Fig. 6 a partial top view of the head section rotated by 90° about the longitudinal center axis of Fig. 5 . Description of the exemplary implementations

[0031] Fig. 1 Figure 1 shows a wood drill bit 100, which includes, among other things, a clamping section 110 for a rotationally fixed connection to a tool holder of a hand-held power tool (not shown), and a head section 200 with a centering geometry 250. A preferably cylindrical shank section 130 runs between the clamping section 110 and the head section 200. The wood drill bit 100 can be designed as a wood twist drill, auger drill, and / or auger drill bit.

[0032] The clamping section 110, which here merely exemplifies six tangential flats, is formed at a first end 202, and the head section 200 with the centering geometry 250 is formed at a second end 204 of the wood drill 100, which faces away from the first end. It should be noted that the clamping section 110 can also have more or fewer than six flats. Furthermore, the clamping section 110 can also be designed as a round shank. The head section 200, for illustrative purposes, has an approximately helical surface geometry 206 with two chip flutes 240, 242 spirally wound around a longitudinal central axis 210. The maximum radius RS of the shank section 130 is, for example, significantly smaller than the maximum outer radius RK of the head section 200 of the wood drill 100. Furthermore, the total axial length L of the wood drill bit can range from 100 to 600 mm.

[0033] The wood drill 100 is preferably designed to be rotationally symmetrical about the longitudinal center axis 210. The head section 200 of the wood drill 100 has, by way of example, two main cutting edges 214, 216 facing a workpiece 150, which are diametrically opposed to each other with respect to the longitudinal center axis 210.

[0034] In order to cut through any metal objects present in the workpiece 150, such as nails, screws, staples, clamps, or the like, more easily and with less wear, the first main cutting edge 214 of the wood drill bit 100 has, by way of example, three steps projecting axially from the second end 204 – not shown here for the sake of clarity in the drawing. In addition, the first main cutting edge 214 of the head section 200 of the wood drill bit 100 preferably has a first radially internal main cutting edge base 260, and correspondingly the second main cutting edge 216 has a second radially internal main cutting edge base 262. According to the invention, there is an angle between the two main cutting edge bases 260, 262 and the longitudinal center axis 210 that is less than 90°, but preferably only slightly less. Here, the two main cutting edge bases 260, 262 of the head section 200 are preferably inclined in the direction of the first end 202.

[0035] An example bore 152, drilled into the workpiece 150 using a wood drill 100, has an approximately cylindrical inner wall 154 and an inner radius of RB. Preferably, the inner radius RB corresponds substantially to the outer radius RK of the head section 200 of the wood drill 100. The outer radius RH of both main cutting edge bases 260, 262 is preferably less than 60%, more preferably less than 50%, of the outer radius of the head section 200. Furthermore, the head section 200 preferably has two secondary cutting edges, of which only one secondary cutting edge 220 is shown and labelled in the drawing.

[0036] Preferably, the wood drill bit 100 comprises at least some sections made of high-strength carbon steel, high-speed steel (HSS), and / or carbide. According to one embodiment, the wood drill bit 100 is made of carbon steel, in particular high-strength carbon steel. Alternatively, at least the main cutting edges 214, 216, or their cutting edges, can be made of high-speed steel (HSS) and / or tungsten carbide. The main cutting edges 214, 216 are preferably designed such that they can be manufactured using conventional machining processes and / or known hot or cold forming processes such as forging, bending, or punching.

[0037] Fig. 2 shows the wood drill bit 100 from Fig. 1 with the clamping section 110, the shank section 130, and the head section 200. The head section 200 preferably has a centering geometry 250 and is rotationally symmetrical about the longitudinal center axis 210. The clamping section 110 is formed at the first end 202, and the head section 200, including the centering section 250, is formed at the second end 204. The exemplary maggot-shaped centering section 250 preferably has a thread 252 with a helically circumferential thread 254 and a centering tip 256. The wood drill 100 has, for illustrative purposes, an overall axial length L of up to 600 mm, i.e., including the clamping, shank, and head sections 110, 130, and 200.

[0038] Fig. 3 shows the wood drill bit 100 from Fig. 2 , wherein the head section 200 of the wood drill 100 has a substantially circular circumferential contour 208. The circumferential contour 208 preferably has a direction of rotation 199 during drilling or cutting operations. The multi-stepped cutting edge 214 with the main cutting base 260 and the multi-stepped cutting edge 216 with the main cutting base 262 are, by way of example, rotationally symmetrical with respect to the centering geometry 250 and the longitudinal center axis 210. A secondary cutting edge 220, extending approximately parallel to the longitudinal center axis 210 in the area of ​​the drawing plane, adjoins the first main cutting edge 214. Similarly, a secondary cutting edge 222 preferably adjoins the second main cutting edge 216. Finally, the two helical chip flutes 240, 242 run circumferentially between the stepped main cutting edges 214, 216.

[0039] Fig. 4 shows the head section 200 of the wood drill bit 100 from Fig. 2 and illustrates the centering geometry 250. Preferably, the head section 200 at the second end 204 of the wood drill 100 has the centering geometry 250 formed coaxially with the longitudinal center axis 210, with the thread 252. The thread 252 preferably has the helical thread 254. The head section 200 of the wood drill 100 has the outer radius RK. The chip groove 240 and the secondary cutting edge 220 are also formed on the head section 200. The main cutting edge 214 has the main cutting edge base 260 and at least two, preferably three, axially recessed steps 230, 232, 234, each with respect to the second end 204, for cutting through a metal object 156 located in the workpiece as required, in particular in the form of a connecting element 158 ​​and / or fastening element during the drilling process. The main cutting edge base 260 has the outer radius RH.

[0040] The metal object 156 located in the workpiece (not shown here), which is represented here only as an example of a connecting element 158 ​​in the form of a nail 162, is, according to the invention, successively divided or broken down into small metal fragments 166 by the action of the multi-stage main cutting edge 214 during the drilling process. As a result, the service life of the wood drill bit 100 can be considerably increased compared to previously known solutions.

[0041] Fig. 5 shows the head section 200 of the wood drill bit 100 from Fig. 4 The wood drill 100 has, at its second end 204, a chip groove 240 and a centering geometry 250 with a thread 252, a thread pitch 254, and an exemplary mandrel-like centering tip 256. The pitch S of the thread pitch 254 of the thread 252 is preferably between 1 mm and 2.5 mm. The longitudinal center axis 210 of the wood drill 100 runs coaxially with the centering geometry 250.

[0042] The main cutting edge 214 preferably has the main cutting edge base 260 and, by way of example, three radially outwardly positioned and axially recessed steps 230, 232, 234. The main cutting edge 214 is subdivided into at least three sections or steps 230, 232, 234, offset axially backwards or toward the first axial end 202. The first step 230 preferably has a step base 270 and a step wall 280. Similarly, the second step 232 preferably has a step base 272 and a step wall 282. The third step 234 has a step base 274 and a step wall 284. The at least two, illustratively three steps 230, 232, 234 of the main cutting edge 214 visible here each step back by an axial step height H in relation to the radially inner main cutting edge base 260 in the direction of the first end 202 of the wood drill 100.A radial step width B of steps 230, 232, 234 is between 1 mm and 10 mm, but preferably between 2 mm and 5 mm.

[0043] For illustrative purposes, the step walls 280, 282, 284 each run approximately parallel to the longitudinal center axis 210, while the step bases 270, 272, 274 each run inclined at a step angle α with respect to the longitudinal center axis 210. The angle α is defined here between a perpendicular 290 to the longitudinal center axis 210 and the respective step base 270, 272, 274 of the steps 230, 232, 234. The step angle α can be in a range between 0° and 65°, with a step angle α of approximately 40° being preferred.

[0044] Fig. 6 shows the head section 200 of the wood drill bit 100 from Fig. 5 and illustrates the two main cutting edges 214, 216 and the centering geometry 250. A profile angle β exists between the at least one main cutting edge 214, 216 and the perpendicular 290 to the longitudinal center axis 210, preferably between 10° and 30°. To achieve improved machining results, the profile angle β preferably has a value between 15° and 25°. A wedge angle γ of the at least one main cutting edge 214, 216 is shown here, by way of example, on the order of approximately 60°. Between the preferably two chip flutes 240, 242 of Fig. 2 , of which only the chip groove 240 is visible here, and the longitudinal center axis 210 each have a rake angle δ, which here is only shown as an example to be about 15°.

Claims

1. Wood drill bit (100), having a clamping portion (110) for co-rotational connection to a tool receiver of a hand-held power tool, and a head portion (200) provided with a centring geometry (250), wherein the clamping portion (110) is realized at a first end (202) of the wood drill bit (100) that faces away from the workpiece and the head portion (200) is realized at a second end (204) that faces toward the workpiece, wherein the clamping portion (110) is connected to the head portion (200) via a shank portion (130), and wherein a maximum outer radius (RK) of the head portion (200) is greater than a maximum outer radius (RS) of the shank portion (130), wherein the head portion (200) has at least one main cutting edge (214, 216) that comprises at least two steps (230, 232, 234) for drilling a hole (152) of a predefined inner radius (RB) into a workpiece (150), and an outer radius (RH) of a main cutting edge base (260) is less than 60 % of an outer radius (RK) of the head portion (200), characterized in that the centring geometry (250) is designed in the manner of a screw having a helically encircling thread (252) that has a pitch (S), wherein there is an angle of less than 90°, inclined in the direction of the first end (202), between the main cutting edge base (260) and a longitudinal central axis (210).

2. Wood drill bit according to Claim 1, characterized in that the head portion (200) has a helically coiled surface geometry (206), having at least one chip groove (240, 242) and having at least one minor cutting edge (220, 222).

3. Wood drill bit according to Claim 1 or 2, characterized in that the at least two steps (230, 232, 234) of the at least one main cutting edge (214, 216) are set back axially by one step height (H) with respect to the radially inner main cutting edge base (260) in the direction of the first end (202) of the wood drill bit (100).

4. Wood drill bit according to Claim 3, characterized in that each of the at least two steps (230, 232, 234) of the main cutting edge (214, 216) has a radial step width (B).

5. Wood drill bit according to Claim 4, characterized in that the radial step width (B) is between 1 mm and 10 mm, preferably between 2 mm and 5 mm.

6. Wood drill bit according to one of the preceding claims, characterized in that each step base (270, 272, 274) of the at least two steps (230, 232, 234) is inclined in each case by a step angle (α) perpendicularly to the longitudinal central axis (210) in the direction of the first end (202) of the wood drill bit (100).

7. Wood drill bit according to Claim 6, characterized in that the step angle (α) is between 0° and 65°, preferably approximately 40°.

8. Wood drill bit according to one of the preceding claims, characterized in that between the at least one main cutting edge (214, 216) and perpendicular to the longitudinal central axis (210) there is a profile angle (β) that is between 10° and 30°, in particular between 15° and 25°.

9. Wood drill bit according to one of the preceding claims, characterized in that a wedge angle (γ) of the at least one main cutting edge (214, 216) is approximately 60°.

10. Wood drill bit according to one of the preceding claims, characterized in that there is some rake angle (δ) between the at least one chip groove (240, 242) and the longitudinal central axis (210).

11. Wood drill bit according to Claim 1, characterized in that the pitch (S) of the thread (252) is between 1 mm and 2.5 mm.

12. Wood drill bit according to one of the preceding claims, characterized in that the wood drill bit (100) is formed from a high-strength carbon steel.