A three-point wood drill

Abstract

The invention relates to a three-blade wood drill, which comprises a drill handle, three flat cutting blade bodies arranged radially on the top end of the drill handle, and a center drill arranged coaxially with the drill handle on the top end of the joint of the three cutting blade bodies; the features are that the three cutting blade bodies are respectively the first, second and third cutting blade bodies in the counterclockwise direction, the included angle formed by the orthographic projection of the first and second cutting blade bodies is denoted as θ1, the included angle formed by the orthographic projection of the second and third cutting blade bodies is denoted as θ2, and the included angle formed by the orthographic projection of the third and first cutting blade bodies is denoted as θ3, wherein the included angles satisfy the following conditions: θ1+θ2+θ3=360°, θ1<θ2<θ3, and θ2-θ1<θ3-θ2. The invention has the advantages that the three cutting blade bodies adopt different distribution angles, and the smooth chip removal, the processing speed and precision are ensured, and the service life of the drill is prolonged by utilizing the specific size ratio relationship of the cutting blade bodies and the position of the cutting groove.

Description

Technical Field

[0001] This invention relates to a woodworking drill, and more particularly to a three-bladed woodworking drill. Background Technology

[0002] Woodworking flat drills are mainly used for machining deep holes. The cutting part of the flat drill is ground into a flat, double-edged structure. The main cutting edge is ground to have a sharp angle and a clearance angle to form the main cutting edge; the secondary cutting edge is ground to have a clearance angle and a secondary rake angle to control the drill hole diameter. In addition, for ease of machining, woodworking flat drills have a locating drill tip in the center for positioning during drilling. The diameter of this drill tip is much smaller than the drill hole diameter between the two secondary cutting edges.

[0003] Because double-edged woodworking flat drills suffer from high cutting resistance, they are insufficient for drilling harder woods, significantly reducing drill bit lifespan. Therefore, to address this issue when drilling harder woods, three- or even four-edged structures with identical structures but different numbers of cutting edges have been developed. The three-edged cutting edges, viewed from the drill shank projection direction, are identical to the double-edged structure, still equidistantly distributed. The increased number of cutting edges reduces drilling resistance, making it better suited for drilling harder woods. However, it still has certain limitations:

[0004] While improved three- and four-flute designs can meet the drilling needs of some harder wood species without significantly reducing lifespan, the initial design of woodworking flat drills only required simple wood drilling with appropriate cutting edge angles and distribution. Drilling speed and precision requirements were not high, and the multi-flute design resulted in less efficient chip removal, affecting both drilling quality and drill bit lifespan. Therefore, in practical applications involving drilling expensive wood species with very high hardness levels, where higher efficiency and precision are required, there is a limitation: drilling speed, drilling precision, and lifespan cannot be simultaneously achieved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a three-bladed woodworking drill with high drilling quality and long service life.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: a three-blade woodworking drill, including a drill shank, three flat cutting blades radially arranged at the top of the drill shank with the drill shank as the axis, and a central positioning drill arranged at the top of the junction of the three cutting blades and coaxial with the drill shank; the innovation is that: the cutting blades include a secondary cutting blade for controlling the drilling diameter and a main cutting blade connected between the top of the secondary cutting blade and the bottom of the central positioning drill; in the direction extending from the end of the drill shank to the central positioning drill, the three cutting blades are defined as the first, second, and third cutting blades in a counterclockwise direction, and the orthographic projections of the first, second, and third cutting blades in this direction form three included angles, and the included angle formed by the orthographic projections of the first and second cutting blades is denoted as θ1, the included angle formed by the orthographic projections of the second and third cutting blades is denoted as θ2, and the included angle formed by the orthographic projections of the third and first cutting blades is denoted as θ3, then each included angle satisfies the following conditions: θ1+θ2+θ3=360°, θ1<θ2<θ3, and θ2-θ1<θ3-θ2.

[0007] Preferably, in the included angles, θ1=97°, θ2=116°, and θ3=147°.

[0008] Preferably, the bottom end of the surface where the secondary cutting edge clearance angle is located is connected to the drill shank through a gradually inwardly tapered smooth curved surface, defining the height of the surface where the secondary cutting edge clearance angle of the first cutting edge body is located in the drill shank axis direction as h1, the height of the surface where the secondary cutting edge clearance angle of the second cutting edge body is located in the drill shank axis direction as h2, and the height of the surface where the secondary cutting edge clearance angle of the third cutting edge body is located in the drill shank axis direction as h3, where h1 > h3 > h2.

[0009] Preferably, the surface of the main cutting edge of the cutting edge body is provided with a cutting groove that penetrates the upper surface of the cutting edge, and the distance between the cutting groove of the first cutting edge body and the drill shank axis is defined as L1, the distance between the cutting groove of the second cutting edge body and the drill shank axis is L2, and the distance between the cutting groove of the third cutting edge body and the drill shank axis is L3; L2 > L3 > L1.

[0010] Preferably, the center positioning drill is a conical structure with a self-tapping threaded groove on the outer circumferential surface of the conical structure; the plane extending from the flat main surface of the cutting edge along the axis of the drill shank is the extension surface, and the portion of the conical structure between adjacent extension surfaces is cut off to form a groove.

[0011] The advantages of this invention are: the three cutting edges are distributed at different angles, and by utilizing the specific dimensional ratio of each cutting edge and the position of the cutting groove, chip removal is smooth, processing speed and accuracy are guaranteed, and the service life of the drill bit is extended. Attached Figure Description

[0012] Figure 1This is a schematic diagram of a three-bladed wood drill structure according to one embodiment of the present invention.

[0013] Figure 2 for Figure 1 Front view of a three-bladed wood drill.

[0014] Figure 3 for Figure 1 Top view of a three-bladed wood drill.

[0015] Figure 4 for Figure 1 View after drilling a three-bladed wood drill.

[0016] Figure 5 This is a schematic diagram of a three-bladed wood drill structure according to another embodiment of the present invention.

[0017] Figure 6 for Figure 5 Top view of a three-bladed wood drill. Detailed Implementation

[0018] This invention is a three-bladed woodworking drill, such as... Figure 1 As shown, it includes a drill shank 2, three flat cutting edges radially arranged at the top of the drill shank 2 with the drill shank 2 as the axis, and a central positioning drill 3 located at the top of the junction of the three cutting edges and coaxial with the drill shank 2.

[0019] In the direction extending from the end of the self-drilling shank towards the center positioning drill, three cutting edges are defined in a counterclockwise direction as the first cutting edge 11, the second cutting edge 12, and the third cutting edge 13. The first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 adopt a typical woodworking drill bit structure, each including a secondary cutting edge 1a for controlling the drilling diameter and a main cutting edge 1b connected between the top of the secondary cutting edge 1a and the bottom of the center positioning drill 3, and a cutting tip 1c is provided at the junction of the top of the secondary cutting edge 1a and the outer end of the main cutting edge 1b.

[0020] like Figures 2-4 As shown, the orthographic projections of the first, second, and third cutting edges in the direction extending from the end of the drill shank towards the center positioning drill form three included angles. The included angle formed by the orthographic projections of the first and second cutting edges is denoted as θ1, the included angle formed by the orthographic projections of the second and third cutting edges is denoted as θ2, and the included angle formed by the orthographic projections of the third and first cutting edges is denoted as θ3. Then, each included angle satisfies the following conditions: θ1 + θ2 + θ3 = 360°, θ1 < θ2 < θ3, and θ2 - θ1 < θ3 - θ2.

[0021] To improve cutting quality and enhance chip removal, the bottom end of the surface 1ab where the clearance angle of the secondary cutting edge 1a is located is connected to the drill shank through a gradually narrowing smooth curved surface. The height of the surface where the clearance angle of the secondary cutting edge 1a of the first cutting edge body 11 is located in the direction of the drill shank 2 axis is defined as h1, the height of the surface where the clearance angle of the secondary cutting edge 1a of the second cutting edge body 12 is located in the direction of the drill shank 2 axis is h2, and the height of the surface where the clearance angle of the secondary cutting edge 1a of the third cutting edge body 13 is located in the direction of the drill shank 2 axis is h3, where h1 > h3 > h2.

[0022] Preferred, such as Figure 5 , 6 As shown, a cutting groove penetrating the upper surface of the cutting edge is provided on the surface 1bb where the back angle of the main cutting edge 1b is located, limiting the distance between the cutting groove 111 of the first cutting edge body 11 and the drill shank axis to L1, the distance between the cutting groove 121 of the second cutting edge body 12 and the drill shank axis to L2, and the distance between the cutting groove 131 of the third cutting edge body 13 and the drill shank axis to L3; more preferably, L2 > L3 > L1.

[0023] The center positioning drill 3 has a conical structure with self-tapping threaded grooves on its outer circumference. This is to further improve the stress distribution of the center positioning drill 3 and extend its service life.

[0024] The flat main surface defining the cutting edge extends along the drill shank axis to form an extension surface. The portion of the conical structure between adjacent extension surfaces is removed to form a groove 31. (See also...) Figure 1 .

[0025] Example 1:

[0026] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0027] This embodiment takes a typical woodworking drill specification with a typical hole diameter as an example. It is made of 65# steel, with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm in the direction of the drill shank axis, a bottom diameter of 9.4mm, a turning radius of the cutting edge of 25.5mm, and a cutting tip that is 1mm higher than the main cutting edge 1b in the direction of the drill shank axis.

[0028] In this embodiment, the angle between the surface where the rake angle of the main cutting edge is located and the axis of the drill shank is 20°, and the angle between the surface where the clearance angle of the main cutting edge is located and the horizontal plane perpendicular to the axis of the drill shank is 25°.

[0029] The included angles θ1, θ2, and θ3 formed between the first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 are 115°, 120°, and 135°, respectively.

[0030] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge rake angle of the first, second, and third cutting edge bodies is located in the axial direction of the drill shank 2 is: h1=h2=h3=17mm.

[0031] The surface 1ab where the clearance angle of the secondary cutting edge 1a is located is nearly parallel to the drill shank axis, but the distance from the upper end (i.e., the tip) of the secondary cutting edge 1a on this surface to the drill shank axis is greater than the distance from the lower end of the secondary cutting edge 1a to the drill shank axis. In this embodiment, the angle between the surface 1ab where the clearance angle of the secondary cutting edge 1a is located and the axis of the drill shank 2 is 1°.

[0032] Example 2:

[0033] This embodiment adopts the same structural design as Embodiment 1, including a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0034] Most parameters are the same:

[0035] The three-blade woodworking drill is made of 65# steel with a cutting edge hardness of 54HRC. The overall height is 150mm, the drill shank diameter is 7.1mm, the center positioning drill 3 is 18mm high in the direction of the drill shank axis, the bottom diameter is 9.4mm, the turning radius of the cutting edge is 25.5mm, and the tip of the cutting edge is 1mm higher than the main cutting edge 1b in the direction of the drill shank axis.

[0036] The angle between the surface containing the rake angle of the main cutting edge and the axis of the drill shank is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the axis of the drill shank is 25°.

[0037] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge rake angle of the first, second, and third cutting edge bodies is located in the axial direction of the drill shank 2 is: h1=h2=h3=17mm.

[0038] The angle between the surface 1ab, where the back angle of the secondary cutting edge 1a is located, and the axis of the drill shank 2 is 1°.

[0039] However, in this embodiment, the included angle formed between the first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 is different from that in embodiment 1. In this embodiment, θ1 is 101°, θ2 is 120°, and θ3 is 151°.

[0040] Example 3:

[0041] This embodiment adopts the same structural design as Embodiment 1, including a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0042] Most parameters are the same:

[0043] The three-blade woodworking drill is made of 65# steel with a cutting edge hardness of 54HRC. The overall height is 150mm, the drill shank diameter is 7.1mm, the center positioning drill 3 is 18mm high in the direction of the drill shank axis, the bottom diameter is 9.4mm, the turning radius of the cutting edge is 25.5mm, and the tip of the cutting edge is 1mm higher than the main cutting edge 1b in the direction of the drill shank axis.

[0044] The angle between the surface containing the rake angle of the main cutting edge and the axis of the drill shank is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the axis of the drill shank is 25°.

[0045] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge rake angle of the first, second, and third cutting edge bodies is located in the axial direction of the drill shank 2 is: h1=h2=h3=17mm.

[0046] The angle between the surface 1ab, where the back angle of the secondary cutting edge 1a is located, and the axis of the drill shank 2 is 1°.

[0047] However, in this embodiment, the included angle formed between the first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 is different from that in embodiment 1. In this embodiment, θ1 is 97°, θ2 is 116°, and θ3 is 147°.

[0048] Example 4:

[0049] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 96°, θ2 is 120°, and θ3 is 156°.

[0050] Example 5:

[0051] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 87°, θ2 is 116°, and θ3 is 157°.

[0052] Comparative Example 1:

[0053] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 is different from that in Embodiment 1. It adopts a conventional equidistant three-edge distribution structure, that is, θ1 is 120°, θ2 is 120°, and θ3 is 120° in this embodiment.

[0054] Comparative Example 2:

[0055] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 115°, θ2 is 122°, and θ3 is 129°.

[0056] Comparative Example 3:

[0057] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 118°, θ2 is 122°, and θ3 is 132°.

[0058] Comparative Example 4:

[0059] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 112°, θ2 is 122°, and θ3 is 126°.

[0060] Comparative Example 5:

[0061] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 110°, θ2 is 120°, and θ3 is 130°.

[0062] Comparative Example 6:

[0063] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 105°, θ2 is 120°, and θ3 is 125°.

[0064] Comparative Example 7:

[0065] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 95°, θ2 is 120°, and θ3 is 145°.

[0066] Comparative Example 8:

[0067] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 91°, θ2 is 116°, and θ3 is 141°.

[0068] Comparative Example 9:

[0069] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 89°, θ2 is 120°, and θ3 is 139°.

[0070] Comparative Example 10:

[0071] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 85°, θ2 is 116°, and θ3 is 135°.

[0072] Comparative Example 11:

[0073] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 90°, θ2 is 120°, and θ3 is 150°.

[0074] Comparative Example 12:

[0075] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 84°, θ2 is 120°, and θ3 is 144°.

[0076] Comparative Example 13:

[0077] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 85°, θ2 is 120°, and θ3 is 155°.

[0078] Comparative Example 14:

[0079] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 75°, θ2 is 116°, and θ3 is 145°.

[0080] Comparative Example 15:

[0081] This embodiment has the same structure and dimensions as Embodiment 1. The only difference is that the included angle formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 is different from that in Embodiment 1. In this embodiment, θ1 is 75°, θ2 is 115°, and θ3 is 165°.

[0082] The table below compares the cutting edge parameters of Examples 1-5 and Comparative Examples 1-15:

[0083]

[0084] To test the effects of Examples 1-5 and Comparative Examples 1-15 with different parameters on drilling quality and service life during wood processing, we used 50mm thick beech wood strips as an example for drilling. For each example or comparative example, 10 woodworking drill bits were used for testing and data collection to obtain a relatively accurate average value.

[0085] The table below compares the test parameters of Examples 1-5 and Comparative Examples 1-15:

[0086]

[0087] As can be seen from the table above, the overall machining speed of Examples 1-5 and Comparative Examples 1-15 is improved to a certain extent compared with the conventional equidistant three-blade structure. This is mainly because the unequal distribution of the three blades results in better chip removal, which in turn affects the machining speed. Examples 1-5 and Comparative Examples 2, 3, 5, 7, 8, 11, 13, and 15 have high machining accuracy, all controlled within ±0.28mm, and a service life of more than 638 holes. Among them, Examples 1-5 have the best machining accuracy, controlled between ±0.14 and ±0.18mm. This is mainly because the included angle difference formed between the cutting blades increases sequentially in the drilling direction, which provides better control over the inertia of the drill bit.

[0088] The machining accuracy of Comparative Examples 4, 6, 9, 10, 12, and 14 is similar to that of the conventional equidistant three-blade structure in Comparative Example 1, around ±0.35mm. Their service life is also basically maintained between 560 and 590 holes. This may be because the vibration during the drilling process was not well controlled, which affected the number of effective holes that met the requirements.

[0089] Example 6:

[0090] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. However, the center positioning drill 3 adopts an integral conical structure and does not have a groove 31 design.

[0091] This embodiment takes a typical woodworking drill specification with a typical hole diameter as an example. It is made of 65# steel, with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm in the direction of the drill shank axis, a bottom diameter of 9.4mm, a turning radius of the cutting edge of 25.5mm, and a cutting tip that is 1mm higher than the main cutting edge 1b in the direction of the drill shank axis.

[0092] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 97°, 116°, and 147°, respectively. The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have identical shapes and dimensions. The height of the surface 1ab containing the clearance angle of the secondary cutting edge of the first, second, and third cutting edges along the axis of the drill shank 2 is h1=h2=h3=17mm. Similarly, the angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the axis of the drill shank 2 is 1°.

[0093] Example 7:

[0094] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts an integral conical structure and does not have a groove 31.

[0095] This embodiment takes a typical woodworking drill specification with a typical hole diameter as an example. It is made of 65# steel, with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm in the direction of the drill shank axis, a bottom diameter of 9.4mm, a turning radius of the cutting edge of 25.5mm, and a cutting tip that is 1mm higher than the main cutting edge 1b in the direction of the drill shank axis.

[0096] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 96°, 120°, and 156°, respectively. The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have identical shapes and dimensions. The height of the surface 1ab containing the clearance angle of the secondary cutting edge of the first, second, and third cutting edges along the axis of the drill shank 2 is h1=h2=h3=17mm. Similarly, the angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the axis of the drill shank 2 is 1°.

[0097] The table below compares the parameters of each cutting edge in Examples 3, 4, 6, and 7:

[0098]

[0099] To compare the impact of differences in center positioning drills on the processing speed, accuracy, and service life of the three-blade woodworking drill, tests were conducted on Examples 3, 4, 6, and 7. We used a 50mm thick beech wood strip as an example for drilling, and 12 woodworking drill bits were used for testing and data statistics in each example to obtain the average value.

[0100]

[0101] As can be seen from the table above, when the center drills in Examples 6 and 7 adopt a conical structure, compared with the grooved conical center drills in Examples 3 and 4, the drilling speed is slightly increased. This is mainly because the chip removal effect affects the processing speed, while the service life remains basically unchanged.

[0102] Example 8

[0103] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0104] In this embodiment, the drill bit is made of 65# steel with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm and a bottom diameter of 9.4mm along the drill shank axis, a turning radius of 25.5mm for the cutting edge, and a cutting tip that is 1mm higher than the main cutting edge 1b along the drill shank axis.

[0105] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the drill shank axis 2 is 1°.

[0106] The included angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 97°, 116°, and 147°, respectively.

[0107] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge clearance angle of the first, second, and third cutting edge bodies is located in the direction of the axis of the drill shank 2 is: h1 is 11mm, h2 is 11mm, and h3 is 11mm.

[0108] Example 9

[0109] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0110] In this embodiment, the drill bit is made of 65# steel with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm and a bottom diameter of 9.4mm along the drill shank axis, a turning radius of 25.5mm for the cutting edge, and a cutting tip that is 1mm higher than the main cutting edge 1b along the drill shank axis.

[0111] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the drill shank axis 2 is 1°.

[0112] The included angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 97°, 116°, and 147°, respectively.

[0113] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge clearance angle of the first, second, and third cutting edge bodies is located in the direction of the axis of the drill shank 2 is: h1 is 22.6 mm, h2 is 22.6 mm, and h3 is 22.6 mm.

[0114] Example 10

[0115] The drill bit in this embodiment has the same structure as that in embodiment 8, including a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0116] This embodiment uses the same drill bit material as Embodiment 8, namely 65# steel, with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm along the drill shank axis, a bottom diameter of 9.4mm, a turning radius of 25.5mm for the cutting edge, and a cutting tip height of 1mm above the main cutting edge 1b along the drill shank axis. Other parameters are also basically the same. The first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 have the same shape and size. The angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the drill shank 2 axis is 1°. The angles θ1, θ2, and θ3 formed between the first cutting edge 11, the second cutting edge 12, and the third cutting edge 13 are also the same as in Embodiment 8.

[0117] The only difference is that the height of the surface 1ab where the secondary cutting edge clearance angle of the first, second, and third cutting edge bodies is located in the direction of the axis of the drill shank 2 is: h1 is 22.6mm, h2 is 11.7mm, and h3 is 17mm.

[0118] To compare the impact of the height of the surface containing the back angle of each cutting edge on the axis of the drill shank on the chip removal effect and service life of the three-blade woodworking drill, tests were conducted on Examples 3, 8, 9, and 10. We used a 50mm thick beech wood strip as an example for drilling, and five woodworking drill bits were used for testing and data statistics in each example to obtain the average value.

[0119] The table below compares the test parameters for Examples 3, 8-10:

[0120]

[0121] As can be seen from the table above, Examples 3, 8, and 10 have better chip removal effects, with Example 8 being the best and having the fastest processing speed. This may be because the height of the secondary cutting edge of the drill bit is relatively low, which is beneficial for chip removal. However, due to the smaller overall size of the cutting edge, the overall strength is reduced, and the number of holes drilled is less. Although Example 9 has a moderate chip removal effect and processing speed, it has the highest processing accuracy and service life. Example 10 has the most balanced chip removal effect, processing speed, processing accuracy, and service life, and is therefore the preferred example.

[0122] Example 11

[0123] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0124] In this embodiment, the drill bit is made of 65# steel with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm and a bottom diameter of 9.4mm along the drill shank axis, a turning radius of 25.5mm for the cutting edge, and a cutting tip that is 1mm higher than the main cutting edge 1b along the drill shank axis.

[0125] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the drill shank axis 2 is 1°.

[0126] The included angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 97°, 116°, and 147°, respectively.

[0127] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge clearance angle of the first, second, and third cutting edge bodies is located in the direction of the axis of the drill shank 2 is: h1 is 22.6 mm, h2 is 11.7 mm, and h3 is 17 mm.

[0128] In this embodiment, see Figure 5 , 6 The surface 1bb where the back angle of the main cutting edge 1b is located is provided with a cutting groove that penetrates the upper surface of the cutting edge. The distance between the cutting groove 111 of the first cutting edge body 11 and the drill shank axis is L1, the distance between the cutting groove 121 of the second cutting edge body 12 and the drill shank axis is L2, and the distance between the cutting groove 131 of the third cutting edge body 13 and the drill shank axis is L3. In this embodiment, the cutting grooves are arranged at equal intervals, i.e., L1=L2=L3=4.8mm.

[0129] Example 12

[0130] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0131] In this embodiment, the drill bit is made of 65# steel with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm and a bottom diameter of 9.4mm along the drill shank axis, a turning radius of 25.5mm for the cutting edge, and a cutting tip that is 1mm higher than the main cutting edge 1b along the drill shank axis.

[0132] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the drill shank axis 2 is 1°.

[0133] The included angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 97°, 116°, and 147°, respectively.

[0134] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge clearance angle of the first, second, and third cutting edge bodies is located in the direction of the axis of the drill shank 2 is: h1 is 22.6 mm, h2 is 11.7 mm, and h3 is 17 mm.

[0135] In this embodiment, see Figure 5 , 6 The surface 1bb where the back angle of the main cutting edge 1b is located is provided with a cutting groove that penetrates the upper surface of the cutting edge. The distance between the cutting groove 111 of the first cutting edge body 11 and the drill shank axis is L1, the distance between the cutting groove 121 of the second cutting edge body 12 and the drill shank axis is L2, and the distance between the cutting groove 131 of the third cutting edge body 13 and the drill shank axis is L3. In this embodiment, the cutting grooves are arranged at equal intervals, i.e., L1=L2=L3=6.6mm.

[0136] Example 13

[0137] This embodiment includes a first cutting edge body 11, a second cutting edge body 12, a third cutting edge body 13, a drill shank 2, and a center positioning drill 3. The center positioning drill 3 adopts a conical structure with three grooves 31.

[0138] In this embodiment, the drill bit is made of 65# steel with a cutting edge hardness of 54HRC, an overall height of 150mm, a drill shank diameter of 7.1mm, a center positioning drill 3 with a height of 18mm and a bottom diameter of 9.4mm along the drill shank axis, a turning radius of 25.5mm for the cutting edge, and a cutting tip that is 1mm higher than the main cutting edge 1b along the drill shank axis.

[0139] In this embodiment, the angle between the surface containing the rake angle of the main cutting edge and the drill shank axis is 20°, and the angle between the surface containing the clearance angle of the main cutting edge and the horizontal plane perpendicular to the drill shank axis is 25°. The angle between the surface 1ab containing the clearance angle of the secondary cutting edge 1a and the drill shank axis 2 is 1°.

[0140] The included angles θ1, θ2, and θ3 formed between the first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 are 97°, 116°, and 147°, respectively.

[0141] The first cutting edge body 11, the second cutting edge body 12, and the third cutting edge body 13 have the same shape and size. The height of the surface 1ab where the secondary cutting edge clearance angle of the first, second, and third cutting edge bodies is located in the direction of the axis of the drill shank 2 is: h1 is 22.6 mm, h2 is 11.7 mm, and h3 is 17 mm.

[0142] In this embodiment, see Figure 5 , 6 The surface 1bb where the back angle of the main cutting edge 1b is located is provided with a cutting groove that penetrates the upper surface of the cutting edge. The distance between the cutting groove 111 of the first cutting edge body 11 and the drill shank axis is L1, the distance between the cutting groove 121 of the second cutting edge body 12 and the drill shank axis is L2, and the distance between the cutting groove 131 of the third cutting edge body 13 and the drill shank axis is L3. In this embodiment, the cutting grooves are arranged at equal intervals, that is, L1 is 4.8mm, L2 is 9.94mm, and L3 is 6.6mm.

[0143] The table below compares the parameters of the cutting grooves of each cutting edge in Examples 10-13:

[0144]

[0145] To compare the effects of the cutting grooves of each main cutting edge on the performance of the three-blade wood drill, tests were conducted on Examples 10-13: We used a 50mm thick beech strip as an example to drill holes, and each example used 5 wood drill bits for testing and data statistics to obtain the average value.

[0146] The table below compares the test parameters for Examples 10-13:

[0147]

[0148] As can be seen from the table above, the average processing speed of Examples 11-13 with cutting grooves is less than 2.1s, which is due to the timely cutting of hardwood chips, making the cutting smoother. Compared with Example 10 without cutting grooves, Examples 11 and 12 with uniformly distributed cutting grooves have a certain degree of decrease in the number of effective holes, which may be because the setting of the cutting grooves has a certain influence on the strength of the cutting edge, thus affecting the service life. Example 13, due to the use of an asymmetrically distributed cutting groove structure, has the best chip breaking effect in the radial direction of the drill bit during the drill bit rotation process, and has the longest processing speed, accuracy and service life, so it is the best example.

Claims

1. A three-blade woodworking drill, comprising a drill shank, three flat cutting edges radially arranged at the top of the drill shank with the drill shank as its axis, and a central positioning drill located at the top of the junction of the three cutting edges and coaxially arranged with the drill shank; characterized in that: The cutting edge body includes a secondary cutting edge for controlling the borehole diameter and a main cutting edge connected between the top of the secondary cutting edge and the bottom of the centrally positioned drill bit. In the direction extending from the end of the self-drilling shank towards the center positioning drill, three cutting edges are defined as the first, second, and third cutting edges in a counterclockwise direction. The orthographic projections of the first, second, and third cutting edges in this direction form three included angles. The included angle formed by the orthographic projections of the first and second cutting edges is denoted as θ1, the included angle formed by the orthographic projections of the second and third cutting edges is denoted as θ2, and the included angle formed by the orthographic projections of the third and first cutting edges is denoted as θ3. Then the included angles satisfy the following conditions: θ1+θ2+θ3=360°, θ1<θ2<θ3, and θ2-θ1<θ3-θ2; The bottom end of the surface where the secondary cutting edge clearance angle is located is connected to the drill shank through a gradually inwardly tapered smooth curved surface, which limits the height of the surface where the secondary cutting edge clearance angle of the first cutting edge body is located in the direction of the drill shank axis to h1, the height of the surface where the secondary cutting edge clearance angle of the second cutting edge body is located in the direction of the drill shank axis to h2, and the height of the surface where the secondary cutting edge clearance angle of the third cutting edge body is located in the direction of the drill shank axis to h3, where h1 > h3 > h2. The surface of the main cutting edge of the cutting edge body is provided with a cutting groove that penetrates the upper surface of the cutting edge. The distance between the cutting groove of the first cutting edge body and the drill shank axis is defined as L1, the distance between the cutting groove of the second cutting edge body and the drill shank axis is L2, and the distance between the cutting groove of the third cutting edge body and the drill shank axis is L3; L2 > L3 > L1.

2. The three-flute wood drill according to claim 1, characterized in that: In the included angles, θ1=97°, θ2=116°, and θ3=147°.

3. The three-bladed wood drill according to claim 1 or 2, characterized in that: The center positioning drill is a conical structure with a self-tapping threaded groove on the outer circumferential surface of the conical structure. The flat main surface of the cutting edge extends along the axis of the drill shank as the extension surface, and the portion of the conical structure between adjacent extension surfaces is cut off to form a groove.

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