Multi-flute twist drill

Abstract

The present invention discloses a multi-edge twist drill, which includes a cutting part, a guiding part and a shank part connected in sequence. The guiding part includes two cutting lips, and two spiral chip flutes are formed between the two cutting lips. The cutting lips are provided with a first land and a second land arranged at intervals. The second land is close to the root edge. A guiding area communicating with the spiral chip flutes is formed between the first land and the second land. At least one notch is provided on a section of the second land close to the shank part, and the notch communicates the guiding area with the spiral chip flutes. This multi-edge twist drill can not only ensure the effective length of the second land to ensure the guiding effect, but also avoid the accumulation of chips in the guiding area, prevent the formation of extrusion marks and scratches on the hole wall surface, and improve the hole surface quality of the multi-edge twist drill.

Description

Technical Field

[0001] The present invention relates to a metal cutting tool, and particularly to a multi-edge twist drill. Background Art

[0002] Drilling is different from machining methods such as milling and turning. It belongs to semi-closed machining. Due to the poor machining conditions, vibration is likely to occur during the machining process, resulting in out-of-tolerance of the straightness, roundness, surface roughness, etc. of the hole, causing the part to be scrapped. To solve such problems, in terms of the structural optimization of the twist drill, the prior art usually designs another pair of "parallel" cutting edges to the existing cutting edge on the outer peripheral surface of the cutting edge lobe of the ordinary single-edge twist drill to strengthen the guiding effect of the cutting edge on the machining process of the twist drill. This structural design technology has been proven to be an effective measure to significantly improve the hole size accuracy and surface quality.

[0003] Although the patent document CN201380056371.5 improves the guiding performance and machining accuracy of the twist drill by designing a double-edge structure. However, strengthening the guiding effect of the cutting edge is only one of the key technical problems to be solved in the design process of the twist drill. Improving the chip evacuation ability of the twist drill is a technical problem that cannot be ignored even more in the design of the twist drill. In machining, the workpiece materials faced by the twist drill are diverse. When the twist drill is used to machine cast iron or die steel materials with a certain hardness, powdery or fine "C-shaped" chips are generated. These chips with a small volume are very likely to enter the narrow area enclosed by the two cutting edges on the same cutting edge lobe of the twist drill and the hole wall along the chisel edge grinding surface and the flank face. If the cutting parameters or the depth of the machined hole are large at this time, it is very difficult for the chips crowded between the cutting edge lobe and the hole wall to be discharged smoothly from the hole opening in time with the flow of the coolant, and extrusion marks and scratches will be formed on the hole wall surface, reducing the hole surface quality. In severe cases, the twist drill may even break due to the large torque caused by chip congestion, resulting in part scrapping.

[0004] Patent document CN110449638A improves the chip evacuation performance of the guiding area enclosed by two cutting edges and the hole wall by designing a multi-cutting-edge structure. In order to prevent the guiding area enclosed by the first cutting edge, the second cutting edge and the cutting blade from being too long, the helix angles of the second cutting edge and the first cutting edge are set to be different. However, this increases the production cost and shortens the length of the second cutting edge, affecting the guiding effect. At the same time, in order to meet the guiding requirements, a second cutting edge auxiliary section located between the first cutting edge and the second cutting edge needs to be provided on the cutting blade, so that the helix angle of the second cutting edge auxiliary section is equal to that of the second cutting edge, and the head end of the second cutting edge auxiliary section is close to the tail end of the second cutting edge and the tail end intersects with the root edge. This makes the processing difficult and the production cost high. Moreover, the front section of the second auxiliary cutting edge occupies part of the space, making it more difficult for the cutting debris entering between the first cutting edge and the second cutting edge to be discharged when flowing to the overlapping part of the second cutting edge and the second cutting edge auxiliary section. In severe cases, it may cause accumulation on the hole wall surface to form extrusion marks and scratches, reducing the hole surface quality. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a multi-cutting-edge twist drill that can not only ensure the effective length of the second cutting edge to ensure the guiding effect, but also avoid chip accumulation in the guiding area, prevent extrusion marks and scratches from forming on the hole wall surface, and improve the hole surface quality.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A multi-cutting-edge twist drill includes a cutting part, a guiding part and a shank part connected in sequence. The guiding part includes two cutting blades, and two spiral chip evacuation grooves are formed between the two cutting blades. The cutting blades are provided with a first cutting edge and a second cutting edge arranged at intervals. The second cutting edge is close to the root edge. A guiding area communicating with the spiral chip evacuation groove is formed between the first cutting edge and the second cutting edge. At least one notch is provided on a section of the second cutting edge close to the shank part, and the notch communicates the guiding area with the spiral chip evacuation groove.

[0008] As a further improvement of the above technical solution:

[0009] The number of notches on the second cutting edge is n, and 1≤n≤5.

[0010] If n>1, the notches on the second cutting edge are evenly distributed along the axial direction of the guiding part.

[0011] The axial length of the first cutting edge along the guiding part is L1, the axial pitch of the notch along the guiding part is L3, and the axial length of the notch along the guiding part is L4. L4≥6mm, and (n - 1)L3 + nL4≤3 / 4L1.

[0012] The axial length of the first cutting edge band along the guiding portion is L1, and the axial distance along the guiding portion between the notch closest to the cutting portion and the cutting portion is L2, where L2 ≥ L1 / 4.

[0013] The included angle between the side wall surface of the notch and the axis of the guiding portion is α, and the helix angle of the first cutting edge band is β, where β + 5° < α ≤ 90°.

[0014] In a cross-section perpendicular to the guiding portion, the width included angle of the cutting blade lobe is γ3, where 40° ≤ γ3 ≤ 100°.

[0015] In a cross-section perpendicular to the guiding portion and passing through the starting points of the first cutting edge band and the second cutting edge band, the included angle between the first cutting edge band and the second cutting edge band is γ4, where γ3 - 30° ≤ γ4 ≤ γ3 - 5°.

[0016] The helix angles of the first cutting edge band, the second cutting edge band, and the spiral chip flute are the same.

[0017] The cutting portion includes two main cutting edges. The first cutting edge band intersects with the spiral chip flute to form a secondary cutting edge, and each main cutting edge is connected to each secondary cutting edge.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] The multi-cutting-edge band twist drill of the present invention has multiple sets of spiral guiding cutting edge bands (the first cutting edge band and the second cutting edge band), which strengthens the guiding function of the cutting edge bands, makes the cutting process of the twist drill more stable, improves the drilling accuracy. At the same time, since at least one notch is provided in a section of the second cutting edge band close to the shank, the notch connects the guiding area with the spiral chip flute. When the twist drill is used to machine materials that produce powdery or finely divided "C-shaped" chips, the chips entering the guiding area surrounded by the two cutting edge bands on the cutting blade lobe and the hole wall can flow into the spiral chip flute along with the coolant. Among them, part of the chips in the guiding area can be discharged into the spiral chip flute from one end directly connected to the spiral chip flute, and the other part of the chips can be discharged into the spiral chip flute through the notch on one side of the guiding area and finally discharged. In this way, it can not only ensure the effective length of the second cutting edge band and the guiding function, but also avoid chip accumulation in the guiding area, prevent extrusion marks and scratches on the hole wall surface, and improve the hole surface quality.

[0020] Furthermore, for the multi-cutting-edge band twist drill of the present invention, the helix angles of the first cutting edge band, the second cutting edge band, and the spiral chip flute are the same. It is convenient for production, reduces production costs, and further ensures the lengths of the first cutting edge band and the second cutting edge band, thus ensuring the guiding function. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a front view structural schematic diagram of Embodiment 1 of the present invention.

[0022] Figure 2It is a schematic diagram of the outer peripheral surface expansion of the first embodiment of the present invention.

[0023] Figure 3 It is Figure 1 the A-A view in

[0024] Figure 4 It is a schematic diagram of the flow of chips entering the guiding area in the first embodiment of the present invention

[0025] Figure 5 It is a schematic front view structure diagram of the second embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram of the outer peripheral surface expansion of the second embodiment of the present invention

[0027] Figure 7 It is Figure 5 the B-B view in

[0028] Each label in the figure represents:

[0029] 1. Cutting part; 11. Main cutting edge; 12. Cross edge; 13. Cross edge grinding surface; 2. Guiding part; 3. Shank part; 4. Spiral chip flute; 5. Blade lobe; 601. Guiding area; 61. First cutting edge band; 62. Second cutting edge band; 7. Tail root edge; 8. Axis; 9. Notch; 91. Side wall surface; 10. Chip. Specific embodiments

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0031] Embodiment 1:

[0032] Figures 1 to 4 An embodiment of the multi-edge-band twist drill of the present invention is shown. The multi-edge-band twist drill includes a cutting part 1, a guiding part 2 and a shank part 3 connected in sequence. The guiding part 2 includes two blade lobes 5. Two spiral chip flutes 4 are formed between the two blade lobes 5. The blade lobe 5 is provided with a first cutting edge band 61 and a second cutting edge band 62 arranged at intervals. The second cutting edge band 62 is close to the tail root edge 7. A guiding area 601 communicating with the spiral chip flute 4 is formed between the first cutting edge band 61 and the second cutting edge band 62. At least one notch 9 is provided on a section of the second cutting edge band 62 close to the shank part 3. The notch 9 connects the guiding area 601 with the spiral chip flute 4. The first cutting edge band 61 and the second cutting edge band 62 play a guiding role, and can extrude the inner wall of the hole during processing to improve the hole surface quality and dimensional accuracy. At least one notch 9 is provided on a section of the second cutting edge band 62 close to the shank part 3. The notch 9 connects the guiding area 601 with the spiral chip flute 4 for the purpose of facilitating chip removal.

[0033] Figure 4The schematic diagram of the chip 10 from generation to entering the space between two land areas is shown. When the twist drill cuts, chips are generated, and the chips are mainly discharged through the spiral chip flute 4. Once the fine chips 10 enter the guiding area 601 surrounded by the first land 61, the second land 62 on the cutting lip 5 and the cutting lip 5, these chips 10 can flow along with the coolant and be discharged into the spiral chip flute 4 through one end directly connected to the spiral chip flute 4 or the notch 9, and are smoothly discharged by the spiral chip flute 4, avoiding the chips from damaging the surface of the hole wall, forming extrusion marks and scratches, and improving the surface quality of the hole.

[0034] The multi-land twist drill of the present invention has multiple sets of spiral guiding lands (the first land 61 and the second land 62), which strengthens the guiding function of the lands, makes the cutting process of the twist drill more stable, and improves the drilling accuracy. At the same time, since at least one notch 9 is provided on a section of the second land 62 close to the shank 3 of the present invention, the notch 9 connects the guiding area 601 with the spiral chip flute 4. When the twist drill is used to machine materials that generate powdery or fine "C-shaped" chips, the chips entering the guiding area 601 surrounded by the two lands on the cutting lip 5 and the hole wall can flow along with the coolant and be discharged into the spiral chip flute 4. Among them, part of the chips in the guiding area 601 can be discharged into the spiral chip flute 4 through one end directly connected to the spiral chip flute 4 of the guiding area 601, and the other part of the chips can be discharged into the spiral chip flute 4 through the notch 9 on one side of the guiding area 601 and finally discharged. In this way, both the effective length of the second land 62 can be ensured to guarantee the guiding function, and the accumulation of chips in the guiding area 601 can be avoided, preventing the formation of extrusion marks and scratches on the surface of the hole wall and improving the surface quality of the hole.

[0035] Further, in this embodiment, the number of notches 9 on the second land 62 is n, and 1 < n ≤ 5.

[0036] Further, in this embodiment, the notches 9 on the second land 62 are evenly distributed along the axial direction of the guiding part 2.

[0037] Further, in this embodiment, the axial length of the first land 61 along the guiding part 2 is L1, the axial spacing of the notches 9 along the guiding part 2 is L3, and the axial length of the notches 9 along the guiding part 2 is L4. L4 ≥ 6 mm, and (n - 1)L3 + nL4 ≤ 3 / 4L1. To ensure the guiding function and chip removal effect, the value of L4 must be reasonably set. If the value of L4 is too large, the actual length of the second land 62 is insufficient, resulting in insufficient guiding function; if the value of L4 is too small, the length of the guiding area 601 excluding the notches 9 surrounded by the first land 61, the second land 62 and the cutting lip 5 becomes longer, and the chip removal stroke of the chips 10 is too long before entering the spiral chip flute 4, there is a risk of chip 10 congestion. Therefore, L4 satisfies: L4 ≥ 6 mm, and (n - 1)L3 + nL4 ≤ 3 / 4L1.

[0038] Further, in this embodiment, the axial length of the first cutting edge band 61 along the guiding portion 2 is L1, the axial distance between the notch 9 closest to the cutting portion 1 and the cutting portion 1 along the guiding portion 2 (the distance from the left side of the notch 9 to the end face of the guiding portion 2 facing the cutting portion 1) is L2, and L2≥L1 / 4.

[0039] Further, in this embodiment, the cutting diameter of the cutting portion 1 is D, preferably D = 6 mm, n = 3, L1 = 30 mm, L2 = 8 mm, L3 = 2 mm, L4 = 6 mm.

[0040] Further, in this embodiment, the included angle between the side wall surface 91 of the notch 9 and the axis 8 of the guiding portion 2 is α, and the helix angle of the first cutting edge band 61 is β, β + 5° < α ≤ 90°, ensuring better chip evacuation. In this embodiment, α is preferably 60°.

[0041] Further, in this embodiment, the helix angle β satisfies: 10° ≤ β ≤ 50°. In this embodiment, β is preferably 30°.

[0042] Further, in this embodiment, in the cross-section perpendicular to the guiding portion 2, the width included angle of the cutting edge lobe 5 is γ3, 40° ≤ γ3 ≤ 100°.

[0043] Further, in this embodiment, in the cross-section perpendicular to the guiding portion 2 and passing through the starting points of the first cutting edge band 61 and the second cutting edge band 62, the included angle between the first cutting edge band 61 and the second cutting edge band 62 is γ4, γ3 - 30° ≤ γ4 ≤ γ3 - 5°. In this embodiment, preferably γ3 = 90°, γ4 = 60°

[0044] Further, in this embodiment, the widths of both the first cutting edge band 61 and the second cutting edge band 62 are L5, preferably L5 = 0.4 mm.

[0045] Further, in this embodiment, the helix angles of the first cutting edge band 61, the second cutting edge band 62, and the spiral chip evacuation groove 4 are the same. It is convenient for production, reduces production costs, and at the same time further ensures the lengths of the first cutting edge band 61 and the second cutting edge band 62, ensuring the guiding effect.

[0046] Further, the cutting portion 1 includes two main cutting edges 11, and the first cutting edge band 61 intersects with the spiral chip evacuation groove 4 to form a secondary cutting edge, and each main cutting edge 11 is connected to each secondary cutting edge. When the twist drill is in use, chips are generated by the main cutting edges 11

[0047] Further, a web 12 is provided between the two main cutting edges 11, and the web 12 has two web grinding surfaces 13, and each web grinding surface 13 intersects with each spiral chip evacuation groove 4. During cutting, the cutting portion 1 is centered by the web 12.

[0048] Embodiment 2:

[0049] Figures 5 to 7 Another embodiment of the multi-edge belt twist drill of the present invention is shown. The structure of the multi-edge belt twist drill in this embodiment is basically the same as that of the first embodiment, except that: the number n of the notches 9 on the second edge belt 62 is 1.

[0050] Furthermore, in this embodiment, the second edge belt 62 on the cutting lip 5 extends to the end of the flute. In this embodiment, preferably D = 6 mm, L1 = 30 mm, n = 1, L2 = 12 mm, L4 = 18 mm.

[0051] In this embodiment, preferably β = 30°, α = 60°, L5 = 0.4 mm, γ3 = 90°, γ4 = 60°.

[0052] Furthermore, in this embodiment, the notch 9 on the second edge belt 62 is located at the end of the second edge belt 62 away from one end of the cutting part 1.

[0053] Embodiment Three:

[0054] Another embodiment of the multi-edge belt twist drill of the present invention. The structure of the multi-edge belt twist drill in this embodiment is basically the same as that of the first embodiment, except that: the helix angles of the first edge belt 61 and the spiral chip flute 4 are the same, and the helix angles of the second edge belt 62 and the spiral chip flute 4 are different, with a difference of 0 to 15° (excluding 0).

[0055] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above-disclosed technical content, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A multi-edge twist drill, comprising a cutting part (1), a guiding part (2) and a shank part (3) connected in sequence, wherein the guiding part (2) includes two cutting lips (5), and two spiral chip flutes (4) are formed between the two cutting lips (5), a first land (61) and a second land (62) are arranged at intervals on the cutting lip (5), the second land (62) is close to the trailing edge (7), and a guiding area (601) communicating with the spiral chip flute (4) is formed between the first land (61) and the second land (62), and is characterized in that: At least one notch (9) is provided on a section of the second cutting edge band (62) close to the handle (3), and the notch (9) communicates the guiding area (601) with the spiral chip flute (4); the number of notches (9) on the second cutting edge band (62) is n, the axial length of the first cutting edge band (61) along the guiding part (2) is L1, the axial pitch of the notches (9) along the guiding part (2) is L3, the axial length of the notch (9) along the guiding part (2) is L4, L4≥6mm, and (n - 1)L3 + nL4≤3 / 4L1. The axial distance between the notch (9) closest to the cutting part (1) and the cutting part (1) along the guiding part (2) is L2, and L2≥L1 / 4.

2. The multi-edge twist drill according to claim 1, wherein: 1≤n≤5。 3. The multi-edge twist drill according to claim 2, characterized in that: If n>1, the notches (9) on the second cutting edge band (62) are evenly distributed axially along the guiding part (2).

4. The multi-edge twist drill according to claim 1, characterized in that: The included angle between the side wall surface (91) of the notch (9) and the axis (8) of the guiding part (2) is α, and the helix angle of the first cutting edge band (61) is β, β + 5° < α ≤ 90°.

5. The multi-edge twist drill according to claim 1, wherein: In a cross-section perpendicular to the guiding part (2), the width included angle of the cutting blade (5) is γ3, 40° ≤ γ3 ≤ 100°.

6. The multi-edge belt twist drill according to claim 5, characterized in that: In a cross-section perpendicular to the guiding part (2) and passing through the starting points of the first cutting edge band (61) and the second cutting edge band (62), the included angle between the first cutting edge band (61) and the second cutting edge band (62) is γ4, γ3 - 30° ≤ γ4 ≤ γ3 - 5°.

7. The multi-edge belt twist drill according to any one of claims 1 to 6, characterized in that: The helix angles of the first cutting edge band (61), the second cutting edge band (62), and the spiral chip flute (4) are the same.

8. The multi-edge belt twist drill according to any one of claims 1 to 6, characterized in that: The cutting part (1) includes two main cutting edges (11). The first cutting edge band (61) intersects with the spiral chip flute (4) to form an auxiliary cutting edge, and each main cutting edge (11) is connected to each auxiliary cutting edge.

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