Small aperture intermittent deep hole machining process

Abstract

A kind of small aperture intermittent deep hole machining process is machined by small aperture intermittent deep hole machining tool group, and the small aperture intermittent deep hole machining tool group includes first tool, second tool, third tool, fourth tool and fifth tool.By first multi-blade support shaft and second multi-blade support shaft, multi-blade support structure plays a supporting and guiding role in the front hole during machining, enhances overall machining rigidity and stability, avoids broken tool, and the whole tool group has low cost, and can efficiently and reliably complete the machining of small aperture intermittent deep hole.

Description

Technical Field

[0001] This invention belongs to the field of cutting tool processing technology, specifically relating to a small-diameter discontinuous deep hole machining process. Background Technology

[0002] With the increasing variety of gearbox types, the related lubrication circuits on housing parts are becoming more complex. Agricultural AT hydraulic gearboxes, such as those used in cotton harvesters, are increasingly featuring small-diameter, discontinuous, deep oil passages with a depth greater than 50 times the diameter (D7 or less). Furthermore, these oil passages often intersect eccentrically with bearing holes, and the discontinuous hole openings have large slopes, making machining extremely difficult. Due to the excessively long tool overhang and weak rigidity, ordinary deep-hole drilling tools experience severe vibration and are prone to breakage, resulting in low machining efficiency and high tool costs.

[0003] Agricultural gearbox housings, in particular, have large external dimensions, resulting in numerous deep cavities and holes. Generally, deep hole machining of oil passages employs a pilot tool + gun drill or a pilot tool + solid alloy deep hole drill. However, both of these methods result in a very high rate of tool breakage in the later stages of machining small-diameter, discontinuous deep holes.

[0004] like Figure 1 The image shows a small-diameter oil hole on our company's AT gearbox. It intersects eccentrically with the bearing hole, dividing the oil hole into two discontinuous sections: a front section and a rear section. The hole diameter is 6 ≤ D ≤ 7 mm, with relatively loose tolerances, the upper tolerance being b = 0.12 mm. The hole depth L is generally over 350 mm, with a length-to-diameter ratio L / D ≥ 50. The axial length L4 of the inclined surface at the rear hole opening is > 1.2 * D, and the slope is greater than 50°. When machining the inclined surface at the rear hole opening using a standard alloy deep-hole drill or gun drill, the drill bit is only subjected to radial force on one side, making it impossible to center, resulting in poor cutting stability and tool tip vibration. Furthermore, because the tool's rear end lacks support in the front hole, the drill bit is prone to deflection and breakage, making the machining of the rear hole extremely difficult. When the hole depth L exceeds the standard alloy bar length of 330 mm, a custom-made non-standard bar is required for the solid alloy deep-hole drill, resulting in extremely high tool costs. Additionally, the excessive tool overhang leads to poor machining rigidity, necessitating reduced cutting parameters and limiting machining efficiency. How to effectively reduce the problems of oscillation and tool breakage in the subsequent hole machining process, and efficiently and reliably complete the machining of small-diameter intermittent deep holes with lower tool costs, is a key issue that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a small-diameter intermittent deep hole machining process, solving the problems of vibration and tool breakage in the later stages of hole machining using existing tools.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes:

[0007] A small-diameter discontinuous deep hole machining process is provided, which is processed by a small-diameter discontinuous deep hole machining tool set, including a first tool, a second tool, a third tool, a fourth tool, and a fifth tool.

[0008] The first cutting tool is a first pilot drill, including a first cutting head;

[0009] The second cutting tool includes a second cutting head, the groove length l21 of the second cutting head is greater than the length of the front hole L1, the diameter d2 of the second cutting head is less than the diameter d1 of the first cutting head, and the drill tip angle α2 of the second cutting head is less than the drill tip angle α1 of the first cutting head.

[0010] The third cutting tool includes a third cutting head and a first support shaft coaxially connected from front to back. The third cutting head and the first multi-blade support shaft have the same diameter, satisfying l31 > L3 and (L1 + L3 + L4) - (l31 + l32) ≤ (25% ~ 30%) * L1; where l31 is the length of the third cutting head, L3 is the distance between the two adjacent ends of the front and rear holes, L4 is the length of the countersunk hole bevel of the rear hole, and l32 represents the length of the first multi-blade support shaft.

[0011] The fourth tool is the second guide drill, which includes a fourth cutter head, a cutter shank, and a second multi-blade support shaft coaxially connected from front to back. The fourth cutter head, the cutter shank, and the second multi-blade support shaft have the same diameter, satisfying l41 > L3 and (L1 + L3 + L4 + 1.5D) - (l41 + l42) ≤ (25% ~ 30%) * L1; where l41 represents the length of the fourth cutter head and the cutter shank after connection, and l42 represents the length of the second multi-blade support shaft;

[0012] The fifth tool includes a fifth cutting head, which has a chip removal groove extending from its front end to its rear end. The length of the chip removal groove is l51 > L1 + L3 + L2.

[0013] The specific steps of the processing technology are as follows:

[0014] S1, use the first tool 1 to drill the guide hole of the front section hole and chamfer the hole opening to remove burrs, and drill to a depth of (1.5~2)*D;

[0015] S2, use the second tool 2 to drill through the front hole to a depth of L1+(4~6)mm;

[0016] S3, using the third tool 3, the inclined portion of the rear hole opening is countersunk into a plane, with a machining depth of L1+L3+L4;

[0017] S4, use the fourth tool 4 to drill the guide hole of the rear section hole, with a machining depth of L1+L3+L4+1.5D;

[0018] S5, use the fifth tool 5 to drill the rear section hole to the depth required by the drawing, machining depth L1+L3+L2.

[0019] Preferably, the diameter d1 of the first cutting head is taken as: The first cutting head has a drill tip angle α1 of 140° and a drill depth l11 of 1.5D to 2D, where D is the diameter of the hole to be machined.

[0020] Preferably, the cutting edge of the second cutter head includes a double-edged edge and a single-edged edge coaxially connected from front to back, and the length l22 of the double-edged edge is 6D to 7D.

[0021] Preferably, the drill diameter d2 of the second tool is taken as... The drill tip angle α2 of the second tool is 136°.

[0022] Preferably, the third cutter head is a 2-tooth flat-bottom cutter head, the cutting edge length l33 of the third cutter head is ≥ 2.5 * L4, and the diameter d3 of the third cutter head is taken as... d2-d3=0.005~0.025; the rake angle α3=90°, the blade width β3=1.5, and the helix angle α31=20~25° of the first multi-blade support shaft.

[0023] Preferably, the diameter of the third cutter head is necked by 0.05 to 0.1 mm on one side.

[0024] Preferably, the first multi-blade support shaft is a 6-blade support shaft.

[0025] Preferably, the drill tip angle α4 of the fourth cutter head is 140°, the cutting length of the fourth cutter head l43 = 4D, the drilling depth is 1.5D~2D, and the diameter d4 of the fourth cutter head is [value missing].

[0026] Preferably, the diameter of the tool holder is necked by 0.05 to 0.1 mm on one side.

[0027] Preferably, the diameter d5 of the fifth cutter head is taken as: The drill tip angle α5 of the fifth cutter head is 120°.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] (1) The present invention provides a small-diameter discontinuous deep hole machining process, wherein the front section hole is used as a guide hole, and the multi-blade support structure plays a supporting and guiding role in the front section hole during machining through the first multi-blade support shaft and the second multi-blade support shaft, thereby enhancing the overall machining rigidity and stability, avoiding tool breakage, and the entire tool set has low cost, and can efficiently and reliably complete the machining of small-diameter discontinuous deep holes.

[0030] (2) A small-diameter discontinuous deep hole machining process of the present invention, wherein the first tool and the second tool are both front-end hole machining tools. The first tool is a front-end hole machining guide drill and the second tool is a front-end hole machining deep hole drill. Machining the front-end hole separately can shorten the tool overhang and maximize the tool rigidity. An integral carbide strip with internal cooling hole can be used. Higher cutting parameters can be used to improve machining efficiency, while ensuring the machining accuracy and hole wall surface of the front-end hole, laying a good foundation for the machining of the subsequent hole.

[0031] (3) In a small-diameter intermittent deep hole machining process of the present invention, the third, fourth and fifth tools are tools for the subsequent hole machining. The third tool is used to countersink the inclined part of the hole opening in the subsequent hole machining. When countersinking the inclined part of the hole opening in the subsequent hole, the first support shaft plays a supporting and guiding role in the previous hole. The first support shaft is simple and easy to manufacture and has good precision. Using the third tool to countersink the inclined part of the hole opening in the subsequent hole into a plane can ensure good centering when the drill tip of the fourth tool enters, avoiding tool breakage. The fourth tool is a guide drill for the subsequent hole machining. The design of the second multi-blade support shaft ensures effective support at all times during machining. The tool is used to drill the guide hole of the subsequent hole, which plays a guiding role for the drill tip of the tool, ensuring that the tool 5 is stably drilled in, and completing the entire deep hole machining. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 A schematic diagram of a small-diameter oil hole on an automatic transmission;

[0034] Figure 2 This is a schematic diagram of the small-diameter discontinuous deep hole machining tool set of the present invention;

[0035] The labels in the diagram are as follows:

[0036] 1. First cutting tool, 1-1. First cutting head;

[0037] 2 Second cutting tool, 2-1 Second cutting head, 2-12 Double-edged band, 2-11 Single-edged band;

[0038] 3. Third cutting tool, 3-1. Third cutting head, 3-2. First multi-blade support shaft, 3-10. Cutting body;

[0039] 4. Fourth cutting tool, 4-1. Fourth cutting head, 4-2. Cutting bar, 4-21. Second multi-blade support shaft;

[0040] 5. Fifth cutting tool, 5-1. Fifth cutting head, 5-10. Chip removal groove. Detailed Implementation

[0041] The invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of this invention.

[0042] It should be noted that the directional terms mentioned herein are consistent with the specific directions on the paper in the accompanying drawings or the corresponding directions of the space shown in the drawings; all components and devices in this invention, unless otherwise specified, are components and devices known in the prior art.

[0043] In this embodiment, the diameter of the hole to be processed is D, where 6 ≤ D ≤ 7 mm, and the diameter tolerance requirement is... b = 0.12. The depth L of the hole to be machined is greater than 350mm, and the length-to-diameter ratio L / D ≥ 50; the axial length L4 of the inclined surface of the hole opening in the latter section is greater than 1.2*D, and the slope is greater than 50°.

[0044] Example

[0045] This embodiment discloses a small-diameter discontinuous deep hole machining process, which is processed by a small-diameter discontinuous deep hole machining tool set, including a first tool 1, a second tool 2, a third tool 3, a fourth tool 4 and a fifth tool 5.

[0046] The first cutting tool 1 is a first guide drill, including a first cutting head 1-1;

[0047] The second cutting tool 2 includes a second cutting head 2-1, the groove length l21 of the second cutting head 2-1 is greater than the length L1 of the front hole, the diameter d2 of the second cutting head 2-1 is less than the diameter d1 of the first cutting head 1-1, and the drill tip angle α2 of the second cutting head 2-1 is less than the drill tip angle α1 of the first cutting head 1-1.

[0048] The third cutting tool 3 includes a third cutting head 3-1 and a first support shaft 3-2 coaxially connected from front to back. The third cutting head 3-1 and the first multi-blade support shaft 3-2 have the same diameter, satisfying l31>L3 and (L1+L3+L4)-(l31+l32)≤(25%~30%)*L1; where l31 is the length of the third cutting head 3-1, L3 is the distance between the two adjacent ends of the front section hole and the rear section hole, L4 is the length of the countersunk flat hole opening of the rear section hole, and l32 represents the length of the first multi-blade support shaft 3-2.

[0049] The fourth cutting tool 4 is the second guide drill, which includes a fourth cutting head 4-1, a cutting shank 4-2, and a second multi-blade support shaft 4-21 coaxially connected from front to back. The fourth cutting head 4-1, the cutting shank 4-2, and the second multi-blade support shaft 4-21 have the same diameter, satisfying l41 > L3 and (L1 + L3 + L4 + 1.5D) - (l41 + l42) ≤ (25% ~ 30%) * L1; where l41 represents the length of the fourth cutting head 4-1 and the cutting shank 4-2 after connection, and l42 represents the length of the second multi-blade support shaft 4-21.

[0050] The fifth cutting tool 5 includes a fifth cutting head 5-1. The fifth cutting head 5-1 has a chip removal groove 5-10 extending from its front end to its rear end. The length of the chip removal groove 5-10 is l51 > L1 + L3 + L2.

[0051] Its function is as follows: the first tool 1 and the second tool 2 are both front-end hole machining tools. The first tool 1 is a guide drill for front-end hole machining, and the second tool 2 is a deep hole drill for front-end hole machining. Machining the front-end hole alone can shorten the tool overhang and maximize the tool rigidity. It can use an integral carbide strip with internal cooling holes, which can not only use higher cutting parameters to improve machining efficiency, but also ensure the machining accuracy and hole wall surface of the front-end hole, laying a good foundation for the machining of the subsequent holes. The third tool 3, the fourth tool 4, and the fifth tool 5 are the tools for machining the rear section of the hole. The third tool 3 is used to countersink the beveled portion of the rear section of the hole. When countersinking the beveled portion of the rear section of the hole, the first support shaft 3-2 plays a supporting and guiding role in the front section of the hole. The first support shaft 3-2 is simple and easy to manufacture and has good precision. Using the third tool 3 to countersink the beveled portion of the rear section of the hole into a flat surface ensures good centering when the drill tip of the fourth tool 4 enters, avoiding tool breakage. The fourth tool 4 is a guide drill for machining the rear section of the hole. The design of the second multi-blade support shaft 4-21 ensures effective support throughout the machining process. The guide hole of the rear section of the hole is drilled using the tool 4, which guides the drill tip of the tool 5, ensuring stable drilling of the tool 5 and completing the entire deep hole machining.

[0052] The main difficulty in machining small-diameter discontinuous deep holes disclosed in this solution lies in the machining of the latter section of the hole. To solve the problem of tool breakage, the former section of the hole is used as a guide hole. During machining, the multi-blade support structure of the first multi-blade support shaft 3-2 and the second multi-blade support shaft 4-21 plays a supporting and guiding role in the former section of the hole, which enhances the overall machining rigidity and stability and effectively solves the problems of tool breakage, high tool cost and low machining efficiency.

[0053] The first cutting tool disclosed in this embodiment is made of cemented carbide, and the diameter d1 of the first cutting tip 1-1 is taken as... The first cutting head 1-1 has a drill tip angle α1 of 140° and a drill depth l11 of 1.5D to 2D; the composite orifice chamfer improves efficiency, increases the shank diameter, and improves rigidity.

[0054] The second cutting tool disclosed in this embodiment is made of cemented carbide. The cutting edge of the second cutting head 2-1 includes a double-edged edge 2-12 and a single-edged edge 2-11 coaxially connected from front to back. The length l22 of the double-edged edge 2-12 is 6D to 7D. The drill diameter d2 of the second cutting tool 2 is... The drill tip angle α2 of the second tool 2 is 136°.

[0055] The third cutting tool disclosed in this embodiment is made of powder metallurgy high-speed steel, which has better toughness than cemented carbide tools, is less prone to breakage, and is less expensive than alloy tools. The third cutting head 3-1 is a 2-tooth flat-bottomed cutting head. During machining, the flat-bottomed cutting head is only subjected to axial force, avoiding the problem of uneven radial force on the drill bit on the inclined plane, which makes it difficult to center. The 2-tooth design ensures sufficient chip clearance. The cutting edge length l33 of the third cutting head 3-1 is ≥ 2.5 * L4, and the diameter d3 of the third cutting head 3-1 is [value missing]. d2-d3 = 0.005~0.025; the rake angle α3 of the first multi-blade support shaft 3-2 is 90°, the blade width β3 is 1.5, and the helix angle α31 is 20~25°. The diameter of the cutter body 3-10 of the third cutter head 3-1 disclosed in this embodiment is reduced by 0.05~0.1mm on one side to avoid jamming when entering the hole; the first multi-blade support shaft 3-2 is a 6-blade support shaft.

[0056] In this embodiment, the drill tip angle α4 of the fourth cutting head 4-1 is 140°, the cutting length l43 of the fourth cutting head 4-1 is 4D, the drilling depth is 1.5D to 2D, and the diameter d4 of the fourth cutting head 4-1 is... The diameter of the tool holder 4-2 is reduced by 0.05 to 0.1 mm on one side to avoid jamming during hole entry. The fourth tool head 4-1 is made of cemented carbide, and the tool holder 4-2 is made of powder metallurgy high-speed steel. The two are sleeved and welded together to increase the contact area and welding strength. At the same time, the welded structure greatly reduces the tool cost compared to a solid cemented carbide drill bit, while the cemented carbide tool head also ensures sufficient tool life and machining efficiency. In addition, the rake angle, cutting width, and helix angle of the second multi-edged support shaft 4-21 disclosed in this embodiment are the same as those of the first multi-edged support shaft 3-2.

[0057] The diameter d5 of the fifth cutter head 5-1 disclosed in this embodiment is [value missing]. The drill tip angle α5 of the fifth cutting head 5-1 is set to 120°. A brazed carbide-tipped gun drill is used. Compared to solid carbide drills, brazed gun drills are less expensive, have better toughness, and are less prone to breakage. The tool features internal cooling for effective chip removal, and the carbide cutting head has a guide bar structure, ensuring stable drilling once it enters the pilot hole.

[0058] The specific steps of the machining process for small-diameter discontinuous deep holes using a tool set in this embodiment are as follows:

[0059] S1, use the first tool 1 to drill the guide hole of the front section hole and chamfer the hole opening to remove burrs, drilling depth (1.5~2)*D;

[0060] S2, use the second tool 2 to drill through the front hole to a depth of L1+(4~6)mm;

[0061] S3, using the third tool 3, countersink the beveled part of the rear hole opening into a flat surface, with a machining depth of L1+L3+L4;

[0062] S4, use the fourth tool 4 to drill the pilot hole of the rear section hole, with a machining depth of L1+L3+L4+1.5D;

[0063] S5, using the fifth tool (5), drill the rear section hole to the depth required by the drawing, machining to a depth of L1+L3+L2, completing the process. Figure 1 The machining of small-diameter discontinuous deep holes is shown.

[0064] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0065] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately. Furthermore, the various different embodiments disclosed in this solution can also be combined arbitrarily, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content of this disclosure.

Claims

1. A process for machining small-diameter discontinuous deep holes, characterized in that, It is processed by a small-diameter discontinuous deep hole machining tool set, which includes a first tool (1), a second tool (2), a third tool (3), a fourth tool (4) and a fifth tool (5); The first cutting tool (1) is a first guide drill, including a first cutting head (1-1); The second cutting tool (2) includes a second cutting head (2-1), the groove length l21 of the second cutting head (2-1) is greater than the length L1 of the front hole, the diameter d2 of the second cutting head (2-1) is less than the diameter d1 of the first cutting head (1-1), and the drill tip angle α2 of the second cutting head (2-1) is less than the drill tip angle α1 of the first cutting head (1-1). The third cutting tool (3) includes a third cutting head (3-1) and a first multi-blade support shaft (3-2) coaxially connected from front to back. The third cutting head (3-1) and the first multi-blade support shaft (3-2) have the same diameter, satisfying l31>L3 and (L1+L3+L4)-(l31+l32)≤(25%~30%)*L1; where l31 is the length of the third cutting head (3-1), L3 is the distance between the two adjacent ends of the front section hole and the rear section hole, L4 is the length of the countersunk hole bevel of the rear section hole, and l32 represents the length of the first multi-blade support shaft (3-2); The fourth cutting tool (4) is a second guide drill, comprising a fourth cutting head (4-1), a cutting shank (4-2), and a second multi-blade support shaft (4-21) coaxially connected from front to back. The fourth cutting head (4-1), the cutting shank (4-2), and the second multi-blade support shaft (4-21) have the same diameter, satisfying l41 > L3 and (L1 + L3 + L4 + 1.5D) - (l41 + l42) ≤ (25% ~ 30%) * L1; where l41 represents the length of the fourth cutting head (4-1) and the cutting shank (4-2) after connection, and l42 represents the length of the second multi-blade support shaft (4-21). The fifth cutting tool (5) includes a fifth cutting head (5-1), and the fifth cutting head (5-1) has a chip removal groove (5-10) from its front end to its rear end. The length of the chip removal groove (5-10) is l51 > L1 + L3 + L2. The specific steps of the processing technology are as follows: S1, using the first tool (1) to drill the guide hole and chamfer the hole opening to remove burrs, drilling to a depth of (1.5~2)*D; S2, use the second tool (2) to drill through the front hole to a depth of L1+(4~6)mm; S3, using the third tool (3), the inclined part of the rear hole opening is countersunk into a plane, with a machining depth of L1+L3+L4; S4, using the fourth tool (4) to drill the guide hole of the rear section hole, with a machining depth of L1+L3+L4+1.5D; S5, use the fifth tool (5) to drill the rear section hole to the depth required by the drawing, and the machining depth is L1+L3+L2.

2. The small-diameter intermittent deep hole machining process as described in claim 1, characterized in that, The diameter d1 of the first cutter head (1-1) is _____. The drill tip angle α1 of the first cutting head (1-1) is 140°, and the drilling depth l11 is 1.5D to 2D. Where D is the diameter of the hole to be processed.

3. The small-diameter intermittent deep hole machining process as described in claim 1, characterized in that, The cutting edge of the second cutter head (2-1) includes a double-edged edge (2-12) and a single-edged edge (2-11) coaxially connected from front to back. The length l22 of the double-edged edge (2-12) is 6D to 7D.

4. The small-diameter intermittent deep hole machining process as described in claim 3, characterized in that, The drill diameter d2 of the second tool (2) is taken as: The drill tip angle α2 of the second tool (2) is 136°.

5. The small-diameter intermittent deep hole machining process as described in claim 1, characterized in that, The third cutting head (3-1) is a 2-tooth flat-bottom cutting head. The cutting edge length l33 of the third cutting head (3-1) is ≥ 2.5 * L4, and the diameter d3 of the third cutting head (3-1) is taken as... d2-d3 = 0.005~0.025; The first multi-blade support shaft (3-2) has a front angle α3 = 90°, a blade width β3 = 1.5, and a helix angle α31 = 20~25°.

6. The small-diameter intermittent deep hole machining process as described in claim 5, characterized in that, The diameter of the blade body (3-10) of the third cutter head (3-1) is reduced by 0.05 to 0.1 mm on one side.

7. The small-diameter intermittent deep hole machining process as described in claim 6, characterized in that, The first multi-blade support shaft (3-2) is a 6-blade support shaft.

8. The small-diameter intermittent deep hole machining process as described in claim 1, characterized in that, The drill tip angle α4 of the fourth cutting head (4-1) is 140°, the cutting length l43 of the fourth cutting head (4-1) is 4D, the drilling depth is 1.5D to 2D, and the diameter d4 of the fourth cutting head (4-1) is...

9. The small-diameter intermittent deep hole machining process as described in claim 8, characterized in that, The diameter of the tool holder (4-2) is reduced by 0.05 to 0.1 mm on one side.

10. The small-diameter intermittent deep hole machining process as described in claim 1, characterized in that, The diameter d5 of the fifth cutter head (5-1) is taken as: The drill tip angle α5 of the fifth cutter head (5-1) is 120°.

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