Screw tap suitable for deep hole thread machining and deep hole thread machining method

Abstract

The invention provides a screw tap suitable for deep hole thread machining and a deep hole thread machining method, and belongs to the technical field of machining. The screw tap comprises a lengthening section and a working section which are connected with each other. The working section comprises a connecting section and a cutting cone which are connected with each other; a plurality of chip removal grooves are formed in the outer surface of the connecting section and the outer surface of the cutting cone in an array mode along the circumference of the working section, and each chip removal groove comprises a first chip removal section, a second chip removal section and a third chip removal section which are sequentially connected. The length of the cutting cone is set to be 2.5-5 screw pitches, and the cutting thickness is increased and chip breaking is facilitated by setting the smaller length of the cutting cone; the chip removal groove is arranged to be of a sectional structure, iron chips cut by the cutting cone are spirally discharged according to the third chip removal section and then are discharged through a straight groove which is transited to the first chip removal section through the second chip removal section, so that the cuttings are broken due to collision; and therefore, the situation that the scrap iron cannot be smoothly guided out due to mutual extrusion of the spiral and mutual winding of the scrap iron due to overlong spiral is prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing, and relates to a tap suitable for deep hole thread processing and a deep hole thread processing method. Background Art

[0002] In the manufacturing process, many important mechanical parts are equipped with threaded holes. For ordinary products, the depth of the threaded hole is 2 to 3 times the thread diameter, and ordinary taps can be used to complete the processing smoothly. However, in some special occasions, the depth of the threaded hole exceeds 3 times the thread diameter, and some threaded holes have a sinker, which greatly increases the difficulty of processing.

[0003] Generally speaking, deep hole threads use large helix angle taps (helix angle greater than 45°) to meet chip removal requirements, but for deep hole threads with sinkers, continuous strips of iron chips are easily knotted at the sinker, making it impossible for the iron chips to be discharged from the hole, causing damage to the tap and quality accidents. Another way to process deep hole threads is to use a thread milling cutter, but because the thread milling cutter has a large overhang depth and the cutting process generates asymmetric cutting forces, it is easy to cause tool vibration, and the thread milling process is inefficient, especially for large workpieces with a large number of threads. The processing cycle is particularly long and the processing cost is high.

[0004] At present, the standard tap length of tool manufacturers generally does not exceed 5 times the thread diameter. For deeper thread hole processing, customization is required, which not only takes a long production cycle but is also expensive.

[0005] Therefore, how to improve the qualified rate of deep hole thread processing with steps and the service life of taps has become an urgent problem to be solved. Summary of the invention

[0006] The present invention provides a tap suitable for deep hole thread processing, comprising an extended section and a working section connected to each other;

[0007] The working section comprises a connecting section and a cutting cone which are connected to each other, wherein the connecting section is connected to the extension section, and the length of the cutting cone is set to a pitch of 2.5-5; and a plurality of chip removal grooves arranged in an array along the circumference of the working section are provided on the outer surfaces of the connecting section and the cutting cone, and a single chip removal groove comprises a first chip removal segment, a second chip removal segment and a third chip removal segment which are connected in sequence;

[0008] The first chip removal segment is connected to the extension segment, and the first chip removal segment is configured as a straight groove structure;

[0009] The second chip removal segment is configured as an arc transition structure;

[0010] The third chip removal segment is configured as a spiral structure, and the length of the third chip removal segment is greater than the length of the cutting cone.

[0011] Optionally, a front chamfer of less than or equal to 5° is provided on the cutting end of the cutting cone.

[0012] Optionally, the helix angle of the third chip removal segment is set to 5°-30°.

[0013] Optionally, the overall length of the chip groove is set to be greater than the sum of the thread length required for processing and the countersunk hole length.

[0014] Optionally, the extension section and the working section are connected to each other by convex welding.

[0015] Optionally, a composite coating is provided on the outer surfaces of the extension section and the working section.

[0016] In addition to the above structure, the tap suitable for deep hole thread processing also includes an inner cooling hole, which runs through the extension section and the working section, and the inner cooling hole is arranged as a tapered structure that decreases successively from the extension section to the working section.

[0017] In addition to the above structure, the tap suitable for deep hole thread processing also includes an internal cooling hole, which passes through the extended section and the working section, and the internal cooling hole is configured to include a structure including a circular hole section and a tapered hole section connected to each other, the circular hole section passes through the extended section and extends to the cutting cone, and the tapered hole section passes through the cutting cone and is connected to the circular hole section.

[0018] The present invention also provides a deep hole thread processing method, and the process of processing the deep hole thread using the tap suitable for deep hole thread processing as described above is as follows:

[0019] Step 1: Processing a deep hole threaded countersunk hole, and processing the bottom of the deep hole threaded countersunk hole into a plane;

[0020] Step 2: Process the thread bottom hole, chamfer the thread bottom hole and clean the iron chips;

[0021] Step 3: Use a flexible tapping tool holder and a torque protection chuck to clamp and fix the tap, and tap the deep hole thread in combination with the internal cooling method; during the tapping process, control the internal cooling pressure to ≥30 bar and set the concentration of the cutting fluid to 10% to 15%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In the present invention, the length of the cutting cone is set to 2.5-5 pitches, and a smaller cutting cone length is set to increase the chip thickness and facilitate chip breaking; and the chip discharge groove is set to a segmented structure, and the iron chips cut by the cutting cone are spirally discharged according to the third chip discharge segment, and then transitioned to the straight groove of the first chip discharge segment through the second chip discharge segment for discharge, so that the chips are impacted and broken, thereby preventing the iron chips from being squeezed by the spiral and being entangled with each other due to the excessive length of the spiral, so that they cannot be smoothly discharged.

[0024] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 It is a schematic structural diagram of a tap suitable for deep hole thread processing in an embodiment of the present invention.

[0027] in:

[0028] 1. Extension section, 2. Working section, 2.1. Connecting section, 2.2. Cutting cone, 2.3. First chip removal section, 2.4. Second chip removal section, 2.5. Third chip removal section. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the present invention more clear and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. It should be noted that the drawings of the present invention are all simplified and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the implementation of the present invention; the "number" mentioned in the present invention is not limited to the specific number in the examples in the accompanying drawings; the directions or positional relationships indicated by "front", "middle", "back", "left", "right", "up", "down", "top", "bottom", "middle", etc. mentioned in the present invention are based on the directions or positional relationships shown in the drawings of the present invention, and do not indicate or imply that the devices or components referred to must have a specific direction, nor can they be understood as limitations on the present invention.

[0030] Example:

[0031] See also Figure 1 As shown, a tap suitable for deep hole thread processing provided by the present invention comprises an extension section 1 and a working section 2 connected to each other;

[0032] The working section 2 includes a connecting section 2.1 and a cutting cone 2.2 connected to each other. The connecting section 2.1 is connected to the extension section 1. The length of the cutting cone 2.2 is set to 2.5-5 pitches. The chip thickness is increased and chip breaking is facilitated by setting a smaller length of the cutting cone 2.2. Preferably, the length of the cutting cone 2.2 is preferably set to 3 pitches; the connecting section 2.1 and the cutting cone 2.2 are integrally formed.

[0033] Preferably, the cutting end of the cutting cone 2.2 is provided with a front chamfer of less than or equal to 5°, so that the strength of the cutting edge is increased, the iron chips are greatly deformed, and debris is easily formed.

[0034] Preferably, the working section 2 is made of high-performance powder metallurgy cobalt-containing high-speed steel; the extension section 1 is made of high-speed steel, which increases toughness and reduces cost.

[0035] Preferably, the extension section 1 and the working section 2 are connected to each other by convex welding, and the torque can be transmitted more stably through convex welding.

[0036] A plurality of chip removal grooves are arranged in an array along the circumference of the working section 2 on the outer surface of the working section 2. A single chip removal groove includes a first chip removal segment 2.3, a second chip removal segment 2.4 and a third chip removal segment 2.5 connected in sequence.

[0037] The first chip removal segment 2.3 is connected to the extension segment 1, and the first chip removal segment 2.3 is preferably configured as a straight groove structure to effectively reduce the chip removal stroke;

[0038] The second chip discharge section 2.4 is preferably configured as an arc transition structure to facilitate smooth discharge of iron chips;

[0039] The third chip removal segment 2.5 is preferably configured as a spiral structure, and the length of the third chip removal segment 2.5 is greater than the length of the cutting cone 2.2, so as to facilitate the iron chips to quickly leave the cutting cone 2.2.

[0040] Preferably, the helix angle of the third chip removal segment 2.5 is preferably set to 5°-30°, and the iron chips can be crushed by setting a small helix angle.

[0041] Preferably, the overall length of the chip removal groove is preferably set to be greater than the sum of the thread length required to be processed and the length of the countersunk hole, so as to ensure that the iron chips are smoothly discharged from the thread area. Further preferably, the length difference between the overall length of the chip removal groove and the sum of the thread length required to be processed and the length of the countersunk hole is preferably set to 1-3 pitches, so as to ensure the strength of the rear end of the tap.

[0042] Preferably, three chip removal grooves are provided.

[0043] As a further embodiment of the present invention, an inner cooling hole is further provided in the tap, and the inner cooling hole runs through the extension section 1 and the working section 2, and the inner cooling hole is configured as a conical structure that decreases successively from the extension section 1 to the working section 2, so that when the cutting fluid flow rate is sufficient, the strength of the cutting part can be ensured, and the flow rate at the cutting edge can be increased, which is convenient for the discharge of iron chips.

[0044] In addition to the above structure, the inner coolant hole can also be set to a structure including a circular hole section and a conical hole section connected to each other. The circular hole section passes through the extension section 1 and extends to the cutting cone 2.2. The conical hole section passes through the cutting cone 2.2 and is connected to the circular hole section. Under the condition of meeting the strength of the tap, since the inner coolant hole at the non-cutting end adopts a larger diameter, the cutting fluid flow rate can be increased. The diameter at the cutting end cutting fluid outlet is smaller, which can ensure the strength of the cutting part and increase the flow rate at the cutting edge, which is helpful for the discharge of iron chips.

[0045] As a further embodiment of the present invention, a composite coating is provided on the outer surfaces of the extension section 1 and the working section 2. Preferably, the composite coating is preferably configured as TIN, TIALN or a composite coating with a lower friction coefficient.

[0046] As a further embodiment of the present invention, the present invention also provides a method for processing deep hole threads using the tap described above, which specifically includes the following steps:

[0047] Step 1, processing a deep hole threaded countersunk hole;

[0048] Specifically, deep hole threaded countersunk holes are processed using drilling tools such as U drills and spade drills;

[0049] When processing deep hole threaded countersunk holes, the cutting speed is set to 80m / min~120m / min and the feed per revolution is set to 0.15mm~0.35mm.

[0050] Step 2: Use a tool to process the bottom of the deep hole thread countersunk hole into a plane to facilitate the centering of the tool when processing the thread bottom hole and prevent deflection.

[0051] Specifically, a flat-bottom milling cutter may be used to process the bottom hole of the countersunk hole.

[0052] Step 3: Process the thread bottom hole. The bottom hole depth should be greater than the required thread depth (the depth should be greater than the length of the thread cutting cone to prevent the tap from hitting the bottom of the thread bottom hole during processing). The bottom hole diameter should meet the requirements of relevant standards and should be greater than the recommended value of 0.1mm to 0.2mm, which is conducive to reducing cutting force and increasing tool life.

[0053] Step 4: Chamfer the bottom hole of the thread. The chamfer angle should be slightly larger than the tap chamfer. The purpose is to guide the tap cutting.

[0054] Step 5: Clean the iron filings at the bottom of the threaded hole to prevent the iron filings from clogging the thread processing when machining the bottom hole.

[0055] Step 6: It is recommended to use a flexible tapping shank and a torque protection chuck for processing, and rely on the tap calibration part to guide the processing of the correct thread. If rigid tapping is used, the tap life may be reduced due to the large axial force.

[0056] Step 7: Use internal cooling during processing. The internal cooling pressure should be sufficient to flush out the iron chips. Preferably, the pressure is not less than 30 bar.

[0057] Step 8: If the internal cooling pressure of the machine tool is not enough to discharge the iron chips in time, the countersink can be processed to be slightly larger than the major diameter of the thread first to reduce the phenomenon of reduced cutting fluid flow rate caused by the increase in the countersink size. After the tapping is completed, the countersink is processed to the predetermined size. When this method is used, the length of the tap chip groove should be longer than the thread countersink hole.

[0058] Step 9: The concentration of synthetic cutting fluid should be controlled at 10-15%. A higher concentration of cutting fluid can ensure the lubrication effect. If necessary, extreme pressure additives should be added to ensure sufficient lubrication of the cutting part.

[0059] Step 10. A vibration sensor is installed on the tap handle, and the machine tool spindle is equipped with a power display panel. The tool vibration and power during normal processing are used as the standard. If one of the above two indicators is abnormal, the processing should be stopped in time to check the tap wear to avoid tap damage or quality accidents.

[0060] Preferably, for large workpieces, since the positioning accuracy is difficult to ensure, the tap and the bottom hole are not concentric during tapping, resulting in uneven cutting force in the circumferential direction during tap processing, causing damage to the tap or unqualified thread quality. A partition processing method can be adopted to reduce the eccentricity. For example, after completing the thread bottom hole and thread processing in area A, go to area B to process the thread bottom hole and thread, and complete all processing content in sequence. The number of partitions can be controlled by the partition chord length. Within a single partition, the repeated positioning accuracy meets the processing requirements.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A tap suitable for deep hole thread processing, characterized in that: It comprises an extension section (1) and a working section (2) which are connected to each other; The working section (2) comprises a connecting section (2.1) and a cutting cone (2.2) which are connected to each other, the connecting section (2.1) is connected to the extension section (1), and the length of the cutting cone (2.2) is set to 2.5-5 pitches; and a plurality of chip removal grooves arranged in an array along the circumference of the working section (2) are provided on the outer surfaces of the connecting section and the cutting cone, and a single chip removal groove comprises a first chip removal segment (2.3), a second chip removal segment (2.4) and a third chip removal segment (2.5) which are connected in sequence; The first chip removal segment (2.3) is connected to the extension segment (1), and the first chip removal segment (2.3) is configured as a straight groove structure; The second chip removal segment (2.4) is configured as an arc transition structure; The third chip removal segment (2.5) is arranged as a spiral structure, and the length of the third chip removal segment (2.5) is greater than the length of the cutting cone (2.2).

2. The tap suitable for deep hole thread processing according to claim 1, characterized in that: The cutting end of the cutting cone (2.2) is provided with a front chamfer of less than or equal to 5°.

3. The tap suitable for deep hole thread processing according to claim 1, characterized in that: The helix angle of the third chip removal segment (2.5) is set to 5°-30°; The overall length of the chip removal groove is set to be greater than the sum of the thread length required for processing and the countersunk hole length.

4. The tap suitable for deep hole thread processing according to claim 1, characterized in that: The extension section (1) and the working section (2) are connected to each other by convex welding.

5. The tap suitable for deep hole thread processing according to any one of claims 1 to 4, characterized in that: A composite coating is also provided on the outer surfaces of the extension section (1) and the working section (2).

6. The tap suitable for deep hole thread processing according to claim 5, characterized in that: It also includes an inner cooling hole, which passes through the extended section (1) and the working section (2), and the inner cooling hole is arranged to be a tapered structure that decreases in size from the extended section (1) to the working section (2).

7. The tap suitable for deep hole thread processing according to claim 5, characterized in that: It also includes an inner cooling hole, which passes through the extension section (1) and the working section (2), and the inner cooling hole is configured to include a circular hole section and a conical hole section that are connected to each other, the circular hole section passes through the extension section (1) and extends to the cutting cone (2.2), and the conical hole section passes through the cutting cone (2.2) and is connected to the circular hole section.

8. A deep hole thread processing method, characterized in that: The process of deep hole thread machining using the tap suitable for deep hole thread machining as claimed in claim 6 or 7 is as follows: Step 1: Processing a deep hole threaded countersunk hole, and processing the bottom of the deep hole threaded countersunk hole into a plane; Step 2: Process the thread bottom hole, chamfer the thread bottom hole and clean the iron chips; Step 3: Use a flexible tapping tool holder and a torque protection chuck to clamp and fix the tap, and tap the deep hole thread in combination with the internal cooling method; during the tapping process, control the internal cooling pressure to ≥30 bar and set the concentration of the cutting fluid to 10% to 15%.

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