Cutter set and method for machining reverse reaming threaded hole

Abstract

The invention discloses a cutter set and method for machining a reverse reaming threaded hole. The cutter set comprises a single-thread reverse reaming T-shaped cutter and a single-thread reverse reaming thread milling cutter. Each of the single-thread reverse-reaming T-shaped cutter and the single-thread reverse-reaming thread milling cutter comprises a cutter head, a round rod and a milling part, the outer diameter of the round rod is smaller than that of the cutter head, the round rod is positioned between the cutter head and the milling part, the round rod and the cutter head are coaxial, the milling part takes the axis of the guide rod as a rotating center, the milling part is a bulge radially extending from the front end of the round rod, and the milling part is a convex part. The outer edge of the bulge is an action area; the acting area of the single-tooth reverse reaming T-shaped cutter is an edge of the outer edge, and the edge is parallel to the axis of the guide rod; the acting area of the single-thread reverse reaming thread milling cutter is a sharp cutting edge; the tool set is reasonably designed, under the control of the numerical control machine tool, the reverse reaming threaded hole in the inner wall of the cavity can be machined in a milling mode, and compared with a tool or a machining method, the machining efficiency and quality can be improved.

Description

Technical Field

[0001] This invention relates to the field of machining, specifically to a tool set and method for machining countersunk threaded holes. Background Technology

[0002] In modern high-end equipment manufacturing, a common type of cavity-like part often appears, where the inner cavity sidewalls require countersunk threaded holes (i.e., the thread opening faces inwards rather than outwards). These countersunk threads are usually accompanied by annular sealing grooves for installing threaded caps with sealing lines. Traditional machining methods face the following challenges: Tool interference: Because the thread is located on the side wall of a closed or semi-closed inner cavity, conventional taps and thread cutting tools cannot reach or effectively machine due to limitations in tool structure or retraction space.

[0003] Machining accuracy is difficult to guarantee: Although electrical discharge machining can be used to form the part, the efficiency is extremely low (it takes several hours to process a single part), and there are problems such as electrode wear and large positioning errors after multiple clamping, resulting in poor dimensional consistency and low pass rate.

[0004] Complex process and high cost: Although it is possible to try using a side milling head with special tooling, the programming is complicated, the number of clamping times is large, the concentricity is difficult to control, and the versatility is poor.

[0005] With the development of five-axis CNC technology, milling has become an efficient and high-precision solution. However, there is a lack of dedicated milling tools on the market that can be directly used to machine such local reverse threads on the sidewalls of internal cavities. Most existing thread milling cutters are integral or general-purpose types, and their tool holder and cutter head structures cannot avoid interference from the internal cavity wall, nor can they efficiently machine the sealing groove at the bottom of the reverse thread. Summary of the Invention

[0006] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a tool set and method for machining countersunk threaded holes. By reasonably designing the tool set, the countersunk threaded holes on the inner wall of the cavity can be machined by milling under the control of a CNC machine tool. Compared with tools or machining methods, this method can improve machining efficiency and quality.

[0007] On one hand, the present invention provides a tool set for machining countersunk threaded holes, including a single-tooth countersunk T-shaped cutter and a single-tooth countersunk thread milling cutter. The single-tooth countersunk T-shaped cutter is used for milling countersunk holes, and the single-tooth countersunk thread milling cutter mills threads based on countersunk holes. The countersunk hole is a countersunk hole located on the inner wall of a cavity, and the countersunk threaded hole is a countersunk hole with threads located on the inner wall of the cavity (i.e., the thread opening faces the inner side of the cavity rather than the outer side). Both the single-tooth countersunk T-cut and the single-tooth countersunk thread milling cutter include a cutter head, a round rod, and a milling part. The outer diameter of the round rod is smaller than the outer diameter of the cutter head and is located between the cutter head and the milling part. The round rod and the cutter head are coaxial. The milling part is a protrusion that extends radially from the front end of the round rod, and the outer edge of the protrusion is the working area. The working area of ​​the single-tooth reverse countersinking T-shaped cutter is the outer edge, which is parallel to the axis of the guide rod. The working area of ​​the single-tooth reverse countersinking thread cutter is a sharp cutting edge formed by one or two bevels on its outer edge.

[0008] Optionally, the tool set also includes a countersunk hole sealing groove tool for milling the annular groove located at the bottom of the countersunk hole; The countersunk hole sealing groove cutter has the same cutter head, round bar, and milling part with working area as the single-tooth countersunk T-cut or single-tooth countersunk thread milling cutter. The working area of ​​the countersunk hole sealing groove cutter is a milling block protruding on the milling part near the cutter head side. The milling block has a milling cutting edge on the side of the cutter head rotation direction.

[0009] In another aspect, the present invention also provides a method for machining countersunk threaded holes, wherein the machining is performed using a tool set for machining countersunk threaded holes, the method comprising: Drill through holes in the cavity; A stepped hole is milled out using a single-tooth reverse countersinking T-cutter, thus forming a reverse countersinking hole; An internal thread is milled into the small diameter hole of the stepped hole using a single-tooth countersunk thread milling cutter, forming a countersunk thread hole.

[0010] Optionally, the method further includes: A ring groove is milled into the inner bottom of the countersunk threaded hole using a countersunk hole sealing groove cutter.

[0011] Optionally, when the single-tooth countersunk T-cutter is milling a stepped hole, the round rod milled by the single-tooth countersunk T-cutter passes through the through hole, and the milling part of the single-tooth countersunk T-cutter enters the inner wall of the cavity and processes from the inner wall of the cavity to the outer wall.

[0012] Optionally, when machining internal threads, the single-tooth countersinking cutter moves synchronously along the Z axis by one pitch when the X and Y axes move one revolution as instructed by the G02 / G03 command on the CNC machine tool.

[0013] Optionally, when machining internal threads, the single-tooth countersinking thread cutter uses climb milling, and the right-hand internal thread is milled from bottom to top.

[0014] The present invention has the following advantages: This invention relates to a tool set and method for machining countersunk threaded holes. By improving the tool, interference is solved: the single-tooth countersunk design combined with the tool holder avoidance structure fundamentally solves the problem of machining space interference in the closed inner cavity sidewall, and can also machine the internal thread of the countersunk hole by milling.

[0015] During the machining process, the high flexibility of the 3+2 five-axis machine tool enables the centralized machining of multi-faceted features of complex cavity parts. The machining of reverse threads and sealing grooves can be completed in one clamping, which greatly improves accuracy and efficiency.

[0016] Compared to electrical discharge machining (EDM), efficiency is increased several times to more than ten times; compared to traditional methods, the pass rate is significantly improved (from approximately 40% to over 98%). Specialized cutting tools have a long lifespan and good dimensional consistency, reducing unit cost and production turnaround time.

[0017] Furthermore, the improved method and tool design principles are clear. By adjusting the tool size and CNC program, it can be applied to the processing of reverse threads and irregular grooves of different specifications, which has high practical value and is easy to promote and apply in the industry. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the single-tooth reverse countersinking T-shaped cutter described in this invention; Figure 2 This is a three-dimensional structural diagram of the single-tooth reverse countersinking T-shaped cutter described in this invention from another perspective; Figure 3 This is a three-dimensional structural schematic diagram of the single-tooth reverse countersinking thread cutter described in this invention; Figure 4 This is a three-dimensional structural diagram of the single-tooth reverse countersinking thread cutter described in this invention from another perspective; Figure 5 This is a three-dimensional structural schematic diagram of the countersink sealing groove knife described in this invention; Figure 6 This is a schematic diagram of the structure of the countersinking cavity type part described in this invention; Figure 7 This is a structural diagram of the countersunk threaded hole with parameters; Figure 8 This is a flowchart illustrating a method for processing countersunk threaded holes according to the present invention; In the diagram: 100, single-tooth countersunk T-cut; 110, cutter head; 120, round bar; 130, milling section; 131, working area; 140, milling block; 141, milling cutting edge; 200, single-tooth countersunk thread cutter; 300, countersunk hole sealing groove cutter; 400, countersunk cavity type parts; 410, countersunk threaded hole. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0020] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0021] As described in the background section, with the development of five-axis CNC technology, milling has become a highly efficient and precise solution. However, there is a lack of dedicated milling tools on the market that can be directly used to machine such local reverse threads on the sidewalls of internal cavities. Existing thread milling cutters are mostly integral or general-purpose types, and their tool holder and head structures cannot avoid interference from the internal cavity wall, nor can they efficiently machine the sealing groove at the bottom of the reverse thread.

[0022] like Figure 6 and Figure 7 As shown, the part to be processed is a countersunk cavity type part 400, which needs to be machined with a countersunk threaded hole 410 as shown in the figure. The fine thread of the countersunk threaded hole extends from the inner cavity side wall to seal the cable cover. The hole processing of this part includes a φ9±0.01mm hole and three M16X0.5 fine threaded holes with a depth of 4mm (i.e., the countersunk threaded holes). The threaded hole processing size is up to φ15.5mm, the hole spacing is 90±0.02mm, the edge distance is 30mm, the hole dimensional accuracy requirement is high, and the surface roughness is Ra1.6.

[0023] Threads that do not allow for relief grooves are difficult to machine to the root using traditional turning methods or taps and dies. Furthermore, for small-diameter threads, especially in high-hardness and high-temperature materials, taps sometimes break, clogging the threaded hole and even rendering the part unusable. Due to the requirements of countersunk threaded holes, taps are not feasible because the inner cavity is close to the wall edge, causing interference from the annular groove. Electrical discharge machining and side milling are also difficult and cannot meet concentricity requirements, leading to multiple clamping errors. Therefore, this embodiment uses milling to process the threaded holes and improves upon the aforementioned tool set for machining countersunk threaded holes.

[0024] Specifically, such as Figures 1-4As shown, a tool set for machining countersunk threaded holes includes a single-tooth countersunk T-shaped cutter 100 and a single-tooth countersunk thread milling cutter 200. The single-tooth countersunk T-shaped cutter is used to mill countersunk holes, and the single-tooth countersunk thread milling cutter mills threads based on countersunk holes. The countersunk hole is a countersunk hole located on the inner wall of a cavity, and the countersunk threaded hole is a countersunk hole with threads located on the inner wall of a cavity. Both the single-tooth countersinking T-cut and the single-tooth countersinking thread milling cutter include a cutter head 110, a round rod 120, and a milling section 130. The outer diameter of the round rod is smaller than the outer diameter of the cutter head and is located between the cutter head and the milling section. The round rod and the cutter head are coaxial. The milling section is a protrusion that extends radially from the front end of the round rod. The outer edge of the protrusion is the working area 131. like Figure 1 and Figure 2 As shown, the working area of ​​the single-tooth reverse countersinking T-shaped cutter is the outer edge, which is parallel to the axis of the guide rod; like Figure 3 and Figure 4 As shown, the working area of ​​the single-tooth countersunk thread milling cutter is a sharp cutting edge formed by one or two bevels on the outer edge.

[0025] For example, the single-tooth back-countercutting T-cut and the single-tooth back-countercutting thread end mill are made of round tungsten steel rod material, with a cutter head diameter of 14 mm, a round rod diameter of 4.8 mm, a round rod length of 16 mm, a milling part thickness of 1.5 mm, a single cutter head (i.e., protrusion) extension of 3.9 mm, and a total tool length of 70 mm; wherein the cutting edge of the single-tooth back-countercutting thread end mill is formed by two cutting surfaces with an included angle of 60°.

[0026] In order to machine the annular groove (for installing the sealing cable cover), the tool set also includes a countersunk hole sealing groove cutter for milling the annular groove located at the bottom of the countersunk hole. like Figure 5 As shown, the countersunk hole sealing groove cutter 300 has a cutter head 110, a round rod 120, and a milling part 130 with an active area, which are the same as the structure of the single-tooth countersunk T-cut or single-tooth countersunk thread milling cutter. The active area of ​​the countersunk hole sealing groove cutter is a milling block 140 protruding on the milling part near the cutter head side. The milling block has a milling cutting edge 141 on the side of the cutter head rotation direction.

[0027] For example, the reverse countersink sealing groove cutter is also made of round tungsten steel rod material, with a cutter head diameter of 14mm, a round rod diameter of 4.8mm, a round rod length of 16mm, a milling part thickness of 1.5mm, and the spacing of the single cutter head (i.e., protrusion) extension is set according to the inner diameter of the annular groove, while the thickness of the cutting block is determined by the depth of the annular groove, and the entire cutter is 70mm long.

[0028] Improved single-tooth countersunk T-cutters, single-tooth countersunk thread milling cutters, and countersunk hole sealing groove cutters are used to machine countersunk threaded holes via milling. Because the improved tools have a round shank section with a diameter smaller than the threaded hole being machined, it can penetrate from the outer wall of the cavity to the inner wall without interference. Even if it breaks, it will not block the threaded hole and is easily removed, preventing part scrap. Furthermore, the coaxial design of the round shank and the cutter head ensures the coaxiality of the machined parts. Compared to taps, thread milling significantly reduces the cutting force, which is especially important for machining large-diameter threads, solving the problem of high machine tool loads preventing taps from operating properly. In addition, the durability of thread milling cutters is more than ten times, even dozens of times, that of taps, and adjusting the thread diameter during CNC thread milling is extremely convenient—something difficult to achieve with taps or dies.

[0029] In another embodiment, a method for machining countersunk threaded holes is also provided, wherein the machining is performed using a tool set for machining countersunk threaded holes, such as... Figure 8 As shown, the method includes: S100, Preliminary Preparations; S200, Drill through holes in the cavity; S300: A stepped hole is milled out using a single-tooth countersinking T-cutter, forming a countersinking hole; S400: An internal thread is milled into the small diameter hole of the stepped hole using a single-tooth countersunk thread milling cutter to form a countersunk thread hole.

[0030] S500: A ring groove is milled into the inner bottom of the countersunk threaded hole using a countersunk hole sealing groove cutter.

[0031] For example, the preliminary preparation in S100 includes at least: Machine tool selection: A 3+2 machining center rotary table can be added. Optional machine tool parameters are shown in Table 1 below: Table 1: Machine Tool Parameters Preparation of fixtures and cutting tools: The fixtures shall be existing or designed according to the shape. The cutting tools shall include one each of the following: Φ10 flat end mill, Φ6 flat end mill, Φ8.5 carbide drill, Φ6x90° chamfering cutter, reverse countersink sealing groove cutter, single-tooth reverse countersink T-cut cutter and single-tooth reverse countersink thread milling cutter.

[0032] For example, in step S300, when the single-tooth back countersink T-cutter is milling the stepped hole, the round rod milled by the single-tooth back countersink T-cutter penetrates the through hole, while the milling part of the single-tooth back countersink T-cutter enters the inner wall of the cavity and processes from the inner wall to the outer wall. This achieves milling precision bottom holes with a 0.05mm allowance on one side for machining through holes as preparation work before milling threads.

[0033] For example, in step S400, when the X and Y axes move one revolution of G02 / G03, the Z axis moves synchronously by a pitch P. The thread accuracy is achieved by the tool radius compensation of the machine tool. To ensure the quality of thread processing, climb milling is used, and the right-hand internal thread is milled from bottom to top.

[0034] For example, when combining CNC machine tool machining, the machining program is illustrated using a single-tooth reverse countersinking thread cutter. The tool rotation is φ12.6mm and the tool width is 8.7mm. For thread machining, the tool needs to be manually clamped and positioned in advance to confirm the tool tip direction. Part of the program is shown in Table 2 below: Table 2: Partial Processing Procedures The above methods are compared with traditional methods, as shown in Table 3 below: Table 3: Comparison Table This invention employs thread milling, which significantly reduces the cutting force compared to taps. This is particularly important for machining large-diameter threads, solving the problem of machine tools being unable to drive taps properly under high loads. Furthermore, the durability of thread milling cutters is more than ten times, even dozens of times, that of taps, and the adjustment of the thread diameter is extremely convenient during CNC thread milling, something that taps and dies cannot achieve.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tool set for machining a counter-bored threaded hole, characterised in that: The single-tooth counter-bore T-shaped cutter is used for milling counter-bore holes, and the single-tooth counter-bore thread milling cutter is used for milling threads on the basis of the counter-bore holes; the counter-bore hole is a counter-bore hole on the inner wall of a cavity, and the counter-bore thread hole is a counter-bore hole with threads on the inner wall of the cavity; The single-tooth counter-bore T-shaped cutter and the single-tooth counter-bore thread milling cutter each comprise a cutter head, a round rod and a milling portion, the round rod has an outer diameter smaller than that of the cutter head and is located between the cutter head and the milling portion, the round rod and the cutter head are coaxial, and the milling portion has a protrusion extending radially from the front end of the round rod and takes the axis of the guide rod as the rotation center, and the outer edge of the protrusion is an action area; The action area of the single-tooth counter-bore T-shaped cutter is a ridge parallel to the axis of the guide rod; The action area of the single-tooth counter-bore thread milling cutter is a sharp cutting edge composed of one or two inclined surfaces.

2. The tool set for machining a reverse-flattened threaded hole according to claim 1, wherein: The counter-bore hole sealing groove cutter is used for milling a ring groove on the inner bottom of the counter-bore hole; The counter-bore hole sealing groove cutter has the same cutter head, round rod and milling portion with the single-tooth counter-bore T-shaped cutter or single-tooth counter-bore thread milling cutter, and the action area of the counter-bore hole sealing groove cutter is a milling block protruding from the milling portion close to the cutter head, and the milling block has a cutting edge on the side of the cutter head rotation direction.

3. A method of machining a reverse-tapped threaded hole, characterized by: The method comprises the following steps: Drilling a processing through hole on the cavity; Milling a stepped hole by the single-tooth counter-bore T-shaped cutter to form a counter-bore hole; Milling internal threads in the small-diameter hole of the stepped hole by the single-tooth counter-bore thread milling cutter to form a counter-bore thread hole.

4. The method of machining a reverse-tapped hole according to claim 3, wherein: The method further comprises the following steps: Milling a ring groove on the inner bottom of the counter-bore thread hole by the counter-bore hole sealing groove cutter.

5. The method of machining a reverse-tapped hole according to claim 3, wherein: When the single-tooth counter-bore T-shaped cutter mills the stepped hole, the round rod of the single-tooth counter-bore T-shaped cutter penetrates the through hole, and the milling portion of the single-tooth counter-bore T-shaped cutter enters the inner wall of the cavity to process from the inner wall to the outer wall of the cavity.

6. The method of machining a reverse-tapped hole according to claim 3, wherein: When the single-tooth counter-bore thread milling cutter mills the internal threads, the Z-axis moves synchronously by one pitch of the single-tooth counter-bore thread milling cutter when the X-axis and Y-axis of the numerical control machine tool execute a G02 / G03 command.

7. A method of machining a reverse-flank-tapped hole according to claim 3 or 6, characterized in that: When the single-tooth counter-bore thread milling cutter mills the internal threads, right-hand internal threads are milled from bottom to top in the direction of the milling cutter.

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