Tool setting ruler and method for turning internal threads with the same lead at a specific spindle speed

Abstract

The present invention provides a tool setting ruler, which includes a ruler body, a fixed ruler and a vernier. The fixed ruler is vertically connected to the ruler body, the vernier is slidably connected to the ruler body, and a positioning contact is arranged on the vernier for engaging with the tooth groove of the internal thread; a tool setting groove is also formed on the vernier for positioning and repairing a tool, and the tool setting groove and the positioning contact have a fixed distance in the direction parallel to the fixed ruler; under the action of an external force, the vernier can move towards the fixed ruler so that the positioning contact cooperates with the fixed ruler to clamp the inner and outer surfaces of the internal thread. This tool setting ruler can assist in accurately marking the axial coordinates of the thread tooth groove during tool repair, facilitating the tool setting operation for internal thread repair. The present invention also provides a method for turning the internal thread with the same lead at a specific spindle speed by using this tool setting ruler.

Description

Technical Field

[0001] The present invention relates to the technical field of thread repair, and particularly relates to a tool setting gauge and a method for turning the internal thread within the same lead at a specific spindle speed. Background Art

[0002] Each year, a large number of threads are processed and repaired by oil drilling technology service enterprises. The oil pipe thread repair service itself is very necessary for the drilling industry to control equipment costs. By means of repair, the service life of oil pipe tools can be extended and equipment investment can be saved. The technical key point of oil pipe thread repair lies in turning along the original helix of the thread, rather than completely removing and reprocessing.

[0003] All along, special pipe lathes have been commonly used in the industry to process threads. Its advantages are simple structure and strong applicability. However, its disadvantages are also obvious. The labor intensity of operators is high, the labor environment is poor, and there are occupational risks such as accidental injuries and disabilities. Using a numerical control lathe to turn and repair threads can reduce the labor intensity. However, there are still the following problems in the numerical control turning repair process of threads:

[0004] (1) The tool setting problem, which is prominently manifested as: the installation of each thread to be repaired on the numerical control lathe is random, that is, the currently installed thread has a large difference in position and angle compared with the previous installation. Most of the processing position data set in the previous program is meaningless for the current processing. And updating all these data will greatly reduce the labor efficiency of the operator, increase the error probability of the program, and increase the risk of damage to the workpiece thread and the repair equipment.

[0005] In the prior art, the following methods are usually used to set the tool for the numerical control lathe when turning and repairing threads:

[0006] 1. Manual adjustment techniques: Usually, when there is no more convenient technical solution, the operator can use the dynamic correction method to set the tool, such as the literature (Gao Xinglan. How to repair threads on a numerical control lathe [J]. Modern Education Science: Middle School Teachers, 2011(7):38-38); the literature (Xiang Jianping. Method for solving the difficult tool setting problem of precision turning worm on a numerical control lathe [J]. Mechanical Workers: Cold Working, 2004(7):24-25) and the literature (Li Hengzheng, Zhang Binhui. Thread repair problem of numerical control lathe [J]. Journal of Suzhou University, 2015, 30(08):97-98+124). This method can be called the starting point marking method, that is, finding and marking the known thread starting point position. None of these methods can accurately find the turning repair starting point at one time, with low efficiency, and are only applicable to individual turning repairs.

[0007] 2. System special function expansion technologies: The earliest available domestic information is from the literature (Wang Ke, Tang Zongjun, Zhao Wenzhen. Several technical issues in the numerical control machining of pipe threads [J]. Petroleum Machinery, 1998, 26(11): 42-43). Its general idea is to add measurement and feedback functions to CNC lathe equipment until the machine tool layout is completely changed. This method is not very economical.

[0008] 3. Thread profile scanning and detection technologies: The earliest method that relevant technicians thought of to solve the problem was to introduce a complete set of workpiece profile scanning systems into CNC equipment to obtain the surface information of the workpiece profile and achieve automatic tool setting, such as the literature (Zhang Yaohui, Wang Qimin, Wang Xiumei, Wang Shili, Li Jibin. Numerical control repair machining method for petroleum drill pipe joint threads [J]. China Mechanical Engineering, 1999(6): 41-43+4-5), the literature (Zhang Yaohui, Wang Xiumei, Wang Qimin, Wang Shili. Numerical control repair machining system for petroleum drill pipe joint threads [J]. Journal of Academy of Armored Force Engineering, 2001, 15(1): 37-41), the literature (Wang Xiao, Wang Qingming. Thread repair method for CNC lathe based on CCD camera [J]. Machine Tool & Hydraulics, 2011, 39(8): 22-25), and the literature (Cai Shanle, Liao Zhonghao, Jiang Junjun. Automatic tool setting for thread machining on CNC lathe based on linear array CCD [J]. Machinery, 2008, 46(4): 53-54).

[0009] This idea has not been widely adopted by relevant enterprises for the following reasons: Due to the characteristics of heavy load cutting, harsh working conditions, diverse workpiece forms, and variable thread types in the turning and repair of petroleum pipe threads, it is determined that the processing equipment used in this process needs to meet the requirements of simple structure, convenient operation, stable reliability, and easy maintenance. However, this method complicates the equipment structure due to the need to add equipment, and the purchase, use, and maintenance costs are high. The probability of equipment damage and failure increases due to the exposed position, reducing the stability, reliability, and operation convenience of the CNC lathe. Therefore, this method is unacceptable for petroleum enterprises with a large demand for thread turning and repair.

[0010] 4. Special system function technologies: The literature (Zhang Dewu, Gong Junyan, Zhang Hui, Zhao Haiyuan. Application of Siemens 828D in repairing threads on CNC pipe thread lathes [J]. Metalworking: Cold Working, 2015(2): 71-72), the literature (Tang Zongjun, Gu Yanling. Continuing cutting of existing threads on CNC lathes [J]. Manufacturing Technology & Machine Tool, 2003(12): 96-97), and the literature (Ma Bin, Yu Li. Application of the thread repair function of the FAGOR system on pipe thread special machines [J]. CNC Machine Tool Market, 2007(12): 108-110) respectively introduced the applications of the thread repair functions provided by the Siemens 828D, FAGOR, and NUM systems. These functions can complete relevant position calculations and coordinate system settings, eliminating some manual labor. However, they do not have the ability to detect the position of the thread to be repaired. For thread turning repair, the characteristic parts of the thread to be repaired are different each time it is installed. Therefore, this technology usually requires an additional position detection device to be installed on the CNC lathe, resulting in an increase in equipment costs. At the same time, due to the limitations of their own functions and application scopes, such systems can only be applied to CNC lathes with corresponding systems and are not applicable to CNC lathes with other systems, lacking universal applicability.

[0011] 5. Zero position signal identification technologies: The ideas in the literature (Cai Shanle, Ma Zhihong. Manual thread tool setting on CNC lathes [J]. Machine Tool & Hydraulics, 2004(9): 177-178), the literature (Meng Shengcai. Tool setting problems when repairing threads on CNC lathes [J]. Mechanical & Electrical Engineering Technology, 2008, 37(4): 100-102 + 112), the literature (Fan Fanghong, Shi Jinyan. Discussion and application of the method for automatically positioning the spindle of a CNC lathe to repair threads [J]. Manufacturing Technology & Machine Tool, 2015(4): 173-176), and the literature (Wan Fawei, Zhao Junyou, Cao Qingyuan, Wang Futao, Cao Jianming, Han Xueyi. Research on the thread repair technology of oil drill pipes [J]. Machine Tool & Hydraulics, 2017, 45(2): 15-19) are to identify the zero position signal of the spindle. This method has insurmountable drawbacks, that is, the distance between the measurement point and the cutting start point on the thread corresponding to the zero position signal is not an integer multiple of the lead. Therefore, the calculated starting point is inaccurate and needs to be corrected, which is inherently determined by the thread feed operation principle of CNC machine tools.

[0012] 6. Manufacturing special tools and measuring instruments: The literature (Li Peimei, Li Xuegang, Song Shunping, Gao Fengwei, Wang Jutang. CNC machining and repair technology application of pipe threads [J]. Oil Field Equipment, 2007(06): 74-75) self-designed a grating digital display thread device with a measuring instrument, claiming that it can measure and display the position deviation value of the tooth profile of the thread to be repaired. It did not introduce the working principle, and the cost of this equipment is relatively high.

[0013] In addition, a Chinese invention patent application with the publication number CN102350548A discloses a tool setting method for repairing threads on a CNC lathe. This method requires setting a "flat plate" perpendicular to the spindle in front of the spindle or using a plane perpendicular to the spindle in front of the spindle. After that, it is necessary to measure the distance L1 from a point on the thread to this plane, and also measure the distance L2 from the corresponding point on the thread to be repaired to this plane, and calculate the difference between L1 and L2. However, in actual operation, this method also has the following disadvantages: 1. The distance L1 cannot be directly obtained from the machine tool. If manual measurement is used, it is difficult to ensure the measurement accuracy of L1. If instrument measurement is used, it will lead to a complex equipment structure; 2. This method also needs to detect and calculate the "angle difference". However, most CNC lathe systems in the prior art do not have the function of displaying the spindle phase angle. Therefore, the applicable range of this method is limited; and to detect the "angle difference", it is necessary to use detection instruments, or modify or transform the machine tool, which complicates the turning and repair operation of each thread, increases the cost investment, and reduces the work efficiency; in addition, the introduction of the "angle difference" makes the position calculation complex, the operation cumbersome, the efficiency low, the cost high, and the applicable range small.

[0014] A Chinese invention patent application with the publication number CN104148752A discloses an automatic extraction and elimination method for the deviation amount in tool setting and grinding of a CNC thread grinder. This method automatically calculates the synchronous following error of the Z-axis and the A-axis as the deviation amount, which is equivalent to the most commonly used test cutting method for turning threads on a CNC lathe. It relies on the operator to visually estimate the distance between the tool and the existing thread teeth, and then adjusts and eliminates the distance repeatedly for many times. The process is relatively complex; and most CNC lathe systems in the prior art do not have the functions of continuous multi-point multi-dimensional data acquisition, recording, storage, and calculation. Therefore, the applicable range of this method is limited.

[0015] A Chinese invention patent application with the publication number CN109799783A discloses a method, a control device, and a CNC machine tool for repairing a threaded pipe body of a CNC machine tool. This method makes a comparison by obtaining the thread trajectory data of this threaded pipe and the CNC machine tool program data, and calculates the data difference between the program helix and the helix to be repaired. This method belongs to the above-mentioned "thread profile scanning detection technology", and it is necessary to add other systems to obtain the information mentioned in the method and simulate turning this thread, resulting in a complex equipment; at the same time, this method needs to obtain the spindle encoder of the CNC machine tool and the angular quantity of the machine tool, making the entire tool setting process relatively complex.

[0016] (2) For the repair of internal threads, since the internal threads are located inside the workpiece, it is difficult to judge the relative position between the turning tool and the internal threads during tool setting. Therefore, it is impossible to accurately mark the axial coordinates of the internal thread tooth grooves during tool setting, resulting in difficult tool setting. Summary of the Invention

[0017] The present invention aims to solve at least one of the above technical problems, and provides a tool setting ruler which can assist a turning tool to accurately mark the axial coordinates of a thread tooth groove, facilitating the tool setting operation for internal thread repair.

[0018] To achieve the above object, the technical solution adopted by the present invention is:

[0019] A tool setting ruler for internal thread repair, comprising a ruler body, a fixed ruler and a vernier. The fixed ruler is vertically connected to the ruler body, the vernier is slidably connected to the ruler body, and a positioning contact is arranged on the vernier for engaging with the tooth groove of the internal thread; a tool setting groove is further formed on the vernier for positioning a repair tool, and the tool setting groove and the positioning contact have a fixed distance L in a direction parallel to the fixed ruler. 0 Under the action of an external force, the vernier can move towards the fixed ruler so that the positioning contact and the fixed ruler cooperate to clamp the inner and outer surfaces of the internal thread.

[0020] Further, the vernier includes a sleeve and a fixing plate connected to the sleeve. The ruler body passes through the sleeve and the fixing plate, and the positioning contact and the tool setting groove are both arranged on the fixing plate and are respectively located on opposite sides of the ruler body.

[0021] Further, the positioning contact protrudes from one side of the fixing plate facing the fixed ruler, and the tool setting groove is recessed from one side of the fixing plate facing away from the fixed ruler.

[0022] Further, the positioning contact forms a V-shaped cross-section with an angle of 60 degrees in the plane where the ruler body and the fixed ruler are located, and the end of the V-shaped cross-section of the positioning contact close to the fixed ruler is an arc end; the tool setting groove forms a V-shaped cross-section with an angle of 60 degrees in the plane where the ruler body and the fixed ruler are located, and the axis of symmetry of the V-shaped cross-section of the tool setting groove is parallel to the axis of symmetry of the V-shaped cross-section of the positioning contact and is perpendicular to the fixed ruler.

[0023] Further, the positioning contact is detachably connected to the fixing plate.

[0024] Further, the tool setting ruler further includes a locking member for locking the vernier on the ruler body.

[0025] Further, a positioning groove is further recessed on one side of the fixed ruler facing the positioning contact, and one end of the positioning groove penetrates through the end of the fixed ruler away from the ruler body.

[0026] Further, the cross-section of the positioning groove is in an inverted equilateral trapezoid shape, and the center of the positioning contact points to the central axis of the positioning groove.

[0027] Further, a rubber pad is laid on the groove surface surrounding the positioning groove.

[0028] The present invention also provides a method for turning and repairing an internal thread with the same lead at a specific spindle speed, comprising the following steps:

[0029] S1, at a preset spindle speed, on the outer surface of a reference workpiece, turn a reference helix with a tool starting point S[X S ,Z S , where X S is the radial coordinate of point S, Z S is the axial coordinate of point S, and the lead of the reference helix is the same as the lead P of the internal thread to be repaired;

[0030] S2, position the tip of the turning tool at point A[X A ,Z A , where X A is the radial coordinate of point A, Z A is the axial coordinate of point A, and Z A makes the tip located at an arbitrary position in the middle of the reference helix;

[0031] S3, rotate the spindle to an angular position that makes the tip point to the reference helix, and mark or memorize this angular position;

[0032] S4, remove the reference workpiece from the chuck of the CNC lathe;

[0033] S5, install the workpiece with the internal thread to be repaired on the chuck, and rotate the spindle to the said angular position. The tool starting point set in the turning and repair program of the internal thread to be repaired is E[X E ,Z E , where X E is the radial coordinate of point E, and Z E is the axial coordinate of point E;

[0034] S6, provide the tool setting ruler as described in claim 1, make the ruler body perpendicular to the axis of the spindle of the CNC lathe, and make the tool setting groove located outside the workpiece with the internal thread to be repaired. Move the cursor so that the positioning contact of the cursor engages with one of the tooth grooves of the internal thread to be repaired, and use the fixed ruler and the positioning contact to clamp the inner and outer surfaces of the internal thread;

[0035] S7, move the turning tool to position the tip of the turning tool at point B[X B ,Z B and point to the center of the tool setting groove, where X B is the radial coordinate of point B, and Z B is the axial coordinate of point B, and remove the tool setting ruler;

[0036] S8, calculate the axial offset distance L' between points B and A = Z B - Z A - L 0-Z E +Z S -FIX((Z B -Z A -L 0 -Z E +Z S ) / P)*P, -P < L' < P, where the function FIX((Z B -Z A -L 0 -Z E +Z S ) / P) represents taking the integer part of the value of (Z B -Z A -L 0 -Z E +Z S ) / P, or calculating the circumferential deviation r between the starting point E' of the tool required for turning repair and the starting point E of the tool set in the turning repair program 0C , r 0C = 360 * L' / P;

[0037] S9. In the working space of the CNC lathe, move the starting point E of the tool set in the turning repair program to the starting point E' of the tool required for turning repair to eliminate the axial offset distance L', or adjust the angular displacement of the starting point E of the tool set in the turning repair program to eliminate the circumferential deviation r 0C ;

[0038] S10. Run the adjusted turning repair program to machine the internal thread to be repaired with the starting point E' of the tool required for turning repair, the lead P, and the preset spindle speed to complete the turning repair of the internal thread to be repaired.

[0039] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

[0040] 1. When the above tool setting gauge is used, the body of the gauge can be perpendicular to the axis of the machine tool spindle. Move the vernier so that the positioning contact fits into the tooth groove of the internal thread. Clamp the inner and outer surfaces of the internal thread with the fixed gauge and the positioning contact. Move the tip of the repair tool to align with the tool setting groove, and the axial coordinate value of the repair tool can be read from the CNC machine tool. Since there is a fixed spacing L between the tool setting groove and the positioning contact in the direction parallel to the fixed gauge 0 , therefore, according to the axial coordinate of the repair tool read from the CNC machine tool and the spacing L 0 the axial coordinate value of the tooth groove that fits with the positioning contact can be calculated to facilitate the tool setting operation for internal thread repair.

[0041] 2. The above tool setting gauge further includes a locking member for locking the vernier on the body of the gauge. After the vernier is moved into place, lock the vernier on the body of the gauge through the locking member to prevent the vernier from accidentally moving relative to the body of the gauge during the tool setting process.

[0042] 3. For the above tool setting ruler, a positioning groove is further provided on the fixed ruler. The cross-section of the positioning groove is in the shape of an inverted equilateral trapezoid. The two contact lines formed by the two inclined groove surfaces of the equilateral trapezoid of the positioning groove and the outer wall of the workpiece, together with the contact point formed by the positioning contact head engaging with the internal thread, jointly constitute a positioning and clamping form of one point and two lines. This not only enables the axis of the workpiece to be parallel to the fixed ruler, which is beneficial to improving the positioning accuracy, but also makes the clamping of the workpiece more stable.

[0043] 4. For the above tool setting ruler, the positioning contact head forms a V-shaped cross-section with an included angle of 60 degrees on the plane where the ruler body and the fixed ruler are located, which is suitable for various thread tooth profiles with a flank angle equal to 1 / 2 of the thread profile angle. The tool setting groove forms a V-shaped cross-section with an included angle of 60 degrees on the plane where the ruler body and the fixed ruler are located. The symmetry axis of the V-shaped cross-section of the tool setting groove is parallel to the symmetry axis of the V-shaped cross-section of the positioning contact head, and it can be used to visually observe the fitting degree with the tool profile angle of the turning tool.

[0044] 5. After adopting the above method, it is possible to turn and repair internal threads with the same lead at a specific spindle speed, solve the tool setting problem during the repair of internal threads on a CNC lathe, without the need to find or mark the zero position of the spindle encoder, and can perform accurate tool setting at one time, making the repair of internal threads more convenient.

[0045] 6. For the above method of turning and repairing internal threads with the same lead at a specific spindle speed, by calculating the axial offset distance L', the position from point E to E’ can be adjusted with the smallest and most economical offset distance, further improving the efficiency of internal thread turning and repair.

[0046] 7. For the above method of turning and repairing internal threads with the same lead at a specific spindle speed, without relying on any external detection instruments and without any modification or refitting of the CNC machine tool, the cost is lower. It is generally applicable to CNC lathes with thread processing functions and applicable to various CNC systems, both straight threads and taper threads are applicable, and they can be used interchangeably, having general applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a front view structural schematic diagram of the tool setting ruler in a preferred embodiment of the present invention.

[0048] Figure 2 For Figure 1 the left view of the shown tool setting ruler.

[0049] Figure 3 For Figure 1 the bottom view structural schematic diagram of the shown tool setting ruler.

[0050] Figure 4 It is a three-dimensional structural schematic diagram of the tool setting ruler in a preferred embodiment of the present invention.

[0051] Figure 5 For Figure 4Schematic diagram of the three-dimensional structure of the tool setting ruler shown from another perspective.

[0052] Figure 6 Flowchart of the method for turning internal threads with the same lead at a specific spindle speed in the preferred embodiment of the present invention.

[0053] Figure 7 Schematic diagram of the principle of the method for turning internal threads with the same lead at a specific spindle speed in the preferred embodiment of the present invention, with the perspective being a top-down view of the horizontal plane where the CNC lathe spindle is located.

[0054] Figure 8 is Figure 7 Enlarged view of a part of the structure.

[0055] Figure 9 Schematic diagram of the structure of the tip part of the turning tool in the embodiment of the present invention.

[0056] Figure 10 Schematic diagram of the structure of the largest internal thread applicable to the tool setting ruler design in the embodiment of the present invention.

[0057] Figure 11 In the embodiment of the present invention, the positioning contact of the tool setting ruler and Figure 10 Schematic diagram of the structure when the positioning contact is engaged with the internal thread shown.

[0058] Figure 12 Schematic diagram of the structure when the positioning contact of the tool setting ruler is engaged with the smallest internal thread applicable to the tool setting ruler design.

[0059] In the drawings, 100 - tool setting ruler, 2 - ruler body, 4 - fixed ruler, 42 - positioning groove, 6 - vernier, 62 - sleeve, 64 - fixing plate, 65 - mounting hole, 7 - positioning contact, 8 - tool setting groove, 9 - locking member, 10 - knob, 200 - workpiece with internal thread to be repaired, 300 - machine tool spindle box; 400 - chuck; 500 - reference workpiece; 600 - turning tool. Detailed implementation manners

[0060] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0062] Please also refer to Figures 1 to 5 , a preferred embodiment of the present invention provides a tool setting ruler 100, which includes a ruler body 2, a fixed ruler 4 and a vernier 6.

[0063] In this embodiment, the ruler body 2 is generally in the shape of a long bar; the fixed ruler 4 is generally in the shape of a long plate, and is perpendicularly connected to the ruler body 2. In this embodiment, the fixed ruler 4 is connected to one end of the ruler body 2. It can be understood that in other embodiments, the fixed ruler 4 can also be connected to other parts of the ruler body 2, and the fixed ruler 4 can be connected to the ruler body 2 by means such as welding. A positioning groove 42 is recessed on one side of the fixed ruler 4, and one end of the positioning groove 42 also penetrates through the end of the fixed ruler 4 away from the ruler body 2, and the cross-section of the positioning groove 42 is in the shape of an inverted equilateral trapezoid.

[0064] Please refer to together Figures 7 to 9 , the vernier 6 is slidably connected to the ruler body 2, a positioning contact 7 is provided on the vernier 6, and the positioning contact 7 is used to engage with the tooth groove of the internal thread; a tool setting groove 8 is also provided on the vernier 6, and the tool setting groove 8 is used to position and repair the tool. In this embodiment, the tool to be repaired is a turning tool 600. The tool setting groove 8 and the positioning contact 7 have a fixed distance L in the direction parallel to the fixed ruler 4 0 . In this embodiment, the direction parallel to the fixed ruler 4 refers to the direction parallel to the length of the fixed ruler 4. Under the action of an external force, the vernier 6 can move towards the fixed ruler 4 so that the positioning contact 7 cooperates with the fixed ruler 4 to clamp the inner and outer surfaces of the internal thread.

[0065] The cursor 6 specifically includes a sleeve 62 and a fixing plate 64 connected to the sleeve 62. Both the sleeve 62 and the fixing plate 64 are sleeved on the scale body 2. The fixing plate 64 is parallel to the fixed scale 4. Specifically, the cursor 6 is provided with a through mounting hole 65. The mounting hole 65 extends from the sleeve 62 to the fixing plate 64. The sleeve 62 and the fixing plate 64 are sleeved on the scale body 2 through the mounting hole 65. In this embodiment, the cross-section of the scale body 2 is square, and the cross-section of the mounting hole 65 is a square structure matching the cross-section of the scale body 2. When the scale body 2 is inserted into the mounting hole 65, through the cooperation of the square cross-section of the scale body 2 and the mounting hole 65, it is possible to prevent the cursor 6 from rotating relative to the scale body 2 when moving the cursor 6, so as to further improve the positioning accuracy. In this embodiment, the fixing plate 64 is connected to one end of the sleeve 62 close to the fixed scale 4 and is integrally formed with the sleeve 62. It can be understood that in other embodiments, the fixing plate 64 and the sleeve 62 can also be connected together by means such as screw connection.

[0066] The positioning contact 7 and the tool setting groove 8 are both arranged on the fixing plate 64 and are respectively located on opposite sides of the scale body 2. The positioning contact 7 protrudes from the side of the fixing plate 64 facing the fixed scale 4 and is on the same side of the scale body 2 as the fixed scale 4. The positioning contact 7 forms a V-shaped cross-section with an included angle α of 60 degrees on the plane where the scale body 2 and the fixed scale 4 are located. The top end of the V-shaped cross-section of the positioning contact 7 close to the fixed scale 4 is an arc end. The tool setting groove 8 is recessed on the side of the fixing plate 64 facing away from the fixed scale 4. The tool setting groove 8 forms a V-shaped cross-section with an included angle β of 60 degrees on the plane where the scale body 2 and the fixed scale 4 are located. The axis of symmetry of the V-shaped cross-section of the tool setting groove 8 is parallel to the axis of symmetry of the V-shaped cross-section of the positioning contact 7 and is perpendicular to the length direction of the fixed scale 4. In this embodiment, the positioning contact 7 is integrally formed with the fixing plate 64. It can be understood that in other embodiments, the positioning contact 7 and the fixing plate 64 can also be connected together by means such as bonding. The positioning contact 7 is opposite to the positioning groove 42, and the center of the positioning contact 7 points to the central axis of the positioning groove 42.

[0067] The tool setting ruler 100 further includes a locking member 9 for locking the cursor 6 on the scale body 2. In this embodiment, the locking member 9 is a locking screw. The locking screw is threadedly connected to the sleeve 62 of the cursor 6 and is located on the side of the sleeve 62 facing away from the positioning contact 7 to be more conducive to operation. One end of the locking screw can extend into the mounting hole 65 of the sleeve 62 and abut against the scale body 2 to lock the cursor 6 on the scale body 2; the other end of the locking screw is located outside the cursor 6 and is fixed with a knob 10 for facilitating the rotation of the locking screw.

[0068] When the above tool setting ruler 100 is used, the ruler body 2 can be perpendicular to the spindle axis of the machine tool, so that the tool setting groove 8 is located outside the workpiece 200. Rotate the locking screw so that one end of the locking screw is disengaged from the ruler body 2. Move the cursor 6 in the direction of the fixed ruler 4 so that the positioning contact 7 of the cursor 6 engages with a certain tooth groove of the internal thread. Then move the ruler body 2 and the fixed ruler 4 so that the fixed ruler 4 and the positioning contact 7 clamp the inner and outer surfaces of the internal thread, thereby fixing the tool setting ruler 100 on the workpiece 200 with the internal thread to be repaired. At this time, the outer surface of the workpiece 200 with the internal thread to be repaired abuts against the inner wall of the positioning groove 42, and the internal thread of the workpiece 200 with the internal thread to be repaired abuts against the positioning contact 7. Please also refer to Figures 10 to 12 , in this embodiment, the workpiece 200 is an oil internal thread pipe, Figure 10 is the largest internal thread applicable to the design of the tool setting ruler 100 in this embodiment. The bottom arc radius R of its internal thread 0 = 0.965 mm, Figure 11 is the fitting situation of the positioning contact 7 with the Figure 10 shown internal thread. It can be seen from the figure that the bottom arc radius R of the internal thread 0 determines the application upper limit of the tool setting ruler 100. As long as the arc radius R1 of the positioning contact 7 of the tool setting ruler 100 is not less than the bottom arc radius of the internal thread, it can ensure that the positioning contact 7 coincides with the symmetric center of the internal thread tooth groove. Preferably, in this embodiment, the arc radius R1 of the positioning contact 7 = 1.00 mm. Figure 12 is the lower limit applicable to the tool setting ruler 100 in this embodiment. From Figure 12 it can be seen that the determining condition is the chord length of the arc end of the positioning contact 7. As long as the chord length of the arc end of the positioning contact 7 is not greater than the top pitch of the internal thread, it can ensure that the positioning contact 7 coincides with the symmetric center of the internal thread tooth groove. Among them,

[0069] the chord length of the arc end of the positioning contact 7: L = R1 * cos[30°] * 2 = 1.732 mm; for the national standard straight thread, the top pitch of the thread = 7 / 8 lead, so the lower limit of the tool setting ruler 100 is an internal thread pipe with a pitch of 1.732 * 8 / 7 = 1.979 ≈ 2.000.

[0070] In this embodiment, the normal use range of the tool setting ruler 100 is the above upper and lower limits. The designed range has included most of the commonly used oil pipe internal threads (the lead range is 11.5 - 4 teeth per inch, that is, the pitch is 2.21 - 6.35 mm). If it is necessary to use the tool setting ruler 100 for internal threads with other pitches, the cursor 6 can be replaced to realize the cooperation with internal threads of different pitches, or the positioning contact 7 can be designed to be detachably connected to the fixing plate 64 by means of screws, plugging, etc. When needed, the positioning contact 7 can be replaced to realize the cooperation with internal threads of different pitches.

[0071] Rotate the locking screw so that one end of the locking screw abuts against the scale body 2; move the tip of the turning tool 600 to align with the tool setting groove 8, and the axial coordinate value of the turning tool 600 can be read from the numerical control machine tool. Since the tool setting groove 8 is located outside the workpiece 200, it does not affect the movement of the turning tool 600 and is convenient for the operator to observe the position of the turning tool 600. Also, since there is a fixed spacing L between the tool setting groove 8 and the positioning contact 7 in the direction parallel to the fixed scale 4 0 , therefore, based on the axial coordinate of the turning tool 600 read from the numerical control machine tool and the said spacing L 0 the axial coordinate value of the internal thread tooth groove engaged with the positioning contact 7 can be calculated to facilitate the tool setting operation for internal thread repair.

[0072] The above-mentioned tool setting ruler 100 further includes a locking member 9 for locking the cursor 6 on the scale body 2. After moving the cursor 6 to the required position, the cursor 6 is locked on the scale body 2 through the locking member 9 to prevent the cursor 6 from accidentally moving relative to the scale body 2 during the tool setting process.

[0073] For the above-mentioned tool setting ruler 100, a positioning groove 42 is further provided on the fixed scale 4. The cross-section of the positioning groove 42 is in the shape of an inverted equilateral trapezoid. When the tool setting ruler 100 is used for the internal thread turning and repair of a cylindrical workpiece 200, the two inclined groove surfaces enclosing the equilateral trapezoid can abut against the outer circumference of the workpiece 200 and contact the outer circumference line of the workpiece 200. The two contact lines formed by the two inclined groove surfaces of the equilateral trapezoid of the positioning groove 42 and the outer wall of the workpiece 200, together with the contact point formed by the engagement of the positioning contact 7 with the internal thread, jointly constitute a positioning and clamping form of one point and two lines. This can not only keep the axis of the workpiece 200 parallel to the fixed scale 4, which is beneficial to improving the positioning accuracy, but also make the clamping of the workpiece 200 more stable. In addition, by abutting the two inclined groove surfaces enclosing the equilateral trapezoid against the outer circumference of the workpiece 200, when the outer diameter of the workpiece 200 changes, the position of the workpiece 200 in the positioning groove 42 can be adjusted to ensure that the workpiece 200 remains in contact with the two inclined groove surfaces of the positioning groove 42. Therefore, the fixed scale 4 can be applied to workpieces 200 with different outer diameters.

[0074] For the above-mentioned tool setting ruler 100, the positioning contact 7 forms a V-shaped cross-section with an included angle of 60 degrees on the plane passing through the scale body 2 and the fixed scale 4, which is suitable for various thread tooth profiles with a flank angle equal to 1 / 2 of the thread profile angle. The tool setting groove 8 forms a V-shaped cross-section with an included angle of 60 degrees on the plane passing through the scale body 2 and the fixed scale 4. The axis of symmetry of the V-shaped cross-section of the tool setting groove 8 is parallel to the axis of symmetry of the V-shaped cross-section of the positioning contact 7, and can be used to visually observe the degree of engagement with the thread profile angle of the turning tool 600.

[0075] For the above-mentioned tool setting ruler 100, the positioning contact 7 and the tool setting groove 8 are respectively located on opposite sides of the scale body 2, which can avoid the influence of the scale body 2 on the movement of the turning tool 600 and is more conducive to the tool setting operation.

[0076] Please also refer to Figures 1 to 8 , the present invention also provides a method for turning internal threads with the same lead at a specific spindle speed, including the following steps:

[0077] S1, at a preset spindle speed, with the tool starting point S[X S ,Z S , turn a reference helix on the outer surface of a reference workpiece 500, as shown in (a) of Figure 7 . The lead of the reference helix is the same as the lead P of the internal thread to be repaired. The coordinate values of the tool starting point S[X S ,Z S are set by the turning program, where X S is the radial coordinate of point S, and Z S is the axial coordinate of point S.

[0078] In step S1, preferably, the center of the end of the reference workpiece 500 away from the chuck 400 is taken as the zero point of the coordinate system to facilitate subsequent coordinate calculations. Preferably, the reference helix is an external thread to facilitate the positioning of the turning tool 600; the reference workpiece 500 is a workpiece that can turn a helix with a visual length of not less than 2 times the lead P to facilitate subsequent operations; the helix refers to the trajectory left by the center point of the tip of the turning tool 600 on the workpiece surface; the spindle speed is set according to actual needs.

[0079] S2, position the tip of the turning tool 600 at point A[X A ,Z A , where X A is the radial coordinate of point A, and Z A is the axial coordinate of point A, and Z A makes the tip located at any position in the middle of the reference helix. The coordinate values of point A[X A ,Z A can be directly obtained from the CNC lathe. Preferably, the radial coordinate X A of point A makes the radial position of the tip greater than the major diameter of the reference helix at point A to prevent the turning tool 600 from colliding with the reference workpiece 500 and causing damage to the turning tool 600 or the reference workpiece 500.

[0080] S3, rotate the spindle to an angular position that makes the tip point to the reference helix, and mark or memorize this angular position.

[0081] In step S3, the spindle can be manually rotated to the angular position; after the spindle is rotated to the angular position, marks can be made on the machine tool spindle box 300 and the chuck 400 with a marker pen or the like to mark this angular position. Specifically, a mark F can be made on the machine tool spindle box 300, and a mark G can be made on the chuck 400. The mark F and the mark G are on the same horizontal line, as shown inFigure 4 in (a) thereof; or memorize the relative position features of the machine tool headstock 300 and the chuck 400.

[0082] S4. Remove the reference workpiece 500 from the chuck 400 of the CNC lathe.

[0083] S5. Install the workpiece 200 with the internal thread to be repaired on the chuck 400, as shown in (b) thereof, and rotate the main shaft to the said angular position. The tool starting point set in the turning program for the internal thread to be repaired is E[X Figure 7 ,Z E ,Z E , where X E is the radial coordinate of point E, and Z E is the axial coordinate of point E. The lead of the internal thread to be repaired is P. The coordinate values of point E[X E ,Z E can be directly obtained from the turning program of the internal thread to be repaired.

[0084] In step S5, when installing the workpiece 200 with the internal thread to be repaired, the main shaft will rotate and its angular position will change. Therefore, after installing the workpiece 200 with the internal thread to be repaired, it is necessary to rotate the main shaft so that the mark F marked on the machine tool headstock 300 and the mark G marked on the chuck 400 are again on the same horizontal line to position the main shaft to the said angular position. The rotation of the main shaft can be carried out manually.

[0085] Preferably, after installing the workpiece 200 with the internal thread to be repaired on the chuck 400, the workpiece 200 with the internal thread to be repaired is preferably corrected so that the central axis of the internal thread to be repaired coincides with the central axis of the main shaft of the CNC lathe, thereby further improving the accuracy of thread repair.

[0086] S6. Provide a tool setting ruler 100, make the ruler body 2 perpendicular to the axis of the main shaft of the CNC lathe, and make the tool setting groove 8 outside the workpiece 200 with the internal thread to be repaired. Move the vernier 6 so that the positioning contact 7 of the vernier 6 engages with one of the tooth grooves of the internal thread to be repaired, and clamp the inner and outer surfaces of the internal thread by using the fixed ruler 4 and the positioning contact 7.

[0087] S7. Move the turning tool 600 so that the tip of the turning tool 600 is positioned at point B[X B ,Z B and points to the center of the tool setting groove 8, where X B is the radial coordinate of point B, and Z B is the axial coordinate of point B. X B and Z B can be directly obtained from the CNC lathe, and remove the tool setting ruler 100.

[0088] In step S7, the steps for removing the tool setting ruler 100 are as follows: Loosen the locking member 9, move the fixed ruler 4 away from the workpiece 200, adjust the position of the vernier 6 so that the tool setting groove 8 is disengaged from the tool tip, and disengage the positioning contact 7 from the tooth groove of the internal thread. After that, the tool setting ruler 100 can be removed from the workpiece 200 with the internal thread to be repaired.

[0089] S8. Calculate the axial offset distance L' between points B and A, where L' = Z B - Z A - L 0 - Z E + Z S - FIX((Z B - Z A - L 0 - Z E + Z S ) / P) * P, where - P < L' < P. In the formula, the function FIX((Z B - Z A - L 0 - Z E + Z S ) / P) represents taking the integer part of the value of (Z B - Z A - L 0 - Z E + Z S ) / P, or calculate the circumferential deviation r between the starting point E' of the tool required for turning repair and the starting point E of the tool set in the turning repair program 0C , r 0C = 360 * L' / P.

[0090] The reason why turning repair of threads is a relatively difficult problem in the application of CNC lathes is mainly that after each internal thread to be repaired is installed on the CNC lathe, the angle of the actual starting point of its thread (relative to the angle of the "main spindle zero position signal") is different for each one, with randomness, and it is not easy to obtain this starting point conveniently and economically. Any angle position within the 360 - degree range of the main spindle circumference is possible. If this starting point cannot be found or accurately located, turning repair cannot be carried out. Therefore, technicians apply various advanced technologies and think of various ways to find this position. For example, methods such as using CCD cameras, magnetic induction, laser ranging, infrared rays, self - made measuring tools, and modifying CNC machine tools are used, resulting in high cost and complex methods for thread turning repair. The significant difference in the idea between this method and other existing technologies is: taking a shortcut and using "comparing with the known" to bypass "measuring the unknown". Specifically, first determine an angular position of the main spindle (i.e., the angular position marked by F - G), compare with point B on each internal thread to be repaired at this position to obtain the deviation, and then eliminate the deviation to achieve tool setting of the CNC lathe.

[0091] S9. In the working space of the CNC lathe, move the tool starting point E set in the turning and threading program to the required tool starting point E' for turning and threading to eliminate the axial offset distance L', or adjust the angular displacement of the tool starting point E set in the turning and threading program to eliminate the circumferential deviation r. 0C 。

[0092] In step S9, for a CNC lathe without macro program function, eliminate the axial offset distance L' by translating the coordinate system or adding tool compensation. For a machine tool with macro program function, various methods can be used, such as translating the coordinate system, adding tool compensation, adjusting the position or angular offset of the tool starting point E set in the turning and threading program in the turning and threading program, setting and calling local coordinate systems G54 - G59, etc. Any of these methods can be used to move the tool starting point E set in the turning and threading program or adjust the angular displacement of the tool starting point E set in the turning and threading program. By using any method to eliminate the axial offset distance L' or circumferential deviation r 0C to ensure that the tip trajectory of the turning tool 600 coincides with the trajectory of the internal thread to be repaired.

[0093] S10. Run the adjusted turning and threading program to machine the internal thread to be repaired with the required tool starting point E', lead P and the preset spindle speed to complete the turning and threading of the internal thread to be repaired. In step S10, the spindle speed during the turning and threading of the internal thread to be repaired is the same as that in step S1.

[0094] If the number of workpieces with internal threads to be repaired is two or more, only need to repeat steps S5 - S10 until the turning and threading of all workpieces is completed.

[0095] The technical principle of the method for turning internal threads with the same lead at a specific spindle speed is as follows:

[0096] In the machine tool space, the spiral trajectory of a specific lead thread is determined by the tool starting point and the spindle speed. At a certain specific spindle speed, any point on the spiral trajectory has a fixed axial and circumferential position relationship relative to the tool starting point. Thus, with a certain fixed point with specific position attributes on the known thread as a reference, find a point with similar attributes to this fixed point on the internal thread to be repaired through the tool setting gauge 100, and the required tool starting point for turning the internal thread to be repaired can be calculated.

[0097] Based on the above principle, any method can be used to adjust the coordinate or angular displacement of the tool starting point set in the turning and threading program to achieve the purpose of making the tip trajectory of the turning tool coincide with the trajectory of the internal thread to be repaired.

[0098] For easy understanding, a specific example provided by the embodiment of the present invention is given below:

[0099] Preparation work:

[0100] 1. Taking the Fanuc numerical control system as an example

[0101] 2. The internal thread cutting tool is No. 3, accurately set the tool, and the tool offset is No. 15

[0102] 3. Prepare a tool that can externally display the position of the internal thread tooth groove. In this example, a "tool setting ruler" is used, and the distance L from the center of the positioning contact to the center of the tool setting groove 0 = 127 mm

[0103] 4. Prepare a practical and reliable internal thread machining program with a lead of 6.35. Set the tool starting point Z E = 12.7, the spindle speed during thread turning is 150 revolutions per minute, and write "M98P9999;" before all codes in the original program

[0104] 5. Write the following codes into the new program O9999

[0105] O9999;

[0106] #502 = 6.35; (thread lead / pitch)

[0107] #503 = 12.7; (refer to the axial coordinate Z of the tool starting point in the thread axis direction S )

[0108] #504 = -50.8; (axial coordinate Z corresponding to the chuck marking angle position point A )

[0109] #510 = 127; (tool setting ruler L 0 = 127 mm)

[0110] #2601 = 0; (eliminate the workpiece coordinate system Z-direction offset of the previous part)

[0111] #1 = #5022; (transfer the current axial coordinate Z B to #1)

[0112] #2 = #1 - #504 - #510 - FIX[[#1 - #504 - #510] / #502]*#502; (calculate the axial offset distance L')

[0113] #2601 = #2; (workpiece coordinate system Z-direction offset)

[0114] G0U-20; (the turning tool moves away from the thread to be repaired in the X direction

[0115] W300; (the turning tool moves away from the thread to be repaired in the Z direction

[0116] M99; (return to the turning and repairing program

[0117] 6. Prepare a reference workpiece. There is no special requirement for the diameter of the reference workpiece. For example, an oil casing with a diameter of Φ139.7 mm and a length of 200 mm.

[0118] 7. Turn a non-tapered helix with a lead of 6.35 mm on the outer surface of the reference workpiece at 150 revolutions per minute. The visually visible length is not less than 12.7 mm. The starting point of the tool is (139, 12.7). Stop the main spindle and move the tool tip to (141, -50.8).

[0119] 8. Rotate the main spindle until the tool tip points to the helix, and mark the current chuck angle position F - G (you can mark F - G with a marker pen or remember the characteristics of the current chuck angle position), then remove the reference workpiece.

[0120] Implementation steps:

[0121] 1. Install and align the internal thread to be repaired, and rotate the chuck to the marked position F - G.

[0122] 2. Install a tool setting ruler in the horizontal plane of the main spindle, so that the positioning contact touches any two adjacent teeth of the internal thread simultaneously (the contact has no axial movement space), and clamp the side wall of the internal thread with the positioning ruler.

[0123] 3. Call the No. 3 internal thread tool with tool offset No. 15, move the turning tool until the center of the tool tip points to the center of the V-shaped tool setting groove of the tool setting ruler, and stop at this position.

[0124] 4. Remove the tool setting ruler.

[0125] 5. Run the internal thread machining program.

[0126] After adopting the above method, it is possible to machine repair the internal thread with the same lead at a specific main spindle speed, solve the tool setting problem of the internal thread in the numerical control lathe repair, without the need to find or mark the zero position of the main spindle encoder, and can perform accurate tool setting at one time, making the repair of the internal thread more convenient; when using this method to repair the internal thread, there is no need to rely on any external detection instruments, and there is no need to modify or refit the numerical control machine tool, with low cost; when using this method to repair the thread, it can perform accurate tool setting at one time, without the need to find or mark the zero position of the main spindle encoder, and adjust the tool position in the machine tool space without modifying the original program, making the repair more convenient; this method is generally applicable to numerical control lathes with thread machining functions and is applicable to various numerical control systems, with general applicability. For numerical control systems with macro program functions, there is no need to manually record, input data and calculate, which is more convenient to use; this method is not affected by tapered threads and has better versatility.

[0127] It can be understood that the shapes of the cursor 6, the scale body 2 and the fixed scale 4 are not limited to this embodiment and can be deformed accordingly as needed.

[0128] It can be understood that the shape of the scale body 2 is not limited to the square rod shape of the present embodiment. For example, in other embodiments, the scale body 2 can be a round rod shape, and the mounting hole 65 is correspondingly a cylindrical through hole. The scale body 2 passes through the mounting hole 65. At this time, a guide rail extending along the length direction of the scale body 2 can also be provided on the scale body 2, and a guide groove slidably matched with the guide rail is provided on the inner wall surrounding the mounting hole 65. Through the cooperation of the guide groove and the guide rail, the movement of the cursor 6 can be guided, and the cursor 6 can be prevented from rotating relative to the scale body 2 to further improve the tool setting accuracy.

[0129] It can be understood that the locking member 9 is not limited to the locking screw of the present embodiment. For example, in other embodiments, when the cursor 6 moves into place, a clamp can be provided at one end of the sleeve 62 away from the fixed plate 64, and the clamp is clamped on the scale body 2 to prevent the cursor 6 from accidentally moving away from the fixed scale 4.

[0130] It can be understood that in other embodiments, a rubber pad can also be laid on the side wall surrounding the positioning groove 42 to increase the friction force on the workpiece 200, prevent relative sliding between the groove surface surrounding the positioning groove 42 and the outer wall of the workpiece 200 after being pressed into contact, make the clamping more stable, and the rubber pad has elasticity and can elastically deform with the size of the workpiece 200 to better cooperate with the positioning contact 7 to clamp the workpiece 200.

[0131] It can be understood that the structure and shape of the fixed scale 4 are not limited to the present embodiment. For example, in other embodiments, the fixed scale 4 can be just a flat plate as long as it can cooperate with the positioning contact 7 to clamp the inner and outer surfaces of the internal thread.

[0132] It can be understood that the workpiece 200 is not limited to the petroleum internal thread pipe in the present embodiment, and it can also be other workpieces with internal threads.

[0133] The above description is a detailed description of the preferred and feasible embodiments of the present invention, but the embodiments are not intended to limit the patent application scope of the present invention. Any equivalent changes or modifications completed under the technical spirit disclosed by the present invention shall fall within the patent scope covered by the present invention.

Claims

1. A tool setting ruler for internal thread repair, characterized in that: The tool setting ruler includes a ruler body, a fixed ruler and a vernier. The fixed ruler is vertically connected to the ruler body. The vernier is slidably connected to the ruler body. A positioning contact is provided on the vernier for engaging with the tooth groove of the internal thread. A tool setting groove is also formed on the vernier for positioning and repairing the tool. The tool setting groove and the positioning contact have a fixed spacing L in the direction parallel to the fixed ruler. 0 Under the action of an external force, the vernier can move towards the fixed ruler so that the positioning contact cooperates with the fixed ruler to clamp the inner and outer surfaces of the internal thread. The vernier includes a sleeve and a fixing plate connected to the sleeve. The ruler body passes through the sleeve and the fixing plate. The positioning contact and the tool setting groove are both provided on the fixing plate and are respectively located on opposite sides of the ruler body. The tool setting ruler further includes a locking member for locking the vernier on the ruler body.

2. The tool setting ruler according to claim 1, characterized in that: The positioning contact protrudes from one side of the fixed plate facing the fixed scale, and the tool setting groove is recessed on the side of the fixed plate facing away from the fixed scale.

3. The tool setting ruler according to claim 2, characterized in that: The positioning contact forms a V-shaped cross-section with an included angle of 60 degrees on the plane where the body of the ruler and the fixed scale are located. The end of the V-shaped cross-section of the positioning contact close to the fixed scale is an arc end; the tool setting groove forms a V-shaped cross-section with an included angle of 60 degrees on the plane where the body of the ruler and the fixed scale are located. The axis of symmetry of the V-shaped cross-section of the tool setting groove is parallel to the axis of symmetry of the V-shaped cross-section of the positioning contact and is perpendicular to the fixed scale.

4. The tool setting ruler according to claim 1, characterized in that: The positioning contact is detachably connected to the fixed plate.

5. The tool setting ruler according to any one of claims 1-4, characterized in that: A positioning groove is further recessed on one side of the fixed scale facing the positioning contact, and one end of the positioning groove penetrates through the end of the fixed scale away from the body of the ruler.

6. The tool setting ruler according to claim 5, characterized in that: The cross-section of the positioning groove is in the shape of an inverted equilateral trapezoid, and the center of the positioning contact points to the central axis of the positioning groove.

7. The tool setting ruler according to claim 5, characterized in that: A rubber pad is laid on the groove surface surrounding the positioning groove.

8. A method for turning internal threads with the same lead at a specific spindle speed, characterized in that, comprising the following steps: S1. At a preset spindle speed, starting from the tool starting point S[X S ,Z S , machine a reference helical line on the outer surface of a reference workpiece. Here, X S is the radial coordinate of point S, and Z S is the axial coordinate of point S. The lead of the reference helical line is the same as the lead P of the internal thread to be repaired; S2, position the tip of the turning tool at point A[X A ,Z A ], where X A is the radial coordinate of point A, Z A is the axial coordinate of point A, Z A Make the tool tip be located at any position in the middle of the reference helix; S3, rotate the spindle to an angular position, which makes the cutting edge point to the reference helix, mark or memorize this angular position; S4, remove the reference workpiece from the chuck of the CNC lathe; S5. Install the workpiece with the internal thread to be repaired on the chuck, and rotate the main shaft to the said angular position. The tool starting point set in the internal thread turning repair program is E[X E ,Z E , where X E is the radial coordinate of point E, and Z E is the axial coordinate of point E; S6, provide the tool setting ruler according to claim 1, make the body of the ruler perpendicular to the axis of the spindle of the CNC lathe, and make the tool setting groove located outside the workpiece with the internal thread to be repaired. Move the cursor so that the positioning contact of the cursor fits into one of the tooth grooves of the internal thread to be repaired, and use the fixed scale and the positioning contact to clamp the inner and outer surfaces of the internal thread; S7, move the turning tool to position the tip of the turning tool at point B[X B ,Z B and point it towards the center of the tool setting groove, where X B is the radial coordinate of point B, and Z B is the axial coordinate of point B. Remove the tool setting ruler; S8, calculate the axial offset distance L' between points B and A = Z B -Z A -L 0 -Z E +Z S -FIX((Z B -Z A -L 0 -Z E +Z S ) / P)*P, -P < L' < P, where the function FIX((Z B -Z A -L 0 -Z E +Z S ) / P) represents taking the integer part of the value of (Z B -Z A -L 0 -Z E +Z S ) / P, or calculate the circumferential deviation r between the starting point E' of the tool required for turning repair and the starting point E of the tool set in the turning repair program 0C , r 0C = 360 * L' / P; S9. Move the tool starting point E set by the turning and dressing program to the required tool starting point E' in the working space of the CNC lathe to eliminate the axial offset distance L', or adjust the angular displacement of the tool starting point E set by the turning and dressing program to eliminate the circumferential deviation r 0C ; S10, run the adjusted turning program, and machine the internal thread to be repaired with the starting point E' of the turning tool, the lead P and the preset spindle speed to complete the turning of the internal thread to be repaired.

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