A method for detecting a tooth preparation for a thread-rolling system, a thread-rolling system and use

Abstract

This invention discloses a method, system, and application for inspecting the trimming of extruded threads. The method utilizes an impedance reference template bound to the material and tap index to simultaneously collect the steady-state AC impedance of each chip removal groove at different thread depths. Deviations are calculated according to groove weights, and two threshold levels are set to generate local or overall anomaly markers. Subsequently, the length and number of continuous intervals of the anomaly markers are statistically analyzed by region to obtain the overall thread quality assessment result. This invention enables real-time, non-destructive testing of the tooth crest trimming quality during the trimming process without affecting the machining cycle, avoiding batch rework or scrap caused by subsequent sampling inspections. It is suitable for mass production of threads with high-quality requirements.

Description

Technical Field

[0001] This invention relates to the field of online inspection technology for metal cutting processes, and in particular to a method for inspecting the repair of extruded threads, an extruded thread system, and its application. Background Technology

[0002] Extrusion threading is a cold forming technology that uses a specialized extrusion tap to force threads into metal materials. During extrusion, the material undergoes plastic deformation, and the thread profile is formed through the flow and redistribution of the material. The extrusion threading process can produce material accumulation and discontinuities at the thread crest, manifesting as out-of-tolerance thread crest dimensions, surface burrs, and localized material non-density. These defects directly affect the thread's fit accuracy and connection reliability; therefore, subsequent thread trimming processes are necessary to precisely trim the thread crest to meet design requirements and usage standards.

[0003] In related technologies, the thread trimming process for extruded threads uses a special tap to cut the threads, removing excess material and burrs from the tooth crests to achieve standard dimensional requirements. During this process, quality inspection primarily relies on offline testing after machining, including using thread gauges and coordinate measuring machines to measure and evaluate the thread's geometric parameters and surface quality. Because inspection is conducted after the entire machining process is complete, when thread quality defects are discovered, not only is the individual workpiece beyond repair, but more importantly, if the quality problem stems from systemic factors such as improper process parameter settings or abnormal tool conditions, multiple workpieces in the same batch may exhibit the same defect. This post-production inspection mechanism cannot detect and correct quality problems in their early stages, thus posing a potential risk of batch scrap. This is particularly problematic in the machining of high-value parts, such as those for aerospace applications, where batch scrap can cause significant economic losses and delivery delays. Summary of the Invention

[0004] The main objective of this invention is to solve the risk of batch defects caused by traditional post-processing inspection mechanisms, and to achieve early identification and timely intervention of processing quality abnormalities.

[0005] Firstly, in order to solve the above-mentioned technical problems, the present invention provides a method for detecting the repair of extruded threads, comprising: Call the impedance reference template corresponding to the specified material grade and tap number in the database. The impedance reference template includes the AC impedance reference value of each chip removal groove at different dental restoration depths. During the dental restoration process, the real-time AC impedance values ​​of each chip removal groove at the current restoration depth are acquired simultaneously to form a real-time impedance dataset. The real-time impedance dataset is compared with the impedance reference template, and the impedance deviation value of each chip removal groove is calculated. When the impedance deviation value of a single chip removal groove at the same dental restoration depth is greater than the first threshold and the average impedance deviation value of multiple chip removal grooves is not greater than the second threshold, a local abnormality mark is generated. When the average impedance deviation value of multiple chip removal grooves is greater than the second threshold, an overall abnormality mark is generated, thus obtaining the quality status mark of each dental restoration depth. Within the entire dental restoration depth range, the quality status markers are statistically analyzed. When the length of the continuous interval and the total number of abnormal markers are both within the preset range, a thread qualification judgment is output; otherwise, a non-qualification judgment is output.

[0006] Secondly, the present invention provides an extrusion thread system, wherein the extrusion thread system employs the extrusion thread repair detection method of the above embodiment.

[0007] Thirdly, the present invention provides an application of extruded threads, wherein the application of extruded threads employs the thread repair and inspection method of the extruded threads described in the above embodiments.

[0008] The technical solution provided in this application first calls an impedance reference template from the database that matches the workpiece material and tap number. Since the template is generated from qualified samples under standard processes and normalized, it records the electrical "health curves" of the chip removal grooves at each thread depth, thus providing a quantifiable reference for subsequent measurement of the machining status. Next, during machining, the steady-state AC impedance values ​​of each chip removal groove are synchronously collected according to the spindle rotation angle and assembled in real time into a depth-groove matrix, ensuring a one-to-one correspondence between the actual cutting position, impedance information, and the time axis. By comparing the measured data point-by-point with the reference template, the deviation of a single groove and the difference between this deviation and the average value of multiple grooves at the same depth can be obtained. If the deviation of a single groove exceeds the first numerical threshold while the average deviation remains within the normal range, it can be inferred that the defect is limited to the local thread ring corresponding to a single groove. If the average deviation of multiple grooves simultaneously crosses the second numerical threshold, it indicates an abnormal overall cutting load, most likely caused by tool wear or cooling failure. Through this local-overall dual-layer interpretation, the method can mark the abnormal depth range before the tool leaves the threaded hole and immediately enter the next sampling cycle, without waiting for the entire part to be machined before gauge inspection.

[0009] After the detection process is completed, the system maps the anomalies marked at consecutive depths into visible sections and compares them with the total thread depth. Only when both the length and the cumulative number of the anomalous sections fall within the preset window is the thread determined to be qualified; otherwise,不合格 is immediately output and the specific depth coordinates are given. In this way, any dimensional drift or burr residue that generates electrical deviations in the initial stage will be captured, enabling the operator to stop the machine for maintenance or adjust the cooling within the processing rhythm of the same machine and the same workpiece, rather than discovering defects only after post-mortem disassembly and sampling inspection. During mass production, this method synchronizes detection and cutting coaxially, eliminating the information lag caused by traditional off-line inspection, avoiding the spread of multiple consecutive defects into a whole batch of rejects from the source, and significantly reducing the invisible costs of rework and tool change. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 FIG. is a schematic diagram of an embodiment of the tooth repair detection method for extrusion threads in an embodiment of the present invention; Figure 2 FIG. is a schematic structural diagram of a cutting tap of an extrusion thread system in an embodiment of the present invention; Figure 3 is Figure 2 a schematic structural diagram of another perspective of the cutting tap of; Figure 4 is Figure 3 a partial enlarged view of part A in; Figure 5 is a metallographic diagram of the thread of the workpiece to be machined (the state before tooth repair of the thread).

[0011] DESCRIPTION OF THE REFERENCE NUMERALS IN THE DRAWINGS: 1. connecting section; 2. cutting section; 21. chip removal surface; 211. chip removal groove; 22. thread surface; 221. cutting thread part; 3. guiding section; 31. guiding thread part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work shall fall within the protection scope of the present invention.

[0013] Specifically, extrusion threading belongs to a cold forming process: when the extrusion tap is screwed into the pre-drilled hole, with the help of high contact pressure and material plastic flow, the metal is pushed along the tooth groove direction and filled into the tooth profile cavity, thereby obtaining an internal thread with continuous fiber streamline and dense surface at one time. Since the metal flows out in an over-arching shape at the tooth tip, after forming, problems such as over-tolerance of tooth tip height, local sharp spurs and metal accumulation often occur, as shown in the attached Figure 5As shown. If these protrusions are not leveled, they will cause stress concentration and reduce fatigue life when the engagement screw is screwed in. Therefore, after the extrusion is completed, a special cutting tap should be used to lightly trim the teeth so that the tooth tip is restored to the designed cylindrical surface and the burrs are removed.

[0014] Thread trimming is essentially a precision finishing operation of extruded threads, typically performed using specialized cutting taps. During the trimming process, the cutting tap is screwed into the extruded thread hole, and its cutting teeth lightly cut the protruding portion of the thread crest at a preset cutting depth. This material removal process shapes the irregular metal buildup into a standard cylindrical profile. In this process, the removed metal chips are discharged through the tap's chip evacuation channels under the influence of coolant, creating a dynamic contact state between chips, coolant, and the channel wall. While this thread trimming process effectively improves the geometric accuracy and surface quality of the threads, minute fluctuations in cutting parameters, gradual changes in tool condition, and local differences in workpiece material can directly affect the trimming effect, making process control a crucial factor in ensuring final quality.

[0015] The thread finishing process itself does not guarantee that dimensions and surface quality will meet standards. Drifting operating parameters, tool wear, or fluctuations in coolant flow can all lead to insufficient cutting or blockage by long chips. Current practices typically involve sampling the workpiece after it is taken offline using gauges or coordinate measuring machines to determine whether to rework or scrap it. If the defect is systemic, such as tool chipping or cooling channel blockage, it is often only discovered after multiple parts have been machined, causing the entire batch of high-value parts to fail simultaneously, resulting in significant waste. Addressing the core issue of "lagging post-processing inspection and inability to identify anomalies early," this solution proposes a thread finishing inspection method for extruded threads, specifically including: Reference Figure 1 The impedance reference template corresponding to the specified material grade and tap number in the database is called. The impedance reference template includes the AC impedance reference value of each chip removal groove at different dental repair depths. In one embodiment of the present invention, the database is obtained through the following steps: Perform a reference tooth repair on the specified material and tap combination, and collect AC impedance values ​​for each chip removal groove at tooth repair depth intervals that are integer multiples of the thread pitch to obtain the original sequence of tooth repair depth-groove impedance. Based on the Rockwell hardness and coolant conductivity of the material, the original sequence of the repair depth-groove impedance is subjected to two-factor normalization to obtain the normalized impedance sequence. The mean and standard deviation of the normalized impedance sequence are calculated and curve smoothing is performed to obtain the impedance reference template; The impedance reference template is indexed and bound to the material grade, hardness range, coolant conductivity range, and cumulative tap cutting length, and then written into the database.

[0016] The following is a detailed description of the steps involved in the above embodiments: Select a standard workpiece whose quality has been confirmed to be acceptable by coordinate measuring machine (CMM), and perform a complete thread trimming operation using a cutting tap. In this scheme, a copper conductive layer with a thickness of 5-10 micrometers is deposited on the inner wall of each chip groove of the cutting tap through an electroplating process. A measuring electrode with a diameter of 0.1-0.2 mm is set at the bottom of the chip groove, and the electrode is connected to the signal interface of the tap shank through an insulated wire. The cutting tap is installed on the CNC machine tool spindle, and the impedance analyzer is connected to the signal interface through a rotary joint to ensure electrical connection during spindle rotation. The process parameters for the thread trimming operation are set to a spindle speed of 200-500 rpm and a feed rate equal to the thread lead value. During the thread trimming process, data is collected using the spindle encoder signal of the CNC system at fixed depth intervals set as integer multiples of the thread pitch. For standard metric threads, 1 pitch is selected as the basic interval. When the tap reaches the preset depth, the CNC system automatically stops the feed and starts the impedance measurement program. The impedance analyzer applies a 1kHz AC test signal to each chip groove, and simultaneously measures and records the impedance amplitude of each groove. After the measurement is completed, the feed continues to the next sampling point. The thread depth-groove impedance raw sequence refers to a three-dimensional data set that organizes multi-groove impedance data at each depth position according to the format of "depth coordinate-groove number-impedance value". The depth coordinate indicates the axial position of the thread, and the groove number distinguishes different chip removal grooves. Using an integer multiple of the thread pitch as the sampling interval ensures that the data acquisition points strictly correspond to the geometric periodic characteristics of the thread, avoiding the impact of sampling position deviation on the accuracy of subsequent impedance analysis.

[0017] Two-factor normalization is a data standardization method that eliminates the influence of variations in material hardness and coolant conductivity on impedance measurement results. First, a Rockwell hardness tester is used to test the hardness at 3-5 points on the unmachined surface of the workpiece, and the average value is taken as the representative hardness value for that workpiece. Then, a portable conductivity meter is used to directly measure the conductivity of the coolant in the coolant reservoir before the dental work begins. The formula for two-factor normalization is: Z norm =Z raw ×(H ref / H actual )×(C ref / C actual ), where Z norm Z represents the normalized impedance value. raw H represents the original measured impedance value. ref H represents the reference hardness value. actual This represents the current actual hardness value, C. ref C represents the reference conductivity value. actualThis represents the current actual conductivity value. The reference hardness value is selected from the median value in the standard specification for this material grade, and the reference conductivity value is selected from the standard value in the technical specifications of this coolant model. Normalization calculations are completed automatically by the data processing software. After the operator inputs the measured hardness and conductivity values, the system automatically corrects and calculates all the original data. The normalized impedance sequence is a standardized data sequence that has been corrected using a two-factor algorithm to eliminate the influence of differences in material hardness and fluctuations in coolant conductivity, ensuring the comparability of impedance data for different batches of materials and different coolant conditions.

[0018] Statistical processing is performed on the normalized impedance sequence to calculate the arithmetic mean and standard deviation of the impedance values ​​of all chip grooves at each depth. The arithmetic mean reflects the average impedance level at that depth, and the standard deviation reflects the dispersion of the data. Curve smoothing employs a moving average filtering algorithm, with the window size determined based on the total number of sampling points: a 3-point window is selected when there are fewer than 20 sampling points, a 5-point window when there are 20-50 sampling points, and a 7-point window when there are more than 50 sampling points. The moving average filtering process involves selecting each data point and its adjacent points to calculate a weighted average, with the weighting coefficient decreasing from the center to both ends, and the center point having the highest weight. The smoothness parameter controls the degree of curve smoothing, ranging from 0.1 to 0.9; in practical applications, a value between 0.3 and 0.5 is used to balance the smoothing effect and information fidelity. The impedance reference template refers to the standard impedance distribution data formed after statistical analysis and smoothing, stored in array form as an array of expected impedance values ​​at each depth under standard dental repair conditions for a specific material-taper combination. Moving average filtering eliminates the effects of random noise and transient interference during the measurement process, making the benchmark template more stable and representative.

[0019] An impedance reference template is indexed and associated with its corresponding process parameters and stored in a relational database. The database uses a MySQL relational database management system, and the reference template data is stored in binary large object format. Material grades use national standard material codes, hardness ranges are divided into 5HRC intervals, conductivity ranges into 500μS / cm intervals, and cumulative tap cutting lengths are recorded in 10-meter intervals. The database storage structure uses a composite index, with the combination of material grade, hardness range, conductivity range, and cumulative cutting length as the primary key, and the impedance reference template data stored as the value field. Integrity checks and repeatability verification are performed during data writing to ensure that each index combination corresponds to only one reference template record. The index binding process is implemented through SQL statements in the database management system, specifically including INSERT statements to insert new records and CREATE INDEX statements to create query indexes. This multi-dimensional indexing mechanism enables the system to quickly locate and call the most matching reference template based on the current processing conditions, ensuring the accuracy and applicability of the comparison reference during real-time detection.

[0020] Please continue to refer to Figure 1 During the dental restoration process, the real-time AC impedance values ​​of each chip removal groove at the current restoration depth are acquired simultaneously to form a real-time impedance dataset. In one embodiment of the present invention, the step of simultaneously acquiring the real-time AC impedance values ​​of each chip removal groove at the current dental restoration depth during the dental restoration process to form a real-time impedance dataset includes: Based on the preset fixed rotation angle of the spindle per revolution, each chip removal groove is sampled synchronously to obtain the instantaneous AC impedance value corresponding to the repair depth and groove position. The instantaneous AC impedance value is integrated and averaged over multiple cycles within a narrow band that matches the measurement frequency recorded by the impedance reference template to obtain the noise-filtered steady-state AC impedance value. The steady-state AC impedance values ​​of each chip removal slot at the same dental restoration depth are combined into a dental restoration depth-slot data slice, and written into the real-time impedance dataset in the order of dental restoration depth.

[0021] The following is a detailed description of the steps involved in the above embodiments: The spindle encoder of the CNC system generates a fixed number of pulse signals per revolution, dividing the 360 ​​degrees into corresponding angular intervals based on the number of chip removal grooves. For example, a 4-groove tap divides each revolution into 90-degree angular intervals. Preset fixed rotation angles are set to 30 degrees or 45 degrees to ensure sampling is triggered when each chip removal groove passes the measurement position. When the spindle encoder count reaches the preset angle value, the data acquisition system automatically sends an impedance measurement command to the corresponding chip removal groove. The impedance analyzer immediately applies a test signal to the groove and records the instantaneous impedance value. The instantaneous AC impedance value refers to the impedance amplitude measured instantaneously at a specific rotation position, reflecting the electrical characteristics of the composite conductive circuit formed by chips, conductive layer, and coolant within the chip removal groove at that moment. The depth-groove correspondence is determined by a combination of signals from the spindle's axial position encoder and angle encoder. The axial encoder provides depth coordinates, and the angle encoder provides groove identification. For example, the impedance value acquired at a depth of 5mm and a 90-degree rotation position is recorded as "5mm-groove 2-impedance value". Synchronous sampling eliminates the impact of measurement time differences between different chip removal grooves on data accuracy, ensuring that data from each groove is obtained under the same cutting conditions.

[0022] First, the narrowband range is determined. This range is centered on the measurement frequency recorded by the impedance reference template, extending 5% above and below that frequency value as the bandwidth. For example, when the reference frequency is 1kHz, the narrowband range is set to 950Hz-1050Hz. The data acquisition system performs bandpass filtering on the instantaneous impedance signal, retaining only the signal components within the narrowband range and filtering out noise interference from other frequencies. Multi-cycle integral averaging refers to continuously acquiring 5-10 complete AC signal cycles, calculating the arithmetic mean of the impedance amplitudes of each cycle, and obtaining the stable impedance value at that measurement point. The integral averaging calculation process is as follows: the average value of the impedance sampling points within each cycle is calculated to obtain the single-cycle impedance value, and then the impedance values ​​of multiple consecutive cycles are averaged again to obtain the steady-state AC impedance value. The steady-state AC impedance value refers to the stable impedance measurement result after filtering and averaging, eliminating the influence of instantaneous fluctuations and random noise. Narrowband filtering and multi-cycle averaging effectively suppress signal noise generated by mechanical vibration, electromagnetic interference, and random chip impacts during the cutting process, resulting in higher stability and reproducibility of the measurement results.

[0023] The data acquisition system collects the steady-state AC impedance values ​​of all chip removal slots at a given depth, sequentially according to slot number, forming a data structure containing depth coordinates and multiple slot impedance values. A dental restoration depth-slot data slice refers to a data unit identified by the dental restoration depth, containing the impedance values ​​of all chip removal slots at that depth. The data format is "depth value - [slot 1 impedance value, slot 2 impedance value, slot 3 impedance value, slot 4 impedance value]". For example, if the impedance values ​​of four chip removal slots collected at a depth of 5mm are 125Ω, 130Ω, 128Ω, and 132Ω respectively, then this data slice is recorded as "5mm - [125, 130, 128, 132]". Data slices are written to the real-time impedance dataset in ascending order of dental restoration depth. The real-time impedance dataset is an ordered array storing data slices at all depth positions throughout the entire dental restoration process. Newly generated data slices are added to the dataset in depth order to maintain the depth order of the data. The data slice structure enables the system to quickly locate multi-slot impedance information at a specific depth, facilitating subsequent deviation calculations and anomaly detection. At the same time, the orderly data arrangement supports the analysis of dynamic trends in the dental restoration process.

[0024] In one embodiment of the present invention, the step of synchronously sampling each chip removal groove according to a preset fixed rotation angle per spindle revolution to obtain the instantaneous AC impedance value corresponding to the repair depth-groove position includes: Obtain the angle between the coolant injection direction and the spindle zero position to determine the coolant noise reduction reference angle; For each chip removal slot, the trigger angle is calculated based on the difference between the coolant noise reduction reference angle and the slot angle, and a synchronous sampling trigger signal is generated. At the trigger angle, the instantaneous AC impedance value of the corresponding chip removal slot is collected.

[0025] The following is a detailed description of the steps involved in the above embodiments: During machine tool commissioning, the operator rotates the spindle to the zero position, which refers to the zero pulse position of the spindle encoder, serving as the starting reference point for angle measurement. The coolant system is then activated, and the direction of coolant ejection from the nozzle is observed. An angle measuring tool or the machine tool's built-in tool setter is used to measure the angle between the coolant spray centerline and the spindle zero position. This angle is recorded as the coolant spray angle. For example, if the coolant nozzle is installed 90 degrees clockwise from the spindle zero position, the coolant spray angle is 90 degrees. The coolant noise-avoidance reference angle is an angle reference determined to avoid direct impact of coolant on the measuring electrodes, which could affect the accuracy of impedance measurement. This angle is equal to the coolant spray angle plus 180 degrees; that is, the position opposite the coolant spray direction is selected as the optimal measurement position. Setting the coolant noise-avoidance reference angle avoids interference from strong coolant scouring on the electrode contact state and the stability of the conductive circuit, ensuring that impedance measurement is performed under relatively stable environmental conditions.

[0026] First, determine the slot angle of each chip removal groove. The slot angle refers to the fixed angular position of each chip removal groove relative to the zero position of the spindle. For example, the slot angles of a 4-groove tap are 0 degrees, 90 degrees, 180 degrees, and 270 degrees. The trigger angle is calculated by comparing the coolant noise reduction reference angle with each slot angle and selecting the angle closest to the noise reduction reference angle as the trigger angle for that groove. For example, when the noise reduction reference angle is 270 degrees, the trigger angle of the chip removal groove with a slot angle of 270 degrees is set to 270 degrees, and the trigger angle of the chip removal groove with a slot angle of 0 degrees is set to 360 degrees (i.e., 0 degrees). The CNC system generates a synchronous sampling trigger signal based on the calculated trigger angle. When the spindle encoder detects that the spindle has rotated to the trigger angle, it automatically sends a trigger signal to the data acquisition system. At the trigger angle position, the corresponding chip removal groove is exactly in a position away from direct impact from the coolant. At this time, the impedance measurement program is started, and the impedance analyzer applies a test signal to the chip removal groove and collects the instantaneous AC impedance value. Precise calculation and control of the trigger angle ensures that impedance measurements of each chip removal groove are performed under optimal environmental conditions, improving the stability and repeatability of the measurement data.

[0027] Please continue to refer to Figure 1 The real-time impedance dataset is compared with the impedance reference template, and the impedance deviation value of each chip removal groove is calculated. When the impedance deviation value of a single chip removal groove at the same dental restoration depth is greater than the first threshold and the average impedance deviation value of multiple chip removal grooves is not greater than the second threshold, a local abnormality mark is generated. When the average impedance deviation value of multiple chip removal grooves is greater than the second threshold, an overall abnormality mark is generated, thus obtaining the quality status mark of each dental restoration depth. In one embodiment of the present invention, the step of comparing the real-time impedance dataset with the impedance reference template, calculating the impedance deviation value of each chip removal groove, generating a local anomaly marker when the impedance deviation value of a single chip removal groove at the same restoration depth is greater than a first threshold and the average impedance deviation value of multiple chip removal grooves is not greater than a second threshold, and generating an overall anomaly marker when the average impedance deviation value of multiple chip removal grooves is greater than the second threshold, thereby obtaining a quality status marker for each restoration depth, including: Read the current dental depth-socket data slice from the real-time impedance dataset; The steady-state AC impedance value of each chip groove in the dental restoration depth-groove data chip is compared with the corresponding value of the impedance reference template to obtain the single groove impedance deviation. Based on the slot number of the chip removal groove in the rotating circumference, the preset slot weight coefficient is called, and the single-slot impedance deviation is multiplied to obtain the weighted single-slot impedance deviation. Check whether the weighted single-slot impedance deviation is greater than the first threshold. If so, calculate the average weighted deviation under the same dental restoration depth and compare it with the second threshold. When the average weighted deviation is not greater than the second threshold, generate a local anomaly marker. When the average weighted deviation is greater than the second threshold, generate an overall anomaly marker. The local or global abnormality markers are combined with the current dental restoration depth to form a quality status marker, and then sequentially written into the quality status marker list.

[0028] The following is a detailed description of the steps involved in the above embodiments: The data processing system performs a search operation in the real-time impedance dataset based on the current dental restoration depth coordinates. The search process uses the depth value as an identifier to locate the data slice that matches the current restoration depth. For example, when the current restoration depth is 8mm, the system searches for the data slice identified as "8mm" in the dataset. This data slice contains the steady-state AC impedance values ​​of all chip removal grooves at a depth of 8mm. The specific format of the data slice is "depth value - [groove 1 impedance value, groove 2 impedance value, groove 3 impedance value, groove 4 impedance value]". During reading, the system extracts the impedance value portion of this format for subsequent processing. This reading operation ensures that the data used for subsequent deviation calculations strictly corresponds to the current restoration position, avoiding judgment errors caused by data misalignment.

[0029] The system first extracts the reference impedance value corresponding to the current dental restoration depth from the impedance reference template. The differential operation uses a subtraction operation, subtracting the reference value at the corresponding depth in the reference template from the measured steady-state AC impedance value of each chip removal groove in the data slice. For example, if the measured impedance value of a chip removal groove at a depth of 8mm is 135Ω, and the reference value at 8mm depth in the reference template is 130Ω, then the single-groove impedance deviation of this groove is 5Ω. The single-groove impedance deviation refers to the difference between the measured impedance value of a single chip removal groove and the reference value; a positive value indicates that the measured impedance is higher than the reference, and a negative value indicates that it is lower than the reference. The differential operation is performed on each chip removal groove individually to obtain the single-groove impedance deviation value for each groove at that depth. The differential operation quantifies the difference between the measured data and the standard reference into a specific numerical value, allowing the degree of anomaly to be accurately measured and compared.

[0030] The system maintains a slot weighting coefficient table, which pre-sets weight values ​​for each chip removal slot based on the cutting load it bears during dental restoration. The slot number refers to the clockwise numbering of the chip removal slots; for example, the slot numbers for a 4-slot tap are 1, 2, 3, and 4. The pre-set slot weighting coefficient is a weighting factor determined based on the differences in cutting edge length and geometric angles of each chip removal slot; slots with longer cutting edges or more favorable geometric angles have higher weighting coefficients. Weighted processing involves multiplying the single-slot impedance deviation by the corresponding slot weighting coefficient to obtain a weighted single-slot impedance deviation. For example, if the single-slot impedance deviation of a major chip removal slot is 5Ω and the weighting coefficient is 1.1, then the weighted single-slot impedance deviation is 5.5Ω. Weighted processing highlights the impact of significant chip removal slot deviations on the overall quality assessment, making the test results more accurately reflect the actual condition of the dental restoration.

[0031] The system checks each chip removal groove individually to see if the absolute value of the weighted single-groove impedance deviation exceeds a first threshold. The first threshold is determined by statistically analyzing the standard deviation of impedance values ​​at each depth in the impedance benchmark template, and is set to 2-3 times the standard deviation, reflecting the critical deviation value for an abnormality in a single chip removal groove. This setting method is based on the 3σ principle in statistics, ensuring that deviations within the normal fluctuation range are not misjudged as abnormal. When the absolute value of the weighted single-groove impedance deviation of any chip removal groove is found to be greater than the first threshold, the system adds up the weighted single-groove impedance deviations of all chip removal grooves at the same repair depth and divides the sum by the total number of chip removal grooves to calculate the average weighted deviation. The average weighted deviation reflects the comprehensive deviation level of multiple chip removal grooves at that depth. The system compares the absolute value of the average weighted deviation with a second threshold, set to 0.6-0.8 times the first threshold, to determine whether the overall cutting state is abnormal. When the absolute value of the average weighted deviation is not greater than the second threshold, the abnormality is determined to be limited to individual chip removal grooves, generating a local abnormality marker; when the absolute value of the average weighted deviation is greater than the second threshold, a systemic problem is determined, generating an overall abnormality marker. The dual-threshold judgment mechanism enables accurate identification and classification of anomaly types, facilitating the implementation of corresponding quality control measures.

[0032] The system combines the generated local or global anomaly markers with the corresponding restoration depth values ​​to form a quality status marker that includes both location and anomaly type information. A quality status marker is a data structure that records quality anomalies at a specific restoration depth, containing two basic elements: depth coordinates and anomaly type. For example, if a local anomaly is detected at a depth of 12mm, the quality status marker is recorded as "12mm-Local Anomaly"; if a global anomaly is detected, it is recorded as "12mm-Global Anomaly". The system writes the quality status markers into a quality status marker list in the order of restoration depth. This list is an ordered record storing information on the location and type of all anomalies throughout the restoration process. Newly generated quality status markers are added to the end of the list, maintaining the increasing depth order. The generation and storage of quality status markers provide complete anomaly distribution information for subsequent statistical analysis and final quality assessment.

[0033] Please continue to refer to Figure 1 Within the entire dental repair depth range, the quality status markers are statistically analyzed. When the length of the continuous interval and the total number of abnormal markers are both within the preset range, a thread qualification judgment is output; otherwise, a non-qualification judgment is output.

[0034] In one embodiment of the present invention, the step of statistically analyzing the quality status markers across the entire dental restoration depth range, and outputting a thread qualification judgment when both the continuous interval length and total number of abnormal markers are within a preset range, and otherwise outputting a non-qualification judgment, includes: Read the list of quality status markers arranged in order of dental restoration depth, identify local abnormality marker intervals and global abnormality marker intervals, and record the start and end depths of each abnormality interval; The percentage of the length of the abnormal interval to the total thread depth is calculated, and the length of each interval is weighted and accumulated according to the local abnormality weight coefficient and the overall abnormality weight coefficient to obtain the weighted continuous interval length and the total number of weighted abnormalities. The weighted continuous interval length is compared with the length threshold, and the weighted total number of anomalies is compared with the number threshold. When both are not greater than the corresponding threshold, a thread qualification judgment is output; otherwise, a non-qualification judgment is output.

[0035] The following is a detailed description of the steps involved in the above embodiments: The system starts from the first record in the quality status marker list and checks the anomaly type of each marker one by one. When consecutive anomaly markers of the same type appear, these consecutive markers are grouped into anomaly intervals. A local anomaly marker interval refers to the depth range of consecutive local anomaly markers, while a global anomaly marker interval refers to the depth range of consecutive global anomaly markers. For example, if the quality status marker list contains "5mm - local anomaly, 6mm - local anomaly, 7mm - local anomaly, 10mm - global anomaly, 11mm - global anomaly," the system identifies a local anomaly marker interval "5mm-7mm" and a global anomaly marker interval "10mm-11mm." The system records the start and end depths of each anomaly interval, which refer to the depth coordinates of the first and last anomaly markers within the interval. Identifying anomaly intervals organizes discrete anomaly points into continuous problem areas, facilitating the assessment of the concentration and impact range of defects.

[0036] The system first calculates the length of each abnormal interval, which is equal to the difference between the start and end depths. Then, it calculates the percentage of the interval length relative to the total thread depth by dividing the interval length by the total thread depth and multiplying by 100%. For example, if a local abnormality marking interval is 3mm long and the total thread depth is 20mm, then this interval represents 15% of the total thread depth. Local abnormality weighting coefficients and overall abnormality weighting coefficients are pre-set weighting factors. The overall abnormality weighting coefficient is higher than the local abnormality weighting coefficient, reflecting the severity of the overall abnormality's impact on thread quality. The weighted accumulation process is as follows: multiply the percentage of each local abnormality marking interval by the local abnormality weighting coefficient, multiply the percentage of each overall abnormality marking interval by the overall abnormality weighting coefficient, and then sum them to obtain the weighted continuous interval length. The total weighted number of abnormalities refers to the sum of the number of local abnormality marking intervals multiplied by the local abnormality weighting coefficient, the number of overall abnormality marking intervals multiplied by the overall abnormality weighting coefficient, and then summed. This weighted processing highlights the differentiated impact of different types of abnormalities on the overall thread quality, making the final judgment more accurate and reasonable.

[0037] The system compares the calculated weighted continuous interval length with a length threshold and the total weighted anomaly count with a quantity threshold. The length threshold is the maximum percentage of the weighted anomaly interval length allowed when the thread quality is acceptable, and the quantity threshold is the maximum number of weighted anomaly intervals allowed when the thread quality is acceptable. These two thresholds are preset based on the thread's functional requirements and quality standards; for example, the thresholds for aerospace threads are more stringent than those for general machinery threads. When both the weighted continuous interval length and the total weighted anomaly count are not greater than their respective thresholds, the system outputs a thread acceptance judgment, indicating that the thread quality meets the usage requirements. When either exceeds its corresponding threshold, the system outputs a failure judgment, indicating that the thread has quality defects that affect its performance. This dual judgment condition ensures that both the concentration and frequency of anomalies are considered, comprehensively assessing the overall quality status of the thread and avoiding the omissions or misjudgments that might occur with a single indicator.

[0038] In one embodiment of the present invention, the step of calculating the percentage of the abnormal interval length to the total thread depth, and weighting and accumulating each interval length according to the local abnormality weight coefficient and the overall abnormality weight coefficient to obtain the weighted continuous interval length and the total number of weighted abnormalities includes: Based on the total thread depth, the repair depth range is divided into the inlet zone, the middle section zone, and the bottom zone; For each partition, calculate the percentage of the length of its local anomaly interval to the depth of the corresponding partition and multiply it by the local anomaly weight coefficient, and calculate the percentage of the length of its overall anomaly interval to the depth of the corresponding partition and multiply it by the overall anomaly weight coefficient to obtain the partition weighted continuous interval length and the partition weighted anomaly number. The weighted continuous interval length is obtained by adding the weighted continuous interval lengths of the three partitions, and the weighted outlier counts of the three partitions are added together to obtain the total weighted outlier count.

[0039] The following is a detailed description of the steps involved in the above embodiments: The system first obtains the total thread depth, which refers to the complete depth distance from the thread opening to the bottom of the thread. The thread is divided into zones using a fixed ratio: the entry zone occupies the first 15% of the total thread depth, the middle zone occupies the middle 70%, and the bottom zone occupies the last 15%. The entry zone is the area near the thread opening, which is responsible for introducing the threaded connection; the middle zone is the middle part of the thread, which is responsible for the main load transfer; and the bottom zone is the area near the bottom of the thread, which affects the root strength of the threaded connection. For example, when the total thread depth is 20mm, the entry zone is 0-3mm, the middle zone is 3-17mm, and the bottom zone is 17-20mm. The system categorizes and archives all quality status markers according to their respective zones based on these depth ranges. This zoning reflects the differences in the impact of different parts of the thread on connection performance; quality defects in the entry and bottom zones have a more significant impact on the reliability of the threaded connection, while the middle zone mainly affects the load-bearing capacity.

[0040] The system performs statistical analysis on abnormal intervals within each partition. First, it calculates the percentage of the length of local anomaly-marked intervals within each partition relative to the partition's depth. This is done by summing the lengths of all local anomaly-marked intervals within the partition, dividing by the partition's depth, and then multiplying by 100%. This percentage is then multiplied by a local anomaly weighting coefficient to obtain the local anomaly weighted value for that partition. Similarly, the percentage of the overall anomaly-marked interval length relative to the corresponding partition depth is calculated and multiplied by an overall anomaly weighting coefficient to obtain the overall anomaly weighted value for that partition. The partition-weighted continuous interval length is the sum of the local anomaly weighting value and the overall anomaly weighting value for that partition. The partition-weighted anomaly count is the result of multiplying the number of local anomaly-marked intervals within the partition by the local anomaly weighting coefficient, plus the sum of the number of overall anomaly-marked intervals multiplied by the overall anomaly weighting coefficient. For example, if there is one local anomaly-marked interval with a length of 1mm in the entry zone, the entry zone depth is 3mm, and the local anomaly weighting coefficient is 1.5, then the local anomaly weighting value for that partition is 33.3% × 1.5 = 50%. Independent calculations within a partition avoid mutual interference from abnormal effects in different functional areas, making quality assessment more accurate and reasonable.

[0041] The system sums the weighted continuous interval lengths of the three zones—entry zone, middle zone, and bottom zone—to obtain the total weighted continuous interval length of the entire thread. Similarly, it sums the weighted anomaly counts of the three zones to obtain the total weighted anomaly count. The weighted continuous interval length reflects the severity of the overall thread anomaly area, while the total weighted anomaly count reflects the frequency of the overall thread anomaly distribution. For example, if the weighted continuous interval length of the entry zone is 50%, the middle zone is 20%, and the bottom zone is 30%, then the total weighted continuous interval length is 100%. The summarization process maintains the weight differences between the zones, with anomalies in important zones having a greater impact on the final result. This zoned summarization method considers both the differences in functional importance of different parts of the thread and achieves a comprehensive evaluation of the overall quality status. Compared to the traditional uniform weighting method, this differentiated weighting summarization method more accurately reflects the actual performance requirements and failure risk distribution of the threaded connection.

[0042] Reference Figures 2 to 4 The present invention provides a press thread system, which adopts the press thread repair detection method of any of the above embodiments, and therefore has the advantages of any of the above embodiments, which will not be repeated here.

[0043] Furthermore, the extrusion thread system includes a cutting tap, which includes a connecting section 1, a cutting section 2, and a guide section 3 connected sequentially along its own length direction; The connecting section 1 is used to connect with the machine tool spindle to transmit rotational torque; The outer peripheral wall of the cutting section 2 includes a chip removal surface 21 and a threaded surface 22. The chip removal surface 21 is recessed with a chip removal groove 211 extending along the length direction of the cutting section 2. The threaded surface 22 is provided with a cutting thread portion 221. The tooth depth of the cutting thread portion 221 is not greater than the tooth depth of the internal thread of the workpiece to be processed. The outer peripheral wall of the guide section 3 is provided with a guide thread 31. The guide thread 31 is coaxially engaged with the internal thread of the workpiece to be processed to guide the cutting section 2 to enter axially. When the guide thread 31 is engaged with the internal thread of the workpiece to be processed, it closes the front end of the chip discharge groove 211 so that the chips and coolant in the chip discharge groove 211 are discharged unidirectionally towards the connecting section 1.

[0044] It's easy to understand that connecting section 1 is the mounting part of the cutting tap, connected to the machining equipment via a standard tap chuck or machine tool spindle interface, and responsible for transmitting spindle rotation torque and axial feed force. Cutting section 2 is the core part for performing thread trimming operations. Its thread-cutting part 221 has a sharp cutting edge (the cutting edge is located on the side of the thread-cutting part 221; the root of the thread-cutting part 221 does not perform cutting action, and its root is smaller than the crest size of the internal thread of the workpiece). When the cutting tap rotates into the extrusion thread hole, the thread-cutting part 221 precisely cuts the thread crest protrusion formed after extrusion, removing excess material and burrs, so that the thread crest achieves the designed cylindrical surface shape. The chip removal groove 211 serves as a chip removal channel, promptly discharging the metal chips generated during the cutting process under the flushing of coolant, preventing chip accumulation from affecting machining quality and tool life.

[0045] The guiding thread 31 of the guiding section 3 is designed according to the thread size to form a precise thread fit with the standard part of the internal thread of the workpiece to be machined, establishing a stable coaxial positioning relationship before cutting begins. Because the internal thread of the workpiece has material accumulation and dimensional deviations at the crest after extrusion, and the guiding thread 31 is designed according to the standard thread size, when the guiding thread 31 engages with the internal thread of the workpiece, it mainly achieves positioning and guidance by contacting the standard part of the workpiece thread with the thread side. Its thread root does not contact the accumulated material at the crest of the workpiece thread, thus avoiding cutting action on the workpiece. This engagement method ensures that the cutting section 2 can accurately enter along the predetermined axial direction, eliminating radial offset and axial oscillation during the cutting process, thereby guaranteeing the dimensional accuracy and surface quality of the thread finishing operation. More importantly, when the guiding thread 31 is fully engaged with the internal thread of the workpiece, the outer diameter of the guiding section 3 effectively closes the front opening of the chip removal groove 211, forcing the metal chips and coolant generated during cutting to flow unidirectionally towards the connecting section 1 along the chip removal groove 211.

[0046] Compared to traditional cutting taps without a guide section 3, the guide section 3 of this invention significantly improves the machining accuracy of thread repair operations by providing precise positioning capabilities, avoiding thread geometric errors and surface defects caused by tool runout. Secondly, the unidirectional chip removal mechanism eliminates the disordered flow of chips within the threaded hole, preventing secondary scratches and contamination of the machined thread surface 22. Most importantly, this predictable unidirectional chip removal flow provides a stable physical basis for the detection method of this invention, ensuring good reproducibility and detectability of the contact state between chips and the conductive layer within the chip groove 211, thereby enabling real-time monitoring and accurate judgment of the quality status during thread repair.

[0047] It should be noted that, in some embodiments of the cutting tap in this application, the chip removal groove 211 may also extend to the connecting section 1 and the guide section 3 (but not to the end of the guide section 3).

[0048] This invention also provides an application of extruded threads. It should be noted that any workpiece processed by the above-mentioned extruded thread repair and inspection method is considered an application of extruded threads.

[0049] For example, the extrusion thread repair and inspection method of this invention is used to process the fixed thread holes of aero-engine blades, ensuring that the geometric accuracy and surface quality of the thread crests meet aerospace standards, significantly improving the reliability and fatigue life of the blade-engine casing connection. After being processed by this invention, the bolt connection holes of automotive engine cylinder blocks have their thread strength and sealing performance effectively guaranteed, avoiding engine oil leaks or loose connections caused by thread quality defects. Applying this invention's technology to the threaded holes of the spindle housings of precision mechanical equipment enables precise control of thread dimensions and timely detection of surface defects, ensuring equipment assembly accuracy and operational stability.

[0050] Furthermore, the threaded connections between ship propellers and propulsion shafts, the fixing threads between wind turbine blades and hubs, and the flange connection threads of various high-pressure vessels, among other critical components, can all be processed using the extrusion thread repair and inspection method of this invention. These applications place extremely high demands on the reliability and safety of threaded connections. Traditional post-processing inspection methods cannot detect quality anomalies in a timely manner, posing a risk of batch scrap. However, the real-time inspection technology of this invention can instantly identify the thread quality status during the repair process, ensuring that each threaded hole meets design requirements, thereby significantly improving the overall quality level and operational safety of the product.

[0051] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for inspecting the repair of extruded threads, characterized in that, include: The impedance reference template corresponding to the specified material grade and tap number is retrieved from the database. The impedance reference template includes AC impedance reference values ​​for each chip removal groove at different repair depths. The database is obtained through the following steps: a reference repair is performed on the specified material and tap combination; AC impedance values ​​are collected for each chip removal groove at repair depth intervals that are integer multiples of the thread pitch, resulting in a raw repair depth-groove impedance sequence; based on the Rockwell hardness of the material and the coolant conductivity, the raw repair depth-groove impedance sequence is subjected to two-factor normalization to obtain a normalized impedance sequence; the mean and standard deviation of the normalized impedance sequence are calculated and curve smoothing is performed to obtain the impedance reference template; the impedance reference template is indexed and bound to the material grade, hardness range, coolant conductivity range, and cumulative tap cutting length before being written into the database. During the dental restoration process, the real-time AC impedance values ​​of each chip removal groove at the current restoration depth are acquired simultaneously to form a real-time impedance dataset. The real-time impedance dataset is compared with the impedance reference template, and the impedance deviation value of each chip removal groove is calculated. When the impedance deviation value of a single chip removal groove at the same dental restoration depth is greater than the first threshold and the average impedance deviation value of multiple chip removal grooves is not greater than the second threshold, a local abnormality mark is generated. When the average impedance deviation value of multiple chip removal grooves is greater than the second threshold, an overall abnormality mark is generated, thus obtaining the quality status mark of each dental restoration depth. Within the entire dental restoration depth range, the quality status markers are statistically analyzed. When the length of the continuous interval and the total number of abnormal markers are both within the preset range, a thread qualification judgment is output; otherwise, a non-qualification judgment is output.

2. The method for detecting the repair of extruded threads according to claim 1, characterized in that, During the dental restoration process, the real-time AC impedance values ​​of each chip removal groove at the current restoration depth are simultaneously acquired to form a real-time impedance dataset, including: Based on the preset fixed rotation angle of the spindle per revolution, each chip removal groove is sampled synchronously to obtain the instantaneous AC impedance value corresponding to the repair depth and groove position. The instantaneous AC impedance value is integrated and averaged over multiple cycles within a narrow band that matches the measurement frequency recorded by the impedance reference template to obtain the noise-filtered steady-state AC impedance value. The steady-state AC impedance values ​​of each chip removal slot at the same dental restoration depth are combined into a dental restoration depth-slot data slice, and written into the real-time impedance dataset in the order of dental restoration depth.

3. The method for detecting the repair of extruded threads according to claim 2, characterized in that, The method of synchronously sampling each chip removal groove according to a preset fixed rotation angle per spindle revolution to obtain the instantaneous AC impedance value corresponding to the repair depth and groove position includes: Obtain the angle between the coolant injection direction and the spindle zero position to determine the coolant noise reduction reference angle; For each chip removal slot, the trigger angle is calculated based on the difference between the coolant noise reduction reference angle and the slot angle, and a synchronous sampling trigger signal is generated. At the trigger angle, the instantaneous AC impedance value of the corresponding chip removal slot is collected.

4. The method for detecting the repair of extruded threads according to claim 1, characterized in that, The process involves comparing the real-time impedance dataset with the impedance reference template, calculating the impedance deviation value of each chip removal groove, and generating a local anomaly marker when the impedance deviation value of a single chip removal groove at the same restoration depth is greater than a first threshold and the average impedance deviation value of multiple chip removal grooves is not greater than a second threshold. Conversely, generating an overall anomaly marker when the average impedance deviation value of multiple chip removal grooves is greater than the second threshold, thus obtaining the quality status marker for each restoration depth, including: Read the current dental depth-socket data slice from the real-time impedance dataset; The steady-state AC impedance value of each chip groove in the dental restoration depth-groove data chip is compared with the corresponding value of the impedance reference template to obtain the single groove impedance deviation. Based on the slot number of the chip removal groove in the rotating circumference, the preset slot weight coefficient is called, and the single-slot impedance deviation is multiplied to obtain the weighted single-slot impedance deviation. Check whether the weighted single-slot impedance deviation is greater than the first threshold. If so, calculate the average weighted deviation under the same dental restoration depth and compare it with the second threshold. When the average weighted deviation is not greater than the second threshold, generate a local anomaly marker. When the average weighted deviation is greater than the second threshold, generate an overall anomaly marker. The local or global abnormality markers are combined with the current dental restoration depth to form a quality status marker, and then sequentially written into the quality status marker list.

5. The method for detecting the repair of extruded threads according to claim 1, characterized in that, Within the entire dental restoration depth range, statistical analysis is performed on the quality status markers. When the length of the continuous interval and the total number of abnormal markers are both within a preset range, a thread qualification judgment is output; otherwise, a failure judgment is output, including: Read the list of quality status markers arranged in order of dental restoration depth, identify local abnormality marker intervals and global abnormality marker intervals, and record the start and end depths of each abnormality interval; The percentage of the length of the abnormal interval to the total thread depth is calculated, and the length of each interval is weighted and accumulated according to the local abnormality weight coefficient and the overall abnormality weight coefficient to obtain the weighted continuous interval length and the total number of weighted abnormalities. The weighted continuous interval length is compared with the length threshold, and the weighted total number of anomalies is compared with the number threshold. When both are not greater than the corresponding threshold, a thread qualification judgment is output; otherwise, a non-qualification judgment is output.

6. The method for detecting the repair of extruded threads according to claim 5, characterized in that, The calculation of the percentage of the abnormal interval length to the total thread depth, and the weighted accumulation of each interval length according to the local abnormality weight coefficient and the overall abnormality weight coefficient, to obtain the weighted continuous interval length and the total number of weighted abnormalities, includes: Based on the total thread depth, the repair depth range is divided into the inlet zone, the middle section zone, and the bottom zone; For each partition, calculate the percentage of the length of its local anomaly interval to the depth of the corresponding partition and multiply it by the local anomaly weight coefficient, and calculate the percentage of the length of its overall anomaly interval to the depth of the corresponding partition and multiply it by the overall anomaly weight coefficient to obtain the partition weighted continuous interval length and the partition weighted anomaly number. The weighted continuous interval length is obtained by adding the weighted continuous interval lengths of the three partitions, and the weighted outlier counts of the three partitions are added together to obtain the total weighted outlier count.

7. A calendered thread system, characterized in that, The extruded thread system employs the thread repair and inspection method for extruded threads as described in claims 1 to 6.

8. The extrusion thread system as described in claim 7, characterized in that, The extrusion thread system includes a cutting tap, which includes a connecting section, a cutting section, and a guide section connected sequentially along its length. The connecting section is used to connect with the machine tool spindle to transmit rotational torque; The outer peripheral wall of the cutting section includes a chip removal surface and a threaded surface. The chip removal surface is recessed with a chip removal groove extending along the length direction of the cutting section. The threaded surface is provided with a cutting thread portion. The tooth depth of the cutting thread portion is not greater than the tooth depth of the internal thread of the workpiece to be processed. The outer peripheral wall of the guide section is provided with a guide thread, which is coaxially engaged with the internal thread of the workpiece to guide the cutting section to enter axially. When the guide thread is engaged with the internal thread of the workpiece, it closes the front end of the chip removal groove so that the chips and coolant in the chip removal groove are discharged unidirectionally towards the connecting section.

9. An application of extruded threads, characterized in that, The method for inspecting the repair of extruded threads as described in any one of claims 1 to 6 is adopted.

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