Multi-head screw tap

Abstract

The invention belongs to the technical field of blind hole tapping screw taps in numerical control machine tools, and discloses a multi-head screw tap which is applied to the numerical control machine tools to conduct tapping operation on blind holes of workpieces, the multi-head screw tap comprises a tapping part and a cooling part, the tapping part is provided with multi-head external threads, the multi-head external threads are used for machining and forming corresponding multi-head internal threads of the blind holes, and the cooling part is used for cooling the multi-head external threads. The cooling part is provided with a plurality of multi-head external threads, the multi-head external threads are provided with a plurality of spiral chip guide grooves, the spiral direction of the chip guide grooves is the same as that of the multi-head external threads, and the lead angle of the chip guide grooves is larger than that of the multi-head external threads. A guide hole is formed in the center of the radial first conical surface, and a guide rod is arranged in the guide hole in a sliding mode. The device has the beneficial effects that the contact area of the two conical surfaces is adjusted by adjusting the sliding of the guide rod, the flow of cooling liquid in the center hole can be adjusted and controlled, and the supply quantity of cooling and lubricating can be adjusted according to the chip generation quantity and tool temperature parameters in the blind hole tapping process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of blind hole tapping tap in numerical control machine tool, and particularly relates to a multi-head tap. BACKGROUND

[0002] In the multi-head tapping operation of the blind hole of the numerical control machine tool, the blind hole is blocked in space, which causes the cutting chip to be difficult to discharge. In the prior art, US20030049081A1 discloses that the series connection tap reduces the accumulation of cutting chips by segmenting different chip removal directions. CN102438786A discloses that the tap with a drill bit reduces the chip removal and cooling by the multi-blade structure and oil hole oil supply.

[0003] However, when the multi-head tap is applied to the blind hole machining, the matching degree of the spiral parameters of the traditional chip guide groove and the external thread is insufficient, the chip removal power is limited, and the cutting chip is prone to be retained, which causes the thread to be scratched or the tap to be broken. At the same time, the existing cooling structure is mainly fixed channel oil supply, and the cooling liquid flow cannot be controlled according to the amount of cutting chips generated in the machining and the temperature of the tool, which is difficult to adapt to the precise demand of the cooling and lubrication of the high-precision machining of the numerical control machine tool, and affects the machining efficiency and quality stability of the multi-head internal thread. On the other hand, there is no hardware device in the existing numerical control machine tool blind hole tapping operation to detect whether the tap reaches the bottom of the blind hole during tapping. It is simply relied on the feed amount of the spindle in the control system to make an estimate, and there is a situation that the estimate does not match the actual position of the tap. SUMMARY

[0004] The application aims to solve the technical problem that in the existing multi-head tapping operation of the blind hole of the numerical control machine tool, the cooling structure is mainly fixed channel oil supply, the cooling liquid flow cannot be controlled according to the amount of cutting chips generated in the machining and the temperature of the tool, which is difficult to adapt to the precise demand of the cooling and lubrication of the high-precision machining of the numerical control machine tool, and affects the machining efficiency and quality stability of the multi-head internal thread.

[0005] In order to achieve the above-mentioned target, the application provides a multi-head tap.

[0006] The specific technical scheme adopted by the application is as follows: A multi-head tap is applied to the tapping operation of a blind hole of a workpiece of a numerical control machine tool, the multi-head tap comprising a tapping portion and a cooling portion, the tapping portion is provided with a multi-head external thread, the multi-head external thread is used for processing a corresponding multi-head internal thread of the blind hole, the multi-head external thread is provided with a plurality of helical chip flutes, the helical direction of the chip flutes is the same as that of the multi-head external thread, and the helical lead angle of the chip flutes is greater than that of the multi-head external thread, the cooling portion comprises a central hole arranged at the center of the tap, the inner wall of the central hole is provided with a radial first taper surface, the center of the radial first taper surface is provided with a guide hole, a guide rod is slidably arranged in the guide hole, the middle and upper part of the guide rod is provided with a solid second taper surface, the first taper surface and the second taper surface are in contact, and the first taper surface and the second taper surface are used for regulating the flow of the cooling liquid in the central hole, and the bottom end of the guide rod can extend out of the bottom outlet of the central hole.

[0007] Further, when the first taper surface and the second taper surface are in contact, the bottom end of the guide rod extends out of the bottom end of the central hole.

[0008] Further, the first taper surface and the second taper surface are located above the top end of the multi-head external thread.

[0009] Further, the plurality of helical chip flutes are provided with a guide groove surface, a plurality of cooling liquid holes are arranged on the guide groove surface along the helical direction, and the cooling liquid holes are in communication with the central hole.

[0010] Further, the bottom end of the guide rod is rotationally connected with a contact, when the contact touches the bottom of the blind hole, the contact stops rotating, and the guide rod can continue to rotate with the tap.

[0011] Further, the inner wall of the central hole of the guide rod is slidably matched, the outer cylindrical surface of the guide rod is circumferentially distributed with a plurality of cooling liquid flow channels; the first taper surface and the second taper surface are divided into a plurality of circumferentially distributed inclined surfaces according to the distribution of the cooling liquid flow channels, the first taper surface is divided into a plurality of first inclined surfaces, and the second taper surface is divided into a plurality of second inclined surfaces; adjacent cooling liquid flow channels are provided with only one first inclined surface and one second inclined surface.

[0012] Further, a plurality of radial support members are arranged in the central hole along the axial direction, the center of the radial support member is provided with a guide hole, the guide rod is slidably arranged in the guide hole, the radial first taper surface is arranged above all the radial support members, and the bottom circle diameter of the solid second taper surface is smaller than that of the radial first taper surface.

[0013] Further, the top end of the guide rod has a plurality of copper rings which are not connected with each other and are insulated and closed, and the copper rings are uniformly arranged along the axis of the guide rod.

[0014] Further, the top end of the guide rod has a plurality of copper rings which are not connected with each other and are insulated and closed, and the copper rings are uniformly arranged along the axis of the guide rod.

[0015] The positive effect of the present application is that the multi-start external thread of the tapping part is processed into a multi-start thread through the multi-start internal thread of the blind hole by a numerical control machine tool, meeting the production needs; the plurality of helical chip flutes with the same helical direction as the multi-start external thread and a larger helical angle can strengthen the chip removal power through the larger angle, solve the problem of chip removal obstruction in the closed space of the blind hole, avoid thread surface scratches and tap breakage caused by chip accumulation, and ensure the continuity of the tapping operation; in the cooling part, the center hole of the tap center provides a passage for the flow of cooling liquid, the radial first conical surface of the inner wall is in contact with the solid second conical surface of the sliding guide rod in the guide hole, the contact area of the two conical surfaces can be adjusted by adjusting the sliding of the guide rod, the flow of the cooling liquid in the center hole can be controlled, the supply amount of cooling and lubrication can be adjusted according to the amount of chip generated and the temperature parameter of the tool during the tapping of the blind hole, the tool wear can be reduced, the waste caused by excessive supply of cooling liquid can be avoided, and the service life of the tap is prolonged; in addition, when the guide rod reaches the bottom of the blind hole before the tap reaches the bottom of the blind hole, the guide rod provides a hardware condition for the control system of the numerical control machine tool to detect whether the tap reaches the bottom, and can forcibly open the contact between the first conical surface and the second conical surface, forcibly increase the supply of cooling liquid, and relieve the breakage problem caused by the poor chip removal condition at the bottom of the blind hole. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a front view of a multi-start tap of the present application; Figure 2 is Figure 1 a multi-start tap N-N view shown in the present application, and the guide rod is removed, to show the groove surface of the plurality of helical chip flutes, a plurality of cooling liquid holes are provided along the helical direction, and the cooling liquid holes are in communication with the center hole; Figure 3 is Figure 1 a multi-start tap N-N view shown in the present application, and the cooling liquid hole is removed, to show the structure of the guide rod; Figure 4 is Figure 3 a local enlarged view of the top part in Figure 5 is Figure 1 a multi-start tap N-N view shown in the present application, and the cooling liquid hole is removed, to show the second structure of the guide rod; Figure 6 is Figure 5 an enlarged view of K in Figure 7 is Figure 5 a M-M view in Figure 8 is to Figure 5 show the application of the guide rod in the second structure of the guide rod, wherein Figure 3 the guide rod in also has the same application function; Figure legend: 1 - fixed driving square head, 2 - multi-start external thread, 3 - chip flute, 4 - cooling liquid hole, 5 - bottom end, 6 - sealing surface, 7 - guide rod top, 8 - copper ring, 9 - radial support, 10 - guide hole, 11 - guide rod bottom, 12 - center hole, 13 - radial plate, 14 - guide rod, 1401 - cooling liquid flow channel, 15 - first taper surface, 16 - second taper surface, 17 - rotary joint, 18 - sensor, 19 - induction block, 20 - tool shank, 21 - spacer ring, 22 - cooling liquid cavity. DETAILED DESCRIPTION

[0017] The application will be described in detail below with reference to the drawings and specific embodiments: In the description of the application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0018] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0019] The specific implementation of the application will be described in detail below with reference to specific embodiments.

[0020] As shown in the structure diagram of a multi-start tap provided by an embodiment of the application, the multi-start tap is applied to tapping work on a blind hole of a workpiece of a numerical control machine tool, and the multi-start tap comprises a tapping part and a cooling part. Figures 1 to 8 The tapping part is provided with a multi-start external thread, and the multi-start external thread is used to process a corresponding multi-start internal thread of the blind hole. The multi-start external thread is provided with a plurality of helical chip flutes, the helical direction of the chip flutes is the same as that of the multi-start external thread, and the helical lead angle of the chip flutes is greater than that of the multi-start external thread. The cooling part comprises a center hole arranged at the center of the tap, an inner wall of the center hole is provided with a radial first taper surface, a center of the radial first taper surface is provided with a guide hole, a guide rod is slidably arranged in the guide hole, a middle upper part of the guide rod is provided with a solid second taper surface, the first taper surface and the second taper surface are in contact, and the first taper surface and the second taper surface are used to control the flow of the cooling liquid in the center hole. The bottom end of the guide rod can extend out of the bottom outlet of the center hole.

[0021] In the embodiment of the application: In one aspect, the multi-start external thread of the tapping part is formed by machining the multi-start internal thread of the blind hole through the numerical control machine tool, meeting the production needs; the plurality of helical chip flutes with the same helical direction as the multi-start external thread and greater helix angle can strengthen the chip removal power through the greater angle, solve the problem of blocked chip removal in the closed space of the blind hole, avoid thread surface scratches and tap breakage caused by chip accumulation, and ensure the continuity of the tapping operation. On the other hand, in the cooling part, the center hole of the tap center provides a passage for the flow of cooling liquid, and the radial first conical surface of the inner wall is in contact with the solid second conical surface of the sliding guide rod in the guide hole, connecting the guide rod and the spindle accessory of the numerical control machine tool, such as a rotary joint, which can be adjusted by the spindle accessory to adjust the sliding of the guide rod and the contact area of the two conical surfaces, thereby adjusting the flow of cooling liquid in the center hole. According to the amount of chip generated during the tapping of the blind hole and the tool temperature parameters, the supply of cooling and lubrication can be adjusted, which can not only reduce tool wear but also avoid waste caused by excessive supply of cooling liquid, prolonging the service life of the tap. In addition, when the tap reaches the bottom of the blind hole, the guide rod reaches the bottom of the blind hole first, providing a hardware condition for the control system of the numerical control machine tool to detect whether the tap has reached the bottom, and at the same time, the contact between the first conical surface and the second conical surface can be forcibly opened, forcibly increasing the supply of cooling liquid, and relieving the problem of breakage caused by poor chip removal conditions at the bottom of the blind hole.

[0022] Specifically: A multi-head tap is applied to the tapping operation of a blind hole of a workpiece of a numerical control machine tool, and the multi-head tap comprises, from top to bottom, a clamping section E, a transition section F, a finishing section C, a roughing section B and a roughing-out section A, wherein the cutting amount of the finishing section C, the roughing section B and the roughing-out section A is increased at one time, and the length of the finishing section C, the roughing section B and the roughing-out section A occupied by the multi-head external thread 2 of the tap is reduced at one time, so that the junction of the finishing section C, the roughing section B and the roughing-out section A can form a chip breaking effect due to the change of the cutting diameter, and the volume of the iron chip and scrap at the bottom is larger than that at the top due to the different cutting amounts, which is more conducive to the spiral discharge of the iron chip through the chip guide groove 3; the multi-head tap comprises a tapping part and a cooling part, the tapping part is provided with a multi-head external thread 2 for processing a corresponding multi-head internal thread of the blind hole, the multi-head external thread 2 is provided with a plurality of spiral chip guide grooves 3, the spiral direction of the chip guide groove 3 is the same as that of the multi-head external thread 2, the spiral angle of the chip guide groove 3 is larger than that of the multi-head external thread 2, and the cooling part comprises a central hole 12 arranged at the center of the tap, the inner wall of the central hole 12 is provided with a radial first taper surface 15, the center of the radial first taper surface 15 is provided with a guide hole 10, a guide rod 14 is slidably arranged in the guide hole 10, the middle and upper part of the guide rod 14 is provided with a solid second taper surface 16, the first taper surface 15 and the second taper surface 16 are in contact, and are used for regulating the flow of the cooling liquid in the central hole 12, and the bottom end 5 of the guide rod 14 can extend out of the bottom outlet of the central hole 12.

[0023] When the first taper surface 15 and the second taper surface 16 are in contact, the guide rod bottom end 11 of the guide rod 12 extends out of the bottom end of the central hole 12.

[0024] The first taper surface 15 and the second taper surface 16 are located above the top end of the multi-head external thread 2.

[0025] The plurality of spiral chip guide grooves 3 are provided with a guide groove surface, a plurality of cooling liquid holes 4 are arranged along the spiral direction, and the cooling liquid holes 4 are in communication with the central hole 12.

[0026] In this way, the finishing section C, the roughing section B and the roughing-out section A at different processing stages are cooled separately, the cooling liquid directly corresponds to the tapping position for direct cooling, and the cooling liquid holes 4 pass through the walls of the finishing section C, the roughing section B and the roughing-out section A to have more contact area with the finishing section C, the roughing section B and the roughing-out section A, thereby increasing the cooling area and improving the cooling efficiency.

[0027] The bottom end of the guide rod 14 is rotationally connected with a contact head, when the contact head touches the bottom of the blind hole, the contact head stops rotating, and the guide rod 14 can continue to rotate with the tap.

[0028] Specifically, the bottom end of the guide rod 14 is provided with a stepped counterbore in the axial direction, which includes an upper step hole, a lower step hole and a bottom end limiting platform. The upper step hole is used to assemble the self-lubricating bushing, the lower step hole is a guide fitting surface for the contact connecting shaft, and the bottom end limiting platform is used to limit the axial displacement of the contact. The outer periphery of the bottom end of the guide rod is chamfered to avoid scratching the inner wall of the blind hole. The self-lubricating bushing is made of polytetrafluoroethylene (PTFE) filled copper-based bushing, so that the bushing has the characteristics of self-lubrication, wear resistance and corrosion resistance to cutting fluid. The outer diameter of the bushing is in interference fit with the upper step hole, and the inner diameter of the bushing is provided with an annular oil groove. The oil groove is pre-coated with solid lubricating grease to enhance the durability of lubrication. The axial length of the bushing is consistent with the depth of the upper step hole to ensure full adhesion. The contact connecting shaft is a steel shaft provided with a circular limiting cap at the top end. The diameter of the circular limiting cap is larger than the inner diameter of the self-lubricating bushing and smaller than the diameter of the upper step hole of the guide rod. The shaft body of the contact connecting shaft is in clearance fit with the inner diameter of the self-lubricating bushing, and the clearance is 0.01mm to 0.03mm to ensure smooth rotation. The contact connecting shaft is provided with a spherical groove for assembly with the contact. The contact is a steel ball with a diameter smaller than the minimum inner diameter of the blind hole to avoid interference with thread processing. The top end of the steel ball is provided with a cylindrical boss, which is assembled with the spherical groove at the bottom end of the connecting shaft through a transition fit. The end surface of the boss is provided with a micro-spherical surface to ensure that the contact can make a small universal swing around the connecting shaft to adapt to the possible inclined surface or residual iron filings at the bottom of the blind hole. The port of the spherical groove of the connecting shaft is provided with an annular chamfer to prevent scratching the boss of the contact.

[0029] Preferably, a return spring is provided between the connecting shaft limiting cap and the self-lubricating bushing to avoid abnormal noise caused by axial movement of the connecting shaft during tapping, and to help the contact always extend out of the center hole without resistance. The inner wall of the lower step hole of the guide rod is coated with a rust-proof lubricating coating to reduce friction and wear between the connecting shaft and the hole wall.

[0030] The specific installation process is as follows: press the self-lubricating bushing into the upper step hole at the bottom end of the guide rod 14 to ensure that the end surfaces of the bushing are flush with the upper and lower end surfaces of the upper step hole respectively. Pre-coat the solid lubricating grease in the oil groove of the inner diameter of the bushing; put the return spring into the upper step hole of the guide rod above the self-lubricating bushing; press the cylindrical boss at the top end of the contact into the spherical groove at the bottom end of the connecting shaft to ensure that the contact can swing freely; insert the connecting shaft with the assembled contact from the bottom end of the guide rod, with the shaft body passing through the self-lubricating bushing, the limiting cap at the top end pressing the return spring, and the lower end surface of the limiting cap being in contact with the upper end surface of the self-lubricating bushing to form axial limiting, thus completing the assembly.

[0031] When the tap drives the guide rod 14 to rotate synchronously, the self-lubricating bushing rotates with the guide rod, the connecting shaft drives the contact to rotate under the driving of the bushing, and the pre-tightening force of the return spring ensures that there is no relative sliding between the connecting shaft and the bushing. The spherical structure of the contact not only plays a guiding role, but also reduces the interference with the inner wall of the blind hole. When the contact head touches the bottom of the blind hole, the bottom supporting force overcomes the pre-tightening force of the reset spring, so that the contact head stops rotating, and the connecting shaft is synchronously stationary with the contact head; the guide rod continues to rotate with the tap, and the self-lubricating bushing and the connecting shaft realize smooth relative sliding through the self-lubricating property of the PTFE material, and at the same time, the oil groove in the bushing continuously provides lubrication, avoiding wear caused by dry friction; if there is an inclined surface or residual iron filings at the bottom of the blind hole, the contact head can make a small universal swing through the cooperation of the boss end face and the spherical groove of the connecting shaft, so as to ensure that the contact head is fully attached to the bottom, avoid the guide rod from being forced to be skewed, and ensure the stability of the tapping process.

[0032] The inner wall of the central hole 12 of the guide rod 14 is slidingly fitted, and the outer cylindrical surface of the guide rod 14 is circumferentially distributed with a plurality of cooling liquid flow channels 1401; the first taper surface 15 and the second taper surface 16 are divided into a plurality of circumferentially distributed inclined surfaces based on the distribution of the cooling liquid flow channels, the first taper surface 15 is divided into a plurality of first inclined surfaces, and the second taper surface 16 is divided into a plurality of second inclined surfaces; adjacent cooling liquid flow channels are provided with only one first inclined surface and one second inclined surface. That is, there is one open cooling liquid flow channel 1401 between every two pairs of first inclined surfaces and second inclined surfaces, and when the flow is needed to be adjusted, the contact gap between the first inclined surface and the second inclined surface is adjusted by moving the guide rod 14 until it is completely open, thereby realizing the adjustment of the flow of the cooling liquid.

[0033] It is worth mentioning that the first taper surface 15 and the second taper surface 16 have three functions: First, for adjusting the sliding of the guide rod through the main shaft accessory to adjust the contact area of the two taper surfaces, the flow of the cooling liquid in the central hole can be controlled; Second, for limiting the guide rod 14 to prevent the guide rod 14 from falling out of the central hole 12 and falling into the blind hole; Third, the centers of the first taper surface 15 and the second taper surface 16 are coaxial, the center of the first taper surface is provided with a guide hole 10, and the guide rod 14 can be guided.

[0034] Specifically, a plurality of radial support members 9 are arranged in the central hole 12 along the axial direction, the center of the radial support member 9 is provided with a guide hole 10, the radial first taper surface 15 is arranged above all the radial support members 9, the center of the first taper surface is also provided with a guide hole 10, the guide rod 14 is slidingly arranged in the guide hole 10, and the bottom circle diameter of the solid second taper surface 16 is smaller than the bottom circle diameter of the radial first taper surface 15.

[0035] The bottom circle diameter of the solid second conical surface 16 is smaller than the bottom circle diameter of the radial first conical surface 15. When the first conical surface 15 and the second conical surface 16 are attached, the cooling liquid passes between the outside of the bottom circle of the second conical surface 16 and the hole wall of the center hole, and then flows out through the radial gaps of the first conical surface 15 which are not blocked by the second conical surface 16, to perform cooling. When the first conical surface 15 and the second conical surface 16 are not attached, the cooling liquid passes between the outside of the bottom circle of the second conical surface 16 and the hole wall of the center hole, and then flows out through the radial gaps of the first conical surface 15, to perform cooling. The flow between the two is directly related to the distance of the attachment of the first conical surface 15 and the second conical surface 16.

[0036] The top end of the guide rod has a plurality of copper rings which are not connected to each other and are insulated and closed. The copper rings are uniformly arranged along the axis of the guide rod.

[0037] The structure of the copper ring is divided into two layers. The core of the copper ring is copper, and the surface is an insulating layer such as rubber or plastic. Adjacent copper rings are separated by an insulating spacer ring, and the material of the spacer ring is also rubber or plastic. The topmost copper ring is fixed to the top end 7 of the guide rod by a nut.

[0038] When a magnetic field is applied outside the clamping section E, the guide rod 14 drives the copper ring 8 to move in the magnetic field. The closed copper ring generates eddy current. The resistivity of copper is much lower than that of steel. The eddy current intensity of the copper ring is 5-10 times that of the metal rod. The copper ring eddy current decays more slowly. Even if the tap drives the guide rod to rotate in the magnetic field to generate eddy current, the copper ring eddy current decays more slowly. The eddy current signal in the copper ring can be detected by the eddy current sensor, and then the real-time position signal of the guide rod is formed, which is used by the machine tool system to judge whether the tap has reached the bottom of the blind hole.

[0039] For example, the application of the guide rod is illustrated by taking Figure 8 as an example. The rotary joint 17 in the figure is a component for connecting the static pipeline and the rotating spindle. It is prior art and is installed at the tail of the spindle, divided into a static end and a rotating end, and isolated in the middle by a sealing structure.

[0040] The static end connects the machine tool cooling liquid fixed pipeline for receiving high-pressure cooling liquid and forms a sealed cavity with the rotating end, which does not rotate with the spindle. The rotating end connects the center interface at the tail of the spindle and rotates synchronously with the spindle to guide the cooling liquid into the internal passage of the spindle. The sealing structure adopts a graphite silicon carbide sealing ring for high-pressure lamination sealing, which can adapt to high-speed rotation of the rotating end with a leakage of ≤5ml / min. It also includes a bearing supporting the rotating end and a dustproof ring for reducing rotation friction and preventing cuttings and dust from entering the sealing surface.

[0041] High-pressure cooling liquid from the static end into the sealing cavity of the rotary joint, due to the graphite side of the sealing ring is fixed, the silicon carbide side rotates with the rotating end, and the precise fit, the cooling liquid cannot leak, can only pass through the central hole of the rotating end into the main shaft inside, that is, into the cooling liquid cavity 22, at this time the static end of the rotary joint 17 remains stationary, the rotating end drives the tap to rotate.

[0042] The side wall of the static end is provided with a fixing hole, and the sensor 18 is sealingly fixed in the fixing hole. The top end of the guide rod is fixed with a sensing block 19. When the bottom end 11 of the guide rod hits the bottom of the blind hole, the top end 7 of the guide rod moves upward, drives the sensing block 19 to sweep the sensing head of the sensor 18, generates a detection signal, and then detects that the bottom end 11 of the guide rod hits the bottom of the blind hole, so that the bottom end 11 of the guide rod hits the bottom of the blind hole during tapping is directly detected, and detection by using a special tool after the tap is withdrawn is not needed.

[0043] For the center hole of the tap center, the central hole provides a channel for cooling liquid flow, the first conical surface of the inner wall is in contact with the second conical surface of the sliding guide rod in the guide hole, and the contact area of the two conical surfaces can be adjusted by adjusting the sliding of the guide rod. The flow of the cooling liquid in the central hole can be adjusted. The specific implementation means of this process can be understood as three cases: The first is passive self-adjustment. When the multi-head tap encounters resistance in the company, for example, when approaching the bottom of the blind hole, the bottom end 11 of the guide rod 14 is pressed by the bottom of the blind hole, so that the guide rod 14 and the tap slide relatively, and then the first conical surface 15 and the second conical surface 16 are opened. The fit realizes the increased supply of cooling liquid, accelerates the cooling adjustment, and at the same time can trigger a detection signal to realize real-time detection of whether the tap reaches the bottom of the blind hole; The second is active adjustment. At this time, the cooling liquid cavity 22 of the rotary joint 17 needs to be provided with a U-shaped or ring-shaped bracket to hold the bottom surface of the sensing block 19, and the top surface of the sensing block 19 is free. The bracket needs to be connected with the external servo motor in the form of a cam or a linear module, and the sensing block 19 is driven upward by the servo motor driving the cam or the linear module. The purpose of the top surface of the sensing block 19 being free is that the bottom end 11 of the guide rod 14 is pressed by the bottom of the blind hole, so that the guide rod 14 and the tap slide relatively, and the sensing block 19 cannot be driven to sweep the sensing head of the sensor 18 to generate a detection signal due to the influence of the bracket.

[0044] The foregoing has broadly outlined some aspects and features of various embodiments, which should be interpreted as merely illustrative of a potential application. Other beneficial results can be obtained by applying the disclosed information in different ways or by combining aspects of the disclosed embodiments. Other aspects and more comprehensive understandings can be obtained by referring to the specific description of the exemplary embodiments in conjunction with the drawings, which are limited by the scope defined by the claims.

[0045] The above embodiments have been described in detail. Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or reductions, and replacements made by those skilled in the art within the spirit and scope of the present application also belong to the protection scope of the present application.

Claims

1. A multi-start tap, used in CNC machine tools for tapping blind holes in workpieces, the multi-start tap comprising a tapping section and a cooling section, the tapping section having a multi-start external thread, the multi-start external thread being used to machine a corresponding multi-start internal thread forming the blind hole, the multi-start external thread having multiple helical chip guide grooves, the helix direction of the chip guide grooves being the same as that of the multi-start external thread, and the helix angle of the chip guide grooves being greater than that of the helix angle of the multi-start external thread, characterized in that... The cooling section includes a central hole located at the center of the tap. The inner wall of the central hole has a radial first conical surface. A guide hole is located at the center of the radial first conical surface. A guide rod is slidably mounted in the guide hole. A solid second conical surface is located in the upper middle part of the guide rod. The first and second conical surfaces are in contact to regulate the flow rate of coolant in the central hole. The bottom end of the guide rod can extend out of the bottom outlet of the central hole.

2. The multi-start tap according to claim 1, characterized in that, When the first and second conical surfaces come into contact, the bottom end of the guide rod extends out from the bottom end of the central hole.

3. A multi-start tap according to claim 2, characterized in that, The first and second conical surfaces are located above the top of the multi-start external thread.

4. A multi-start tap according to claim 3, characterized in that, The plurality of spiral chip guide grooves are provided with guide groove surfaces, and a number of coolant holes are provided along the spiral direction of the guide groove surfaces, the coolant holes being connected to the central hole.

5. A multi-start tap according to any one of claims 1 to 4, characterized in that, The bottom end of the guide rod is rotatably connected to a contact. When the contact touches the bottom of the blind hole, the contact stops rotating, and the guide rod can continue to rotate with the tap.

6. A multi-start tap according to claim 5, characterized in that, The inner wall of the central hole of the guide rod is slidably fitted, and the outer cylindrical surface of the guide rod is evenly distributed with several coolant channels. The first and second conical surfaces are divided into several evenly distributed circumferential inclined surfaces based on the distribution of the coolant channels. The first conical surface is divided into several first inclined surfaces, and the second conical surface is divided into several second inclined surfaces. Adjacent coolant channels have only one first inclined surface and one second inclined surface.

7. A multi-start tap according to claim 5, characterized in that, Several radial support members are arranged along the axial direction inside the central hole. A guide hole is provided at the center of the radial support frame. The guide rod is slidably arranged in the guide hole. The radial first conical surface is located above all the radial support members. The bottom circle diameter of the solid second conical surface is smaller than the bottom circle diameter of the radial first conical surface.

8. A multi-start tap according to claim 6, characterized in that, The top of the guide rod has several non-connected and insulated copper rings, which are evenly arranged along the axis of the guide rod.

9. A multi-start tap according to claim 7, characterized in that, The top of the guide rod has several non-connected and insulated copper rings, which are evenly arranged along the axis of the guide rod.

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