Cold heading die for high-precision machining of bolt and cold heading technology of cold heading die

Abstract

The invention relates to the field of bolt manufacturing, and discloses a cold heading die for bolt high-precision machining, the cold heading die comprises a movable die component and a fixed die component, the fixed die component comprises a fixed cylindrical shell, an upper end cover is arranged at the upper opening end of the fixed cylindrical shell, an upper mounting groove is coaxially formed in the end face of the upper end cover, and a lower avoiding hole is coaxially formed in the groove bottom of the upper mounting groove; a bracket is arranged in the upper mounting groove in a sleeved mode, a bracket groove matched with the shape of the head of a blank bolt is formed in the upper surface of the bracket, a penetrating hole is formed in the groove bottom of the bracket groove, a third spring is arranged between the bracket and the groove bottom of the upper mounting groove, and a tooth plate is arranged in the fixed cylindrical shell in a sliding mode in the radial direction. The sides, facing the axis of the fixed column shell, of the tooth plates are arranged to be arc faces, rolling threads are arranged on the arc faces, the multiple tooth plates are arranged in the circumferential direction of the fixed column shell in an array mode, the arc faces of all the tooth plates can form a complete cylindrical outer circle face, and the cylindrical outer circle face and the fixed column shell are coaxial.

Description

Technical Field

[0001] The present invention relates to the field of bolt manufacturing, specifically to the field of cold heading of bolts, and particularly to a cold heading die for high-precision machining of bolts and its cold heading process. Background Art

[0002] A thread cold heading machine is an efficient cold forming equipment for mass-producing threaded fasteners (such as bolts, screws, studs, etc.). It realizes high-efficiency and high-precision thread forming through cold heading + thread rolling. Its cold heading process includes shearing a wire rod to a preset length to obtain a blank, upsetting the blank into a preset shape, and thread rolling the blank. Among them, the quality of the thread obtained by rolling is one of the important factors affecting the production precision of fasteners.

[0003] In the prior art, the blank is fed between multiple thread rolling wheels of a thread rolling machine. Through the rotation of the thread rolling wheels, the blank is driven to rotate and axially feed. At the same time, the tooth profile of the thread rolling wheels continuously extrudes the surface of the blank to form a thread. This method has some deficiencies. For example, on the one hand, there are generally 2-3 thread rolling wheels. When in use, if the blank is not calibrated and has a taper or diameter fluctuation itself, the roundness deviation is likely to occur in the threaded area after thread rolling. In addition, uneven pressure of the thread rolling wheels is also likely to cause roundness deviation, which may lead to local deformation or ovalization. On the one hand, when in use, the blank is directly subjected to cold plastic deformation according to the set requirements, that is, the thread is formed in one step without a gradual process. And because cold plastic deformation is a chip-free machining process, the material is not cut off, but only displaced and redistributed. Therefore, directly causing large plastic deformation of the material is likely to affect the final thread quality. On the one hand, when machining a thread, it is generally necessary to spray a lubricant into the machining area. However, a thread rolling machine is generally open or has a cover outside, and this method cannot make the sprayed lubricant act on the thread rolling wheels and the blank to the greatest extent, and the utilization rate of the lubricant is low.

[0004] Based on the above, the present invention proposes a cold heading die for high-precision machining of bolts and its cold heading process. Summary of the Invention

[0005] To solve the problems mentioned in the above background, the present invention provides a cold heading die for high-precision machining of bolts and its cold heading process.

[0006] To achieve the above technical objectives, the technical solutions adopted by the present invention are as follows.

[0007] A cold heading die for high-precision machining of bolts includes a moving die member and a fixed die member;

[0008] The fixed mold component includes a fixed column shell arranged vertically, the upper end of the fixed column shell is open and provided with an upper end cover, and the lower end is closed, the end surface of the upper end cover is coaxially provided with an upper mounting groove, the bottom of the upper mounting groove is coaxially provided with a lower avoidance hole, a bracket is sleeved in the upper mounting groove, the upper surface of the bracket is provided with a bracket matching the shape of the blank bolt head, the bottom of the bracket is provided with a through hole, and a third spring is provided between the bracket and the bottom of the upper mounting groove;

[0009] A tooth plate is provided inside the fixed cylindrical shell for radial sliding. The side of the tooth plate facing the axis of the fixed cylindrical shell is provided with an arc surface and a rolling thread is provided on the arc surface. A plurality of tooth plates are arranged in an array along the circumferential direction of the fixed cylindrical shell, and the arc surfaces of all the tooth plates can form a complete cylindrical outer surface and the cylindrical outer surface is coaxial with the fixed cylindrical shell.

[0010] The fixed mold component also includes a driving assembly, which is used to drive the tooth plate to move by the downward movement of the movable mold component.

[0011] Furthermore, a side of the tooth plate away from the axis of the fixed column shell is provided with an inclined surface 1, and the distance between the inclined surface 1 and the axis of the fixed column shell decreases from bottom to top;

[0012] The driving assembly includes a push seat which is slidably arranged in the fixed column shell along the vertical direction. The push seat is arranged to form a second inclined plane on the side facing the axis of the fixed column shell. The first inclined plane is fitted with the second inclined plane and the two form a sliding connection along the inclined direction of the first inclined plane. There are multiple push seats corresponding to the number of tooth plates. A convex rod is arranged on the upper surface of the push seat. The upper end of the convex rod extends out of the fixed column shell. All the convex rods are connected by a fixing ring.

[0013] Furthermore, the movable mold component includes an external pressure column coaxially located above the fixed column housing, a lower end surface of the external pressure column is coaxially provided with a lower mounting groove, and a groove bottom of the lower mounting groove is coaxially provided with an upper mounting hole;

[0014] A rotating shaft is coaxially installed in the upper mounting hole, and a linking piece and a coil spring are arranged between the two. When relative displacement occurs between the external pressure column and the rotating shaft, the rotating shaft can be driven to rotate through the linking piece.

[0015] Furthermore, a slot is provided at the upper end of the rotating shaft, one end of the coil spring is connected to the upper mounting hole, and the other end is inserted into the slot.

[0016] Furthermore, the linkage member includes a spiral convex strip arranged on the wall of the upper mounting hole and a spiral slide groove arranged on the outer circumferential surface of the rotating shaft, and the spiral convex strip is located in the spiral slide groove.

[0017] Further, a limiting ring column is coaxially arranged at the lower end of the rotating shaft. A first spring is arranged between the upper end of the limiting ring column and the bottom of the lower mounting groove. A spline groove is coaxially arranged on the lower end surface of the rotating shaft. An inserting shaft is arranged in the spline groove. The lower end of the inserting shaft is arranged in a shape matching the inner hexagonal hole of the blank bolt head.

[0018] Feed the blank into the fixed die member. The bolt head of the blank is supported by the support seat. During the downward movement of the external pressure column, the lower end of the inserting shaft first inserts into the inner hexagonal hole of the blank bolt head. Then, the external pressure column continues to move downward, and the second spring is compressed. When the compression amount of the second spring reaches the maximum, the lower end of the limiting ring column contacts the notch of the upper mounting groove. At the same time, the lower end of the external pressure column contacts the upper end of the fixed ring.

[0019] Further, the inserting shaft is arranged in the spline groove through a spline. And when relative displacement occurs between the inserting shaft and the rotating shaft, power connection is maintained between the two through the spline. A second spring is arranged between the inserting shaft and the bottom of the spline groove.

[0020] Further, a ring groove is coaxially arranged at the lower closed end of the fixed column shell. A lower end cover is arranged at the notch of the ring groove. A piston is sleeved in the ring groove. A fourth spring is arranged between the piston and the lower end cover. A connecting rod is arranged at the bottom of the pushing seat. The lower end of the connecting rod extends into the ring groove and is connected to the piston.

[0021] A first channel is arranged in the fixed column shell. A connecting hole communicating with the first channel is arranged on the groove wall of the ring groove. A first one-way valve is arranged in the first channel. The first one-way valve is used to make the lubricant in the ring groove flow into the first channel unidirectionally.

[0022] An inlet is arranged on the lower end cover. A second one-way valve is arranged at the inlet. The second one-way valve is used to make the external lubricant flow into the ring groove unidirectionally.

[0023] An outlet is coaxially arranged on the end face of the lower end cover. An output pipe is arranged at the lower orifice of the outlet. The outlet communicates with the thread processing area.

[0024] A second channel is arranged in the pushing seat. The area between the arc surfaces of multiple tooth plates is named the thread processing area. The second channel is used to realize the communication between the first channel and the thread processing area.

[0025] A cold heading process for a cold heading die for high-precision bolt processing includes the following steps:

[0026] Step 1: Feed the blank into the fixed die member. The bolt head of the blank is supported by the support seat.

[0027] Step 2: Drive the external pressure column to move downward. During the downward movement, the lower end of the insertion shaft first inserts into the hexagonal socket in the head of the blank bolt. Then, the external pressure column continues to move downward, compressing the second spring. When the compression of the second spring reaches its maximum, the lower end of the limit ring column contacts the notch of the upper installation groove. At the same time, the lower end of the external pressure column contacts the upper end of the fixed ring.

[0028] Step 3: The external pressure column continues to move downward and pushes the fixed ring downward together, thus gradually closing the tooth plates to form a complete cylindrical outer surface. That is, the rolled threads on the arc surface of the tooth plates gradually squeeze the blank. At the same time, the downward movement of the external pressure column can cause the rotating shaft to rotate through the linkage. The rotating shaft drives the insertion shaft and the blank to rotate together. While the blank rotates, it also moves downward. Thread processing is achieved by gradually squeezing the blank with the rolled threads and the blank rotating and moving downward at the same time.

[0029] At the same time, the push seat will drive the piston to move downward together, thus pushing the lubricant in the ring groove. The lubricant flows into the thread processing area through the connecting hole, the first one-way valve, the first channel, and the second channel in sequence to achieve the lubrication purpose. The lubricated lubricant flows downward under the action of gravity and is output outward through the outlet and the output pipe.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] In this solution, the rolled threads on the arc surface of the tooth plates are driven to gradually squeeze the blank, and the blank rotates and moves downward at the same time, thereby realizing thread processing. The advantages are as follows: 1. When the thread processing is completed, the bolt screw part of the blank is located inside the complete cylindrical outer surface. Therefore, it can achieve the purpose of coaxial correction, ensure the coaxiality of the bolt screw part, and thus solve the first problem mentioned in the background art; 2. During the thread processing, the rolled threads gradually squeeze the blank. That is to say, the threads on the blank are not formed in one step, but have a cyclic progressive extrusion plastic deformation process. Therefore, compared with the one-step forming method, the threads processed by this solution have higher quality, solving the second problem mentioned in the background art; 3. When processing threads in this solution, the tooth plates gradually close. Therefore, the lubricant can smoothly flow into the rolled threads and be distributed at various positions of the rolled threads. The lubrication effect is better, and the lubricant can be maximally applied to the thread processing position. The utilization rate of the lubricant is higher, that is, during processing, less lubricant can achieve the desired lubrication effect, solving the third problem mentioned in the background art. Brief Description of the Drawings

[0032] Figure 1 is a schematic structure of the present invention Figure 1 ;

[0033] Figure 2 is a schematic structure of the present invention Figure 2 ;

[0034] Figure 3 is a cross-sectional view of the present invention;

[0035] Figure 4 is a cross-sectional view of the moving die member;

[0036] Figure 5 is a partial exploded view of the moving die member;

[0037] Figure 6 is an overall cross-sectional view of the fixed die member;

[0038] Figure 7 is a partial cross-section of the fixed die member Figure 1 ;

[0039] Figure 8 is a partial cross-section of the fixed die member Figure 2 ;

[0040] Figure 9 is a schematic diagram of the push seat and the tooth plate.

[0041] The reference numerals in the drawings are:

[0042] 100, moving die member; 101, external pressure column; 1011, lower mounting groove; 1012, upper mounting hole; 1013, spiral rib; 102, rotating shaft; 1021, spiral chute; 1022, spline groove; 103, coil spring; 104, limit ring column; 105, first spring; 106, insertion shaft; 107, second spring; 200, fixed die member; 201, fixed column shell; 2011, upper end cover; 2012, upper mounting groove; 2013, lower avoidance hole; 2014, ring groove; 2015, lower end cover; 2016, connection hole; 2017, first channel; 2018, first one-way valve; 202, tooth plate; 203, push seat; 2031, convex rod; 2032, fixed ring; 2033, second channel; 204, support seat; 205, third spring; 206, ejector rod; 207, piston; 208, fourth spring. Detailed implementation manners

[0043] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features and their effects of the present invention as follows.

[0044] In the attached drawings of this solution, a refers to a bolt.

[0045] This solution realizes thread processing by cold heading, and one of the cores lies in the cold heading die used for thread processing.

[0046] Embodiment 1

[0047] Refer toFigures 1 - 9 , a cold heading die for high-precision machining of bolts, includes a moving die member 100 and a stationary die member 200. When in use, the blank is fed into the stationary die member 200, and then by driving the moving die member 100 to move downward. During the downward movement, through the cooperation of the moving die member 100 and the stationary die member 200, the thread machining of the blank is realized. Among them, the existing hydraulic technology can be used to drive the moving die member 100 to move downward or upward, which will not be elaborated here.

[0048] Stationary die member 200:

[0049] Refer to Figures 6 - 9 , the stationary die member 200 includes a fixed column shell 201 arranged vertically.

[0050] The upper end of the fixed column shell 201 is open and provided with an upper end cover 2011, and the lower end is closed. The end face of the upper end cover 2011 is coaxially provided with an upper mounting groove 2012. The bottom of the upper mounting groove 2012 is coaxially provided with a lower avoidance hole 2013. A support seat 204 is sleeved in the upper mounting groove 2012. The shape of the support seat 204 is matched with the shape of the bolt head of the blank, that is, the upper surface of the support seat 204 is provided with a hexagonal-shaped support groove. The bottom of the support groove is provided with a through hole for avoiding the bolt screw of the blank. Therefore, the support seat 204 places the bolt head of the blank through the support groove and restricts the blank from moving radially. A third spring 205 is arranged between the support seat 204 and the upper mounting groove 2012.

[0051] A die plate 202 is slidably arranged radially inside the fixed column shell 201. The side of the die plate 202 facing the axis of the fixed column shell 201 is set as an arc surface and a rolling thread is arranged on the arc surface. A plurality of die plates 202 are arranged in an array along the circumferential direction of the fixed column shell 201, and the arc surfaces of all die plates 202 can form a complete cylindrical outer surface and there is a complete rolling thread on this cylindrical outer surface, and this cylindrical outer surface is coaxial with the fixed column shell 201.

[0052] The fixed mold member 200 further includes a driving assembly for driving the tooth plate 202 to move. Specifically, one side of the tooth plate 202 facing away from the axis of the fixed column shell 201 is provided with a first inclined surface, and the distance between the first inclined surface and the axis of the fixed column shell 201 decreases from bottom to top. The driving assembly includes a push seat 203 slidably arranged in the fixed column shell 201 in the vertical direction. One side of the push seat 203 facing the axis of the fixed column shell 201 is provided with a second inclined surface. The first inclined surface and the second inclined surface are in contact and form a sliding connection along the inclined direction of the first inclined surface. Therefore, when the push seat 203 moves downward, it can push the tooth plate 202 to move closer to the axis of the fixed column shell 201. When adjacent tooth plates 202 are in contact with each other, the complete cylindrical outer surface mentioned above is formed. On the contrary, when the push seat 203 moves upward, it can pull the tooth plate 202 to move away from the axis of the fixed column shell 201. A plurality of push seats 203 are correspondingly arranged according to the number of tooth plates 202. Further, a convex rod 2031 is provided on the upper surface of the push seat 203. The upper end of the convex rod 2031 passes through the upper end cover 2011 and extends out of the fixed column shell 201. All the convex rods 2031 are connected by a fixing ring 2032. The push seat 203 is driven to move by driving the fixing ring 2032.

[0053] Moving mold member 100:

[0054] Refer to Figure 4 With Figure 5 As shown in, the moving mold member 100 includes an outer pressure column 101 coaxially located above the fixed column shell 201. A lower mounting groove 1011 is coaxially provided on the lower end surface of the outer pressure column 101, and an upper mounting hole 1012 is coaxially provided at the bottom of the lower mounting groove 1011.

[0055] A rotating shaft 102 is coaxially installed in the upper mounting hole 1012, and a linkage and a coil spring 103 are arranged between the two. A slot is provided at the upper end of the rotating shaft 102. One end of the coil spring 103 is connected to the upper mounting hole 1012, and the other end is inserted into the slot. Therefore, when the rotating shaft 102 moves with reference to the coil spring 103, the coil spring 103 still maintains its connection with the rotating shaft 102. When a relative displacement occurs between the outer pressure column 101 and the rotating shaft 102, the rotating shaft 102 can be driven to rotate through the linkage. Specifically, the linkage includes a spiral convex strip 1013 provided on the inner wall of the upper mounting hole 1012 and a spiral chute 1021 provided on the outer cylindrical surface of the rotating shaft 102. The spiral convex strip 1013 is located in the spiral chute 1021. Preferably, the pitch of the spiral convex strip 1013 and the spiral chute 1021 is relatively large. Therefore, when a relative displacement occurs between the outer pressure column 101 and the rotating shaft 102, the rotating shaft 102 can be rotated through the cooperation of the spiral convex strip 1013 and the spiral chute 1021.

[0056] A limit ring column 104 is coaxially arranged at the lower end of the rotating shaft 102, and a first spring 105 is arranged between the upper end of the limit ring column 104 and the bottom of the lower mounting groove 1011.

[0057] A spline groove 1022 is coaxially arranged on the lower end face of the rotating shaft 102. An insertion shaft 106 is arranged in the spline groove 1022 through a spline. When a relative displacement occurs between the insertion shaft 106 and the rotating shaft 102, the two are in power connection through the spline. A second spring 107 is arranged between the insertion shaft 106 and the bottom of the spline groove 1022.

[0058] The lower end of the insertion shaft 106 is set to a shape matching the inner hexagonal hole of the blank bolt head.

[0059] The blank is fed into the fixed die member 200. The bolt head of the blank is supported by the support seat 204. Then, the external pressure column 101 is driven to move downward by the existing hydraulic technology. During the downward movement, the lower end of the insertion shaft 106 first inserts into the inner hexagonal hole of the blank bolt head. Then, the external pressure column 101 continues to move downward, and the second spring 107 is compressed. When the compression amount of the second spring 107 reaches the maximum, the lower end of the limit ring column 104 contacts the notch of the upper mounting groove 2012. At the same time, the lower end of the external pressure column 101 contacts the upper end of the fixed ring 2032.

[0060] After that, the external pressure column 101 continues to move downward. The external pressure column 101 pushes the fixed ring 2032 to move downward together, so that the tooth plates 202 gradually close together to form a complete cylindrical outer surface. That is, the rolling threads on the arc surface of the tooth plates 202 gradually extrude the blank. At the same time, the rotating shaft 102 rotates through the linkage member. The rotating shaft 102 drives the insertion shaft 106 and the blank to rotate together. Due to the existence of the rolling threads, the blank rotates and moves downward at the same time. That is to say, by driving the rolling threads on the arc surface of the tooth plates 202 to gradually extrude the blank, and adding the rotation and downward movement of the blank, the processing of the thread is realized. The advantages are as follows: 1. When the thread processing is completed, the bolt screw part of the blank is located inside the complete cylindrical outer surface. Therefore, it can achieve the purpose of coaxial correction, ensure the coaxiality of the bolt screw part, and thus solve the first problem mentioned in the background technology; 2. During the thread processing, the rolling threads gradually extrude the blank. That is to say, the threads on the blank are not formed in one step, but have a cyclic progressive extrusion plastic deformation process. Therefore, compared with the one-step forming method, the threads processed by this scheme have higher quality, and solve the problem 2 mentioned in the background technology.

[0061] In addition, during the thread processing, when the blank rotates and moves downward, the second spring 107 continuously releases elastic force, so that the insertion shaft 106 continuously inserts into the inner hexagonal hole of the blank bolt head, ensuring that the movement of the blank rotating and moving downward can proceed smoothly.

[0062] Preferred embodiment, referring to Figure 6 , after the thread is processed, a top hole can be coaxially provided at the lower closed end of the fixed column shell 201, and a top rod 206 is arranged in the top hole. The top rod 206 is of a telescopic rod structure, such as an electric telescopic rod, and the blank is pushed out through the top rod 206 to facilitate the output of the processed blank.

[0063] Embodiment Two

[0064] When processing the thread in Embodiment One, it is necessary to spray lubricant at the processing position. Therefore, Embodiment Two is proposed.

[0065] Referring to Figures 6 - 9 , a ring groove 2014 is coaxially provided at the lower closed end of the fixed column shell 201. A lower end cover 2015 is provided at the notch of the ring groove 2014. A piston 207 is sleeved in the ring groove 2014. A fourth spring 208 is arranged between the piston 207 and the lower end cover 2015. A connecting rod is provided at the bottom of the push seat 203. The lower end of the connecting rod extends into the ring groove 2014 and is connected to the piston 207. Therefore, when the push seat 203 moves, the piston 207 moves together.

[0066] A first channel 2017 is arranged in the fixed column shell 201. A connecting hole 2016 communicating with the first channel 2017 is arranged on the groove wall of the ring groove 2014. A first one-way valve 2018 is arranged in the first channel 2017. The first one-way valve 2018 is used to make the lubricant in the ring groove 2014 flow into the first channel 2017 unidirectionally.

[0067] An inlet is arranged on the lower end cover 2015. A second one-way valve is arranged at the inlet. The second one-way valve is used to make the external lubricant flow into the ring groove 2014 unidirectionally. For example, the lubricant is injected into the inlet through technologies such as a peristaltic pump and a water pump. Further, the aperture of the top hole mentioned above is larger than the diameter of the top rod 206. An outlet is coaxially arranged on the end face of the lower end cover 2015. A sleeve is arranged in the outlet through a bracket. The top rod 206 is sleeved in the sleeve. An output pipe is further arranged at the lower orifice of the outlet. An avoidance opening for avoiding the top rod 206 is arranged on the output pipe. The outlet is communicated with the top hole. Therefore, the used lubricant will be output outward through the top hole, the outlet and the output pipe. The inlet and the second one-way valve are not shown in the figure.

[0068] A second channel 2033 is arranged in the push seat 203. The area between the arc surfaces of the plurality of tooth plates 202 is named as the thread processing area. The second channel 2033 is used to realize the communication between the first channel 2017 and the thread processing area.

[0069] Working process of Embodiment Two:

[0070] During the thread machining process, when the pushing seat 203 moves downward, it will drive the piston 207 to move downward together, thereby pushing the lubricant in the annular groove 2014. The lubricant sequentially passes through the connecting hole 2016, the first one-way valve 2018, the first channel 2017, and the second channel 2033 and flows into the thread machining area to achieve the lubrication purpose. After lubrication, the lubricant flows downward under the action of gravity and is output outward through the top hole, the outlet, and the output pipe. In addition, the lubricant in the annular groove 2014 can be replenished by existing technologies such as peristaltic pumps and water pumps;

[0071] It should be noted that, referring to Figure 7 , what is shown is the initial situation. As the pushing seat 203 moves downward, the second channel 2033 will communicate with the thread machining area.

[0072] As can be seen from the above: When machining threads according to this solution, the lubricant can be maximally applied to the thread machining position, and the utilization rate of the lubricant is higher. That is, during machining, less lubricant can achieve the desired lubrication effect, solving the third problem mentioned in the background technology. In addition, during the thread machining process of this solution, the die plates 202 gradually close. Therefore, the lubricant can smoothly flow into the rolled threads and be distributed at various positions of the rolled threads. Therefore, the lubrication effect is better.

[0073] The above are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content without departing from the technical solution scope of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A cold heading die for high-precision bolt processing, characterized in that: It comprises a movable mold component (100) and a fixed mold component (200); The fixed mold component (200) comprises a fixed column shell (201) arranged vertically, the upper end of the fixed column shell (201) is open and provided with an upper end cover (2011), and the lower end is closed, the end surface of the upper end cover (2011) is coaxially provided with an upper mounting groove (2012), the bottom of the upper mounting groove (2012) is coaxially provided with a lower avoidance hole (2013), a bracket (204) is sleeved in the upper mounting groove (2012), the upper surface of the bracket (204) is provided with a bracket matching the shape of the blank bolt head, the bottom of the bracket is provided with a through hole, and a third spring (205) is provided between the bracket (204) and the bottom of the upper mounting groove (2012); A tooth plate (202) is radially slidably arranged inside the fixed column shell (201), and a side of the tooth plate (202) facing the axis of the fixed column shell (201) is arranged as an arc surface and a rolled thread is arranged on the arc surface. A plurality of tooth plates (202) are arranged in an array along the circumferential direction of the fixed column shell (201), and the arc surfaces of all the tooth plates (202) can form a complete cylindrical outer circumferential surface, and the cylindrical outer circumferential surface is coaxial with the fixed column shell (201); The fixed mold component (200) also includes a driving component, which is used to drive the tooth plate (202) to move by the downward movement of the movable mold component (100).

2. A cold heading die for high-precision bolt machining according to claim 1, characterized in that: A side of the tooth plate (202) away from the axis of the fixed column housing (201) is provided as an inclined surface 1, and the distance between the inclined surface 1 and the axis of the fixed column housing (201) decreases from bottom to top; The driving assembly comprises a push seat (203) slidably arranged in a fixed column shell (201) along a vertical direction, a second inclined plane is arranged on one side of the push seat (203) facing the axis of the fixed column shell (201), the first inclined plane is in contact with the second inclined plane and the two form a sliding connection along the inclined direction of the first inclined plane, a plurality of push seats (203) are arranged corresponding to the number of tooth plates (202), a convex rod (2031) is arranged on the upper surface of the push seat (203), the upper end of the convex rod (2031) extends out of the fixed column shell (201), and all the convex rods (2031) are connected by a fixing ring (2032).

3. A cold heading die for high-precision bolt machining according to claim 2, characterized in that: The movable mold component (100) comprises an external pressure column (101) coaxially located above the fixed column housing (201), a lower end surface of the external pressure column (101) is coaxially provided with a lower mounting groove (1011), and a groove bottom of the lower mounting groove (1011) is coaxially provided with an upper mounting hole (1012); A rotating shaft (102) is coaxially mounted in the upper mounting hole (1012), and a linkage and a coil spring (103) are arranged between the two. When relative displacement occurs between the external pressure column (101) and the rotating shaft (102), the rotating shaft (102) can be driven to rotate through the linkage.

4. A cold heading die for high-precision bolt machining according to claim 3, characterized in that: A slot is provided at the upper end of the rotating shaft (102); one end of the coil spring (103) is connected to the upper mounting hole (1012) and the other end is inserted into the slot.

5. The cold heading die for high-precision bolt machining according to claim 3, characterized in that: The linkage member comprises a spiral convex strip (1013) arranged on the hole wall of the upper mounting hole (1012) and a spiral slide groove (1021) arranged on the outer circumferential surface of the rotating shaft (102), and the spiral convex strip (1013) is located in the spiral slide groove (1021).

6. A cold heading die for high-precision bolt machining according to claim 3, characterized in that: A limiting ring column (104) is coaxially arranged at the lower end of the rotating shaft (102), a first spring (105) is arranged between the upper end of the limiting ring column (104) and the bottom of the lower mounting groove (1011), a spline groove (1022) is coaxially arranged at the lower end surface of the rotating shaft (102), an insert shaft (106) is arranged in the spline groove (1022), and the lower end of the insert shaft (106) is arranged in a shape matching the hexagonal hole of the head of the blank bolt; The blank is fed into the fixed mold component (200), and the bolt head of the blank is supported by the bracket (204). During the downward movement of the external pressure column (101), the lower end of the insertion shaft (106) is first inserted into the hexagonal hole of the bolt head of the blank, and then the external pressure column (101) continues to move downward, and the second spring (107) is compressed. When the compression amount of the second spring (107) reaches the maximum, the lower end of the limiting ring column (104) contacts the notch of the upper mounting groove (2012), and at the same time, the lower end of the external pressure column (101) contacts the upper end of the fixing ring (2032).

7. A cold heading die for high-precision bolt machining according to claim 6, characterized in that: An insertion shaft (106) is arranged in the spline groove (1022) via a spline, and when relative displacement occurs between the insertion shaft (106) and the rotating shaft (102), the two are kept in dynamic connection via the spline, and a second spring (107) is arranged between the insertion shaft (106) and the bottom of the spline groove (1022).

8. The cold heading die for high-precision bolt machining according to claim 6, characterized in that: A ring groove (2014) is coaxially arranged at the lower closed end of the fixed column housing (201), a lower end cover (2015) is arranged at the notch of the ring groove (2014), a piston (207) is sleeved in the ring groove (2014), a fourth spring (208) is arranged between the piston (207) and the lower end cover (2015), a connecting rod is arranged at the bottom of the push seat (203), and the lower end of the connecting rod extends into the ring groove (2014) and is connected to the piston (207); A first channel (2017) is provided in the fixed column housing (201), a connecting hole (2016) communicating with the first channel (2017) is provided on the groove wall of the annular groove (2014), a first one-way valve (2018) is provided in the first channel (2017), and the first one-way valve (2018) is used to allow the lubricant in the annular groove (2014) to flow into the first channel (2017) in a one-way manner; The lower end cover (2015) is provided with an inlet, and a second one-way valve is provided at the inlet, and the second one-way valve is used to allow external lubricant to flow into the annular groove (2014) in a one-way manner; An outlet is coaxially arranged on the end surface of the lower end cover (2015), an output pipe is arranged at the lower opening of the outlet, and the outlet is connected to the thread processing area; A second channel (2033) is provided in the push seat (203), and the area between the arc surfaces of the plurality of tooth plates (202) is named a thread processing area. The second channel (2033) is used to achieve communication between the first channel (2017) and the thread processing area.

9. The cold heading process of a cold heading die for high-precision bolt processing as claimed in claim 8, characterized in that: The steps include: Step 1: feeding the blank into the fixed die member (200), and the bolt head of the blank is supported by the bracket (204); Step 2: drive the external pressure column (101) to move downward. During the downward movement, the lower end of the insertion shaft (106) is first inserted into the hexagonal hole of the blank bolt head. Then, the external pressure column (101) continues to move downward, and the second spring (107) is compressed. When the compression amount of the second spring (107) reaches the maximum, the lower end of the limit ring column (104) contacts the notch of the upper mounting groove (2012). At the same time, the lower end of the external pressure column (101) contacts the upper end of the fixing ring (2032). Step 3: The external pressure column (101) continues to move downward and pushes the fixing ring (2032) downward together, so that the tooth plate (202) gradually closes to form a complete cylindrical outer surface, that is, the rolled thread on the arc surface of the tooth plate (202) gradually squeezes the blank. At the same time, the downward movement of the external pressure column (101) can cause the rotating shaft (102) to rotate through the linkage, and the rotating shaft (102) rotates with the insertion shaft (106) and the blank. The blank will move downward while rotating, and the rolling thread gradually squeezes the blank and the blank rotates and moves downward to achieve thread processing; At the same time, the push seat (203) will move downward with the piston (207), thereby pushing the lubricant in the annular groove (2014), and the lubricant will flow into the thread processing area through the connecting hole (2016), the first one-way valve (2018), the first channel (2017) and the second channel (2033) in sequence to achieve the purpose of lubrication. The lubricated lubricant flows downward under the action of gravity and is output to the outside through the outlet and the output pipe.

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