T-shaped centering combined milling cutter

Abstract

The application provides a T-shaped centering composite milling cutter and relates to the technical field of drilling and milling composite cutters.The T-shaped centering composite milling cutter comprises a shaft section, the end of the shaft section is an avoidance section, the end of the avoidance section away from the shaft section is provided with a connecting section, the connecting section is provided with a milling groove cutter seat, the milling groove cutter seat is fixed with a milling groove cutter edge, the end of the connecting section away from the avoidance section is provided with a reamer section, and the end of the reamer section away from the connecting section is provided with a centering chamfer end.The centering chamfer end first completes centering and chamfering, the reamer section is reamed to the designed size along the guide hole, the milling groove cutter edge mills the hole wall to form a T-shaped sink groove, the three are gradually fed based on the same rotation axis, and the centering, reaming and milling groove three processes can be completed through one clamping, the cutter does not need to be replaced and the positioning error introduced by multiple clamping in the traditional step-by-step processing is avoided, and the coaxiality of the sink groove and the hole axis is ensured.

Description

Technical Field

[0001] This invention relates to the field of drilling and milling composite tool technology, and more particularly to a T-type centering composite milling cutter. Background Technology

[0002] In the field of medical device manufacturing, a large number of T-shaped groove structures need to be processed in structures such as bone screw grooves, bone plate countersinks, and intramedullary nail lock holes. The traditional processing method usually adopts a step-by-step process: first, a centering drill is used to process the guide hole, then a reamer is used to ream and finish the guide hole, and finally a T-slot milling cutter is used to mill the hole wall to form the inner groove.

[0003] The following problems are commonly found in existing technologies: Although some existing drilling and milling composite tools integrate drilling and milling functions in their structure, the connection between the drilling section and the milling section is mostly a step-like abrupt change. When the tool feeds axially and the functional sections alternately enter the workpiece, stress concentration is easily generated at the abrupt section, and chips are easy to accumulate and block at the abrupt section. For slender tools commonly used in medical device processing, the above problems are even more prominent. Furthermore, in medical device processing, the cutting tools have a large overall length-to-slenderness ratio and a small processing space. The chip removal path is long and the resistance is high. The chip morphology generated by drilling and milling is different. In existing multi-functional composite tools, the chip removal channels for drilling and milling are independent or poorly connected. Necking or turning is easy to occur in the chip removal path, resulting in chip blockage, severe tool overheating, and a decline in the quality of the processed surface. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and propose a T-type centering composite end mill.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a T-shaped centering composite milling cutter, comprising a shaft section, one end of which is a clearance section, a connecting section at the end of the clearance section away from the shaft section, a milling cutter holder on the connecting section, a milling cutter blade fixed on the milling cutter holder, a reamer section at the end of the connecting section away from the clearance section, and a centering chamfer end at the end of the reamer section away from the connecting section.

[0006] Furthermore, the shaft section, clearance section, connecting section, reamer section, and centering chamfer end are integrally coaxially arranged.

[0007] Furthermore, the outer diameter of the clearance section is smaller than the outer diameter of the reamer section, and the outer diameter of the reamer section is smaller than the maximum outer diameter of the centering chamfer end. The clearance section and the reamer section, as well as the reamer section and the centering chamfer end, are smoothly connected by a conical surface.

[0008] Furthermore, the drill tip at the centering chamfer end protrudes axially from the end face of the reamer section, and the outermost end of the milling cutter protrudes radially from the outer circumferential surface of the reamer section; the protrusion of the drill tip is greater than the axial retraction of the milling cutter, so that the centering guide takes precedence over the milling cutter entry.

[0009] Furthermore, there are multiple milling cutting edges, which are evenly distributed around the circumference of the milling cutter holder. The cutting direction of each milling cutting edge is consistent with the rotation direction of the T-shaped centering composite milling cutter. A chip removal gap is formed between adjacent milling cutting edges, and the chip removal gap is axially connected to the outer peripheral surface of the clearance section.

[0010] Furthermore, a helical cutting edge is provided axially on the outer peripheral surface of the reamer section. The helical cutting edge is formed on the base of the reamer section by grinding, and the helical direction of the helical cutting edge is the same as the cutting direction of the milling cutter.

[0011] Furthermore, a chip-receiving groove is provided on the connecting section, the chip-receiving groove extends along the axial direction of the connecting section, the bottom of the chip-receiving groove is smoothly connected to the outer peripheral surface of the clearance section, and the chip-receiving groove and the outer peripheral surface of the clearance section are correspondingly connected in the axial direction; the groove wall of the chip-receiving groove is correspondingly connected in the circumferential direction to the cutting surface of the milling cutter.

[0012] Furthermore, the milling cutter blade and the milling cutter holder are fixedly connected by a brazing layer.

[0013] Furthermore, a centering drill tip is provided at the end of the centering chamfer end away from the reamer section. The conical surface of the centering drill tip and the end face of the centering chamfer end form a chamfering cutting edge. The conical surface of the centering drill tip and the outer peripheral surface of the reamer section form a concentric positioning structure under axial coaxial constraint.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are as follows: In this invention, during processing, the centering and chamfering end is first centered and chamfered, the reamer section reams along the guide hole to the designed size, and the milling cutter then mills a T-shaped groove on the hole wall. All three processes are fed sequentially with the same axis of rotation as the reference. Centering, reaming, and milling can be completed in a single clamping operation, eliminating the need for tool changes and repeated positioning. This avoids positioning errors introduced by multiple clamping operations in traditional step-by-step machining and ensures the coaxiality of the groove and the hole axis. Adjacent sections are smoothly connected via a tapered surface, avoiding stress concentration and jamming caused by abrupt changes in the stepped structure during alternating feeds. The milling cutter is embedded in the milling cutter holder and fixedly connected by a brazing layer. The stability of the cutting edge is mainly achieved through welding, ensuring its stability under high-impact milling conditions and preventing it from falling off or cracking. The outer circumferential surfaces of the chip groove and the clearance section are axially connected, and the groove wall of the chip groove is circumferentially connected to the cutting face of the milling cutter. Milling chips are discharged axially through the chip clearance gap, chip groove, and outer circumferential surface of the clearance section. The chip path runs through the milling area to the clearance section without interruption or necking during the entire machining process, preventing chip accumulation and blockage in the chip removal path. Centering, reaming, and milling are performed sequentially in a fixed time sequence without interfering with each other, avoiding hole wall scratches or tool breakage caused by disordered timing. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the T-type centering composite end mill of the present invention; Figure 2 This is a schematic diagram showing the combination of the slotting cutter holder and the slotting cutting edge of the T-type centering composite milling cutter of the present invention; Figure 3 This is a schematic diagram showing the dimensions of the T-type centering composite end mill of the present invention; Figure 4 This is a flowchart illustrating the manufacturing process of the T-type centering composite end mill of the present invention.

[0016] Figure label: 1. Shaft section; 2. Clearance section; 3. Connecting section; 4. Milling cutter holder; 5. Milling cutter edge; 6. Reamer section; 7. Centering chamfer end. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0018] like Figures 1 to 3As shown, the present invention provides a technical solution: a T-shaped centering composite milling cutter, including a shaft section 1, one end of the shaft section 1 is a clearance section 2, the clearance section 2 is provided with a connecting section 3 at the end away from the shaft section 1, a milling cutter holder 4 is provided on the connecting section 3, a milling cutter edge 5 is fixed on the milling cutter holder 4, a reamer section 6 is provided at the end of the connecting section 3 away from the clearance section 2, and a centering chamfer end 7 is provided at the end of the reamer section 6 away from the connecting section 3.

[0019] in: The shaft section 1, the clearance section 2, the connecting section 3, the reamer section 6, and the centering chamfer end 7 are coaxially arranged. The outer diameter of the clearance section 2 is smaller than the outer diameter of the reamer section 6, and the outer diameter of the reamer section 6 is smaller than the maximum outer diameter of the centering chamfer end 7. The clearance section 2 and the reamer section 6, and the reamer section 6 and the centering chamfer end 7 are smoothly connected by tapered surfaces. The drill tip of the centering chamfer end 7 protrudes axially from the end face of the reamer section 6, and the outermost end of the milling cutter 5 protrudes radially from the outer circumferential surface of the reamer section 6; the protrusion of the drill tip is greater than the axial retraction of the milling cutter 5. There are multiple milling cutter edges 5. In this embodiment, there are four milling cutter edges 5. The four milling cutter edges 5 are evenly distributed around the circumference of the milling cutter holder 4. The cutting direction of each milling cutter edge 5 is consistent with the rotation direction of the T-shaped centering composite milling cutter. A chip removal gap is formed between adjacent milling cutter edges 5. The chip removal gap is axially connected to the outer peripheral surface of the clearance section 2. The milling cutter edges 5 are embedded in the milling cutter holder 4. The top surface of the milling cutter edge 5 protrudes from the outer peripheral surface of the connecting section 3. The milling cutter edges 5 and the milling cutter holder 4 are fixedly connected by a brazing layer. A helical cutting edge is provided on the outer circumferential surface of the reamer section 6 along the axial direction, and the helical direction of the helical cutting edge is the same as the cutting direction of the milling cutter edge 5; A chip groove is provided on the connecting section 3. The chip groove extends along the axial direction of the connecting section 3. The bottom of the chip groove is smoothly connected to the outer peripheral surface of the clearance section 2, and the chip groove and the outer peripheral surface of the clearance section 2 are correspondingly connected in the axial direction. The groove wall of the chip groove is correspondingly connected to the cutting surface of the milling cutter 5 in the circumferential direction. The centering chamfer end 7 is provided with a centering drill tip at the end away from the reamer section 6. The conical surface of the centering drill tip and the end face of the centering chamfer end 7 form a chamfering cutting edge. The conical surface of the centering drill tip and the outer peripheral surface of the reamer section 6 form a concentric positioning structure under axial coaxial constraint.

[0020] In this embodiment, the specific dimensions of each structure are as follows: The sum of the lengths of the reamer section 6 and the centering chamfer end 7 is 6mm; The included angle of the drill bit at the centering chamfer end 7 is 90°; The axial projection distance between the drill tip of the centering chamfer end 7 and the milling cutter edge 5 is 8mm ± 0.02mm; The thickness of the milling cutter blade 5 is 0.84mm, the upper deviation is 0, and the lower deviation is 0.01mm; The diameter of the surface swept by the milling cutter 5 is 8.95mm, with an upper deviation of 0 and a lower deviation of 0.01mm. The diameter of the clearance section 2 is 1.9 mm, the upper deviation is 0, and the lower deviation is 0.01 mm; The thickness of the milling cutter holder 4 is 0.74 mm, the upper deviation is 0, and the lower deviation is 0.01 mm. The diameter of the reamer section 6 is 1.58 mm, the upper deviation is 0, and the lower deviation is 0.005 mm; The sum of the lengths of the clearance section 2, the connecting section 3, the reamer section 6, and the centering chamfer end 7 is 12.5mm, with an upper deviation of 0.05mm and a lower deviation of 0. The diameter of shaft section 1 is 6mm, the upper deviation is 0, and the lower deviation is 0.02mm; The overall length of the T-type centering compound end mill is 50mm; In the above dimensions, an upper deviation of 0 indicates that the dimension is only allowed to deviate in the negative direction, that is, it must not exceed the nominal value; a lower deviation of 0 indicates that the dimension is only allowed to deviate in the positive direction, that is, it must not be less than the nominal value.

[0021] In this embodiment, the clearance section 2, reamer section 6, milling cutter edge 5, and milling cutter holder 4 all adopt a tolerance configuration with an upper deviation of 0. That is, all key outer diameter and wall thickness dimensions are only allowed to be equal to or less than the nominal value, so as to avoid interference or frictional heat generation between the tool and the workpiece hole wall due to the excessive size when the tool is rotating at high speed, and to ensure the dimensional stability and fit safety of the tool in the precision machining of medical devices. The sum of the lengths of the clearance section 2, connecting section 3, reamer section 6 and centering chamfer end 7 are only allowed to be equal to or greater than the nominal value, so as to ensure that the effective cutting length is not less than the design value. Example 2

[0022] like Figure 4 As shown, this embodiment provides a method for preparing a T-type centering composite end mill, used to prepare the T-type centering composite end mill of Embodiment 1, specifically including the following steps: Step 1: Base Prefabrication: The shaft section 1, clearance section 2, connecting section 3, reamer section 6 mandrel, and centering chamfer end 7 mandrel are machined into an integral base blank using a one-piece molding process. Each section is coaxially arranged, and adjacent sections are smoothly connected by a conical surface. The outer diameter of the reamer section 6 mandrel is smaller than the design outer diameter of the finished reamer section 6, and the outer diameter of the centering chamfer end 7 mandrel is smaller than the design outer diameter of the finished centering chamfer end 7. A mounting surface for the milling slot cutter holder 4 is reserved on the connecting section 3. The base blank is rough-machined and semi-finished, with a fine grinding allowance reserved. At this time, the base is in the annealed state. Step 2: Fabrication of Pre-made Cutting Edges: Pre-made cutting edges for the reamer section 6, the centering and chamfering end 7, and the milling cutting edge 5 are fabricated independently. The outer circumferential surface of the reamer section 6 has a spiral band along the axial direction. The pre-made cutting edge of the reamer section 6 is a sheet-like structure that fits the surface of the spiral band. The pre-made cutting edge of the centering and chamfering end 7 is a conical sleeve structure with a centering drill tip and a chamfering cutting edge at the front end. The milling cutting edge 5 is a block structure with a contour that matches the mounting surface of the milling cutter holder. This pre-made cutting edge is made of superhard material using powder metallurgy and is in a sintered state. Step 3: Pre-made blade assembly and brazing: Assemble each pre-made blade at its corresponding mounting position on the base blank, apply a brazing layer at each joint interface, and place it in a vacuum brazing furnace for brazing; specifically, fit the pre-made blade of the reamer section 6 onto the outside of the mandrel of the reamer section 6, fit the pre-made blade of the centering chamfer end 7 onto the outside of the mandrel of the centering chamfer end 7, and embed the milling cutter 5 into the mounting surface of the milling cutter holder 4, so that each pre-made blade and the corresponding mounting surface of the base blank form a contact fit, apply a brazing layer at each joint interface, place it in a vacuum brazing furnace for brazing, so that the brazing filler fills the micro gaps of the joint interface, and form a brazed bonding layer after cooling; Step 4, Overall Quenching: The whole completed in Step 3 is placed in a vacuum quenching furnace, heated to the austenitizing temperature and held at that temperature, and then rapidly cooled to give the matrix a hardened structure. The pre-made cutting edge is simultaneously hardened during this process. Step 5, Segmented Differential Temperature Tempering: Prepare a split cylindrical ceramic tempering mold. The mold material is heat-insulating ceramic with low thermal conductivity. The inner cavity of the mold is divided into the shaft section temperature zone, the clearance section temperature zone, the connecting section temperature zone, the reamer section temperature zone, and the centering and chamfering end temperature zone in sequence along the axis. The inner wall of each temperature zone is in a close fit with the outer wall of the corresponding section after step 4. The mold as a whole is divided into multiple small units in a way that fits the shape of the tool without interference, which facilitates the overall wrapping of the tool. Multiple heating wires are embedded axially along the inner wall of the mold; the arrangement of each heating wire is distinguished by its location: In the mold area outside the mounting surface of the milling cutter holder in the shaft section, the clearance section and the connecting section, the heating wire is embedded in the inner wall surface of the mold and is directly opposite to the outer wall of the base. In the mold parts corresponding to the pre-made blades in the reamer section and the pre-made blades in the centering chamfer end, the heating wire runs through the interior of the ceramic mold matrix. The blade and the heating wire are isolated by the ceramic matrix layer. The heat generated by the heating wire is conducted through the ceramic layer and then attenuated to the outer wall of the blade. At the corresponding mold positions of the pre-made cutting edge of the reamer section and the brazing joint surface of the reamer section mandrel, the pre-made cutting edge of the centering chamfer end and the mandrel of the centering chamfer end, and the brazing joint surface of the milling cutter 5 and the mounting surface of the milling cutter holder, an independent heating wire is provided, which runs through the interior of the ceramic substrate. The axial position of the heating wire is directly opposite to the height of the brazing joint surface, and the center of the heat field it generates is aligned with the plane of the joint interface. Each heating wire is connected to an independent power control switch circuit, and the power output of each heating wire is independently controlled by the corresponding PID adjustment module. K-type thermocouples are embedded in the inner wall of the mold. The number of thermocouples is the same as the number of heating wires and their positions correspond one-to-one. The temperature measurement signal of each thermocouple is independently transmitted back to the corresponding PID adjustment module, forming an independent closed-loop temperature control circuit for a single heating wire. The whole piece, which has been quenched in step four, is placed into a ceramic mold and the mold is closed and locked; the mold containing the whole piece is sent into an atmosphere protection furnace and a protective atmosphere is introduced. Activate the independent power control circuit for each heating element and set the tempering temperature as follows: The heating wire at the corresponding position of shaft section 1 is set to the high-temperature tempering temperature; The heating wires at the corresponding positions of the evacuation section 2 and the connecting section 3 are set to the medium-temperature tempering temperature; The heating wires at the corresponding positions of the pre-formed blades of the reamer section and the pre-formed blades of the centering chamfer end are set to a low-temperature tempering temperature. Since there is a ceramic substrate layer between the heating wire and the blade body, the actual temperature that the blade body is subjected to is lower than the set temperature of the heating wire. The difference is determined by the thickness and thermal conductivity of the ceramic layer. Each brazed joint surface has an independent heating wire at the corresponding position, and its set temperature is matched with the tempering requirements of the materials on both sides of the joint surface. The independent heating wire can be set to a temperature different from that of the adjacent blade area, and is not limited by the low-temperature tempering of the blade body. At the corresponding positions of the cone surface, the set temperatures of each heating wire are arranged to increase or decrease one by one along the axial direction, and the set temperature difference between adjacent heating wires is equal, so that the tempering temperature at the cone surface forms a continuous linear gradient transition along the axial direction. The heating rate of each heating wire is set independently: the heating wire in the shaft section temperature zone heats up rapidly at full power, the heating wire in the clearance section and connecting section temperature zone heats up at medium speed, and the heating wire in the blade area and the brazing joint surface heats up slowly. Each temperature zone reaches the set temperature at the same time and has the same holding time. After the heat preservation is completed, turn off the power to all heating wires; do not open the mold, and use the low thermal conductivity of ceramics to slowly cool the whole in the mold to below the set temperature, then open the mold and take it out to air cool to room temperature; during this slow cooling process, each section will shrink differently due to different tempering temperatures, forming a preset residual compressive stress field in the conical transition area; due to the tempering effect of the independent heating wires, the residual stress at the joint interface of each brazed joint surface is released in a targeted manner. Step Six: Finishing: Perform finishing grinding on the entire assembly completed in Step Five. Example 3

[0023] like Figure 3 As shown, this embodiment describes the axial, radial, chip removal and overall machining effects based on the structure and dimensional parameters described in Embodiment 1.

[0024] Specifically: Axial dimension fit: The sum of the lengths of the clearance section 2, connecting section 3, reamer section 6, and centering chamfer end 7 is 12.5mm (positive error 0.05 / negative error 0), that is, the actual length is ≥12.5mm; the minimum sum of the lengths of the reamer section 6 and the centering chamfer end 7 is 6mm, that is, the length of the centering chamfer end 7 is equal to 6mm minus the actual length of the reamer section 6; when the length of the reamer section 6 is designed to be the shortest effective length to meet the reaming requirements, the centering chamfer end 7 obtains the maximum axial length, ensuring sufficient axial travel during the centering and guiding process; when there is an inclination or unevenness at the entrance of the machined hole, the combination of the reamer section 6 with a length ≥6mm and the centering chamfer end 7 can provide sufficient guiding travel, ensuring that the tool axis and the workpiece pre-hole axis are coaxial before reaming, avoiding hole misalignment due to insufficient guidance.

[0025] Radial dimension fit: The diameter of the surface swept by the milling cutter 5 is 8.95mm (positive error 0 / negative error 0.01mm), and the diameter of the reamer section 6 is 1.58mm (positive error 0 / negative error 0.005mm). After reaming, the inner diameter of the workpiece is 1.58mm (actual ≤1.58mm), and the diameter swept by the milling cutter 5 is 8.95mm (actual ≤8.95mm), forming a diameter difference of approximately 7.37mm. With the axis as the reference, the cutting radius of the milling cutter 5 is approximately 4.475mm, the radius of the reamer section 6 is approximately 0.79mm, and the radial single-sided protrusion of the milling cutter 5 protruding from the outer circumference of the reamer section 6 is approximately 3.685mm. This protrusion determines the radial depth of the inner groove in the milling process.

[0026] When the diameter of the surface swept by the milling cutter 5 is 8.95mm and the inner diameter of the workpiece is 1.58mm, the radial depth of the milling cutter 5 cutting into the hole wall is (8.95-1.58) / 2=3.685mm. This cutting depth directly corresponds to the radial depth of the inner groove; the greater the cutting depth, the deeper the groove. When the diameter of the surface swept by the milling cutter 5 reaches the upper limit of 8.95mm due to machining error, the cutting depth reaches the maximum value of 3.685mm. When the downward deviation is 0.01mm, i.e., the actual diameter is 8.94mm, The depth of cut is 3.68mm, with a difference of only 0.005mm, ensuring the consistency of the groove depth processed by the same batch of tools; the diameter of the reamer section 6 is 1.58mm (only ≤1.58mm is allowed), ensuring that the diameter of the hole after reaming does not exceed the design value, providing an accurate hole diameter reference for subsequent milling; the drill bit included angle of the centering chamfer end 7 is 90°, forming a standard 90° conical surface positioning during the centering process, which cooperates with the spiral cutting edge on the outer periphery of the reamer section 6 to realize the sequential processing of centering, reaming and milling under concentric constraints.

[0027] Coordination of air clearance and chip removal: The diameter of the clearance section 2 is 1.9 mm (positive error 0 / negative error 0.01 mm), and the diameter of the reamer section 6 is 1.58 mm (positive error 0 / negative error 0.005 mm), meaning the diameter of the clearance section 2 is larger than the diameter of the reamer section 6 (1.9 mm > 1.58 mm). Since the reamer section 6 is located at the end of the connecting section 3 furthest from the clearance section 2 (i.e., in front of the tool), and the clearance section 2 is located at the end of the connecting section 3 closest to the shaft section 1 (i.e., behind the tool), when the tool advances forward, the reamer section 6 and the centering chamfer end 7 enter the workpiece pre-cutting section first. The clearance section 2 then enters the already reamed hole section. The diameter of clearance section 2 is 1.9 mm, which is larger than the diameter of reamer section 6 (1.58 mm), but smaller than the diameter of the already reamed hole (i.e., the actual diameter of the hole machined by the reamer section) and the diameter of the groove bottom formed by the rotating sweep of the milling cutter 5 (8.95 mm). That is, the diameter of clearance section 2 is larger than the diameter of reamer section 6, but much smaller than the diameter of the rotating sweep of the milling cutter, so that clearance section 2 will not interfere with the already reamed hole wall when it moves axially in and out of the hole, and can provide sufficient radial escape space for the chips generated by the milling groove.

[0028] Meanwhile, the radial difference between the outer diameter of the clearance section 2 (1.9 mm) and the diameter of the surface swept by the milling cutter 5 (8.95 mm) forms an annular clearance area. The chips generated by the milling cutter 5 enter this clearance area through the chip clearance gap between adjacent milling cutters 5, and are then discharged outward along the chip clearance groove. When the diameter of the clearance section 2 is 1.9 mm, the radial width of this clearance area is (8.95-1.9) / 2=3.525 mm, which is sufficient to accommodate the short chips generated by the milling groove without causing blockage.

[0029] Overall processing: When this tool is in operation, the 90° drill tip of the centering chamfer end 7 first centers the workpiece surface and drills into the guide hole. Then, the reamer section 6 performs reaming along the guide hole to finish the hole diameter to 1.58mm. After reaming, the milling cutter 5 mills the hole wall to produce an inner countersink. The thickness of the milling cutter 5 is 0.84mm (≤0.84mm is allowed only), which limits the axial width of the countersink, that is, the width of the countersink does not exceed 0.84mm, ensuring that the axial dimension of the countersink does not exceed the design value. The clearance section 2 provides a chip discharge channel during the milling process to ensure that the bottom of the countersink is not scratched or dimensionally deviated due to chip accumulation. The overall tool length is 50mm, with a large slenderness ratio (length / diameter), making it suitable for countersinking of deep holes in medical devices.

[0030] In this embodiment, the drill bit included angle of the centering chamfer end 7 is 90°, which together with the reaming diameter of 1.58mm of the subsequent reamer section 6 and the diameter of the surface swept by the milling cutter 5 is 8.95mm, forming a three-stage stepped cutting structure of "centering - reaming - milling". All machining processes from centering, reaming to milling can be completed in one clamping, avoiding multiple tool changes and repeated positioning errors in traditional step-by-step machining.

[0031] Working principle: like Figures 1 to 3 As shown, during operation, the present invention first clamps the shaft section 1 onto the machine tool spindle, and the entire tool rotates with the spindle and feeds axially; the 90° centering drill tip of the centering and chamfering end 7 first contacts the workpiece surface, drilling a guide hole in the workpiece to complete the centering and chamfering machining; then the reamer section 6 enters the workpiece along the guide hole machined by the centering and chamfering end 7, and the helical cutting edge on the outer circumference of the reamer section 6 reams the hole wall to finish the hole diameter to the design size; after reaming is completed, the milling cutter 5 continues with the tool. The milling cutter 5 is axially advanced into the hole. The outermost end of the milling cutter 5 protrudes radially from the outer circumferential surface of the reamer section 6, milling the hole wall and machining a T-shaped countersink in the hole. There are multiple milling cutters 5, which are evenly distributed circumferentially. The cutting direction of each milling cutter is consistent with the rotation direction of the tool. Adjacent milling cutters form a chip removal gap. The chips generated by the milling cutter enter the chip receiving groove on the connecting section 3 through the chip removal gap, and then enter the outer circumferential surface area of ​​the clearance section 2 through the chip receiving groove, and are discharged outward along the axial direction of the clearance section 2.

[0032] In the above process, the drill tip of the centering chamfer end 7 protrudes axially from the end face of the reamer section 6, and the protrusion of the drill tip is greater than the axial retraction of the milling cutter edge 5. This ensures that during axial feed of the tool, the centering chamfer end 7 always contacts the workpiece before the reamer section 6 and the milling cutter edge 5, achieving priority in centering guidance. The outer diameter of the clearance section 2 is smaller than the outer diameter of the reamer section 6, and the outer diameter of the reamer section 6 is smaller than the maximum outer diameter of the centering chamfer end 7. This allows each section of the tool to form a stepped feed path that gradually transitions from small to large when entering the workpiece, avoiding interference between the milling cutter edge 5 and the hole wall during drilling and reaming. The smooth transition of the conical surface between the reamer section 6 and the centering chamfer end 7 ensures that the tool... The force distribution is smooth during the transition from drilling to reaming, avoiding stress concentration caused by abrupt changes in cross-section. The axial projection distance between the drill tip of the centering chamfer end 7 and the milling cutter edge 5 is 8mm. This distance determines the axial travel from the completion of centering to the start of milling, ensuring that the milling cutter edge 5 accurately enters the reaming position after reaming. The thickness of the milling cutter edge 5 limits the axial width of the milling groove, and the diameter of the surface swept by the milling cutter edge 5 limits the radial depth of the milling groove. The diameter of the clearance section 2 is larger than the diameter of the reamer section 6 but smaller than the diameter of the surface swept by the milling cutter edge 5, so that the clearance section 2 can move freely in and out of the hole without interfering with the hole wall, and also provides sufficient radial discharge space for the chips.

[0033] Throughout the entire process, the centering chamfer end 7, the reamer section 6, and the milling cutter edge 5 enter the workpiece sequentially, completing the three processes of centering, reaming, and milling respectively. A single clamping setup can achieve the complete machining from centering to reaming to milling without the need for tool changes or repeated positioning. At the same time, the dimensional fit between each section, including the outer diameter of the clearance section 2 being smaller than the outer diameter of the reamer section 6, the outer diameter of the reamer section 6 being smaller than the maximum outer diameter of the centering chamfer end 7, and the smooth transition of the conical surfaces between the reamer section 6 and the centering chamfer end 7, together ensure the smoothness of the tool when it alternates entering the workpiece.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A T-type centering composite end mill, comprising a shaft section (1), one end of which is a clearance section (2), characterized in that, The end of the clearance section (2) away from the shaft section (1) is provided with a connecting section (3), the connecting section (3) is provided with a milling cutter holder (4), the milling cutter holder (4) is fixed with a milling cutter blade (5), the milling cutter blade (5) and the milling cutter holder (4) are fixedly connected by a brazing layer, the end of the connecting section (3) away from the clearance section (2) is provided with a reamer section (6), the end of the reamer section (6) away from the connecting section (3) is provided with a centering chamfer end (7), the shaft section (1), clearance section (2), connecting section (3), reamer section (6) and centering chamfer end (7) are integrated and coaxially arranged.

2. The T-type centering composite end mill according to claim 1, characterized in that: The outer diameter of the clearance section (2) is smaller than the outer diameter of the reamer section (6), and the outer diameter of the reamer section (6) is smaller than the maximum outer diameter of the centering chamfer end (7). The clearance section (2) and the reamer section (6), and the reamer section (6) and the centering chamfer end (7) are respectively connected by a smooth transition through a conical surface.

3. The T-type centering composite end mill according to claim 1, characterized in that: The drill tip of the centering chamfer end (7) protrudes axially from the end face of the reamer section (6), and the outermost end of the milling cutter (5) protrudes radially from the outer circumferential surface of the reamer section (6); the protrusion of the drill tip is greater than the axial retraction of the milling cutter (5), so that the centering guide takes precedence over the milling cutter entry.

4. The T-type centering composite end mill according to claim 1, characterized in that: There are multiple milling cutter edges (5), which are evenly distributed along the circumference of the milling cutter holder (4). The cutting direction of each milling cutter edge (5) is consistent with the rotation direction of the T-shaped centering composite milling cutter. Adjacent milling cutter edges (5) form a chip removal gap, which is axially connected to the outer circumferential surface of the clearance section (2).

5. The T-type centering composite end mill according to claim 1, characterized in that: The outer circumferential surface of the reamer section (6) is provided with a spiral cutting edge along the axial direction. The spiral cutting edge is formed on the base of the reamer section (6) by grinding, and the spiral direction of the spiral cutting edge is the same as the cutting direction of the milling cutter edge (5).

6. The T-type centering composite end mill according to claim 1, characterized in that: The connecting section (3) is provided with a chip groove, which extends along the axial direction of the connecting section (3). The bottom of the chip groove is smoothly connected to the outer peripheral surface of the clearance section (2), and the chip groove and the outer peripheral surface of the clearance section (2) are correspondingly connected in the axial direction. The groove wall of the chip groove is correspondingly connected to the cutting surface of the milling cutter (5) in the circumferential direction.

7. The T-type centering composite end mill according to claim 1, characterized in that: The centering chamfer end (7) is provided with a centering drill tip at the end away from the reamer section (6). The conical surface of the centering drill tip and the end face of the centering chamfer end (7) form a chamfering cutting edge. The conical surface of the centering drill tip and the outer peripheral surface of the reamer section (6) form a concentric positioning structure under axial coaxial constraint.

8. The T-type centering composite end mill according to claim 1, characterized in that: It also includes the manufacturing process for machining T-type centering end mills, specifically including the following steps: Step 1, Prefabrication of the base: The shaft section (1), the clearance section (2), the connecting section (3), the mandrel of the reamer section (6) and the mandrel of the centering chamfer end (7) are processed into an integral base blank through an integrated molding process. Each section is set coaxially and the adjacent sections are smoothly connected by a conical surface. The outer diameter of the mandrel of the reamer section (6) is smaller than the design outer diameter of the finished reamer section (6), and the outer diameter of the mandrel of the centering chamfer end (7) is smaller than the design outer diameter of the finished centering chamfer end (7). The connecting section (3) is reserved with a mounting surface for the milling slot cutter holder (4). Step 2, Pre-made cutting edge: independently make the pre-made cutting edge of the reamer section (6), the pre-made cutting edge of the centering chamfer end (7), and the milling cutting edge (5); Step 3: Assembly and brazing of prefabricated blades: Assemble each prefabricated blade at the corresponding installation position on the base blank, apply a brazing layer at each joint interface and place it in a vacuum brazing furnace for brazing. Step 4, Overall Quenching: The whole assembly completed in Step 3 is placed into a vacuum quenching furnace for overall quenching; Step 5, Segmented Differential Temperature Tempering: Prepare a segmented ceramic tempering mold with internal heating wires. The inner wall of the mold is in a fitted state with the outer wall of each segment after step 4. The whole is installed into the mold. Each heating wire is set with an independent tempering temperature according to its position. The shaft section (1) is tempered at high temperature, the clearance section (2) and the connecting section (3) are tempered at medium temperature, and the pre-made blades of the reamer section and the pre-made blades of the centering chamfer end are tempered at low temperature. The independent heating wires corresponding to each brazing joint surface are set with separate tempering temperatures. There is a continuous temperature gradient between adjacent heating wires at the corresponding positions of the cone surfaces. After heat preservation, the mold is slowly cooled. Step Six: Finishing: Perform finishing grinding on the entire assembly completed in Step Five.

9. The T-type centering composite end mill according to claim 8, characterized in that: In step five, the segmented, bonded ceramic tempering mold is a split cylindrical structure made of low thermal conductivity insulating ceramic. After mold closing, the inner wall is bonded to the outer wall of each segment. Multiple heating wires are embedded axially along the inner wall of the mold, with the planes of each heating wire parallel to each other. At the mold locations corresponding to the pre-formed blades in the reamer section and the centering chamfer end, the heating wires pass through the ceramic substrate and are separated from the blades by a ceramic layer. At each brazing joint surface, an independent heating wire is provided. The heating wire runs through the interior of the ceramic substrate, with the center of its thermal field aligned with the plane of the brazing joint. Each heating wire is connected to an independent power control switch circuit and an independent thermocouple, forming a single closed-loop temperature control circuit. The set temperature of each heating wire is independent, with the set temperature of the heating wire at the larger cross-section being higher than that at the smaller cross-section. The set temperatures of adjacent heating wires are continuously arranged along the axial direction without jumps. After the heat preservation is completed, the heating wire slowly cools with the mold. Different sections undergo differentiated shrinkage due to different tempering temperatures, and the conical transition zone has a residual compressive stress field.

Images