Auxiliary device for positioning inner hole of workpiece with large diameter-to-length ratio

Abstract

The utility model discloses an auxiliary device for positioning an inner hole of a workpiece with a large diameter-to-length ratio, which comprises a centering disc, a connecting disc and an expansion bolt, and the centering disc is provided with a conical central hole; the centering disc is composed of at least three sector plates. The outer circle of the centering disc serves as a workpiece centering face. One end face of the connecting disc is fixedly connected with the centering disc; a boss is formed on the other end surface; the boss is matched with a central hole of a four-axis connecting seat of a processing machine tool; an expansion bolt is arranged in the conical center hole of the centering disc and the center hole of the connecting disc in a penetrating mode, and concentric positioning of the centering disc and the connecting disc is achieved. According to the utility model, the coaxiality of a workpiece and the four-axis connecting seat can be controlled through the cooperation of the four-axis connecting seat, the connecting disc, the centering disc and the expansion bolt for transmitting the coaxiality. The tool is detachable and easy and convenient to operate, the positioning precision of the inner hole with the diameter-length ratio larger than 20 can be remarkably improved, the clamping safety risk is reduced, and the rejection rate is reduced.

Description

Technical Field

[0001] This utility model relates to a machining auxiliary equipment, specifically to an auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio. Background Technology

[0002] In the machining industry, high precision is often required for the positional accuracy, perpendicularity, and coaxiality of machined dimensions relative to the centerline of an inner cylinder or a certain plane. Currently, centering for simple workpieces or those with low machining precision requirements can be achieved using three-jaw chucks, four-jaw chucks, and centers. Three-jaw chucks clamp circular workpieces by synchronously moving three jaws radially. While simple in structure, they are difficult to use for clamping workpieces with short reference holes. Four-jaw chucks allow for manual and independent adjustment of the four jaws, but their positioning accuracy depends on the operator's experience, resulting in low clamping efficiency. Like three-jaw chucks, they also face the problem of difficulty clamping workpieces with short holes. Furthermore, existing jaw centering methods suffer from jaw wear and transmission clearance issues. Centers use front and rear centers in conjunction with center holes for centering, but they are mostly used for long shaft parts and require high precision machining of the center holes at both ends of the workpiece.

[0003] The above centering method is commonly used in the conventional machining industry, but it is not suitable for positioning large workpieces, large diameters and lengths (D / L>20), and high precision requirements for internal holes. Otherwise, safety hazards may arise due to the clamping length being too short, or the product may be scrapped due to low positioning accuracy. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide an auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio, which can accurately center the inner hole of a workpiece with a diameter-to-length ratio greater than 20 during machining.

[0005] To solve the above-mentioned technical problems, the technical solution of this utility model for an auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio is as follows:

[0006] The assembly includes a centering disc 22, a connecting disc 21, and expansion bolts 24. The centering disc 22 has a tapered central hole. The centering disc 22 is composed of at least three sector plates. The outer circle of the centering disc 22 serves as the workpiece centering surface A. One end face of the connecting disc 21 is fixedly connected to the centering disc 22. The other end face of the connecting disc 21 has a boss 213. The boss 213 matches the central hole of the four-axis connecting seat 1 of the machine tool. One end of the central hole of the connecting disc 21 is an expansion bolt positioning hole, and the other end is a threaded hole. The threaded hole is... The expansion bolt positioning holes are connected; the connecting plate 21 has multiple threaded holes 211 along the circumference, which correspond to the threaded holes of the workpiece to be processed; the connecting plate 21 has multiple countersunk holes 212 along the circumference, which correspond to the mounting holes of the four-axis connecting seat 1 of the processing machine tool; the expansion bolt 24 passes through the tapered center hole of the centering plate 22 and the center hole of the connecting plate 21 to achieve concentric positioning of the centering plate 22 and the connecting plate 21.

[0007] In another embodiment, one end of the expansion bolt 24 is formed with an external thread 242, which matches the threaded hole of the connecting disc 21; the other end of the expansion bolt 24 is formed with a conical surface 243, which matches the conical center hole of the centering disc 22; and the middle part of the expansion bolt 24 is formed with a cylindrical surface 241, which matches the expansion bolt positioning hole of the connecting disc 21.

[0008] In another embodiment, the four-axis connecting seat 1 is concentric with the connecting plate 21, the connecting plate 21 is concentric with the expansion bolt 24, the expansion bolt 24 is concentric with the centering plate 22, and the centering plate 22 is concentric with the workpiece 3.

[0009] In another embodiment, the sector plate has radially extending waist holes as bolt holes; a centering disc fixing bolt 23 passes through the bolt holes, and the sector plate is fixedly connected to the connecting disc 21 through the centering disc fixing bolt 23.

[0010] In another embodiment, the outer circle of the boss 213 is the positioning surface H between the connecting plate 21 and the center hole of the four-axis connecting seat of the machine tool;

[0011] The inner ring of one end face of the connecting plate 21 is the contact surface D with the centering plate 22, and the outer ring of the same end face of the connecting plate 21 is the contact surface C with the workpiece; the outer ring of the other end face of the connecting plate 21 serves as the contact surface E with the four-axis connecting seat of the machine tool.

[0012] The expansion bolt 24 and the expansion bolt positioning hole of the connecting plate 21 form a coaxial mating surface F; the expansion bolt 24 and the threaded hole of the connecting plate 21 form a threaded connection G.

[0013] In another embodiment, the workpiece centering surface A, the contact cone surface B between the expansion bolt 24 and the centering disk 22, the coaxial mating surface F between the expansion bolt 24 and the connecting disk 21, and the boss 213 and the positioning surface H of the machine tool are coaxially arranged.

[0014] In another embodiment, the coaxial mating surface F of the expansion bolt 24 and the connecting plate 21 is perpendicular to the mating surface D of the connecting plate 21 and the centering plate 22.

[0015] In another embodiment, the coaxial mating surface F of the expansion bolt 24 and the connecting plate 21 is perpendicular to the mating surface E of the connecting plate 21 and the machine tool.

[0016] In another embodiment, the workpiece centering surface A is perpendicular to the mating surface D of the connecting disk 21 and the centering disk 22.

[0017] In another embodiment, the contact surface E between the connecting disc 21 and the machine tool is parallel to the contact surface C between the connecting disc 21 and the workpiece.

[0018] The technical effects that this utility model can achieve are:

[0019] This invention achieves coaxiality control between the workpiece and the four-axis connecting seat by using a four-axis connecting seat, connecting plate, centering plate, and expansion bolts to transmit coaxiality. This invention is detachable, easy to operate, and can significantly improve the positioning accuracy of internal holes with a diameter-to-length ratio greater than 20, reduce clamping safety risks, and lower the scrap rate.

[0020] This invention can solve the problem of high precision for inner holes with a diameter-to-length ratio greater than 20 in the machining industry, avoiding problems such as unsafe clamping and scrap due to insufficient precision. Attached Figure Description

[0021] Those skilled in the art will understand that the following description is merely illustrative of the principles of this invention, and these principles can be applied in various ways to achieve many different alternative implementations. These descriptions are only intended to illustrate the general principles of the teachings of this invention and are not intended to limit the inventive concept disclosed herein.

[0022] Embodiments of the present invention are illustrated in conjunction with the accompanying drawings, which are incorporated in and form part of this specification, and together with the foregoing general description and the following detailed description of the drawings, serve to explain the principles of the present invention.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0024] Figure 1 This is a schematic diagram of the auxiliary device for positioning inner holes with a large diameter-to-length ratio according to this utility model;

[0025] Figure 2 This is a cross-sectional schematic diagram of the present invention;

[0026] Figure 3 This is a schematic diagram of the expansion bolt of this utility model;

[0027] Figure 4 This is a schematic diagram of the working state of this utility model.

[0028] Explanation of the reference numerals in the figure:

[0029] 21 is the connecting plate, and 22 is the centering plate.

[0030] 23 is the centering plate fixing bolt, and 24 is the expansion bolt.

[0031] 211 is a threaded hole, and 212 is a countersunk hole.

[0032] 213 is a boss.

[0033] 241 is a cylindrical surface, and 242 is an external thread.

[0034] 243 is a cone surface.

[0035] 1 is the four-axis connector, 3 is the workpiece.

[0036] 4 is the locking bolt for the connecting plate, and 5 is the positioning sleeve.

[0037] A is the centering plane of the workpiece.

[0038] B is the contact cone surface between the expansion bolt and the centering disc.

[0039] C represents the contact surface between the connecting disc and the workpiece.

[0040] D is the mating surface between the connecting plate and the centering plate.

[0041] E represents the mating surface between the connecting plate and the four-axis connecting seat.

[0042] F represents the coaxial mating surface between the expansion bolt and the connecting disc.

[0043] G represents the threaded connection between the expansion bolt and the connecting disc.

[0044] H is the positioning surface between the boss of the connecting plate and the center hole of the four-axis connecting seat. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this utility model pertains. The terms "first," "second," and similar words used herein do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Words such as "comprising" mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0046] like Figure 1 , Figure 2 As shown, the present invention is a positioning auxiliary device for an inner hole with a large diameter-to-length ratio, including a connecting plate 21. One end of the central hole of the connecting plate 21 is an expansion bolt positioning hole, and the other end is a threaded hole; the threaded hole is connected to the expansion bolt positioning hole.

[0047] One end face of the connecting plate 21 is fixedly connected to the centering plate 22; the centering plate 22 has a tapered center hole with a smaller inner diameter and a larger outer diameter at its rotation center; the outer circle of the centering plate 22 serves as the centering surface A of the workpiece.

[0048] Expansion bolts 24 pass through the conical center hole of the centering plate 22 and the center hole of the connecting plate 21 in sequence to achieve a fixed connection between the centering plate 22 and the connecting plate 21, and the centering plate 22 and the connecting plate 21 are concentrically positioned.

[0049] The inner ring of one end face of the connecting plate 21 serves as the contact surface D with the centering plate 22; the outer ring of the same end face of the connecting plate 21 serves as the contact surface C with the workpiece.

[0050] The outer ring of the other end face of the connecting plate 21 serves as the contact surface E with the four-axis connecting seat 1 of the processing machine tool;

[0051] The expansion bolt 24 and the expansion bolt positioning hole of the connecting plate 21 form a coaxial mating surface F;

[0052] A threaded connection G is formed between the expansion bolt 24 and the threaded hole of the connecting plate 21;

[0053] Preferably, the centering plate 22 is composed of three sector plates; the sector plates are provided with radially extending waist holes (not shown in the figure) as bolt holes, and centering plate fixing bolts 23 are inserted into the bolt holes. The sector plates are fixedly connected to the connecting plate 21 through the centering plate fixing bolts 23; during the installation process, the sector plates can move radially to adjust the diameter of the centering plate 22.

[0054] Furthermore, such as Figure 3 As shown, one end of the expansion bolt 24 has an external thread 242; the external thread 242 matches the threaded hole of the connecting disc 21.

[0055] The other end of the expansion bolt 24 has a conical surface 243, which matches the conical center hole of the centering disc 22; a contact conical surface B is formed between the conical surface 243 of the expansion bolt 24 and the conical center hole of the centering disc 22.

[0056] The expansion bolt 24 forms a cylindrical surface 241 in the middle; the cylindrical surface 241 matches the expansion bolt positioning hole of the connecting plate 21;

[0057] A boss 213 is formed on the other end face of the connecting plate 21; the boss 213 matches the center hole of the four-axis connecting seat 1 of the machine tool.

[0058] The outer circle of the boss 213 serves as the positioning surface H between the connecting plate 21 and the center hole of the four-axis connecting seat of the machine tool; the boss 213 can cooperate with the center hole of the four-axis connecting seat to achieve precise positioning.

[0059] The connecting disc 21 has multiple threaded holes 211 along its circumference; these threaded holes 211 correspond to the threaded holes of the workpiece to be processed.

[0060] The connecting plate 21 has multiple countersunk holes 212 along its circumference; these countersunk holes 212 correspond to the mounting holes of the four-axis connecting seat 1 of the machine tool.

[0061] This utility model has multiple positioning surfaces, including the workpiece centering surface A, the contact cone surface B between the expansion bolt 24 and the centering plate 22, the mating surface C between the connecting plate 21 and the workpiece 3, the mating surface D between the connecting plate 21 and the centering plate 22, the mating surface E between the connecting plate 21 and the machine tool, the coaxiality mating surface F between the expansion bolt 24 and the connecting plate 21, and the positioning surface H between the boss 213 and the machine tool.

[0062] Furthermore, the workpiece centering surface A, the contact cone surface B between the expansion bolt 24 and the centering plate 22, the coaxial mating surface F between the expansion bolt 24 and the connecting plate 21, and the boss 213 and the positioning surface H of the machining tool are coaxially arranged.

[0063] The coaxial mating surface F of the expansion bolt 24 and the connecting plate 21 is perpendicular to the mating surface D of the connecting plate 21 and the centering plate 22;

[0064] The coaxial mating surface F of the expansion bolt 24 and the connecting plate 21 is perpendicular to the contact surface E of the connecting plate 21 and the machining tool.

[0065] The centering surface A of the workpiece is perpendicular to the mating surface D of the connecting plate 21 and the centering plate 22.

[0066] In use, this utility model is installed on the four-axis connecting seat 1 of the machine tool, and then the workpiece 3 to be processed is installed on this utility model, so that the workpiece 3 can be machined. The specific installation method is as follows:

[0067] like Figure 4 As shown, first, a positioning sleeve 5 with internal threads is placed in the mounting hole of the four-axis connecting seat 1 of the machining tool and the two are fixedly connected; then, the connecting plate locking bolts 4 are passed through the countersunk hole 212 of the connecting plate 21 and the threaded hole of the positioning sleeve 5 in sequence, and the connecting plate 21 and the four-axis connecting seat 1 are fixedly connected by multiple connecting plate locking bolts 4.

[0068] The centering plate 22 is installed on the connecting plate 21 by the centering plate fixing bolt 23. At this time, it is not locked, so that space is reserved for the centering plate 22 to slide radially and for the centering plate fixing bolt 23 to move axially.

[0069] Then, the workpiece locking bolts are passed through the threaded holes of the workpiece 3 and the threaded holes 211 of the connecting plate 21 in sequence. The workpiece 3 and the connecting plate 21 are fixedly connected by multiple workpiece locking bolts, so that the end face of the workpiece 3 is close to the end face of the connecting plate 21 to form a mating surface C. At this time, the workpiece locking bolts are not locked to ensure that the workpiece 3 can slide along the mating surface C under the expansion action of the centering plate 22.

[0070] Finally, tighten the expansion bolt 24. During the axial movement, the expansion bolt 24 forces the three sector plates of the centering plate 22 to move radially outward through the contact cone surface B of the centering plate 22, causing the outer circle of the centering plate 22 to expand outward until it is in close contact with the inner hole of the workpiece 3. At the same time, the workpiece 3 slides along the contact surface C under the expansion action of the centering plate 22, and finally forms the workpiece centering surface A, thereby achieving high-precision centering.

[0071] Finally, tighten the centering plate fixing bolt 23 and lock the workpiece locking bolt.

[0072] This utility model achieves a high-precision clearance fit between the connecting plate 21 and the four-axis connecting seat 1 by controlling the coaxiality of the outer circle of the boss 213 and the center hole of the connecting plate of the four-axis connecting seat 1 of the machine tool.

[0073] This utility model controls the coaxiality of the expansion bolt positioning hole of the connecting plate 21 and the outer circular surface of the boss 213, so that the coaxiality mating surface F of the expansion bolt 24 and the connecting plate 21 is perpendicular to the contact surface D of the connecting plate 21 and the centering plate 22, and the coaxiality mating surface F of the expansion bolt 24 and the connecting plate 21 is perpendicular to the contact surface E of the connecting plate 21 and the processing machine tool.

[0074] This utility model controls the coaxiality of the conical center hole of the centering disk 22 and the outer circle of the centering disk 22 to make the centering surface A of the workpiece perpendicular to the contact surface D of the centering disk 22.

[0075] This utility model controls the coaxiality of the cylindrical surface 241 and the conical surface 243 of the expansion bolt 24.

[0076] This invention achieves high-precision positioning of the workpiece by controlling the above four coaxialities, as well as the parallelism between the contact surface E of the connecting plate 21 and the contact surface C of the connecting plate 21 and the workpiece.

[0077] This invention enables precise positioning of the inner hole of a workpiece with a large diameter-to-length ratio by forming a workpiece centering surface A. Specifically, during the formation of the workpiece centering surface A, the tightening of the expansion bolt 24 causes the conical surface 243 of the expansion bolt 24 to move axially. This results in the diameter of the conical surface 243 of the expansion bolt 24 at the contact conical surface B being slightly larger than the diameter of the conical center hole of the centering disk 22. This creates two contact lines. The centering disk 22 is subjected to a force pointing in the direction of the inner normal of the conical surface along these two contact lines. These two forces can push the centering disk 22 to move radially outward. As the centering disk 22 moves outward, it contacts the inner surface of the workpiece 3. Since the outer diameter of the centering disk 22 is slightly smaller than the inner hole diameter of the workpiece 3 (the diameter difference is controlled within 0.1 mm), through the principle of three-point circle positioning, the three sector plates of the centering disk 22 form three contact lines on the cylindrical surface A, thereby achieving concentricity between the centering disk 22 and the workpiece 3.

[0078] On the three contact lines of cylindrical surface A, the centering disk 22 is subjected to a force pointing in the direction of the normal to the inner arc. After the expansion bolt 24 is tightened, the above three forces reach equilibrium after the three sector plates of the centering disk 22 are tightened. At this time, the centering process is completed and a stable centering position is formed.

[0079] Considering that the centering plate 22 may rotate around the centering plate fixing bolt 23, resulting in centering error, the centering plate 22 can be hardened by quenching to improve surface hardness and wear resistance, so that the centering plate 22 will not seize with the workpiece 3.

[0080] Furthermore, the three forces along the in-plane normal directions on the contact cone surface B and the workpiece centering surface A will force the centering disk 22 back to a position where it only moves radially. In reality, under pressure, the material will undergo a slight elastic deformation at the contact line position, which will cause the contact line to become a contact surface. Although this contact surface is very narrow, it will make the force on the centering disk 22 more uniform, which will also promote the centering disk 22 to slide radially better.

[0081] In summary, this utility model achieves high-precision centering of the workpiece by sequentially realizing the concentricity of the four-axis connecting seat 1 and the connecting plate 21, the concentricity of the connecting plate 21 and the expansion bolt 24, the concentricity of the expansion bolt 24 and the centering plate 22, and the concentricity of the centering plate 22 and the workpiece 3 through chain transmission.

[0082] Meanwhile, the parallelism between mating surface E and mating surface C ensures that the reference end face of workpiece 3 is parallel to the end face of the four-axis connector 1. The final test, which cumulatively measures the error, controls the coaxiality of workpiece 3 and the four-axis connector 1 to within φ0.03mm and the parallelism to within 0.03mm.

[0083] This invention is simple to operate. After installing the workpiece 3, simply tighten the central expansion bolt 24 to achieve positioning. Then tighten the centering plate fixing bolt 23 to prevent axial movement of the centering plate 22, and finally tighten the workpiece locking bolt. Disassembly is similar: first loosen the expansion bolt 24, then loosen the centering plate fixing bolt 23 and the workpiece locking bolt in sequence. Overall, this invention is simple to operate and can achieve high-precision hole positioning for large diameters.

[0084] The centering plate 22 of this utility model is composed of three sector plates, which can have the function of dispersed expansion centering; through the coaxiality of the internal expansion centering structure, this utility model can effectively achieve high-precision positioning of large-diameter inner holes, successfully avoiding the problems of unsafe clamping and insufficient positioning accuracy.

[0085] This invention is applicable to auxiliary centering in turning, milling, grinding and other processes of inner holes of workpieces with a diameter-to-length ratio greater than 20.

[0086] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. An auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio, characterized in that, include: A centering disk has a tapered central hole; the centering disk is composed of at least three sector plates; the outer circle of the centering disk serves as the centering surface of the workpiece. A connecting plate has a centering plate fixedly connected to one end face; a boss is formed on the other end face; the boss matches the center hole of the four-axis connecting seat of the machine tool; one end of the center hole of the connecting plate is an expansion bolt positioning hole, and the other end is a threaded hole; the threaded hole communicates with the expansion bolt positioning hole; the connecting plate has multiple threaded holes along its circumference, which correspond to the threaded holes of the workpiece to be processed; the connecting plate has multiple countersunk holes along its circumference, which correspond to the mounting holes of the four-axis connecting seat of the machine tool; and Expansion bolts are inserted into the conical center hole of the centering plate and the center hole of the connecting plate to achieve concentric positioning of the centering plate and the connecting plate.

2. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, One end of the expansion bolt has an external thread that matches the threaded hole of the connecting disc; the other end of the expansion bolt has a conical surface that matches the conical center hole of the centering disc; and the middle part of the expansion bolt has a cylindrical surface that matches the expansion bolt positioning hole of the connecting disc.

3. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The four-axis connecting seat is concentric with the connecting plate, the connecting plate is concentric with the expansion bolt, the expansion bolt is concentric with the centering plate, and the centering plate is concentric with the workpiece.

4. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The sector plate has radially extending waist holes as bolt holes; a centering disc fixing bolt passes through the bolt holes, and the sector plate is fixedly connected to the connecting disc through the centering disc fixing bolt.

5. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The outer circle of the boss is the positioning surface between the connecting plate and the center hole of the four-axis connecting seat of the machine tool; The inner ring of one end face of the connecting plate is the contact surface with the centering plate, and the outer ring of the same end face of the connecting plate is the contact surface with the workpiece; the outer ring of the other end face of the connecting plate serves as the contact surface with the four-axis connecting seat of the machine tool. The expansion bolt and the expansion bolt positioning hole of the connecting plate form a coaxial mating surface; the expansion bolt and the threaded hole of the connecting plate form a threaded connection.

6. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The workpiece centering surface, the contact cone surface between the expansion bolt and the centering plate, the coaxial mating surface between the expansion bolt and the connecting plate, and the boss and the positioning surface of the machine tool are coaxially arranged.

7. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The coaxial mating surface of the expansion bolt and the connecting plate is perpendicular to the mating surface of the connecting plate and the centering plate.

8. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The coaxial mating surface of the expansion bolt and the connecting plate is perpendicular to the contact surface between the connecting plate and the machine tool.

9. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The centering surface of the workpiece is perpendicular to the mating surface of the connecting plate and the centering plate.

10. The auxiliary device for positioning the inner hole of a workpiece with a large diameter-to-length ratio according to claim 1, characterized in that, The contact surface between the connecting plate and the machine tool is parallel to the contact surface between the connecting plate and the workpiece.

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