CN215616631U - Positioning device for special-shaped workpiece to be machined - Google Patents

Abstract

The disclosure relates to a positioning device for a special-shaped workpiece to be machined, and belongs to the technical field of mechanical manufacturing. The positioning device includes: the box-type body comprises a fixed part and a support arm, wherein the fixed part is fixedly connected with the processing lathe, the support arm is connected with the fixed part, and the support arm is provided with an inner cavity for accommodating the special-shaped workpiece to be processed and a plurality of first through holes; each fixing piece penetrates through the corresponding first through hole and is abutted against the outer surface of the special-shaped workpiece to be machined, and the length of the fixing piece penetrating through the inner cavity is adjustable. In the embodiment of the disclosure, the fixing part of the box-shaped body is fixedly connected with the processing lathe, the special-shaped workpiece to be processed is placed into the inner cavity of the support arm, the length of the fixing part extending into the inner cavity is adjusted to abut against the outer surface of the special-shaped workpiece to be processed, and meanwhile, the position of the special-shaped workpiece to be processed is adjusted. Therefore, the fastening position of the special-shaped workpiece to be machined on the machining lathe can be realized, and the machining precision of the special-shaped workpiece to be machined in the process of machining the threaded connecting hole is ensured.

Description

Positioning device for special-shaped workpiece to be machined

Technical Field

The disclosure relates to the technical field of machine manufacturing, in particular to a positioning device for a special-shaped workpiece to be machined.

Background

At present, for the workpiece to be processed in the abnormal shape, due to the irregular shape profile, when the workpiece to be processed in the abnormal shape is clamped by a processing lathe, the clamping stability is difficult to ensure, and even if the workpiece to be processed in the abnormal shape can be stably clamped, the processing precision of the workpiece to be processed in the abnormal shape is also difficult to ensure.

Taking a special-shaped workpiece to be machined for processing a steering tie rod head as an example, as shown in fig. 1, the special-shaped workpiece to be machined comprises a connecting part, a fixing part and a hinge part, wherein the connecting part is of a frustum pyramid structure; the fixing part is in a prismatic structure, the first end of the fixing part is fixedly connected with the end with the smaller end area of the connecting part, and the end face of the second end of the fixing part is used for machining a threaded connecting hole; the hinge part comprises a first lug plate and a second lug plate, the first lug plate and the second lug plate are provided with coaxial pin holes, and the first end of the first lug plate and the first end of the second lug plate are fixedly connected with the end with the larger end area of the connecting part.

Because the outer contour dimension of the hinge part is different from that of the fixing part, the fixing part or the hinge part of the special workpiece to be machined can be clamped only by the machining lathe. When the fixing part is clamped, the threaded connecting hole can be machined only from one end where the hinging part is located, and the machining precision of the threaded connecting hole is influenced due to the fact that the length of the special-shaped workpiece to be machined is long; when the hinge part is clamped, the hinge part is composed of two lug plates, and the lug plates are easy to deform when the lug plates are clamped, so that pin holes on the two lug plates are not coaxial. Therefore, a positioning device for a special-shaped workpiece to be machined is needed.

It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

The utility model aims to provide a positioner of machined part is treated to abnormal shape can realize the fastening location of the machined part is treated to the abnormal shape, improves the machining precision to the machined part is treated to the abnormal shape simultaneously.

According to one aspect of the present disclosure, there is provided a positioning device for a profiled workpiece to be machined, comprising:

the box-type body comprises a fixed part and a support arm, wherein the fixed part is fixedly connected with a processing lathe, the support arm is connected with the fixed part, and the support arm is provided with an inner cavity for accommodating the special-shaped workpiece to be processed and a plurality of first through holes;

each fixing piece penetrates through the corresponding first through hole and is abutted against the outer surface of the special-shaped workpiece to be machined, and the length of the fixing piece extending into the inner cavity is adjustable.

In the positioning device according to any of the above claims, the first through hole is a threaded hole, the fixing element is a threaded element, and the threaded element is screwed into the corresponding threaded hole.

In the positioning device as set forth in any of the above, the cross section of the arm is rectangular.

According to the positioning device, the two opposite sub-support arms of the support arm are respectively provided with the first through holes.

The positioning device as set forth in any one of the above, the first and second opposite sub-arms each have three first through holes that are not collinear, and the third and fourth opposite sub-arms each have two first through holes that are distributed along the center line direction.

According to the positioning device, the special-shaped workpiece to be machined is used for machining to obtain the steering tie rod head;

the first through holes on the first sub-support arm are enclosed into an isosceles triangle, the waist length of the enclosed isosceles triangle is 320 mm, the length of the bottom side of the enclosed isosceles triangle is 170 mm, and the distance between the first through holes on the third sub-support arm is 174 mm.

In the positioning device as set forth in any of the above, the cross section of the arm is circular.

The positioning device as claimed in any one of the above claims, wherein the support arm has a plurality of sets of the first through holes, and each set of the first through holes is arranged along the peripheral direction of the support arm.

The positioning device further comprises a limiting rod and a positioning mandrel, and the fixing part is provided with a second through hole;

the first end of the limiting rod penetrates through the second through hole, and the second end of the limiting rod is used for limiting on a main shaft of the machining lathe along the axial direction;

the first end of the positioning mandrel is abutted against the first end of the limiting rod, the second end of the positioning mandrel is detachably used for penetrating through the positioning hole of the special-shaped workpiece to be machined and abutting against the tailstock of the machining lathe, and the positioning mandrel and the limiting rod are coaxial.

According to the positioning device, the end part of the second end of the limiting rod is of a circular truncated cone-shaped structure, and the second end of the limiting rod is used for limiting in the limiting hole of the spindle.

In the embodiment of the disclosure, the fixing part of the box-shaped body is fixedly connected with the processing lathe, the special-shaped workpiece to be processed is placed into the inner cavity of the support arm, the length of the fixing part extending into the inner cavity is adjusted to abut against the outer surface of the special-shaped workpiece to be processed, and meanwhile, the position of the special-shaped workpiece to be processed is adjusted. Therefore, the fastening position of the special-shaped workpiece to be machined on the machining lathe can be realized, and the machining precision of the special-shaped workpiece to be machined in the process of machining the threaded connecting hole is ensured.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.

Fig. 1 is a front view structural diagram of a special-shaped workpiece to be machined for machining a tie rod head according to the related art.

Fig. 2 is a schematic front view of a positioning device according to an embodiment of the present disclosure.

Fig. 3 is a schematic top view of a positioning device according to an embodiment of the present disclosure.

Fig. 4 is a schematic right-view structural diagram of a positioning device according to an embodiment of the present disclosure.

Fig. 5 is a schematic front view of a positioning device according to an embodiment of the present disclosure.

Fig. 6 is a schematic top view of a positioning device according to an embodiment of the present disclosure.

Reference numerals:

the related technology comprises the following steps:

1. a connecting portion; 2. a fixed part; 3. a hinge portion; 31. a first ear plate; 32. a second ear panel; 33. a pin hole.

The embodiment of the disclosure:

1. a box-shaped body; 2. a fixing member; 3. a limiting rod; 4. positioning a mandrel; 5. shaping the workpiece to be machined; 6. a chuck; 7. a main shaft; 8. a tailstock;

11. a fixed part; 111. a second through hole; 12. a support arm; 121. a first through hole; 122. a first sub-arm; 123. a second sub-arm; 124. a third sub-arm; 125. and a fourth sub-support arm.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted. Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale.

The terms "a," "an," "the," "said," and "at least one" are used to indicate the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first," "second," and "third," etc. are used merely as labels, and are not limiting on the number of their objects.

The disclosed embodiment provides a positioning device for a special-shaped workpiece to be machined, and as shown in fig. 2 or fig. 3, the positioning device for machining comprises a box-shaped body 1, a positioning mechanism and a positioning mechanism, wherein the box-shaped body 1 comprises a fixing part 11 fixedly connected with a machining lathe, and a support arm 12 connected with the fixing part 11, and the support arm 12 is provided with an inner cavity for accommodating the special-shaped workpiece to be machined 5 and a plurality of first through holes 121; each fixing part 2 penetrates through the corresponding first through hole 121 and is abutted against the outer surface of the special-shaped workpiece to be machined 5, and the length of the fixing part 5 extending into the inner cavity is adjustable.

In the embodiment of the disclosure, the fixing portion 11 of the box-shaped body 1 is fixedly connected to the processing lathe, the special-shaped workpiece 5 to be processed is placed in the inner cavity of the support arm 12, and then the length of the fixing member 5 extending into the inner cavity is adjusted to abut against the outer surface of the special-shaped workpiece 5 to be processed, and the position of the special-shaped workpiece 5 to be processed is adjusted. Therefore, the fastening position of the special-shaped workpiece 5 to be machined on the machining lathe can be realized, and the machining precision of the special-shaped workpiece 5 to be machined in the threaded connection hole is ensured.

In the actual implementation process, the special-shaped workpiece 5 to be processed is placed at one end of the support arm 12 far away from the fixing part, the hinge part 3 of the special-shaped workpiece 5 to be processed faces the fixing part 11, and then the special-shaped workpiece 5 to be processed is accommodated in the inner cavity of the support arm 12.

Wherein, the thread machining end can be all accommodated in the inner chamber of support arm 12, certainly also can stretch out support arm 12, and the length that stretches out support arm 12 is adjustable, as long as guarantee that a plurality of mounting 2 can cooperate the tight heterotypic of top and treat the machined part 5, the realization treat the fastening location of machined part 5 to the heterotypic can.

In the actual machining process, after the fastening and positioning of the special-shaped workpiece to be machined 5 are realized, taking machining of a threaded connecting hole of M90X 3-6H as an example, a bottom hole with the diameter of 87 mm is bored in the end face of the fixing part 2 of the special-shaped workpiece to be machined 5, and then the threaded connecting hole of M90X 3-6H is turned on the basis of the bottom hole.

In some embodiments, when machining the threaded connection hole, friction force is generated between the tool and the shaped workpiece 5 to be machined, so that the tool may drive the shaped workpiece 5 to be machined to rotate synchronously. So, in order to avoid the cutter to drive the heterotypic condition of treating that the machined part 5 takes place synchronous revolution, the tip design of mounting 2 to when the surface of the machined part 5 is treated to the mounting 2 butt heterotypic, improve the frictional force between mounting 2 and the heterotypic piece 5 of treating, thereby further improve the fastening degree to the heterotypic piece 5 of treating machined.

In some embodiments, the first through hole 121 is a threaded hole, the fixing member 5 is a threaded member, the threaded member is screwed into the corresponding threaded hole, and the length of the threaded member extending into the inner cavity of the arm 12 is adjusted by the screwing degree. The screw is a fixing bolt or a screw. Of course, for the first through hole 121 on the support arm 12, the fixing element 5 may also have other structures as long as it can fix with the support arm 12 and the length of the first through hole extending into the inner cavity of the support arm 12 is adjustable, which is not limited in the embodiment of the present disclosure. Illustratively, the fixing member 5 includes a ring detachably fitted on the arm 12, the ring having a threaded hole at a position corresponding to the first through hole 121, and a bolt screwed into the corresponding threaded hole and passing through the corresponding first through hole 121 to extend into the inner cavity of the arm 12.

In the embodiment of the present disclosure, when the box-shaped body 1 cooperates with the fixing member 2 to position the special-shaped workpiece 5, the supporting arm 12 may have a prismatic structure, or of course, may have a cylindrical structure. When the arm 12 is in a prism structure, as shown in fig. 4, the cross section of the arm 12 is rectangular; when the arm 12 is cylindrical, the arm 12 is circular in cross-section.

When the cross section of support arm 12 is the rectangle, box body 1 includes fixed part 11 (base) and fixes four risers with one side in fixed part 11, and four risers are central symmetry, and four risers enclose support arm 12 of city box body 1. Thus, as shown in fig. 4, the arm 12 of the box-type body 1 includes a first sub-arm 122 and a second sub-arm 123 opposite to each other, and a third sub-arm 124 and a fourth sub-arm 125 opposite to each other.

When the first through hole 121 is formed in the support arm 12 of the box-shaped body 1, in order to ensure the fastening and positioning of the special-shaped workpiece 5, at least two opposite sub-support arms of the support arm 12 are provided with a plurality of first through holes 121.

Illustratively, the first sub arm 122 and the second sub arm 123 each have three non-collinear first through holes 121. Thus, the fixing parts 2 screwed into the first through holes 121 on the two opposite sub support arms 12 clamp the special-shaped workpiece 5 to be machined, and the special-shaped workpiece 5 to be machined is prevented from moving in a plane parallel to the sub support arms 12; the three fixing members 2 screwed into the three first through holes 121 on any one sub-support arm 12 can enclose a triangle to prevent the special-shaped workpiece 5 to be machined from rotating according to the stability of the triangle, so that the special-shaped workpiece 5 to be machined can be tightly fixed.

Illustratively, as shown in fig. 4, 5 and 6, the arm 12 includes three first through holes 121 that are not collinear in each of the first sub-arm 122 and the second sub-arm 123, and the arm 12 includes two first through holes 121 that are distributed along the center line O-O in each of the third sub-arm 124 and the fourth sub-arm 125.

Therefore, the fixing parts 2 screwed into the first through holes 121 on the four sub-support arms clamp the special-shaped workpiece 5 to be machined, and the special-shaped workpiece 5 to be machined is prevented from moving in any direction; the three fixing members 2 screwed into the three first through holes 121 on the first sub support arm 122 and the second sub support arm 123 can enclose a triangle, so that the rotation of the special-shaped workpiece 5 to be processed is avoided according to the stability of the triangle, and thus the fastening position of the special-shaped workpiece 5 to be processed can be realized.

For the special-shaped workpiece to be machined 5 for machining the steering tie rod head, because one end, close to the fixing part 11, of the special-shaped workpiece to be machined 5 is an ear plate end, in order to ensure that the fixing part 2 can be abutted to the special-shaped workpiece to be machined 5, two first through holes 121 corresponding to two vertexes of the bottom edge of a triangle surrounded by three non-collinear first through holes 121 correspond to the side edges of two ear plates respectively.

In addition, the three first through holes 121 on the first sub arm 122 enclose an isosceles triangle, the waist length of the enclosed isosceles triangle is 320 mm, the bottom side length of the enclosed isosceles triangle is 170 mm, and the distance between the two first through holes 121 on the third sub arm 124 is 174 mm. The distribution of the three first through holes 121 on the second sub-arm 123 can refer to the distribution of the three first through holes 121 on the first sub-arm 122, and the distribution of the two first through holes 121 on the fourth sub-arm 125 can refer to the distribution of the two first through holes 121 on the third sub-arm 124.

When the arm 12 has a circular cross section, the box-shaped body 1 includes a fixing portion 11 (base) and a cylinder fixed to one side of the fixing portion 11, the cylinder forming the arm 12 of the box-shaped body 1.

When the first through holes 121 are provided in the arm 12 of the box-type body 1, in order to secure the fastening and positioning of the special-shaped member to be machined 5, the arm 12 has a plurality of sets of first through holes 121, and each set of first through holes 121 is arranged in the circumferential direction of the arm 12.

Wherein, each group includes at least three first through-holes 121, and at least three first through-holes 121 evenly distribute along the peripheral direction of support arm 12, and of course, at least three first through-holes 121 also can distribute wantonly, as long as can realize waiting to process the fastening location of piece 5 to the abnormal shape. Of course, each group may also include two first through holes 121, and the positions of the two first through holes 121 may refer to the related art, which is not limited in the embodiments of the present disclosure.

In the embodiment of the disclosure, in order to ensure the coaxiality of the threaded connecting hole when the threaded connecting hole is machined on the special-shaped workpiece to be machined 5, as shown in fig. 5 or fig. 6, the machining and positioning device further comprises a limiting rod 3 and a positioning mandrel 4, wherein the fixing part 11 is provided with a second through hole 111; the first end of the limiting rod 3 penetrates through the second through hole 111, and the second end of the limiting rod 3 is used for limiting on the spindle 7 of the machining lathe along the axial direction; the first end of the positioning mandrel 4 is abutted against the first end of the limiting rod 3, the second end of the positioning mandrel 4 is detachably used for penetrating through a positioning hole of the special-shaped workpiece to be machined 5 and abutted against a tailstock 8 of a machining lathe, and the positioning mandrel 4 is coaxial with the limiting rod 3.

After the positioning mandrel 4 penetrates through the positioning hole of the special-shaped workpiece to be machined 5, the axial direction of the positioning mandrel 4 is overlapped with the axial direction of the positioning hole, and meanwhile, no moving space exists between the positioning mandrel 4 and the special-shaped workpiece to be machined 5 along the radial direction of the positioning hole, so that the positioning mandrel 4 can limit the special-shaped workpiece to be machined 5 in the radial direction of the positioning hole. Illustratively, the outer diameter of the positioning mandrel 4 is equal to the diameter of the positioning hole of the profiled workpiece 5 to be machined. Of course, the aperture of the positioning hole of the special-shaped workpiece to be machined 5 may also be slightly larger than the outer diameter of the positioning spindle 4, as long as the axial direction of the positioning spindle 4 can be ensured to coincide with the axial direction of the positioning hole, and meanwhile, a moving space is prevented from being formed in the radial direction of the positioning hole relative to the special-shaped workpiece to be machined 5 by the positioning spindle 4, which is not limited in the embodiment of the disclosure.

Since the second end of the limiting rod 3 is limited on the main shaft 7 along the axial direction, the axial direction of the limiting rod 3 is overlapped with the axial direction of the main shaft 7 of the processing lathe. Thus, when the positioning spindle 4 is clamped between the first end of the stopper rod 3 and the tailstock 8, the positioning spindle 4 is necessarily coaxial with the main shaft 7 of the machining lathe at this time because the positioning spindle 4 is coaxial with the stopper rod 3. The positioning mandrel 4 is combined with the above-described radial direction of the positioning hole to limit the special-shaped workpiece to be machined 5, so that the positioning hole of the special-shaped workpiece to be machined 5 is ensured to be coaxial with the main shaft 7 of the machining lathe, and therefore, when the threaded connecting hole is machined in the special-shaped workpiece to be machined 5, the coaxiality of the threaded connecting hole is ensured, and the machining precision of the special-shaped workpiece to be machined 5 is improved. In addition, the positioning mandrel 4 can position the specially-shaped workpiece to be machined 5, so that the specially-shaped workpiece to be machined 5 is positioned under the condition that the positioning mandrel 4 is clamped between the limiting rod 3 and the tailstock 8, the length of the fixing part 2 screwed into the inner cavity of the box-type body 1 is prevented from being adjusted when the specially-shaped workpiece to be machined 5 is tightly jacked by the plurality of fixing parts 2, and the fastening efficiency of the specially-shaped workpiece to be machined 5 is improved.

In combination with the actual machining process of the threaded connecting hole described above, since the special-shaped workpiece to be machined 5 has the positioning hole, hole expansion can be performed on the basis of the positioning hole to bore a bottom hole with a larger bore. Before boring out a bottom hole on the basis of the positioning hole, the positioning mandrel 4, the limiting rod 3, the special-shaped workpiece to be machined 5 and the tailstock 8 are all detachable, so that the tailstock 8 of the machining lathe is controlled to loosen the limit on the second end of the positioning mandrel 4, and then the positioning mandrel 4 is pulled out of the positioning hole to remove the obstruction formed by the positioning mandrel 4.

In some embodiments, the spindle 7 of the machine tool has a stop hole in which the second end of the stop rod 3 is stopped.

The shape of the cross section of the limiting hole in the main shaft 7 is the same as that of the cross section of the second end part of the limiting rod 3, and the taper of the limiting hole in the main shaft 7 is the same as that of the second end part of the limiting rod 3, so that the limiting accuracy of the second end of the limiting rod 3 in the limiting hole is guaranteed.

The shape of the cross section of the second end portion of the stopper rod 3 may be designed according to the shape of the cross section of the stopper hole in the spindle 7 of the machining lathe. Exemplarily, the limiting hole on the spindle 7 of the processing lathe is a circular truncated cone groove, and at this time, as shown in fig. 5 or fig. 6, the end of the second end of the limiting rod 3 is a circular truncated cone-shaped structure, and the circular truncated cone-shaped structure of the second end of the limiting rod 3 is limited in the circular truncated cone groove of the spindle 7; or, the limiting hole on the machining lathe spindle 7 is a conical groove, the end of the second end of the limiting rod 3 is a conical structure or a truncated cone-shaped structure at this time, and the conical structure or the truncated cone-shaped structure of the second end of the limiting rod 3 is limited in the conical groove of the spindle 7.

Continuing with the above example, when the limiting hole is a circular truncated cone groove and the end of the second end of the limiting rod 3 is a circular truncated cone-shaped structure, the taper of the circular truncated cone groove on the main shaft 7 of the machining lathe is 1:20, and at this time, the taper of the end of the second end of the limiting rod 3 is also 1: 20.

In some embodiments, the end face of the first end of the positioning mandrel 4 has a first central groove for limiting the first end of the stop rod 3.

Like this, spacing when the first end of gag lever post 3 in first centre groove, avoided gag lever post 3 and location mandrel 4 along the radial relative motion who takes place of location mandrel 4, improved the butt efficiency between the first end of gag lever post 3 and the first end of location mandrel 4 simultaneously, be convenient for guarantee gag lever post 3 and the coaxial of location mandrel 4.

The first central groove is a conical groove, correspondingly, the end part of the first end of the limiting rod 3 is in a conical structure or a circular truncated cone-shaped structure, or the first central groove is a circular truncated cone groove, correspondingly, the end part of the first end of the limiting rod 3 is in a circular truncated cone-shaped structure. Of course, the first central groove may also be a groove with other structures as long as the first end of the limiting rod 3 can be limited, which is not limited in the embodiments of the present disclosure.

In some embodiments, the end face of the second end of the positioning spindle 4 has a second central groove for limiting the tip of the tailstock 8.

Like this, the spacing when tailstock 8 of second centre groove, avoided the relative motion of the relative tailstock 8 of location mandrel 4 along the radial emergence of location mandrel 4, improved the butt efficiency between 8 tops of tailstock and the second end of location mandrel 4 simultaneously, be convenient for guarantee the coaxial of gag lever post 3 and location mandrel 4.

Wherein, the top of the tail seat 8 is collinear with the axial direction of the main shaft 7, and the second central groove is a conical groove.

The structures corresponding to the three embodiments described above may be used either as a mutual structure or as a single structure. Illustratively, the main shaft 7 of the machining lathe is provided with a limiting hole, the second end of the limiting rod 3 is limited in the limiting hole, the end surface of the first end of the positioning mandrel 4 is provided with a first central groove, the end surface of the second end of the positioning mandrel 4 is provided with a second central groove, the first central groove is used for limiting the first end of the limiting rod 3, and the second central groove is used for limiting the tip of the tailstock 8.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims (10)

1. A positioning device for a piece to be machined of a profiled shape, characterized by comprising:

the box-type body comprises a fixed part and a support arm, wherein the fixed part is fixedly connected with a processing lathe, the support arm is connected with the fixed part, and the support arm is provided with an inner cavity for accommodating the special-shaped workpiece to be processed and a plurality of first through holes;

each fixing piece penetrates through the corresponding first through hole and is abutted against the outer surface of the special-shaped workpiece to be machined, and the length of the fixing piece extending into the inner cavity is adjustable.

2. The positioning device of claim 1, wherein the first through hole is a threaded hole, and the fixing member is a threaded member that is screwed into the corresponding threaded hole.

3. A positioning device as set forth in claim 1 or 2 wherein said arms are rectangular in cross-section.

4. The positioning device according to claim 3, wherein at least two of said opposing sub-arms have a plurality of said first through holes.

5. The positioning device according to claim 4, wherein each of the first and second opposing sub-arms has three of said first through-holes that are not collinear, and each of the third and fourth opposing sub-arms has two of said first through-holes that are distributed along the centerline direction.

6. The positioning device according to claim 5, wherein the profiled member to be machined is used for machining a tie rod head;

the first through holes on the first sub-support arm are enclosed into an isosceles triangle, the waist length of the enclosed isosceles triangle is 320 mm, the length of the bottom side of the enclosed isosceles triangle is 170 mm, and the distance between the first through holes on the third sub-support arm is 174 mm.

7. A positioning device as set forth in claim 1 or 2 wherein said arms are circular in cross-section.

8. The positioning device according to claim 7, wherein said arm has a plurality of sets of said first through holes, each set of said first through holes being arranged in a circumferential direction of said arm.

9. The positioning device according to claim 1 or 2, wherein the positioning device further comprises a stopper rod and a positioning mandrel, and the fixing portion has a second through hole;

the first end of the limiting rod penetrates through the second through hole, and the second end of the limiting rod is used for limiting on a main shaft of the machining lathe along the axial direction;

the first end of the positioning mandrel is abutted against the first end of the limiting rod, the second end of the positioning mandrel is detachably used for penetrating through the positioning hole of the special-shaped workpiece to be machined and abutting against the tailstock of the machining lathe, and the positioning mandrel and the limiting rod are coaxial.

10. The positioning device as set forth in claim 9, wherein the second end of the stop lever is terminated with a truncated cone-shaped structure, and the second end of the stop lever is adapted to be retained in the retaining hole of the spindle.

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