WO2019168570A1

WO2019168570A1 - Grinding jig for a multi-fiber optical connector

Info

Publication number: WO2019168570A1
Application number: PCT/US2018/060899
Authority: WO
Inventors: Yongjun YUAN; Peter Viviane Leopold Bos; Hang Li; Zongsheng Leng; Zhenghui Zhang
Original assignee: Commscope Technologies Llc
Priority date: 2018-02-27
Filing date: 2018-11-14
Publication date: 2019-09-06
Also published as: CN208231543U

Abstract

A grinding jig for a multi-fiber optical connector is disclosed. The grinding jig includes a body having a plurality of openings. Each opening is positioned in the body such that a major axis is directed towards a center of the body and a minor axis is directed in the circumferential direction of the body. Each opening extends through first and second surfaces of the body and is configured to receive a ferrule of the multi-fiber optical connector.

Description

GRINDING JIG FOR A MULTI-FIBER OPTICAL CONNECTOR

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is being filed on November 14, 2018 as a PCT International Patent Application and claims the benefit of Chinese Utility Model Patent Application No.

201820278104.2, filed on February 27, 2018, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates generally to the field of fiber optic communications. More specifically, the present disclosure relates to a grinding jig for a multi-fiber optical connector.

BACKGROUND

[0003] In fiber optic communications networks, multi-fiber optical connectors are commonly used to connect fiber optic cables so that a plurality of optical fibers in one fiber optic cable are connected with a plurality of optical fibers in another fiber optic cable. A multi-fiber optical connector may have various configurations such as MPO, MTP, HMFOC, and the like.

[0004] A multi-fiber optical connector typically includes a ferrule that has a plurality of bores. Each bore receives one optical fiber therein. For example, a ferrule for a 12 fiber multi-fiber connector will have 12 bores. Each optical fiber may be fixed in a respective bore of the ferrule with an adhesive. After fixing the optical fibers, high-precision grinding and polishing treatments are performed on the optical fibers that project from the end surface of the ferrule to achieve a desired or predetermined optical performance. Grinding and polishing operations require time and consumables such as polishing pads, polishing fluid, and the like. [0005] Generally, a plurality of ferrules are fixed to a grinding jig. Thereafter, the grinding jig is placed on a grinder to perform grinding and polishing treatments on the ferrules.

[0006] FIGS. 1 and 2 show a conventional grinding jig that includes a body 1 and a plurality of fasteners 2. The body 1 is provided with a plurality of openings along a circumferential direction of the body 1. Each opening extends through upper and lower surfaces of the body 1 and receives a ferrule 3 of a multi-fiber optical connector. Each of the fasteners 2 is positioned on a lateral surface of the body 1 and fixes the inserted ferrule 3 to the body 1.

[0007] In the conventional grinding jig of FIGS. 1 and 2, the openings in the body 1 and the ferrules 3 inserted therein are arranged such that their major axes (e.g., long axis) are generally perpendicular to a radial line between the center of the opening (or the center of the ferrule 3) and the center of the body 1. In such arrangements, the long edge of the ferrule 3 occupies a larger portion of the circumference of the body 1 which limits the amount of ferrules 3 that can be received by the body 1, and therefore limits the number of ferrules 3 that can polished at one time. For example, the grinding jig of FIGS. 1 and 2 is limited to receiving 10 to 12 ferrules from the multi-fiber optical connectors. Thus, the efficiency of the grinding jig is reduced.

[0008] Therefore, improvements are needed for a grinding jig that can hold a greater number of ferrules at one time during grinding and polishing treatments.

SUMMARY OF THE INVENTION

[0009] The object of the present disclosure is to provide a grinding jig for a multi-fiber optical connector capable of overcoming drawbacks in the art.

[0010] One aspect relates to a grinding jig for a multi-fiber optical connector, the grinding jig includes a body having a plurality of openings. Each opening is positioned in the body such that a major axis of each opening is directed towards a center of the body and a minor axis of each opening is directed in the circumferential direction of the body. Each opening extends through first and second surfaces of the body and is configured to receive the ferrule. [0011] In some examples, the major axis of each opening is within a range of 0 to 30 degrees of a radial line connecting the center of the opening and the center of the body. In certain examples, the major axis of each opening coincides with a radial line connecting the center of the opening and the center of the body.

[0012] In some examples, each opening has a rectangular shape. In other examples, each opening has an elliptical shape. In yet further examples, each opening has a semi-elliptical shape. The plurality of openings are equally spaced apart. In one example, the body has 24 or more openings. In another example, the body has 32 or more openings.

[0013] In some examples, the body has a circular shape, and the plurality of openings are positioned along a circumferential direction of the body. In other examples, the body has a polygon shape, and the plurality of openings are positioned along the perimeter of the body in a substantially similar polygon distribution.

[0014] In some examples, the grinding jig includes a plurality of fasteners each configured to fix the ferrule to the body. The plurality of fasteners are disposed on a lateral surface of the body, the lateral surface being substantially orthogonal to the first and second surfaces of the body. In certain examples, the plurality of fasteners are bolts or screws.

[0015] Another aspect relates to a method for polishing a plurality of optical fibers inserted and fixed inside a ferrule of a multi-fiber optical connector. The method includes: inserting an end surface of the ferrule into an opening of a body of the grinding jig, a major axis of the ferrule and a radial line connecting the center of the ferrule and the center of the grinding jig being within a range of 0 to 30 degrees. The method may further include attaching the grinding jig to a grinding machine; and operating the grinding machine to polish the end surface of the ferrule.

[0016] The method may further include using polishing pads to polish the end surface of the ferrule, each polishing pad having a different level of grit. Also, the method may include removing the grinding jig from the grinding machine; removing the ferrule from the body of the grinding jig; and inspecting the quality of the end surface of the ferrule. In some examples, the method includes using a fastener that can be turned in clockwise or counterclockwise directions to fix the ferrule to the body of the grinding jig. [0017] According to another aspect of the present disclosure, there is provided a grinding jig for a multi-fiber optical connector, wherein the multi -fiber optical connector includes a ferrule and a plurality of optical fibers inserted and fixed in the ferrule, the grinding jig comprising: a body provided with a plurality of openings along a circumferential direction of the body, the plurality of openings being provided to extend through upper and lower surfaces of the body for receiving the ferrule of the multi-fiber optical connector inserted therein; and a plurality of fasteners for fixing the inserted ferrule to the body. Each of the plurality of openings is provided such that an absolute value of an angle defined by a long axis of the opening and a connection line connecting a center of the opening and a center of the body is within a range of 0 to 30 degrees.

[0018] In one embodiment of the grinding jig, each of the plurality of openings is provided such that the long axis of the opening is directed to the center of the body.

[0019] In one embodiment of the grinding jig, the plurality of openings are all in a rectangular shape, or an elliptical shape, or a semi-elliptical shape.

[0020] In one embodiment of the grinding jig, the plurality of openings are provided at substantially equal spacing.

[0021] In one embodiment, each of the plurality of openings is provided such that the absolute value of the angle defined by the long axis of the opening and a connection line connecting a center of the opening and a center of the body is substantially equal with that of other openings.

[0022] In one embodiment of the grinding jig, the body of the grinding jig has a circular shape, and the plurality of openings are distributed in a substantially circular shape along the circumferential direction of the body.

[0023] In one embodiment of the grinding jig, the body of the grinding jig has a regular polygonal shape, and the plurality of openings are distributed in a substantially similar regular polygonal shape along the circumferential direction of the body.

[0024] In one embodiment of the grinding jig, each of the plurality of fasteners is disposed on a lateral surface of the body along the circumferential direction of the body. [0025] In one embodiment of the grinding jig, the number of the plurality of openings is 24 or more. In one embodiment of the grinding jig, the number of the plurality of openings is 32 or more. In one embodiment of the grinding jig, the fasteners are bolts or screws.

[0026] For the grinding jig for a multi-fiber optical connector according to the present disclosure, since the openings on the body of the grinding jig are disposed in a specific orientation, the amount of the openings can be significantly increased so that the grinding jig can accommodate and treat more ferrules of multi -fiber optical connectors at one time, improving the production efficiency, and further reducing the production costs by saving consumables.

[0027] A variety of additional inventive aspects will be set forth in the description that follows. The inventive aspects can relate to individual features and to combinations of features. It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the examples disclosed herein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The following drawing figures, which form a part of this application, are illustrative of described technology and are not meant to limit the scope of the disclosure in any manner.

[0029] FIG. l is a perspective view of a plurality of ferrules received by an existing grinding jig.

[0030] FIG. 2 is a partially enlarged view of FIG. 1.

[0031] FIG. 3 is a perspective view of an example of a grinding jig in accordance with the present disclosure.

[0032] FIG. 4 is a perspective view of a plurality of multi-fiber optical connectors each having a ferrule received by the grinding jig of FIG. 3.

[0033] FIG. 5 is a partially enlarged view of FIG. 4.

[0034] FIG. 6 is a perspective view of another example of a grinding jig in accordance with the present disclosure. [0035] FIG. 7 is a perspective view of a plurality of multi-fiber optical connectors each having a ferrule received by the grinding jig of FIG. 6.

[0036] FIG. 8 is a partially enlarged view of FIG. 7.

[0037] FIG. 9 is a perspective view of another example of a grinding jig in accordance with the present disclosure.

[0038] FIG. 10 is a perspective view of a plurality of multi-fiber optical connectors each having a ferrule held by the grinding jig of FIG. 9.

[0039] FIG. 11 is a partially enlarged view of FIG. 10.

[0040] FIG. 12 illustrates a method for grinding and polishing a multi-fiber optical connector.

DETAILED DESCRIPTION

[0041] Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims.

[0042] FIGS. 3-5 show a first example of a grinding jig 100 according to an embodiment of the present disclosure. As shown in FIG. 3, the grinding jig 100 includes a body 102 and a plurality of fasteners 104. The body 102 is made from a material having excellent corrosion resistance, heat resistance, and wear resistance. For example, the body 102 can be made from stainless steel, glass fiber, etc. The body 102 is a platen-shaped body having a circular or polygon shape.

[0043] As shown in FIGS. 4 and 5, each fastener 104 fixes the ferrule 20 of a multi-fiber optical connector 10 to the body 102 of the grinding jig 100. In some examples, the fasteners 104 are bolts or screws. As shown in FIGS. 4 and 5, the fasteners 104 are arranged on a lateral surface 106 of the body 102 along an outside perimeter of the body 102. As shown in FIGS. 4 and 5, the lateral surface 106 is substantially orthogonal to a first surface 108 and a second surface 110 of the body 102. Additional configurations are possible.

[0044] Referring now to FIG. 3, a plurality of openings 112 are positioned in the body 102. The openings 112 extend through the first and second surfaces 108, 110. Each opening 112 is configured to receive a ferrule 20 of a multi-fiber optical connector 10. In the example body 102 shown in FIG. 3, each opening 112 has a rectangular shape. Each opening 112 is machined to ensure that a ferrule 20 can be precisely and reliably positioned into the opening 112 and to ensure that the ferrule 20 can be securely fixed to the body 102 of the grinding jig 100.

[0045] As further shown in FIG. 3, in examples where the body 102 has a circular shape, the plurality of openings 112 are positioned in a substantially circular distribution along the circumferential direction of the body 102 of the grinding jig 100.

[0046] Alternatively, in examples where the body 102 has polygon shape, the plurality of openings 112 are positioned along the perimeter of the body in a substantially similar polygon distribution along the circumferential direction of the body 102.

[0047] The plurality of openings 112 are positioned in the body 102 such that the major axis 1 (e.g., long axis) of each opening 112 is directed towards the center O of the body 102, and the minor axis m (e g., short axis) of each opening 112 is directed in a circumferential direction relative to the center O of the body 102. The minor axis m is substantially perpendicular to the major axis 1. The center O of the body 102 may substantially coincide with the axis of rotation of a polishing pad attached to a platen of a grinding machine. As further shown, the plurality of openings 112 are equally spaced apart about the circumferential direction of the body 102.

[0048] With reference to FIGS. 3 and 4, the short edges of the openings 112 and the ferrules 20 are positioned along the circumferential direction of the body 102. The length of the short edge occupies a smaller portion of the overall circumferential length of the body 102 compared to the long edges of the opening 112 and the ferrule 20. Accordingly, more ferrules 20 can be inserted into the body 102 of the grinding jig 100 and more multi fiber optical connectors 10 can be processed by the grinding jig 100 at one time, which increases the production efficiency of the grinding jig 100. Additionally, production costs can be reduced by saving the consumables. [0049] As shown in FIG. 3, each of the plurality of openings 112 is positioned on the body 102 of the grinding jig 100 such that the value of an angle qi, 02 between a major axis h, l₂ of the opening 112 and the radial line L connecting the center C of the opening 112 and the center O of the body 102 is within a range of 0 to 30 degrees. In this manner, the number of openings 112 positioned along the circumferential direction of the body 102 is increased, and the number of ferrules 20 that can be inserted into the body 102 of the grinding jig 100 is also increased.

[0050] In some examples, the plurality of openings 112 are positioned in a twisted orientation around the circumferential direction of the body 102 such that the major axis h, l₂ of the opening 112 and the radial line L connecting the center C of the opening 112 and the center O of the body 102 intersect. In other examples, the plurality of openings 112 are positioned in a radial orientation such that the major axis lo of the opening 112 coincides with the radial line L connecting the center C of the opening 112 and the center O of the body 102.

[0051] In some examples, the body 102 of the grinding jig 100 includes 24 or more openings 112. In such examples, the grinding jig 100 can receive 24 or more ferrules at one time. In some examples, the grinding jig 100 includes 32 or more openings in the body 102. In such examples, the grinding jig 100 can receive 32 or more ferrules at one time. Thus, the grinding jig 100 is more efficient because it can hold an increased number ferrules at one time. The grinding jig 100 is suitable for various multi-fiber optical connectors (e.g., MPO, MTP, HMFOC, etc.).

[0052] FIGS. 6-8 show a grinding jig 200 in accordance with another example. As shown in FIGS. 6-8, the grinding jig 200 includes a body 202, a plurality of fasteners 204, and a plurality of openings 212 positioned along a circumferential direction of the body 202. Like in the first example described above, the fasteners 204 are used to fix the ferrules 20 of the multi-fiber optical connectors 10 to the body 202 of the grinding jig 200.

[0053] In the example illustrated in FIGS. 6-8, the structure and arrangement of the grinding jig 200 and the multi-fiber optical connector 10 are generally the same as in the first example described above with reference to FIGS. 3-5. However, the grinding jig 200 differs from the first example in that each of the plurality of openings 212 has an elliptical shape. As described herein, the term elliptical shape may include oval, circular, rounded, and other similar shapes.

[0054] In the example grinding jig 200 of FIGS. 6-8, the elliptical shape of the openings 212 can facilitate the installation and removal of the ferrules 20, and avoid damage to the ferrules 20 due to the insertion and removal of the ferrules 20 from the grinding jig 200. Also, the elliptical shape of the openings 212 can reduce the adverse effects caused by cured adhesive or dirt that can result from the high-precision grinding and polishing treatments.

[0055] In accordance with the first example described above with reference to FIGS. 3-5, the positioning of the openings 212 of the grinding jig 200 of FIGS. 6-8 may be set in different orientations along the circumferential direction of the body 202 of the grinding jig 200 so that a greater number of ferrules 20 can be positioned into the body 202 of the grinding jig 200.

[0056] FIGS. 9-11 show a grinding jig 300 in accordance with another example. As shown in FIGS. 9-11, the grinding jig 300 includes a body 302, a plurality of fasteners 304, and a plurality of openings 312 positioned on the body 302 along a circumferential direction of the body 302. Like in the first and second examples described above, the fasteners 304 can be used to fix the ferrules 20 of the multi-fiber optical connectors 10 to the body 302 of the grinding jig 300.

[0057] In the example illustrated in FIGS. 9-11, the structure and arrangement of the grinding jig 300 and the multi -fiber optical connector 10 are generally the same as the aforementioned examples described above. However, the grinding jig 300 differs from the examples previously described in that each of the plurality of openings 312 has a semi elliptical shape.

[0058] The plurality of openings 312 having a semi-elliptical shape that is a hybrid between the rectangular shape of FIG. 3 and the elliptical shape of FIG. 6.

Advantageously, the semi-elliptical shape of the openings 312 can facilitate the installation and removal of the ferrules 20, and avoid damage to the ferrules 20.

Additionally, the semi-elliptical shape of the openings 312 can reduce the adverse effects caused by cured adhesive or dirt that can result from the high-precision grinding and polishing treatments. [0059] Further, the semi-elliptical shape of the plurality of openings 312 can provide a support surface for the fasteners 304 to fix the ferrules 20 to the body 302 of the grinding jig 300. The semi-elliptical shape of the plurality of openings 312 can thus provide a better contact surface for positioning the ferrules 20 inside the body 302 of the grinding jig 300.

[0060] In accordance with the first example described above with reference to FIGS. 3-5, the positioning of the openings 312 of the grinding jig 300 of FIGS. 9-11 may be set in different orientations along the circumferential direction of the body 302 of the grinding jig 300 so that a greater number of ferrules 20 can be positioned into the body 302 of the grinding jig 300.

[0061] FIG. 12 illustrates a method 400 for grinding and polishing a multi-fiber optical connector 10. The method 400 includes a step 402 of inserting a ferrule 20 of the multi- fiber optical connector 10 into an opening 112 of the grinding jig 100. As described above, the opening 112 extends through first and second surfaces 108, 110 of the body 102 of the grinding jig 100. The opening 112 may have a rectangular shape (see FIG. 3), an elliptical shape (see FIG. 6), or a semi-elliptical shape (see FIG. 9). During step 402, an end surface of the ferrule 20 is inserted into the opening 112 of the body 102 of the grinding jig 100 such that an angle between the major axis of the ferrule 20 and a radial line that connects the center of the ferrule 20 and the center O of the grinding jig 100 is within a range of 0 to 30 degrees.

[0062] Next, the method 400 includes a step 404 of fixing the ferrule 20 to the body 102 of the grinding jig 100. In some examples, the ferrule 20 is fixed to the body 102 using the fasteners 104 described above. For example, the fasteners 104 can be in the form of bolts or screws that can be turned in clockwise or counterclockwise directions to fix the ferrule 20 to the body 102 of the grinding jig 100. Other arrangements are possible.

[0063] Afterwards, the method 400 includes a step 406 of attaching the grinding jig 100 to a grinding machine. In some examples, the grinding jig 100 is attached to the grinding machine such that the grinding jig 100 is fixed relative to the grinding machine. In other examples, the grinding jig 100 can move relative to the grinding machine when attached thereto.

[0064] Next, the method 400 includes a step 408 of operating the grinding machine to grind and polish the end surface of ferrule 20 held by the grinding jig 100. In some examples, the grinding machine includes a surface that rotates relative to the grinding jig 100 during grinding and polishing. In other examples, the grinding jig 100 rotates relative to a fixed surface of the grinding machine during grinding and polishing. In further alternative examples, the grinding machine produces a random orbital movement relative the grinding jig 100.

[0065] During grinding and polishing, the grinding machine uses consumables such as polishing pads to polish the end surface of the ferrule 20. During step 408, various types of polishing pads can be used by the grinding machine. For examples, polishing pads each having a different level of grit or coarseness can be used by the grinding machine.

Accordingly, in some examples, step 408 includes multiple polishing operations that follow a sequence of using coarse to fine grit polishing pads. In some examples, the method 400 includes performing about 5 to 6 grinding and polishing operations, each using a polishing pad having a different level of grit.

[0066] After the grinding and polishing operations are completed, the method 400 includes a step 410 of removing the grinding jig 100 from the grinding machine.

Thereafter, the method 400 includes a step 412 of removing the ferrule 20 from the body 102 of the grinding jig 100. In some examples, the ferrule 20 is removed from the body 102 by loosening the fasteners 104 described above. For example, the fasteners 104 can be turned in clockwise or counterclockwise directions to loosen the ferrule 20 from the body 102 of the grinding jig 100.

[0067] Next, the method includes a step 414 of inspecting the quality of the end surface of the ferrule 20. Step 414 can include inspecting the ferrule 20 to determine whether there are excessive scratches, depressions, and the like on the end surface. In some further examples, step 414 can include inspecting the geometrical parameters of the ferrule 20 such as the curvature of the end surface, the height of the optical fiber, and the like. If the ferrule 20 does not meet certain minimum requirements, steps 402-414 can be repeated as necessary.

[0068] The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and application illustrated and described herein, and without departing from the true spirit and scope of the following claims.

Claims

What is claimed is:

1. A grinding jig for a multi-fiber optical connector that includes a ferrule and a plurality of optical fibers inserted and fixed in the ferrule, the grinding jig comprising: a body having a plurality of openings, each opening positioned in the body such that a major axis of each opening is directed towards a center of the body and a minor axis of each opening is directed in the circumferential direction of the body, each opening extends through first and second surfaces of the body and is configured to receive the ferrule.

2. The grinding jig of claim 1, wherein the major axis of each opening is within a range of 0 to 30 degrees of a radial line connecting the center of the opening and the center of the body.

3. The grinding jig of claim 1, wherein the major axis of each opening coincides with a radial line connecting the center of the opening and the center of the body.

4. The grinding jig of claim 1, wherein each opening has a rectangular shape.

5. The grinding jig of claim 1, wherein each opening has an elliptical shape.

6. The grinding jig of claim 1, wherein each opening has a semi-elliptical shape.

7. The grinding jig of claim 1, wherein the plurality of openings are equally spaced apart.

8. The grinding jig of claim 1, wherein the body has a circular shape, and the plurality of openings are positioned along a circumferential direction of the body.

9. The grinding jig of claim 1, wherein the body has a polygon shape, and the plurality of openings are positioned along the perimeter of the body in a substantially similar polygon distribution.

10. The grinding jig of claim 1, further comprising a plurality of fasteners each configured to fix the ferrule to the body.

11. The grinding jig of claim 10, wherein the plurality of fasteners are disposed on a lateral surface of the body, the lateral surface being substantially orthogonal to the first and second surfaces of the body.

12. The grinding jig of claim 1, wherein the plurality of fasteners are bolts or screws.

13. The grinding jig of claim 1, wherein the body has 24 or more openings.

14. A method for polishing a plurality of optical fibers inserted and fixed inside a ferrule of a multi-fiber optical connector, the method comprising:

inserting an end surface of the ferrule into an opening of a body of the grinding jig, a major axis of the ferrule and a radial line connecting the center of the ferrule and the center of the grinding jig being within a range of 0 to 30 degrees.

15. The method of claim 14, further comprising:

attaching the grinding jig to a grinding machine; and

operating the grinding machine to polish the end surface of the ferrule.

16. The method of claim 15, further comprising:

using polishing pads to polish the end surface of the ferrule, each polishing pad having a different level of grit.

17. The method of claim 16, further comprising:

removing the grinding jig from the grinding machine;

removing the ferrule from the body of the grinding jig; and

inspecting the quality of the end surface of the ferrule.

18. The method of claim 14, further comprising:

using a fastener that can be turned in clockwise or counterclockwise directions to fix the ferrule to the body of the grinding jig.

19. A grinding jig for a multi-fiber optical connector, characterized in that the multi fiber optical connector includes a ferrule and a plurality of optical fibers inserted and fixed in the ferrule, the grinding jig comprising:

a body provided with a plurality of openings along a circumferential direction of the body, the plurality of openings being provided to extend through upper and lower surfaces of the body for receiving the ferrule of the multi-fiber optical connector inserted therein; and

a plurality of fasteners for fixing the inserted ferrule to the body,

wherein each of the plurality of openings is provided such that an absolute value of an angle defined by a long axis of the opening and a connection line connecting a center of the opening and a center of the body is within a range of 0 to 30 degrees.

20. The grinding jig according to claim 19, characterized in that each of the plurality of openings is provided such that the long axis of the opening is directed to the center of the body.

21. The grinding jig according to claim 19, characterized in that the plurality of openings are all in a rectangular shape, or an elliptical shape, or a semi-elliptical shape.

22. The grinding jig according to any one of claims 19 to 21, characterized in that the plurality of openings are provided at substantially equal spacing.

23. The grinding jig according to any one of claims 19 to 21, characterized in that each of the plurality of openings is provided such that the absolute value of the angle defined by the long axis of the opening and a connection line connecting a center of the opening and a center of the body is substantially equal with that of other openings.

24. The grinding jig according to any one of claims 19 to 21, characterized in that the body of the grinding jig has a circular shape, and the plurality of openings are distributed in a substantially circular shape along the circumferential direction of the body.

25. The grinding jig according to any one of claims 19 to 21, characterized in that the body of the grinding jig has a regular polygonal shape, and the plurality of openings are distributed in a substantially similar regular polygonal shape along the circumferential direction of the body.

26. The grinding jig according to any one of claims 19 to 21, characterized in that each of the plurality of fasteners is disposed on a lateral surface of the body along the circumferential direction of the body.

27. The grinding jig according to any one of claims 19 to 21, characterized in that the number of the plurality of openings is 24 or more.

28. The grinding jig according to any one of claims 19 to 21, characterized in that the fasteners are bolts or screws.