Vernier caliper

Abstract

The invention discloses a vernier caliper, and belongs to the technical field of precise instruments, the vernier caliper comprises a main scale, a vernier and an inner measuring claw, the vernier is slidably mounted on the main scale, the inner measuring claw comprises a fixed claw and a sliding claw, the fixed claw is fixed at one end of the main scale, the sliding claw is fixed on the vernier, and the fixed claw is fixed on the main scale. The main ruler is detachably provided with a vertical diameter assembly, the vertical diameter assembly comprises a saddle installed on the main ruler, the saddle is provided with a chord ruler, the two ends of the chord ruler are provided with contacts abutting against the inner wall of a measured hole, and the connecting line of the fixed claw and the sliding claw is located on the vertical bisector of the chord ruler. The vernier caliper solves the technical problem that the connecting line of the measuring claws in the existing vernier caliper is difficult to accurately position to pass through the circle center, so that the inner diameter is difficult to accurately and quickly measure, and is widely applied to precision measurement.

Description

Technical Field

[0001] The invention belongs to the field of precision instruments, and in particular relates to a vernier caliper. Background Art

[0002] A vernier caliper is a tool commonly used for precision measurement. It is mainly used to measure dimensions such as inner diameter, outer diameter, and depth. Its basic principle is to improve measurement accuracy by comparing the vernier with the main scale. Since its invention, the basic structure and principle of the vernier caliper have not changed fundamentally. However, with the improvement of measurement accuracy requirements, traditional vernier calipers have limitations in measuring inner diameters. Since the connecting line of the inner measuring claws is difficult to accurately locate through the center of the circle, it is impossible to accurately measure the inner diameter, resulting in the inability to meet the needs of accurate and quick measurement of the inner diameter in situations with high precision requirements.

[0003] In the prior art, for example, a Chinese patent (application number: 202211655496.7) discloses "a vernier caliper for measuring the diameter height of a variable diameter inner hole". This patent proposes a vernier caliper for measuring the height of a variable diameter inner hole. The device breaks through the limitations of the traditional measurement space by setting up three measuring devices in different directions, thereby achieving more accurate inner hole height measurement. The problem with this method is that it only focuses on improving the accuracy of height measurement, and does not fully guarantee the accuracy of inner diameter measurement.

[0004] Another example is a Chinese patent (application number: 202310406569.7) that discloses a "mechanical vernier caliper". This patent forms a determined plane perpendicular to the axis of the structure by clamping a pair of outer measuring jaws to the outside of the structure to be measured and rotating the limit plate to make it fit the outer wall. This plane helps to more accurately position the outer measuring jaws, thereby improving the accuracy of the measurement process. However, this method only focuses on the measurement of the outer diameter and ignores the accuracy of the inner diameter.

[0005] Therefore, in the field of precision instrument technology, there is still a need for research and improvement of vernier calipers, which is also a research hotspot and focus in the field of precision instrument technology, and is also the starting point for the completion of the present invention. Summary of the invention

[0006] To this end, the technical problem to be solved by the present invention is to provide a vernier caliper to solve the technical problem that the connecting line of the measuring claws in the existing vernier caliper is difficult to accurately locate to the center of the circle, resulting in difficulty in meeting the requirements of accurate and fast measurement of the inner diameter.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a vernier caliper, comprising a main scale, a vernier and an inner measuring claw, the vernier is slidably installed on the main scale, the inner measuring claw comprises a fixed claw and a sliding claw, the fixed claw is fixed to one end of the main scale, and the sliding claw is fixed to the vernier, characterized in that a vertical diameter assembly is detachably installed on the main scale, the vertical diameter assembly comprises a saddle installed on the main scale, a string scale is provided on the saddle, contacts are provided at both ends of the string scale that press against the inner wall of the measured hole, and the connecting line of the fixed claw and the sliding claw is located on the perpendicular bisector of the string scale.

[0008] As an improvement, the saddle has a wedge-shaped slide groove that is adapted to the main scale and is larger at the top and smaller at the bottom. Both sides of the wedge-shaped slide groove are provided with inclined surfaces with a slope of less than 1 degree.

[0009] As another improvement, the saddle has a square slide groove matched with the main ruler, a locking screw with an end extending into the square slide groove is threadedly connected to the saddle, and a spring ball is installed on the inner wall of the square slide groove.

[0010] As a further improvement, the string ruler includes a tuning rod fixedly arranged on the saddle, and the contacts are respectively located at two ends of the tuning rod.

[0011] As a further improvement, the string ruler includes a wedge-shaped body fixedly mounted on the saddle, the wedge-shaped body being provided with an open groove for accommodating the fixing claw, the contacts being respectively located at the ends of the wedge-shaped body on both sides of the open groove, the saddle being threadedly connected with a supporting screw, the end of the supporting screw extending into the open groove.

[0012] As a further improvement, the chord ruler includes a bidirectional screw and two threaded sleeves. The bidirectional screw is rotatably mounted on the saddle, and the threaded sleeves are respectively threadedly connected to the threaded ends of the bidirectional screw. The contact is arranged at the end of the threaded sleeve, and a positioning screw is threadedly connected to the threaded sleeve.

[0013] As a further improvement, the contact includes a pointed contact point.

[0014] As a further improvement, the contact is arranged on the threaded sleeve, and the contact is offset from the center line of the threaded sleeve.

[0015] As a further improvement, the contact includes a contact wire adapted to the busbar of the measured hole.

[0016] As a further improvement, the contact is rotatably mounted on the string scale, and a locking element is provided between the contact and the string scale.

[0017] After adopting the above technical solution, the beneficial effects of the present invention are:

[0018] The two ends of the chord ruler of the present invention are provided with contacts pressed against the inner wall of the measured hole, and the line connecting the fixed claw and the sliding claw is located on the perpendicular bisector of the chord ruler. According to the perpendicular diameter theorem and its corollary, the perpendicular bisector of the chord passes through the center of the circle. By constructing a chord perpendicular to the line connecting the two inner measuring claws between the inner measuring claws of the vernier caliper, and ensuring that the chord is bisected by the line connecting the two inner measuring claws, the distance measured by the inner measuring claws is the true inner diameter of the measured object. That is to say, the two contacts of the chord ruler determine the chord of the circle where the measured hole is located, and the line connecting the fixed claw and the sliding claw must pass through the center of the circle. Therefore, the distance measured by the inner measuring claw must be the diameter of the circle, and the inner diameter of the measured hole can be measured quickly and accurately.

[0019] Since the contact head includes a pointed contact, the pointed contact is in point contact with the measured hole, and the two pointed contacts are coplanar with the fixed claw and the sliding claw, four contacts are formed during measurement, ensuring fast and accurate measurement of the inner hole.

[0020] Since the contact includes a contact wire that matches the busbar of the measured hole, the vertical diameter component makes line contact with the measured hole, which increases the contact length, avoids measurement errors caused by contact tilt, and improves the accuracy and efficiency of inner hole measurement.

[0021] Since the threaded sleeves are respectively threadedly connected to the threaded ends of the bidirectional screw, and the threads at both ends of the bidirectional screw have opposite rotation directions, the threaded sleeves can be telescopically adjusted by rotating the dial to meet the measurement requirements of different inner diameters.

[0022] Since the contact is rotatably mounted on the string ruler through a pin shaft, the contact includes a contact wire that is compatible with the busbar of the measured hole. This structure can measure the inner diameter of the tapered hole. When in use, the contact wire is made consistent with the busbar of the measured tapered hole, and the inner measuring claw can measure the inner diameter of the tapered hole at that position. The operation is convenient and quick, which further expands the usability of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0024] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0025] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0026] Figure 2 is a schematic structural diagram of a vertical diameter assembly in Embodiment 1 of the present invention;

[0027] Figure 3 is a schematic structural diagram of a saddle in Embodiment 1 of the present invention;

[0028] Figure 4 is a schematic diagram of the use status of the first embodiment of the present invention;

[0029] Figure 5 is a structural schematic diagram of another vertical diameter assembly in Embodiment 1 of the present invention;

[0030] Figure 6 is a schematic diagram of the structure of the saddle in the second embodiment of the present invention;

[0031] Figure 7 is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0032] Figure 8 is a schematic structural diagram of a vertical diameter assembly in Embodiment 3 of the present invention;

[0033] Fig. 9 is a schematic structural diagram of another vertical diameter assembly in Embodiment 3 of the present invention;

[0034] Fig.10 is a schematic structural diagram of a fourth embodiment of the present invention;

[0035] Fig.11 is a schematic structural diagram of a vertical diameter assembly in a fourth embodiment of the present invention;

[0036] Fig.12 It is a schematic diagram of the exploded structure of the vertical diameter assembly in the fourth embodiment of the present invention;

[0037] Fig.13 It is a schematic structural diagram of a threaded sleeve in a fourth embodiment of the present invention;

[0038] Fig.14 is a structural schematic diagram of another vertical diameter assembly in the fourth embodiment of the present invention;

[0039] Fig.15 is a schematic structural diagram of a vertical diameter assembly in Embodiment 5 of the present invention;

[0040] Fig.16 is a schematic structural diagram of another vertical diameter assembly in Embodiment 5 of the present invention;

[0041] Fig.17 is a schematic structural diagram of a vertical diameter assembly in Embodiment 6 of the present invention;

[0042] In the figure: 1, main scale, 2, vernier, 3, fixed claw, 4, sliding claw, 5, vertical diameter assembly, 501, saddle, 5011, wedge-shaped slide groove, 5012, inclined surface, 5013, spring ball, 5014, locking screw, 502, string ruler, 5021, tuning rod, 5022, wedge body, 5023, open groove, 5024, supporting screw, 5025, dial wheel, 5026, bidirectional screw, 5027, threaded sleeve, 5028, positioning screw, 5029, sliding sleeve, 5030, pin shaft, 503, pointed contact, 504, contact wire, 505, connecting ear, 6, measured workpiece. DETAILED DESCRIPTION

[0043] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The terms such as "front", "back", "left", "right", "inside", "outside", "middle", etc. cited in this specification are only for the convenience of description and are not intended to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as within the scope of implementation of the present invention without substantially changing the technical content.

[0045] Embodiment 1:

[0046] like Figure 1 As shown, the present invention provides a vernier caliper, comprising a main scale 1, a vernier 2 and an inner measuring claw, wherein the vernier 2 is slidably mounted on the main scale 1, and the inner measuring claw comprises a fixed claw 3 and a sliding claw 4, wherein the fixed claw 3 is fixed to one end of the main scale 1, and the sliding claw 4 is fixed to the vernier 2, and scale lines are provided on both the main scale 1 and the vernier 2. This structure is a common structure of a vernier caliper and will not be described in detail herein. A vertical diameter component 5 is detachably mounted on the main scale 1, such as Figure 2As shown, the perpendicular diameter assembly 5 includes a saddle 501 mounted on the main scale 1, and a chord scale 502 is provided on the saddle 501. The extension direction of the chord scale 502 is perpendicular to the extension direction of the main scale 1. Contacts are provided at both ends of the chord scale 502 to press against the inner wall of the measured hole. The line connecting the fixed claw 3 and the sliding claw 4 is located on the perpendicular bisector of the chord scale 502. According to the perpendicular diameter theorem and its corollary, the perpendicular bisector of the chord passes through the center of the circle. By constructing a chord perpendicular to the line connecting the two inner measuring claws between the inner measuring claws of the vernier caliper, and ensuring that the chord is bisected by the line connecting the two inner measuring claws, the distance measured by the inner measuring claws is the true inner diameter of the measured object. In other words, the two contacts of the chord scale 502 determine the chord of the circle where the measured hole is located, and the line connecting the fixed claw 3 and the sliding claw 4 must pass through the center of the circle. Therefore, the distance measured by the inner measuring claw must be the diameter of the circle, so that the inner diameter of the measured hole can be measured quickly and accurately.

[0047] The string ruler 502 includes a tuning rod 5021 fixedly set on the saddle 501. Usually, the tuning rod 5021 and the saddle 501 are designed as an integral whole. The contacts are respectively located at both ends of the tuning rod 5021. The contacts include pointed contacts 503. The pointed contacts 503 are in point contact with the measured hole. The two pointed contacts 503 are coplanar with the fixed claw 3 and the sliding claw 4. Four contacts are formed during measurement, which ensures that the inner hole measurement is fast and accurate.

[0048] like Figure 3 As shown, the saddle 501 has a wedge-shaped slot 5011 which is adapted to the main scale 1 and is larger at the top and smaller at the bottom. Correspondingly, the slide rail part of the main scale 1 is adapted to the shape of the wedge-shaped slot 5011. The top surface of the wedge-shaped slot 5011 is a plane, which matches the top surface of the main scale 1. The two side surfaces of the wedge-shaped slot 5011 are provided with inclined surfaces 5012 with a slope less than 1 degree, which match the side surfaces of the main scale 1, thereby ensuring that the saddle 501 and the main scale 1 are tightly matched during the sliding process, avoiding the generation of gaps or displacements between the saddle 501 and the main scale 1, and making the inner hole measurement more accurate.

[0049] When using, Figure 4 As shown, first install the vertical diameter component 5 on the main scale 1, place the vertical diameter component 5 in the measured hole of the workpiece 6, and press the fixed claw 3 against the inner wall of the measured hole. Adjust the position of the vertical diameter component 5, press the contact against the inner wall of the measured hole so that the three contact points are coplanar, move the cursor 2, and drive the sliding claw 4 to move horizontally. After the sliding claw 4 touches the inner wall of the measured hole, read the values ​​of the main scale 1 and the cursor 2, and obtain the inner diameter value of the measured hole.

[0050] As another improvement, Figure 5 As shown, the contact includes a contact wire 504 adapted to the busbar of the measured hole, so that the vertical diameter component 5 makes line contact with the measured hole, which increases the contact length, avoids measurement errors caused by contact tilt, and improves the accuracy and efficiency of inner hole measurement.

[0051] Embodiment 2:

[0052] The present invention provides a vernier caliper, the structure of which is basically the same as that of the first embodiment, except that: Figure 6 As shown, the saddle 501 has a square slideway matched with the main ruler 1, and a locking screw 5014 whose end extends into the square slideway is threadedly connected to the saddle 501, which is used to fix the position of the saddle 501 on the main ruler 1. A spring ball 5013 is installed on the inner wall of the square slideway, and usually two groups of spring balls 5013 are arranged on the inner walls of both sides of the square slideway. The spring ball 5013 can effectively absorb the external force to prevent damage to the device or deviation of the measurement result due to excessive pressure. This structure makes the vertical diameter assembly 5 easy to install and disassemble, and easy to operate and use.

[0053] Embodiment three:

[0054] like Figure 7 As shown, the present invention provides a vernier caliper, whose structure is basically the same as that of the second embodiment, except that: Figure 8 As shown, the chord ruler 502 includes a wedge-shaped body 5022 fixedly arranged on the saddle 501, and an open groove 5023 for accommodating the fixed claw 3 is provided on the wedge-shaped body 5022, and the contacts are respectively located at the ends of the wedge-shaped body 5022 on both sides of the open groove 5023, and a supporting screw 5024 is threadedly connected to the saddle 501, and the end of the supporting screw 5024 extends into the open groove 5023, and the threaded end of the supporting screw 5024 is supported on the fixed claw 3, ensuring that the vertical diameter component 5 is always in a vertical state, and the contact includes a pointed contact 503, and the pointed contact 503 is in point contact with the measured hole, and the two pointed contacts 503 are coplanar with the fixed claw 3 and the sliding claw 4, so that four contacts are formed during measurement, ensuring quick and accurate measurement of the inner hole.

[0055] As another improvement, Fig. 9 As shown, the contact includes a contact wire 504 adapted to the busbar of the measured hole, so that the vertical diameter component 5 makes line contact with the measured hole, which increases the contact length, avoids measurement errors caused by contact tilt, and improves the accuracy and efficiency of inner hole measurement.

[0056] Embodiment 4:

[0057] like Fig.10 As shown, the present invention provides a vernier caliper, whose structure is basically the same as that of the second embodiment, except that: Fig.11As shown, the string ruler 502 includes a bidirectional screw 5026 and two threaded sleeves 5027. The bidirectional screw 5026 is rotatably mounted on the saddle 501. Usually, a connecting ear 505 is fixedly provided on the saddle 501. The bidirectional screw 5026 is rotatably mounted on the connecting ear 505. A thumbwheel 5025 is provided on the bidirectional screw 5026 at the position of the connecting ear 505. The thumbwheel 5025 and the bidirectional screw 5026 are coaxially arranged for convenient rotation of the bidirectional screw 5026. For ease of installation, the thumbwheel 5025 and the bidirectional screw 5026 can be connected using a spline or a key, or the thumbwheel 5025 and the bidirectional screw 5026 can be arranged as one body, and the connecting ear can be connected to the connecting ear. 505 is detachably connected to the saddle 501 through fasteners, the threads at both ends of the bidirectional screw 5026 are in opposite directions, and the threaded sleeves 5027 are respectively threadedly connected to the threaded ends of the bidirectional screw 5026. By rotating the dial 5025, the threaded sleeve 5027 can be adjusted to meet the measurement requirements of different inner diameters. The contact is set at the end of the threaded sleeve 5027, and the shape of the contact is set to be conical. The threaded sleeve 5027 is threadedly connected with a positioning screw 5028 for positioning the adjusted position of the threaded sleeve 5027 to ensure the firmness of the connection and prevent loosening due to vibration or improper operation during the measurement process, thereby avoiding measurement errors. The contact includes a pointed contact 503, the pointed contact 503 is in point contact with the measured hole, and the two pointed contacts 503 are coplanar with the fixed claw 3 and the sliding claw 4, forming four contacts during measurement, ensuring the quick and accurate measurement of the inner hole.

[0058] In order to facilitate adjustment, the threaded sleeve 5027 is prevented from rotating with the bidirectional screw 5026 when the dial wheel 5025 is rotated. After in-depth research, the inventor of the present application has found that Fig.12 and Fig.13 As shown, a sleeve 5029 is mounted on the bare rod position of the bidirectional screw 5026, one end of the sleeve 5029 is fastened to the connecting ear 505, and the other end extends into the threaded sleeve 5027, the bidirectional screw 5026 passes through the sleeve 5029 and is threadedly connected with the threaded sleeve 5027, the outer surface of the sleeve 5029 is provided with a guide plane, the mounting hole of the connecting ear 505 is adapted to the cross-sectional shape of the sleeve 5029, and the shape of the center hole of the threaded sleeve 5027 is also adapted to the cross-sectional shape of the sleeve 5029, so that the threaded sleeve 5027 can be When the sliding sleeve 5029 slides and the bidirectional screw 5026 rotates, the sliding sleeve is clamped by the connecting ear 505. Due to the action of the guiding plane, the sliding sleeve 5029 does not rotate. At the same time, the guiding plane of the sliding sleeve 5029 constrains the threaded sleeve 5027, so that the threaded sleeve 5027 only slides axially and does not rotate with the bidirectional screw 5026. The sliding sleeve 5029 is marked with size scales to facilitate quick reading of measurement values ​​during use and ensure the symmetry of the threaded sleeve 5027 during measurement, that is, it is perpendicularly bisected by the line connecting the fixed claw 3 and the sliding claw 4.

[0059] As another improvement, Fig.14 As shown, the contact includes a contact wire 504 adapted to the busbar of the measured hole, so that the vertical diameter component 5 makes line contact with the measured hole, which increases the contact length, avoids measurement errors caused by contact tilt, and improves the accuracy and efficiency of inner hole measurement.

[0060] Embodiment five:

[0061] The present invention provides a vernier caliper, the structure of which is basically the same as that of the fourth embodiment, except that the contact is arranged on the threaded sleeve 5027, the contact includes a pointed contact point 503, and the contact is offset from the center line of the threaded sleeve 5027. Fig.15 As shown, the pointed contact 503 is the conical point of the asymmetric cone, and the conical point of the asymmetric cone is advanced relative to the axis of the threaded sleeve 5027, so that the vertical diameter component 5 can quickly contact the inner wall of the object to be measured within a smaller moving range when measuring the inner diameter. Fig.16 As shown, the distance between the pointed contact 503 and the axis of the threaded sleeve 5027 is greater than the radius of the threaded sleeve 5027, so that the pointed contact 503 is located at the outer periphery of the threaded sleeve 5027. When measuring the inner diameter, the moving range is further reduced, which is suitable for measuring inner holes with shallow depths.

[0062] Embodiment six:

[0063] The present invention provides a vernier caliper, the structure of which is basically the same as that of the fourth embodiment, except that: Fig.17 As shown, the contact is rotatably mounted on the string ruler 502 through the pin shaft 5030, and the contact includes a contact wire 504 adapted to the busbar of the measured hole. A locking element is provided between the contact and the string ruler 502, and the locking element can be integrated with the pin shaft 5030, using a bolt structure, or a set screw structure can be provided separately. Those skilled in the art can set it by themselves according to needs, and no further description is given here. This structure can measure the inner diameter of a tapered hole. When in use, the contact wire 504 is made consistent with the busbar of the measured tapered hole, and the inner measuring claw can measure the inner diameter of the tapered hole at this position. The operation is convenient and quick, and the use performance of the present invention is further expanded.

[0064] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A vernier caliper, comprising a main scale, a vernier and an inner measuring claw, wherein the vernier is slidably mounted on the main scale, the inner measuring claw comprises a fixed claw and a sliding claw, the fixed claw is fixed to one end of the main scale, and the sliding claw is fixed to the vernier, characterized in that: A vertical diameter assembly is detachably mounted on the main scale, and the vertical diameter assembly includes a saddle mounted on the main scale, a string scale is arranged on the saddle, contacts are arranged at both ends of the string scale against the inner wall of the measured hole, and a line connecting the fixed claw and the sliding claw is located on the perpendicular bisector of the string scale.

2. The vernier caliper according to claim 1, characterized in that: The saddle has a wedge-shaped slide groove that is matched with the main ruler and is larger at the top and smaller at the bottom. Both sides of the wedge-shaped slide groove are provided with inclined surfaces with an inclination of less than 1 degree.

3. The vernier caliper according to claim 1, characterized in that: The saddle has a square slide groove matched with the main ruler, a locking screw with an end extending into the square slide groove is threadedly connected to the saddle, and a spring ball is installed on the inner wall of the square slide groove.

4. The vernier caliper according to claim 2, characterized in that: The string ruler comprises a tuning rod fixedly arranged on the saddle, and the contacts are respectively located at two ends of the tuning rod.

5. The vernier caliper according to claim 2, characterized in that: The string ruler includes a wedge-shaped body fixedly arranged on the saddle, the wedge-shaped body is provided with an open groove for accommodating the fixing claw, the contacts are respectively located at the ends of the wedge-shaped body on both sides of the open groove, the saddle is threadedly connected with a supporting screw, and the end of the supporting screw extends into the open groove.

6. The vernier caliper according to claim 3, characterized in that: The string ruler includes a bidirectional screw and two threaded sleeves. The bidirectional screw is rotatably mounted on the saddle. The threaded sleeves are respectively threadedly connected to the threaded ends of the bidirectional screw. The contact is arranged at the end of the threaded sleeve. A positioning screw is threadedly connected to the threaded sleeve.

7. The vernier caliper according to claim 4, 5 or 6, characterized in that: The contact includes a pointed contact point.

8. The vernier caliper according to claim 6, characterized in that: The contact is arranged on the threaded sleeve, and the contact is offset from the center line of the threaded sleeve.

9. The vernier caliper according to any one of claims 1 to 6, characterized in that: The contact includes a contact wire matched with the busbar of the measured hole.

10. The vernier caliper according to claim 9, characterized in that: The contact is rotatably mounted on the string ruler, and a locking element is provided between the contact and the string ruler.

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