Centering vice structure

Abstract

Centering vice structure which includes: a base (1) having a receiving slot (11) communicating with a top surface (12) and two end surfaces (13) of the base (1), wherein a zero point slot (14) is located at a center of a bottom of the receiving slot (11), a plurality of zero point positioning pins (16) are provided on a bottom surface of the base (1), wherein the zero point positioning pins (16) are adapted to fit into a machining table of a machine tool; a vice (2) having a first movable jaw block (21) and a second movable jaw block (22) which are opposite to each other and symmetrical to the zero point slot (14), wherein the first movable jaw block (21) has a first embedding part (211) connected to a bottom thereof, wherein a second embedding part (221) is connected to a bottom of the second movable jaw block (22), the first and second embedding parts (211, 221) are arranged in the receiving slot (11) of the base (1), the first embedding part (211) and the second embedding part (221) have a first internal thread part (212) and a second internal thread part (222) respectively, wherein spiral directions of the internal threads of the first internal thread part (212) and the second internal thread part (222) are different; a transmission shaft (3) having a first external thread part (31) and a second external thread part (32) which are arranged respectively on two sides of a central rotary joint (30), wherein the first external thread part (31) and the second external thread part (32) are respectively connected to the first internal thread part (212) and the second internal thread part (222) of the first embedding part (211) and the second embedding part (221) of the vice (2), wherein two ends of the transmission shaft (3) are connecting ends (33), and a support seat (4), the lower part of which is connected to the zero point slot (14), while an upper part of the support seat (4) is connected to the center rotary joint (30) of the transmission shaft (3) to support and position the transmission shaft (3), wherein by using a hand tool (7) to connect to one of the connecting ends (33) of the transmission shaft (3), and rotating the transmission shaft (3), the vice (2) grips or releases a workpiece (5).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to the technical field of mechanical processing machines, and in particular to a centering vice structure. 2. Description of the state of the art

[0002] The centering vise (or central vise) is a tool used to hold and fix workpieces during machining. Its main feature is that when a workpiece is clamped, the two jaw blocks on either side move simultaneously toward the center of the vise, allowing the workpiece to remain at the central zero point position. This type of centering vise is suitable for clamping and machining symmetrical workpieces. In addition, when machine tools process workpieces, coolant is usually applied to cutting tools and workpieces to protect them from overheating and damage. This results in the coolant containing chips and metal powder after use.

[0003] However, in current centering vises, the two jaw blocks are designed as a single component, meaning they are manufactured in one piece with two internally threaded parts connecting to the two externally threaded parts of a transmission shaft. The coolant, which contains chips and metal powder, clogs the internal transmission shaft with these chips and powder, while also allowing them to penetrate the internally threaded parts of the two jaw blocks. This leads to rapid wear between the jaw blocks and the transmission shaft, necessitating replacement of the entire vise, thus shortening the service life of the centering vise and increasing the machining costs of the workpieces.

[0004] Furthermore, current centering vises lack a fine-adjustment mechanism for the center zero position. This means that if existing centering vises develop offset errors in the center zero position after a certain period of use, they cannot be adjusted or reset to zero. Therefore, based on the aforementioned deficiencies of existing centering vises, there is a real need for improvement.

[0005] The present invention intends to provide a centering vise structure to eliminate the above-mentioned weaknesses. SUMMARY OF THE INVENTION

[0006] The present invention relates to a centering vise structure and includes a base having a receiving slot communicating with an upper surface and two end surfaces of the base. A zero-point slot is located at a center of a bottom of the receiving slot. A plurality of zero-point positioning pins are provided on a bottom surface of the base. These zero-point positioning pins fit into a machining table of a machine tool. A vise has a first movable jaw block and a second movable jaw block that oppose each other and are symmetrical to the zero-point slot. The first movable jaw block has a first embedding part connected to a bottom surface thereof. A second embedding part is connected to a bottom surface of the second movable jaw block. The first and second embedding parts are located in the receiving slot of the base.The first embedding part and the second embedding part respectively have a first internal thread part and a second internal thread part, wherein spiral directions of the internal threads of the first internal thread part and the second internal thread part are different.

[0007] A transmission shaft has a first external thread part and a second external thread part located on two sides of a center pivot thereof, respectively. The first external thread part and the second external thread part are connected to the first internal thread part and the second internal thread part of the first embedding part and the second embedding part of the vise, respectively. Two ends of the transmission shaft are defined as connecting ends. A support seat has a lower part thereof connected to the zero point slot. An upper part of the support seat is connected to the center pivot of the transmission shaft to support and position the transmission shaft. By using a hand tool connected to one of the connecting ends of the transmission shaft and rotating the transmission shaft, the vise grips or releases a workpiece.

[0008] Preferably, the zero point slot is a circular slot with two connecting through holes defined in its inner bottom. A block body extends upward from a circular portion of the support seat. The block body has a receiving pin hole for supporting the center pivot of the transmission shaft. The circular portion has two connecting screw holes arranged corresponding to the two connecting through holes of the base for connecting the support seat to the zero point slot using two screws.

[0009] Preferably, the center pivot of the transmission shaft is a circular flange. Two annular grooves are defined correspondingly on two sides of the circular flange to allow the installation of two O-rings. A cover body with a center through hole is connected to the block body of the support seat to cover the receiving pin hole of the support seat and the center pivot of the transmission shaft.

[0010] Preferably, the first embedding part and the second embedding part of the vise are two separate component bodies, wherein the first embedding part and the second embedding part are combined with the first movable jaw block and the second movable jaw block using a plurality of screws. A projection and a recess are formed respectively between the first embedding part and the first movable jaw block, and between the second embedding part and the second movable jaw block.

[0011] Preferably, a guide groove and a guide block are formed between two sides of the first embedding part and the second embedding part of the vise, and two sides of the receiving slot of the base, respectively. The first external thread part and the second external thread part are both ACME threads.

[0012] Preferably, the first internal thread part and the second internal thread part of the vise are two individual component bodies, wherein a plurality of screws combine the first internal thread part and the second internal thread part respectively with a first bushing hole and a second bushing hole in the first embedding part and the second embedding part.

[0013] Preferably, each of the first internally threaded part and the second internally threaded part comprises a triangular head combined with a threaded tube sleeve. Each triangular head has three evenly spaced slots through which a plurality of screws extend. The first embedding part and the second embedding part have a plurality of screw holes arranged corresponding to the three evenly spaced slots.

[0014] Preferably, two brush ring assemblies are connected to the inner edges of the first internally threaded portion and the second internally threaded portion of the vise. The two brush ring assemblies each consist of a brush ring and a cover body with a central through-hole.

[0015] Preferably, the base has two side slots formed on two sides thereof. Two embedding slots are formed on an inner end wall of the two side slots. A bottom positioning slot, a plurality of positioning holes, and two limit positioning pins are arranged at a center of the bottom of the base.

[0016] Preferably, two upper mounting slots are defined at a center of the two side slots of the base. A first scale is formed on one of the two sides of the base, and a second scale is formed on a top surface of the vise.

[0017] The main objective of the present invention is to provide a centering vise that has multiple zero-point positioning pins or multiple positioning holes on the base bottom, along with the two sides of the base, the two side slots, the two embedding slots, and / or the bottom positioning slot, making it possible to use the centering vise for conventional machining centers, semi-automatic machines, and fully automatic machine tools. This makes the centering vise widely applicable and highly practical.

[0018] By installing two brush ring assemblies, including brush rings or O-rings, in the vise, the centering vise blocks or removes metal chips and powder that adhere to the first external threaded portion and the second external threaded portion of the transmission shaft during the machining process. Thus, the two brush ring assemblies of the centering vise prevent the metal chips and powder from entering the first internal threaded portion and the second internal threaded portion. This reduces abrasion between the first internal threaded portion, the second internal threaded portion of the vise, the first external threaded portion, and the second external threaded portion of the transmission shaft, thereby extending the service life of the first internal threaded portion, the second internal threaded portion, and the transmission shaft while maintaining the machining precision of the workpiece.

[0019] Similarly, the two O-rings on the transmission shaft, in combination with the cover body, also serve to prevent metal chips and powder from entering the gap between the transmission shaft's center pivot and the support seat's locating pin hole. In addition to reducing wear, this extends the service life of the support seat and transmission shaft and maintains the smoothness of the transmission shaft's rotational transmission.

[0020] The first internal thread part and the second internal thread part of the centering vise both adopt a separate design, which means that when the service life of the first internal thread part or the second internal thread part ends, only the components of the first internal thread part or the second internal thread part need to be replaced, thus avoiding the replacement of the entire vise and reducing the operating cost of the vise of this utility model.

[0021] In addition, when the centering vise develops an offset error in the position of the center zero point (i.e., the machining reference center point), since both the first internal thread part and the second internal thread part are equipped with triangular heads, the triangular heads can be rotated and adjusted in coordination with the first scale on the side of the base, thus enabling the adjustment and zeroing of the center zero point position where the centering vise grips the workpiece. This avoids machining errors in the workpiece caused by errors in the center zero point position, thereby improving the machining precision of the workpiece.

[0022] The present invention will become more apparent from the following description when considered in conjunction with the accompanying drawings which, for illustrative purposes only, show a preferred embodiment according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the centering vise structure of the present invention; Fig. 2 is a three-dimensional exploded view of the centering vise structure of the present invention; Fig. 3 is a side view of the centering vise structure of the present invention; Fig. 4 is another side view of the centering vise structure of the present invention; Fig. 5 is a plan view of the centering vise structure of the present invention; Fig. 6 is a longitudinal sectional view of the centering vise structure of the present invention; Fig. 7 is a longitudinal sectional view and schematic operational illustration of the centering vise structure of the present invention; Fig. 8 is a bottom view of the centering vise structure of the present invention; Fig. 9 is a schematic representation of the centering vise structure of the present invention implemented on a machining table within a machine tool, and Fig. Figure 10 is a schematic illustration of the use of the centering vise structure of the present invention and the center zero offset error pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] The present invention relates to a centering vise structure as shown in Fig. 1, Fig. 9 and Fig. 10, which is intended for clamping a workpiece 5 for conventional machining centers, semi-automatic, fully automatic, and other machine tools. The centering vise structure "A" includes a base 1, a vise 2, a transmission shaft 3, and a support seat 4.

[0024] The base 1, as in Fig. 2, Fig. 6 and Fig. 8, has a receiving slot 11 communicating with the top surface 12 and both end surfaces 13 of the base 1, and has a zero point slot 14 in the center of the bottom of the receiving slot 11. The so-called zero point refers to the machining reference center of the workpiece 5, that is, the center point 141 of the zero point slot 14 is the machining reference center (commonly referred to as the zero point), and the zero point slot 14 is formed as a circular slot with two communication through holes 142 therein. Furthermore, there are two side slots 15 on the two sides of the base 1, and two embedding slots 151 are arranged on an inner end wall of these two side slots 15, and two upper fastening slots 152 are placed in the center of these two side slots 15.Furthermore, a plurality of positioning holes 19 are arranged on the bottom of the base 1, with the side slot 15 working with supports, and the plurality of positioning holes 19 working with an equal number of positioning columns, which can fix the vise to the machining table of traditional machining tools. Additionally, a plurality of zero-point positioning pins 16 and a bottom positioning slot 17 are arranged on the underside of the base 1. The plurality of zero-point positioning pins 16, working with the two embedding slots 151, provide a mechanical arm for gripping and fixing the vise by inserting these plurality of zero-point positioning pins 16 into a plurality of positioning holes 61 arranged on the machining table 6 within more advanced machine tools. This facilitates the clamping and fixing of the workpiece 5 and its alignment to the zero point for machining.

[0025] As in Fig. 2 to 4 and Fig. As shown in Fig. 6, the vise 2 includes a first movable jaw block 21 and a second movable jaw block 22, which are opposite to each other and symmetrical about the center point 141 of the zero point slot 14, and a first embedding part 211 and a second embedding part 221, which are located below the first movable jaw block 21 and the second movable jaw block 22, placed in the receiving slot 11 of the base 1. In addition, between the two sides of the first embedding part 211 and the second embedding part 221 of the vise 2 and the two sides of the receiving slot 11 of the base 1, there are two guide grooves 111, a guide block 2112, and a guide block 2212, respectively.The first embedding part 211 and the second embedding part 221 are respectively provided with a first internal thread part 212 and a second internal thread part 222, and the spiral directions of an internal thread 2125 and an internal thread 2225 defined in the first internal thread part 212 and the second internal thread part 222 are set to be different.

[0026] Furthermore, the first embedding part 211 and the second embedding part 221 are both designed as separate component bodies, and the first embedding part 211 and the second embedding part 221 are combined with the first movable jaw block 21 and the second movable jaw block 22 by a plurality of screws 23. A projection 210 and a recess 2111 are respectively disposed between the first embedding part 211 and the first movable jaw block 21, and a projection 220 and a recess 2211 are respectively disposed between the second embedding part 221 and the second movable jaw block 22.Furthermore, the first internal thread part 212 and the second internal thread part 222 of the vise 2 are both designed as separate component bodies, wherein with a plurality of through-bolts, the first internal thread part 212 and the second internal thread part 222 are combined respectively with a first bushing hole 213 and a second bushing hole 223 arranged in the first embedding part 211 and the second embedding part 221.

[0027] Furthermore, the first internal thread part 212 and the second internal thread part 222 are both designed as a triangular head 2121, 2221, which is combined with a threaded tube sleeve 2122 and a threaded tube sleeve 2222, respectively. The two triangular heads 2121 and 2221 each have three evenly distributed slots 2124, 2224, while the first embedding part 211 and the second embedding part 221 have a plurality of screw holes 2113, 2213 corresponding to the three evenly distributed slots 2124 and the three evenly distributed slots 2224. This arrangement allows a plurality of screws 2123 and a plurality of screws 2223 to extend through the three evenly spaced slots 2124 and the three evenly spaced slots 2224 and to be secured to the plurality of screw holes 2113 and the plurality of screw holes 2213.Additionally, a brush ring assembly 24 is installed on each of the inner edges of the first internally threaded portion 212 and the second internally threaded portion 222. Each brush ring assembly 24 is composed of a brush ring 241 (or an O-ring made of rubber or plastic material may replace the brush ring 241) and a cover body 242 having a central through-hole 2421.

[0028] In addition, two limit positioning pins 26 are respectively mounted at both ends of the receiving slot 11 of the base 1, as shown in Fig. 6 and Fig. 7, these two limit positioning pins 26 are locked in corresponding screw holes 261 to limit excessive opening between the first movable jaw block 21 and the second movable jaw block 22 of the vise 2, resulting in insufficient grip. That is, this limits the maximum opening width between the first embedding part 211 and the second embedding part 221 to prevent excessive opening of the jaws of the vise of the present invention.

[0029] As in Fig. 2, Fig. 5 and Fig. As shown in Figure 6, the transmission shaft 3 has a first male threaded portion 31 and a second male threaded portion 32, respectively arranged on both sides of a center pivot joint 30. The first male threaded portion 31 and second male threaded portion 32 are respectively connected to the first female threaded portion 212 and the second female threaded portion 222 of the first embedding portion 211 and the second embedding portion 221 of the vise 2. In addition, the first male threaded portion 31 and the second male threaded portion 32 are both designed as ACME threads to improve the situation where the previously used Whitworth screw thread would break, and to improve the stability and precision of the vise's transmission. The center slewing ring 30 is designed as a circular flange 301 and two annular grooves 302 and 303 are arranged respectively on both sides of the circular flange 301 to provide installation for two O-rings 304 and 305.Furthermore, the two ends of the transmission shaft 3 are formed as two connecting ends 33 and 34, respectively. In this embodiment, the connecting end 33 is a hexagon socket slot, while the other connecting end 34 is designed as a hexagon head.

[0030] As in Fig. 2, Fig. 5 and Fig. As shown in Figure 6, the support seat 4 has a lower part connected to the zero point slot 14, and an upper part connected to the center pivot 30 of the transmission shaft 3 to support and position the transmission shaft 3. The support seat 4 is formed from a circular part 41 extending upward to a block body 42, and the circular part 41 is designed in a round shape to provide it with a degree of freedom for deflection. In addition, the block body 42 has a receiving pin hole 421 for supporting the center pivot 30 of the transmission shaft 3. Furthermore, the circular part 41 has two connecting screw holes 411 arranged corresponding to the two connecting through holes 142 of the zero point slot 14 of the base 1 to facilitate the connection of the support seat 4 to the zero point slot 14 of the base 1 by means of two screws 43.A cover body 44 having a center through hole 441 is additionally installed on the block body 42 to cover the receiving pin hole 421 and the center pivot 30 of the transmission shaft 3.

[0031] The present invention provides a better solution for a centering vise structure as in Fig. 8 and Fig. 9, with the plurality of zero-point positioning pins 16, the positioning holes 19, the two side slots 15, the two embedding slots 151, and / or the lower positioning slot 17 arranged on the underside of the base 1, so that the centering vise of the present invention is applicable to conventional processing machines, semi-automatic and fully automatic machine tools. In other words, the centering vise has wide applicability and high practicality.

[0032] When using the centering vise structure “A” of the present invention as shown in Fig. 1 and Fig. 7, the vise 2 may be opened in advance, then the second scale 25 on the top of the vise 2 is used to center the workpiece 5 and place it between the first movable jaw block 21 and the second movable jaw block 22 of the vise 2. Thereafter, a hand tool 7 is connected to one of the two connecting ends 33, 34 of the transmission shaft 3, and the transmission shaft 3 is rotated by operating the hand tool 7.Since the first external thread part 31 and the second external thread part 32 of the transmission shaft 3 have different external thread directions, when the transmission shaft 3 is rotated clockwise or counterclockwise, the displacement of the internal thread 2125 and the internal thread 2225 disposed in the first movable jaw block 21 and the second movable jaw block 22 can be driven simultaneously, thereby driving the first movable jaw block 21 and the second movable jaw block 22 toward or away from each other. This causes the first movable jaw block 21 and the second movable jaw block 22 to approach or move away from the center origin of the workpiece 5 to grip or release the workpiece 5.

[0033] It will be repeated again Fig. 2, Fig. 6 and Fig. 7. In order to extend the service life of the first internal thread portion 212, the second internal thread portion 222, and the transmission shaft 3, as well as to maintain the machining accuracy of the workpiece 5, the centering vise of the present invention has the two brush ring assemblies 24 of the vise 2 for blocking or removing metal chips and powder adhering to the first external thread portion 31 and the second external thread portion 32 of the transmission shaft 3 during the machining process, thereby preventing them from entering the first internal thread portion 212 and the second internal thread portion 222. This can reduce the wear between the first internal thread portion 212, the second internal thread portion 222 of the vise 2, the first external thread portion 31, and the second external thread portion 32 of the transmission shaft 3.This extends the service life of the first internal thread part 212, the second internal thread part 222, and the transmission shaft 3 while maintaining the machining accuracy of the workpiece 5. Similarly, the O-ring 304 and the O-ring 305 of the transmission shaft 3, which are combined with the cover body 242 of the support seat 4, also serve to prevent metal chips and powder from entering the gap between the center pivot 30 of the transmission shaft 3 and the receiving pin hole 421 of the support seat 4, so that their wear can be reduced, the service life of the support seat and the transmission shaft 3 can be extended, and the smooth operation of the transmission shaft 3 can be maintained.

[0034] At the same time, in order to reduce the operating cost of the centering vise of the present invention, the first internal thread part 212 and the second internal thread part 222 both employ a separate arrangement, which means that when the service life of the first internal thread part 212 or the second internal thread part 222 ends, only the components of the first internal thread part 212 or the second internal thread part 222 need to be replaced.

[0035] In addition, if the centering vise of the present invention develops a position error in the center zero point (i.e., the machining reference center point) after a certain period of use, Fig. 6, Fig. 7 and Fig. 10, wherein, because the first internal thread part 212 and the second internal thread part 222 are both equipped with the triangular head 2121 and its three evenly distributed slots 2124 and the triangular head 2221 and its three evenly distributed slots 2224, after loosening the plurality of screws 2123 and the plurality of screws 2223, the triangular head 2121 and the three evenly distributed slots 2124 can be rotated and adjusted relative to the first embedding part 211, as well as the triangular head 2221 and the three evenly distributed slots 2224 relative to the second embedding part 221. During the aforementioned zero-point position adjustment process, the screws 43 of the circular part 41 of the support seat 4 can also be loosened to utilize the degree of freedom provided by the round shape of the circular part 41. which will be more advantageous for the operation to adjust the zero point position.

[0036] In addition, in coordination with the first scale 18 on the side of the base 1, the center zero position where the vise 2 grips the workpiece 5 can be adjusted to prevent machining errors in the workpiece 5 caused by errors in the center zero position, thereby improving the machining precision of the workpiece 5. For example, the first movable jaw block 21 and the second movable jaw block 22 of the centering vise of the present invention can grip a calibration standard 5a with a standard width of 40 mm, as shown in Fig.10. After the support seat 4 connected to the transmission shaft 3 is zeroed and fixed, the center zero position of the calibration standard 5a is distorted to the right side. Therefore, after loosening the screws 2123 and screws 2223, and then rotating and adjusting the triangular head 2121 and its three evenly spaced slots 2124, the triangular head 2221 and its three evenly spaced slots 2224, each of the triangular head 2121 and the triangular head 2221 with its extended threaded tube sleeve 2122 and threaded tube sleeve 2222 can separately or simultaneously generate a thread displacement on the transmission shaft 3 through the internal thread 2125 and the internal thread 2225 disposed inside their tube bodies.This enables fine adjustment of the first embedding part 211 and the second embedding part 221, which are extended at the first bushing hole 213 and the second bushing hole 223, thereby driving the displacement of the first movable jaw block 21 and the second movable jaw block 22 combined with each embedding part. In coordination with the first scale 18 on the side of the base 1, the center zero position at which the vise 2 grips the calibration standard 5a can be adjusted to move toward the left side, thereby achieving zero adjustment of the center zero position of the centering vise. After that, the screws 2123 and 2223 are tightened to secure the adjusted positions of the triangular head 2121 and the triangular head 2221.

[0037] Thus, when assembling or using the vise 2 for the first time to place the workpiece 5, calibration (zero-positioning) can always be performed to allow the first movable jaw block 21 and the second movable jaw block 22 to reach the center point zero or be zeroed. The practical application of center point zero adjustment using the support seat 4 located at the center of the screw rod of the transmission shaft 3 and the triangular heads 2121 and 2221 located on both sides is necessary because the machining precision of current domestic machining equipment cannot meet the requirements of one-piece vise products.Therefore, the centering vise of the present invention adopts a structure where the transmission shaft 3 has the support seat 4 with the circular part 41 located underneath it in its central portion. On both sides of the vise, the triangular heads 2121 and 2221 are provided with three evenly spaced slots 2124 and 2224, as well as the threaded tube sleeves 2122 and 2222 with internal threads. These components work together on the transmission shaft 3 to adjust the left-to-right displacement of the first movable jaw block 21 and the second movable jaw block 22, thereby enabling the adjustment and control of the center zero position. This facilitates effective zero point correction in advance when clamping workpieces for processing or calibration, and during the actual machining process.

[0038] Accordingly, a centering vise structure includes a base with two sides, two side slots, and / or two embedding slots. Several zero-point positioning pins are connected to a bottom of the base. A vise is placed on the base. A transmission shaft includes two externally threaded parts with different thread directions, which are connected to two internally threaded parts of the vise, respectively. A support seat is located inside the base and is used to support and position the transmission shaft. Before a mechanical arm grips the vise and installs it in a machine tool, the vise grips the workpiece by rotating one end of the transmission shaft and automatically aligns itself to its machining reference center position.

[0039] Although the embodiment according to the present invention has been shown and described, it should be apparent to those skilled in the art that other embodiments are feasible without departing from the scope of the present invention.

Claims

[1] Centering vice structure, which includes: a base (1) having a receiving slot (11) communicating with a top surface (12) and two end surfaces (13) of the base (1), wherein a zero point slot (14) is located at a center of a bottom of the receiving slot (11), a plurality of zero point positioning pins (16) are provided on a bottom surface of the base (1), wherein the zero point positioning pins (16) are adapted to fit into a machining table of a machine tool; a vice (2) having a first movable jaw block (21) and a second movable jaw block (22) which are opposite to each other and symmetrical to the zero point slot (14), wherein the first movable jaw block (21) has a first embedding part (211) connected to a bottom thereof, wherein a second embedding part (221) is connected to a bottom of the second movable jaw block (22), the first and second embedding parts (211, 221) are arranged in the receiving slot (11) of the base (1), the first embedding part (211) and the second embedding part (221) have a first internal thread part (212) and a second internal thread part (222) respectively, wherein spiral directions of the internal threads of the first internal thread part (212) and the second internal thread part (222) are different; a transmission shaft (3) having a first external thread part (31) and a second external thread part (32) which are arranged respectively on two sides of a central rotary joint (30), wherein the first external thread part (31) and the second external thread part (32) are respectively connected to the first internal thread part (212) and the second internal thread part (222) of the first embedding part (211) and the second embedding part (221) of the vice (2), wherein two ends of the transmission shaft (3) are connecting ends (33), and a support seat (4), the lower part of which is connected to the zero point slot (14), while an upper part of the support seat (4) is connected to the center rotary joint (30) of the transmission shaft (3) to support and position the transmission shaft (3), wherein by using a hand tool (7) to connect to one of the connecting ends (33) of the transmission shaft (3), and rotating the transmission shaft (3), the vice (2) grips or releases a workpiece (5). [2] The centering vise structure according to claim 1, wherein the zero point slot (14) is a circular slot having two connecting through holes (142) defined in an inner bottom thereof, a block body (42) extends upward from a circular part (41) of the support seat (4), the block body (42) has a receiving pin hole (421) for supporting the center pivot joint (30) of the transmission shaft (3), the circular part (41) has two connecting screw holes (411) arranged corresponding to the two connecting through holes (142) of the base (1) for connecting the support seat (4) to the zero point slot (14) by means of two screws (43). [3] The centering vise structure according to claim 2, wherein the center pivot joint (30) of the transmission shaft (3) is a circular flange (301), two annular grooves (302, 303) are formed respectively in both sides of the circular flange (301) to ensure the installation of two O-rings (304, 305), a cover body (242) having a center through hole (2421) is connected to the block body (42) of the support seat (4) to cover the receiving pin hole (421) of the support seat (4) and the center pivot joint (30) of the transmission shaft (3). [4] The centering vise structure according to claim 1, wherein the first embedding part (211) and the second embedding part (221) of the vise (2) are two single component bodies, wherein a plurality of screws (23) combine the first embedding part (211) and the second embedding part (221) with the first movable jaw block (21) and the second movable jaw block (22), wherein a projection (210) and a recess (2111) are formed respectively between the first embedding part (211) and the first movable jaw block (21), and between the second embedding part (221) and the second movable jaw block (22). [5] The centering vise structure according to claim 4, wherein a guide groove (111) and a guide block (2112) are formed respectively between two sides of the first embedding part (211) and the second embedding part (221) of the vise (2), and two sides of the receiving slot (11) of the base (1), wherein the first external thread part (212) and the second external thread part (222) are both an ACME thread. [6] The centering vise structure according to claim 1, wherein the first internally threaded part (212) and the second internally threaded part (222) of the vise (2) are two single component bodies, wherein a plurality of screws (23) combine the first internally threaded part (212) and the second internally threaded part (222) respectively with a first socket hole (213) and a second socket hole (223) in the first embedding part (211) and the second embedding part (221). [7] The centering vise structure according to claim 6, wherein each of the first internally threaded portion (212) and the second internally threaded portion (222) comprises a triangular head (2121, 2221) combined with a threaded tubular sleeve (2122), each triangular head (2121, 2221) having three equally spaced slots (2124, 2224) through which a plurality of screws (2223) extend, the first embedding portion (211) and the second embedding portion (221) having a plurality of screw holes (2113, 2213) arranged corresponding to the three equally spaced slots (2124, 2224) thereof. [8] The centering vise structure according to claim 1, wherein two brush ring assemblies (24) are connected to inner edges of the first internally threaded part (212) and the second internally threaded part (222) of the vise (2), and the two brush ring assemblies (24) are each composed of a brush ring (241) and a cover body (242) having a central through-hole (2421). [9] The centering vise structure according to claim 1, wherein the base (1) has two side slots (15) formed on two sides thereof, two embedding slots (151) are formed on an inner end wall of the two side slots (15), a lower positioning slot (17), a plurality of positioning holes (19), and two limit positioning pins (26) are arranged in a center of the bottom of the base (1). [10] Centering vise structure according to claim 9, wherein the two upper fastening slots (152) are defined in a center of the two side slots (15) of the base (1), a first scale (18) is formed on one of the two sides of the base (1), a second scale (25) is formed on an upper surface of the vise (2).

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