Method and mechanical structure for drilling center hole in large shaft workpiece

Abstract

The invention relates to the technical field of machining, in particular to a method and a mechanical structure for drilling a center hole in a large shaft workpiece, the mechanical structure for drilling the center hole in the large shaft workpiece comprises a long base (4), two bench drills and two sets of clamps, and the two bench drills and the two sets of clamps are arranged on the central axis of the long base; the positions of the two clamps on the long base are adjusted and determined according to the length of the large-scale shaft workpiece, the large-scale shaft workpiece is stably placed on the clamps, and the center line of the large-scale shaft workpiece is kept to be aligned with the center of the clamps; the position of a bench drill on the long base is determined according to the length of the large shaft workpiece, and then the height of the bench drill is adjusted to enable a drill bit to be just located at the center point of the end face of the large shaft workpiece; and the bench drill is used for drilling from the center points of the two end faces of the large shaft workpiece, and the mechanical center hole drilling process of the large shaft workpiece is completed. And the method has the substantive characteristics and progresses of prevention of drilling deviation and waste, high machining qualification rate, high production efficiency and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of machining, in particular to a method and mechanical structure for drilling a center hole in a large shaft workpiece, which is suitable for machining a center hole in a large workpiece. BACKGROUND

[0002] In production practice, when machining a large shaft workpiece, a center hole needs to be drilled at the center position of the end of the blank round steel before using a lathe for machining, which serves as the rotation center during lathe machining. The position accuracy and perpendicularity of the center hole will affect the entire subsequent machining process.

[0003] In the prior art, since the length of a large shaft workpiece is often 10-20 meters or more, and its weight is often 20-30 tons, it is difficult to use existing machine tools to machine a center hole in a large shaft workpiece. Therefore, the prior art generally chooses to use a manually operated electric drill to machine the center hole. This manually operated electric drill method has the problems of easy deviation and waste during drilling, low machining qualification rate, and low efficiency. Therefore, there is an urgent need for a large shaft workpiece center hole drilling structure with high machining accuracy, high machining qualification rate, and high production efficiency to improve machining accuracy, qualification rate, and production efficiency.

[0004] After searching the Chinese patent announcements, no technical solution for drilling a center hole in a large long shaft workpiece has been found in the Chinese patent announcements. Although some technical solutions for drilling a center hole in a shaft workpiece have been disclosed in the Chinese patent announcements, such as the inventions with application numbers 2024109614055, 2024108280926, and 2024102736579, and the utility model with application number 2022223824311, although the technical solutions can solve the technical problems of drilling a center hole in a shaft workpiece and have certain technical effects, because the tooling fixtures of these technical solutions cannot clamp a large shaft workpiece with a length of more than 8 meters and a weight of more than 10 tons, they are not suitable for drilling a center hole in a large long shaft workpiece and cannot solve the problems of manually holding an electric drill to drill a center hole in a large long shaft workpiece in the prior art. Therefore, the method and structure for drilling a center hole in a large long shaft workpiece provided by the present technical solution can solve the problems of manually holding an electric drill to drill a center hole in the prior art, and can also solve the problems of complex equipment structure and high cost of the technical solutions disclosed in the aforementioned patent announcements. SUMMARY

[0005] The purpose of the present application is to solve the problems of easy deviation and waste during drilling, low machining qualification rate, and low production efficiency in the prior art method of manually drilling a center hole in a large shaft workpiece, and to provide a method and mechanical structure for drilling a center hole in a large shaft workpiece. The present application has the substantial features and progress of preventing workpiece deviation and waste during manual drilling, high machining qualification rate, high production efficiency, and simple equipment structure.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for drilling center holes in large shaft-like workpieces includes the following steps: 1) Setting up a mechanical structure for drilling center holes in large shaft-like workpieces, the mechanical structure including a long base and two bench drills and two sets of clamps arranged on the central axis of the long base; 2) Adjusting and determining the position of the two sets of clamps on the long base according to the length of the large shaft-like workpiece to ensure that the large shaft-like workpiece is clamped and fixed on the long base; 3) Placing the large shaft-like workpiece stably on the clamps and keeping the center line of the large shaft-like workpiece aligned with the center of the clamps, and fixing the large shaft-like workpiece on the long base using the two sets of clamps; 4) Determining the position of the bench drills on the long base according to the length of the large shaft-like workpiece to ensure that the drill bits of the bench drills located on both sides of the large shaft-like workpiece are close to the end face of the large shaft-like workpiece and aligned with the center line of the large shaft-like workpiece, and then adjusting the height of the bench drills so that the drill bits are exactly at the center point of the end face of the large shaft-like workpiece; 5) Drilling holes from the center points of the two end faces of the large shaft-like workpiece using the bench drills to complete the mechanical drilling of the center hole in the large shaft-like workpiece.

[0007] Furthermore, when adjusting and determining the position of the two sets of fixtures on the long base, the fixtures on both sides are installed by selecting the fixture positioning screw holes to accommodate workpieces of different lengths.

[0008] Furthermore, when adjusting the height of the bench drill, use the lifting handwheel to adjust the height of the bench drill so that the drill bit is at the center point of the end face of the large shaft workpiece. Start the bench drills on both sides respectively, and then rotate the feed handwheel to move the bench drills back and forth to process the center hole of the set depth.

[0009] The objective of this invention can also be achieved through the following technical solutions: A mechanical structure for drilling center holes in large, long-shaft workpieces is characterized by the following features: It includes a long base and two bench drills and two sets of clamps mounted on the central axis of the long base; the two sets of clamps are symmetrically arranged, and the two bench drills are located outside the two sets of clamps and are also symmetrically arranged; several evenly distributed clamp positioning screw holes are provided at both ends of the two flanges of the long base for connecting and adjusting the position of the clamps on the long base to accommodate different lengths of the large, long-shaft workpieces; several evenly distributed bench drill positioning screw holes are provided at both ends of the central axis of the long base for connecting and adjusting the position of the bench drills on the long base to accommodate different lengths of the large, long-shaft workpieces; the length of the long base is such that both ends of the large, long-shaft workpiece are within the projection range of the long base; the bench drills have a drill bit height adjustment structure for adjusting the height of the drill bit to accommodate large, long-shaft workpieces of different specifications, ensuring that the drill bits located outside the two ends of the large, long-shaft workpiece are aligned with the central axis of the large, long-shaft workpiece.

[0010] Furthermore, the long base is made of cast iron and is 10-25 meters long; there are raised mountain-shaped guide rails on both sides of the long base, and the positioning screw holes of the clamp are set on the mountain-shaped guide rails; corresponding to the mountain-shaped guide rails, the fixing clamp has a groove with the same shape as the mountain-shaped guide rails to lock the mountain-shaped guide rails in place, so as to improve stability.

[0011] Furthermore, the fixing fixture includes an upper pressure plate, a positioning V-block, and an adjustable shim. The positioning V-block is connected to the mountain-shaped guide rail of the long base by screws for load bearing. The upper pressure plate is connected to the positioning V-block by screws for clamping and fixing large long shaft-type workpieces to prevent movement. The adjustable shim is set in the groove of the fixture and connected to the positioning V-block by internal countersunk screws for supporting large long shaft-type workpieces.

[0012] Furthermore, the thickness of the adjustable shim is determined according to the diameter of the large long shaft workpiece to accommodate the lifting of the large long shaft workpiece.

[0013] Furthermore, the fixing fixture has grooves that match the shape of the mountain-shaped guide rail to engage with the mountain-shaped guide rail to improve stability. Different screw hole positions are used to adjust the installation position of the fixture according to the length of large long shaft workpieces.

[0014] Furthermore, the long base has two rows of symmetrical drill position adjustment screw holes oriented towards the center line. The drill is mounted on these screw holes with screws, allowing for adjustment of the drill's mounting position by connecting the screw holes at different locations according to the length of large, long-shaft-type workpieces. Additionally, the drill is equipped with a feed handwheel and a lifting handwheel. The lifting handwheel is used to adjust the drill's height according to the placement height of the large, long-shaft-type workpiece, while the feed handwheel controls the drill's forward and backward movement.

[0015] This invention has the following characteristics and beneficial effects: 1. The present invention relates to a method for drilling center holes in large shaft-type workpieces. This method incorporates a mechanical structure for drilling center holes in large shaft-type workpieces. This structure includes a long base, two bench drills, and two sets of fixtures, all positioned on the central axis of the long base. The positions of the two sets of fixtures on the long base can be adjusted according to the length of the large shaft-type workpiece. The position of the bench drills on the long base is also determined based on the length of the workpiece. The height of the bench drills is then adjusted so that the drill bit is positioned at the center point of the end face of the large shaft-type workpiece. The bench drills are used to drill holes from the center points of both end faces of the large shaft-type workpiece, thus completing the mechanical drilling of the center hole in the large shaft-type workpiece. The entire processing is mechanical, thereby solving the problems of workpiece defects due to manual drilling of large shaft-type workpieces, such as workpiece defects from misalignment, low processing pass rate, and low production efficiency. This method offers substantial advantages and advancements, including preventing workpiece defects from manual drilling, high processing pass rate, high production efficiency, and simple equipment structure.

[0016] 2. The mechanical structure for drilling center holes in large, long-shaft workpieces, as disclosed in this invention, includes a long base, two bench drills, and two sets of clamps. The two bench drills and two sets of clamps are arranged on the central axis of the long base. Several evenly distributed clamp positioning screw holes are provided at both ends of the two flanges of the long base for connecting and adjusting the position of the clamps on the long base to accommodate different lengths of the large, long-shaft workpiece. Several evenly distributed bench drill positioning screw holes are provided at both ends of the central axis of the long base for connecting and adjusting the position of the bench drills on the long base to accommodate different lengths of the large, long-shaft workpiece. The length of the long base is such that both ends of the large, long-shaft workpiece are within the projection range of the long base. The bench drills have a drill bit height adjustment structure for adjusting the height of the drill bit to accommodate large, long-shaft workpieces of different specifications, so that the drill bits located on the outer sides of both ends of the large, long-shaft workpiece are directly aligned with the central axis of the large, long-shaft workpiece. The mechanical structure described herein enables the machining process of the workpiece, thus solving the problems of workpiece damage due to mis-drilling, low machining pass rate, and low production efficiency in existing manual drilling methods for large shaft workpieces. It features and improves upon existing methods by preventing workpiece damage due to mis-drilling, achieving a high machining pass rate, high production efficiency, and simple structure.

[0017] 3. Because the long base of this invention is long enough to hold large long shaft workpieces of 10-20 meters, and several evenly distributed clamping positioning screw holes are set on the long base for connecting and adjusting the position of the clamps on the long base to adapt to different lengths of large long shaft workpieces, this invention can be used to drill center holes for large long shaft workpieces of various sizes and specifications. It has the characteristics of wide applicability and convenient adjustment.

[0018] 4. This invention features several evenly distributed positioning screw holes for the bench drill, used to connect and adjust the position of the bench drill on the long base to accommodate different lengths of large long shaft workpieces. Therefore, it can be used to drill center holes for large long shaft workpieces of various sizes and specifications. Regardless of the length of the workpiece (within the range of 10-20 meters), mechanical drilling of the center hole can be achieved. It has the characteristics and advancements of preventing workpieces from being drilled off-center and wasting, high processing qualification rate, high production efficiency, and simple structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall mechanical structure for drilling center holes in large, long-shaft workpieces, as per the present invention.

[0020] Figure 2 yes Figure 1 A schematic diagram showing the installation positions of the fixtures and bench drill involved. Detailed Implementation

[0021] Specific embodiments of the present invention are described below.

[0022] Reference Figure 1and Figure 2 This embodiment relates to a mechanical structure for drilling center holes in large, long-shaft workpieces, including a long base 4, two bench drills 2, and two sets of clamps 3. The two bench drills 2 and the two sets of clamps 3 are arranged on the central axis of the long base 4; the two sets of clamps 3 are arranged symmetrically from left to right, and the two bench drills 2 are located outside the two sets of clamps 3 and are also arranged symmetrically from left to right; several evenly distributed clamp positioning screw holes 4-2 are provided at both ends of the two flanges on both sides of the long base 4, for connecting and adjusting the position of the clamps 3 on the long base 4 to accommodate different lengths of large, long-shaft workpieces; on the long base... The central axis of the 4 is provided with several evenly distributed bench drill positioning screw holes 4-3 at both ends, which are used to connect and adjust the position of the bench drill 2 on the long base 4 to adapt to different lengths of large long shaft workpieces; the length of the long base 4 is to ensure that both ends of the large long shaft workpiece are within the projection range of the long base 4; the bench drill 2 has a drill bit height position adjustment structure, which is used to adjust the height position of the drill bit of the bench drill 2 to adapt to large long shaft workpieces of different specifications, so that the drill bit of the bench drill 2 located on the outer side of both ends of the large long shaft workpiece is directly facing the central axis of the large long shaft workpiece.

[0023] In this embodiment: The long base 4 is made of cast iron and has a length of 10 meters, 12 meters, 15 meters, 17 meters, 19 meters, 21 meters, 23 meters or 25 meters. There are raised mountain-shaped guide rails 4-1 on both sides of the long base 4, and the clamp positioning screw holes 4-2 are set on the mountain-shaped guide rails 4-1. Corresponding to the mountain-shaped guide rails 4-1, the fixing clamp 3 has a groove with the same shape as the mountain-shaped guide rail, which fits into the mountain-shaped guide rail to improve stability.

[0024] Furthermore, the fixing fixture 3 includes an upper pressure plate 3-1, a positioning V-block 3-2, and an adjustable shim 3-3. The positioning V-block 3-2 is connected to the mountain-shaped guide rail 4-1 of the long base 4 by screws for load bearing. The upper pressure plate 3-1 is connected to the positioning V-block 3-2 by screws for clamping and fixing large long shaft-type workpieces to prevent movement. The adjustable shim 3-3 is set in the groove of the fixture 3 and connected to the positioning V-block 3-2 by internal countersunk screws for supporting large long shaft-type workpieces.

[0025] Furthermore, the thickness of the adjustable shim 3-3 is determined according to the diameter of the large long shaft workpiece to accommodate the lifting of the large long shaft workpiece. Furthermore, the fixing fixture 3 has a groove that matches the shape of the mountain-shaped guide rail, which fits perfectly into the mountain-shaped guide rail to improve stability, and the installation position of the fixture can be adjusted using different screw hole positions according to the length of the large shaft workpiece 1 (10-25 meters of round steel).

[0026] Furthermore, the long base 4 is provided with two rows of bench drill position adjustment screw holes 4-3 symmetrical about the center line. The bench drill 2 is installed at the position adjustment screw holes 4-3 by screws, so as to connect the screw holes 4-3 at different positions according to the length of large long shaft workpieces to adjust the installation position of the bench drill.

[0027] Furthermore, the bench drill 2 is equipped with a feed handwheel 2-1 and a lifting handwheel 2-2. The lifting handwheel 2-2 is used to adjust the lifting of the bench drill according to the height of the large long shaft workpiece, and the feed handwheel 2-1 is used to control the forward and backward movement of the bench drill.

[0028] The method for drilling center holes in large shaft-type workpieces according to this embodiment includes the following steps: 1) Setting up a mechanical structure for drilling center holes in large shaft-type workpieces, the mechanical structure includes a long base 4, two bench drills 2, and two sets of clamps 3, with the two bench drills 2 and the two sets of clamps 3 arranged on the central axis of the long base 4; 2) Adjusting and determining the position of the two sets of clamps 3 on the long base 4 according to the length of the large shaft-type workpiece to ensure that the large shaft-type workpiece is clamped and fixed on the long base 4; 3) Placing the large shaft-type workpiece stably on the clamps 3 and keeping the center line of the large shaft-type workpiece aligned with the center of the clamps 3, and fixing the large shaft-type workpiece on the long base 4 by the two sets of clamps 3; 4) Determine the position of the bench drill 2 on the long base 4 according to the length of the large shaft workpiece, so as to ensure that the drill bits of the bench drill 2 located on both sides of the large shaft workpiece are close to the end face of the large shaft workpiece and aligned with the center line of the large shaft workpiece. Then adjust the height of the bench drill 2 so that the drill bit is exactly at the center point of the end face of the large shaft workpiece; 5) Drill holes from the center point of both end faces of the large shaft workpiece using the bench drill 2 to complete the mechanical drilling of the center hole of the large shaft workpiece.

[0029] Furthermore, when adjusting and determining the position of the two sets of fixtures 3 on the long base 4, the fixtures 3 on both sides are installed by selecting the fixture positioning screw holes 4-2 to accommodate workpieces of different lengths.

[0030] Furthermore, when adjusting the height of the bench drill 2, use the lifting handwheel 2-2 to adjust the height of the bench drill 2 so that the drill bit is exactly at the center point of the round steel end face. Start the bench drills 2 on both sides respectively, and then rotate the feed handwheel 2-1 to move back and forth to process the center hole of a suitable depth.

[0031] The working principle of this embodiment is described below with reference to the accompanying drawings: Reference Figure 2The long base 4, made of cast iron, has raised mountain-shaped guide rails 4-1 on both sides. The long base 4 has two rows of machined drill position adjustment screw holes 4-3 symmetrically aligned with the center line. The mountain-shaped guide rails 4-1 have machined clamp position adjustment screw holes 4-2. The drill 2 is mounted on the position adjustment screw holes 4-3 with screws, and the mounting position of the drill 2 can be adjusted using different screw hole positions according to the length of the workpiece 1. The clamping fixture 3 has grooves that match the shape of the mountain-shaped guide rails, fitting snugly onto the guide rails to improve stability. The clamping fixture 3 also has different screw hole positions according to the length of the workpiece 1. The clamping fixture 3 consists of an upper pressure plate 3-1, a positioning V-block 3-2, and an adjustable shim 3-3. The positioning V-block 3-2 is placed on the long cast iron base 4 and connected to the mountain-shaped guide rails 4-1 with screws for load-bearing. The upper pressure plate 3-1 is connected to the positioning V-block 3-2 with screws to clamp and fix the workpiece 1 to prevent movement. Adjustable shims 3-3 are placed in the groove of the fixture and connected to the positioning V-block 3-2 via internal countersunk screws. Shims of different thicknesses can be selected to support the large shaft workpiece 1 (10-25 meters long round steel) according to its diameter. The bench drill 2 has a feed handwheel 2-1 and a lifting handwheel 2-2. The lifting handwheel 2-2 adjusts the height of the bench drill according to the placement height of the large shaft workpiece 1 (10-25 meters long round steel), while the feed handwheel 2-1 controls the forward and backward movement of the bench drill.

[0032] The specific processing steps in this embodiment are as follows: 1) Select the appropriate fixture position adjusting screw hole 4-2 according to the length of the large shaft workpiece 1 (10-25 meters long round steel) and install the fixtures on both sides. Select the appropriate adjustable shim 3-3 according to the diameter of the large shaft workpiece 1 (10-25 meters long round steel). Place the round steel stably on the fixture and align the center line of the round steel with the center of the fixture; 2) Select the appropriate bench drill position adjusting screw hole 4-3 according to the length of the large shaft workpiece 1 (10-25 meters long round steel) and install the bench drills on both sides. Make the drill bits of the bench drills 2 on both sides close to the end face of the large shaft workpiece 1 (10-25 meters long round steel) and aligned with the center line of the large shaft workpiece 1 (10-25 meters long round steel). Use the lifting handwheel 2-2 to adjust the height of the bench drill 2 so that the drill bit is exactly at the center point of the end face of the round steel. Start the bench drills 2 on both sides respectively, and then rotate the feed handwheel 2-1 to move back and forth to process the center hole of the appropriate depth.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of application of the present invention. Therefore, any equivalent changes made to the principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for drilling center holes in large shaft-type workpieces, characterized in that... Includes the following steps: 1) A mechanical structure for drilling center holes for large shaft workpieces is provided. The mechanical structure includes a long base (4) and two bench drills (2) and two sets of fixtures (3) set on the central axis of the long base (4). 2) Determine the position of the two sets of clamps (3) on the long base (4) according to the length of the large shaft workpiece, so as to ensure that the large shaft workpiece is clamped and fixed on the long base (4); 3) Place the large shaft workpiece stably on the fixture (3) and keep the center line of the large shaft workpiece aligned with the center of the fixture (3). Fix the large shaft workpiece on the long base (4) using two sets of fixtures (3). 4) Determine the position of the bench drill (2) on the long base (4) according to the length of the large shaft workpiece, so as to ensure that the drill bits of the bench drill (2) located on both sides of the large shaft workpiece are close to the end face of the large shaft workpiece and aligned with the center line of the large shaft workpiece. Then adjust the height of the bench drill (2) so that the drill bit is exactly at the center point of the end face of the large shaft workpiece. 5) Use the bench drill (2) to drill holes from the center points of both ends of the large shaft workpiece to complete the mechanical drilling of the center hole of the large shaft workpiece.

2. The method for drilling center holes in large shaft-type workpieces according to claim 1, characterized in that: When adjusting and determining the position of the two sets of fixtures (3) on the long base (4), the fixtures (3) on both sides are installed by selecting the fixture positioning screw holes (4-2) to accommodate workpieces of different lengths.

3. The method for drilling center holes in large shaft-type workpieces according to claim 1, characterized in that: When adjusting the height of the bench drill (2), use the lifting handwheel (2-2) to adjust the height of the bench drill (2) so that the drill bit is at the center point of the end face of the large shaft workpiece. Start the bench drills (2) on both sides respectively, and then rotate the feed handwheel (2-1) to move the bench drill (2) back and forth to process the center hole of the set depth.

4. A mechanical structure for drilling center holes in large, long-shaft workpieces, characterized in that: Includes a long base (4) and two bench drills (2) and two sets of clamps (3) set on the central axis of the long base (4); the two sets of clamps (3) are arranged symmetrically on the left and right, and the two bench drills (2) are located on the outside of the two sets of clamps (3) and arranged symmetrically on the left and right; at both ends of the two flanges of the long base (4), there are several evenly distributed clamp positioning screw holes (4-2) for connecting and adjusting the position of the clamps (3) on the long base (4) to adapt to the different lengths of large long shaft workpieces; at both ends of the central axis of the long base (4), there are several evenly distributed clamp positioning screw holes (4-2). The distributed bench drill positioning screw holes (4-3) are used to connect and adjust the position of the bench drill (2) on the long base (4) to accommodate different lengths of large long shaft workpieces; the length of the long base (4) is to ensure that both ends of the large long shaft workpiece are within the projection range of the long base (4); the bench drill (2) has a drill bit height position adjustment structure to adjust the height position of the drill bit of the bench drill (2) to accommodate large long shaft workpieces of different specifications, so that the drill bit of the bench drill (2) located on the outer side of both ends of the large long shaft workpiece is aligned with the central axis of the large long shaft workpiece.

5. A mechanical structure for drilling center holes in large shaft-type workpieces according to claim 4, characterized in that: The long base (4) is made of cast iron and is 10-25 meters long. There are raised mountain-shaped guide rails (4-1) on both sides of the long base (4), and the clamp positioning screw holes (4-2) are set on the mountain-shaped guide rails (4-1). Corresponding to the mountain-shaped guide rails (4-1), the fixing clamp (3) has a groove with the same shape as the mountain-shaped guide rails to hold the mountain-shaped guide rails in order to improve stability.

6. A mechanical structure for drilling center holes in large shaft-type workpieces according to claim 4, characterized in that: The fixing fixture (3) includes an upper pressure plate (3-1), a positioning V-block (3-2), and an adjustable shim (3-3). The positioning V-block (3-2) is connected to the mountain-shaped guide rail (4-1) of the long base (4) by screws for bearing weight. The upper pressure plate (3-1) is connected to the positioning V-block (3-2) by screws for clamping and fixing large long shaft-type workpieces to prevent movement. The adjustable shim (3-3) is set in the groove of the fixture (3) and connected to the positioning V-block (3-2) by internal countersunk screws for supporting large long shaft-type workpieces.

7. A mechanical structure for drilling center holes in large shaft-type workpieces according to claim 6, characterized in that: The thickness of the adjustable shim (3-3) is determined according to the diameter of the large long shaft workpiece to accommodate the lifting of the large long shaft workpiece.

8. A mechanical structure for drilling center holes in large shaft-type workpieces according to claim 4, characterized in that: The fixed fixture (3) has a groove that matches the shape of the mountain-shaped guide rail and is engaged with the mountain-shaped guide rail to improve stability. Different screw hole positions are used to adjust the installation position of the fixture according to the length of the large long shaft workpiece (1).

9. A mechanical structure for drilling center holes in large shaft-type workpieces according to claim 4, characterized in that: Two rows of bench drill position adjustment screw holes (4-3) symmetrical about the center line are provided on the long base (4). The bench drill (2) is installed at the position adjustment screw hole (4-3) by screws, so as to connect the screw holes (4-3) at different positions according to the length of the large long shaft workpiece to adjust the installation position of the bench drill.

10. A mechanical structure for drilling center holes in large shaft-type workpieces according to claim 4, characterized in that: The bench drill (2) is equipped with a feed handwheel (2-1) and a lifting handwheel (2-2). The lifting handwheel (2-2) is used to adjust the lifting of the bench drill according to the height of the large long shaft workpiece. The feed handwheel (2-1) is used to control the forward and backward movement of the bench drill.

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