Magnetic stands are highly utilized auxiliary tools in the mechanical processing site and precision inspection process. They securely fix measuring tools such as dial indicators, micrometers, and lever gauges onto the machine tool guideways, worktables, or workpiece surfaces through magnetic attraction, providing a stable measurement reference for operators. The magnetic force range of magnetic table stands typically varies from 60 kilograms of force to 120 kilograms of force. While exerting their clamping function, the appropriate selection and correct usage method directly affect the credibility and stability of the measurement readings. This article starts from the structural characteristics of magnetic table stands and sorts out their typical applications in scenarios such as turning, grinding, inspection, and marking lines.
1. The core working component of the magnetic table stand is the permanent magnet magnetic circuit system. Inside, neodymium iron boron or ferrite magnetic steel is combined with a magnetic conductor plate to form a closed magnetic circuit. By rotating the handle to switch the magnetic circuit direction, the magnetic force can be turned on or off. When the magnetic circuit is in the conducting state, the magnetic lines of force pass through the bottom of the base and guide the adsorbed workpiece surface, forming a closed adsorption force. The adsorption force of the commonly used circular base magnetic table stand is in the range of 60 to 80 kilograms of force. The rectangular base style has a larger contact area and can reach 100 to 120 kilograms of force. The actual exertion degree of the adsorption force depends on the flatness and material magnetic conductivity of the adsorbed surface. Surfaces with a roughness of 3 microns or less on smooth cast iron or steel can reach more than 90% of the nominal adsorption force.
2. The supporting arm system of the magnetic table base usually consists of three to four connecting rods, and the connection points adopt spherical joints or conical locking structures, allowing operators to adjust the posture and orientation of the measuring instrument within the spatial range. The material of the supporting arms is divided into steel and aluminum alloys. The steel arms have high rigidity and good vibration resistance, but they are relatively heavy; the aluminum arms are lightweight and flexible, suitable for use in vertical planes or suspended positions. The design of the joint locking force needs to balance the stability of fixation and the convenience of operation. The empirical value is that the locking torque is between three and five Newton-meters. When the torque is insufficient, the pointer of the table may easily undergo slow displacement under vibration conditions, which directly affects the continuity of measurement.
3. The bottom of the magnetic table base is usually equipped with a precisely ground base surface, with a flatness control within 0.005 millimeters. This base surface accuracy ensures that after adsorption, the base is tightly adhered to the surface of the workpiece without generating additional tilt errors. The bottom of the base also features a V-shaped groove structure, which enables stable adsorption on the surface of cylindrical workpieces. When used on cylindrical working surfaces such as crankshafts and optical shafts, the V-shaped groove forms a line contact with the cylindrical surface, and is locked by magnetic force, ensuring a positioning stability no less than that of flat adsorption. This design expands the application scenarios of magnetic table bases in lathe processing.
1. In the turning processing site, one of the most common applications of magnetic table holders is the clamping and alignment of workpieces. Operators attach the magnetic table holder to the slide plate or tool holder of the lathe, place the measuring head of the micrometer against the outer circle or end face of the workpiece, manually rotate the spindle to make the workpiece rotate at a low speed, and observe the swing amplitude of the micrometer pointer. When the swing amplitude is controlled within 0.02 millimeters, it can be determined that the axis of the workpiece is basically coincident with the axis of the spindle rotation, and the normal turning process can be entered. The accuracy of using magnetic table holders for alignment is five to ten times higher than that of simply relying on visual marking method, especially suitable for strict control of coaxiality when processing multiple consecutive processes.
2. During the tool alignment operation, the magnetic table base also plays an indispensable auxiliary role. Align the tool tip on the tool holder with the measuring head of the dial indicator, and by manually moving the slide plate to observe the contact deflection of the dial pointer, the starting coordinate positions of the tool in the x-axis and z-axis directions can be accurately determined. The positioning accuracy of using a micrometer combined with the magnetic table base for tool alignment can reach 0.005 millimeters. Compared with the trial cutting method for tool alignment, the efficiency is increased by approximately 40%, and the generation of trial cutting waste is reduced. In batch processing on CNC lathes, the magnetic table base tool alignment method has become a key step in the standard operating procedure.
3. During the processing, the on-line monitoring of dimensions is also a practical function of the magnetic table base. Before the rough machining ends and the fine machining begins, the magnetic table base is adsorbed at the fixed position on the guide rail, and the probe contacts the machined surface to confirm whether the current dimension is within the intermediate tolerance range. During single-piece processing, this operation can promptly detect the size deviation caused by tool wear or thermal deformation, avoiding the batch of products from exceeding the tolerance limit. The stability of the measurement benchmark provided by the magnetic table base in this stage directly determines the reliability of the monitoring data.
1. In surface grinding machines and cylindrical grinding machines, magnetic table mounts combined with lever micrometers are commonly used for tracking and detecting the dimensions of workpieces during the grinding process. During grinding, a large amount of coolant washes over the workpiece surface and the temperature is relatively high. Operators cannot use handheld measuring tools for rapid measurements. By attaching the magnetic table mount to the side of the grinding machine's magnetic base or the bracket of the grinding wheel guard, the measuring head of the lever micrometer contacts the surface to be measured of the workpiece. This allows for real-time observation of the trend of size changes without stopping the machine. When the grinding reaches the predetermined size value, the feed can be stopped promptly. The stability of the magnetic table mount's attachment in such vibration and coolant splashing environments is particularly crucial.
2. The auxiliary detection of the grinding wheel dressing amount also cannot do without the magnetic table base. The magnetic table base is fixed on the worktable, and the measuring head of the micrometer is aligned with the tip of the diamond dressing tool or the outer circle surface of the grinding wheel. By comparing the readings before and after each dressing, the removal amount of each dressing can be determined. The single dressing amount of the external circle grinding wheel is generally controlled within 0.02 to 0.05 millimeters. Exceeding this range will cause the grinding wheel to wear out too quickly or result in the surface roughness of the workpiece exceeding the standard. With the stable clamping of the magnetic table base, the precise control of the dressing amount can reduce unnecessary wear and loss of the grinding wheel, and extend the service life of the grinding wheel by approximately 15% to 20%.
3. After the grinding process is completed, the magnetic table base can also be used for rapid inspection of the parallelism and perpendicularity of the workpiece. Place the workpiece on a flat surface, and the magnetic table base adheres to the edge of the flat surface. The dial gauge moves evenly along the upper surface of the workpiece, and the fluctuation amplitude of the pointer is the deviation of parallelism. For precision ground parts, the parallelism requirement is usually within the range of 0.005 to 0.015 millimeters. The rigid support provided by the magnetic table base combined with the high-precision flat surface can meet the measurement requirements of this magnitude, eliminating the turnaround time for sending the workpiece to the metrology room.
