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II. Some details to be aware of when machining shaft parts!

- Jan 21, 2019 -

Second, the pre-processing of shaft parts


Before the turning of the outer part of the shaft part, some preparatory process is required. This is the pre-processing of the shaft part. The most important preparation process is straightening. Because the workpiece blank is often bent during deformation during manufacturing, transportation, and storage. In order to ensure reliable clamping and uniform distribution of machining allowance, straightening is performed by various presses or straightening machines in the cold state.


Third, the positioning standard of the machining of shaft parts


The first is the center hole of the workpiece as the positioning reference for the machining. In the machining of shaft parts, the coaxiality of each outer circular surface, tapered hole and thread surface, and the perpendicularity of the end surface to the rotation axis are important manifestations of positional accuracy. These surfaces are generally designed with the centerline of the shaft as the reference and are positioned with the center hole to conform to the principle of reference coincidence. The center hole is not only the positioning reference for turning to the machine but also the positioning reference and inspection standard for other machining processes, which conforms to the principle of unified standards. When positioning with two center holes, it is possible to process a plurality of outer circles and end faces in a single clamping.


The second is the outer circle and the center hole as the positioning reference for the machining. This method effectively overcomes the shortcomings of poor positioning rigidity of the center hole, especially when machining a heavy workpiece, the center hole positioning may cause the clamping to be unstable, and the cutting amount may not be too large. You don't have to worry about this problem by using the outer circle and the center hole as the positioning reference. In roughing, the method of using the outer surface of the shaft and a center hole as the positioning reference can withstand large cutting moments during machining, which is the most common positioning method for shaft parts.


The third is to use two outer circular surfaces as the positioning reference for processing. When machining the inner bore of the hollow shaft, the center hole cannot be used as the positioning reference, so the two outer circular surfaces of the shaft should be used as the positioning reference. When machining the machine tool spindle, the two support journals are often used as the positioning reference, which can effectively ensure the concentricity of the taper hole relative to the supporting journal, and eliminate the error caused by the misalignment of the reference.


Finally, a cone plug with a central hole is used as the positioning reference for the machining. This method is most commonly used in the machining of the outer surface of hollow shafts.


Fourth, the clamping of the shaft parts


The processing of the cone plug and the tapered mandrel must have high machining accuracy. The center hole is not only the positioning reference made by itself but also the reference for the outer circle finishing of the hollow shaft. It must ensure the taper on the cone or cone sleeve. It has a high degree of concentricity with the center hole. Therefore, when selecting the clamping method, it should be noted that the number of installations of the cone plug should be minimized, thereby reducing the repeated installation error of the parts. In actual production, after the cone plug is installed, it is generally not removed or replaced in the middle of processing before processing.