Axle workpiece in the turning process, will meet the accuracy and surface roughness of less than the requirements and other issues. According to the specific process of turning, analysis. First, the dimensional accuracy of less than the requirements of the reasons and solutions 1. As the operator carelessness, measuring errors when measuring children, or the wrong dials and improper use in the measurement, we must carefully and correctly use the dial is Very important, in the carriage handle dial, the dial of various models of lathe is not the same, each small cell dial can be calculated using the following formula: Scale to a moving tool distance = carriage screw Distance / dial a total of the number of engraved lines (mm) Know each grid after the value, but also pay attention to the use of Because there is a gap between the screw and nut, and sometimes the dial although the rotation, but the knife does not necessarily move, After the gap is complete turning tool to move. Therefore, when in use, if the scale is over the grid number, never allow only a few back Inverted, but to turn one turn later, and then re-align the scale. (2) The measuring tool itself is not correct or use the measuring instrument before use, must be carefully checked and adjusted to be put into use. 3. Due to temperature changes, the workpiece size change In cutting, the chip deformation, the chip of the various molecules move each other, but they move friction generated a lot of heat. In addition, due to the friction between the chip and the front of the turning tool, the friction between the back of the turning tool and the surface of the turning tool generates heat, which directly affects the cutting tool and the workpiece. Of course, the highest heat is the chip (about 75%), followed by the turning tool (about 20%) and the workpiece (about 4%, and 1% in the air). When the workpiece is heated, the diameter increases (about 0.01 ~ 0.05 mm, cast iron changes than steel), the diameter of the contraction after cooling, resulting in waste. It can not be measured when the workpiece temperature is high. If you must side of the amount of pouring sufficient cutting fluid in the turning, the workpiece temperature does not increase; followed by coarse fine car separate method. 4. I am not enough blank rough bending itself is not straight, and the center hole hit the other causes.