金属切削机床都有一定的精度,因而它也就有着某些偏差。由于机床的偏差,和机床零件、刀具的变形,以及刀具的磨损,所以加工出来的工件的几何形状总是有些不准确的。例如,零件常会产生凹肚、凸肚、不平行、不垂直等不准确的毛病。有时,工件的尺寸达到了要求,而几何形状却不能令人满意。因此,就要规定零件的形状只能有某一范围的偏差,这个偏差范围就叫做零件的几何精度。 Metal cutting machine tools have a certain accuracy, so it also has some deviations. The geometry of a machined part is always somewhat inaccurate due to machine variations, machine tool parts, tool deformation, and tool wear. For example, parts often produce concave belly, convex, uneven, not vertical and other inaccurate problems. Sometimes, the size of the workpiece to meet the requirements, but the geometry is not satisfactory. Therefore, it is necessary to specify the shape of the part can only have a range of deviations, the scope of this deviation is called the geometric accuracy of the parts.