由於機械製造的高度發展,對零件加工質量的要求越來越高,不但要求工件的各個尺寸準確,並且要求加工表面的光潔度符合規定。以前,工件的表面光潔度只是用▽,▽▽,▽▽▽,▽▽▽▽等符號來表示,這些符號,只能表示工件的表面由粗糙逐步光潔,而沒有一個量值來表示加工表面的光潔度,所以是不很精確的。 Due to the high degree of development of mechanical manufacturing, the quality of parts processing requirements are getting higher and higher, not only requires the accuracy of the various dimensions of the workpiece, and the requirements of the processing surface finish in line with the provisions. Previously, the surface finish of the workpiece was only represented by symbols such as ▽, ▽ ▽, ▽ ▽ ▽, ▽ ▽ ▽ ▽, these symbols can only indicate that the surface of the workpiece is gradually roughened by roughness without a value indicating the Finish, so it is not very accurate.