Turning is generally divided into two categories: roughing and finishing (including semi-finishing). Roughing aims to improve turning efficiency by using a large depth of cut and a large feed rate without reducing the cutting speed, but the machining accuracy can only reach IT11, and the surface roughness is Ra20-10 micrometers. Semi-finishing and finishing use high speed and small feed rate and depth of cut as much as possible, and the machining accuracy can reach IT10-7, with a surface roughness of Ra10-0.16 micrometers. High-speed finishing of non-ferrous metal parts on a high-precision lathe using a finely honed diamond tool can achieve a machining accuracy of IT7-5 and a surface roughness of Ra0.04-0.01 micrometers. This type of turning is called "mirror turning". If concave and convex shapes of 0.1-0.2 micrometers are honed on the cutting edge of the diamond tool, the turned surface will produce finely textured and neatly arranged stripes.
Under the diffraction of light, it will present a satin-like luster and can be used as a decorative surface. This type of turning is called "iridescent turning". In turning, if the cutting tool rotates in the same direction as the workpiece at a corresponding speed ratio (the tool speed is generally several times the workpiece speed), the relative motion trajectory between the tool and the workpiece can be changed, allowing the machining of workpieces with polygonal cross-sections (triangles, squares, rhombuses, hexagons, etc.). If, during the longitudinal feed of the cutting tool, a periodic radial reciprocating motion is added to the tool holder relative to the workpiece for each revolution, cams or other non-circular cross-section surfaces can be machined. On gear hobbing lathes, a similar working principle can be used to machine the flank face of certain multi-tooth cutting tools (such as form milling cutters and gear hobs), a process known as "flank hobbing."