The selection principle of cutting consumption is: to improve the productivity in rough processing, while taking into account the economic and processing costs; Conventional Lathe During semi-finishing and finishing, the machining quality of parts should be ensured while cutting efficiency and processing cost should be taken into account. It is worth noting that the cutting parameter (spindle rotation, cutting depth and feed) is an organic whole, to adapt to each other, only three at the most reasonable matching values, to get the best cutting parameter. Determine the cutting dosage should be according to the nature of the processing, the processing requirements, the size and material properties of the workpiece material and tool of specific requirements, through the consult the manual cutting and combining with the experience to determine, determining cutting parameter in addition to follow the general principles and methods, should also consider the following factors: (1) tool difference, the influence of different cutting tool manufacturer production tooling quality difference is very big, so the cutting parameter to modify it according to the practical use knives and field experience. (2) Conventional Lathe influence of machine tool characteristics -- the cutting performance is subject to the power of CNC machine tool and the rigidity of the machine tool,Conventional Lathe which must be selected within the scope of the machine tool specification. Avoid the phenomenon of stuffy car due to the lack of power of the machine tool or the vibration of the machine, which affects the machining quality, precision and surface roughness of the parts. (3) the influence of the CNC machine productivity, high cost of nc machine tool's working hours, relatively speaking, low proportion of the wastage of the cutting tool cost, should try to use high cutting parameter, through appropriate to reduce the knives' service life to improve the productivity of CNC machine tools.