In the field of nc machining, the first part put fixed in the benchmark in the numerical control lathe, in numerical control parameter Settings interface, and then put the presetting the part machining dimension of input, the numerical control lathe automatic processing according to manually set the size of the part, but the processing of product and setting the standard size of actual size are biased, the condition of the CNC lathe processing out there is actual size error of parts are the main reasons are: (1) CNC lathe tool wear: In the process of machining part, CNC lathe control tool will have certain abrasion, cause tool feeding path and does not conform to the actual Settings, when machining product feed does not reach the designated position, cause of the actual processing to taste the real size (e.g. milling out of products on the high side, a ministry to taste the small hole diameter on the hole) and the set of standard size does not conform to the; (2) CNC lathe itself processing accuracy is not enough: CNC lathe operation control tool drive stroke (X, Y, Z direction) is not accurate, so that the cause of the tool to go milling parts of the travel deviation, will also appear out of the actual size of the parts and the set standard size deviation.