The article analyzes the signification and difference between the two machining instructions in the thread cutting circle machining of the numerical control lathe in the FANUC numerical control system.

The article expatiates on the difference and application of the FANUC numerical thread cutting circle command G92 and G76,analyzes the working feature and accuracy,and puts forward the reference plan of how to select thread cutting circle command reasonably.

This paper researches the processing method of screw cutting in automatic programming system,analyzes the key questions,including cutting direction,feeding mode,cutting thickness and multiple thread processing method and develops the processing algorithm and post method which is verified by experiments at last.