遼字石油化工大學⊙ 4. Operation Step: An operation step is the basic element of an operation. One operation step is defined as an operation that is completed under the condition when the surface to be manufactured the cutting parameters and cutting tool remain the same. When any of the cutting parameters is changed, it will become another operation 5. Cutting pass: When the amount of metal to be removed is large, several cutting passes may need to be carried out a cutting pass is a kind of operation step that is completed by a single type of tool to cut the same surface under the same cutting parameters4. Operation Step: An operation step is the basic element of an operation. One operation step is defined as an operation that is completed under the condition when the surface to be manufactured, the cutting parameters and cutting tool remain the same. When any of the cutting parameters is changed, it will become another operation step. 5. Cutting pass: When the amount of metal to be removed is large, several cutting passes may need to be carried out. A cutting pass is a kind of operation step that is completed by a single type of tool to cut the same surface under the same cutting parameters