The present report aims at developing chlorine free additives in cutting oil for TiN coated hob and new (Al, Ti) N coated hob, and investigating the influence of these coating materials on viscosity effect of base oils and tool wear reduction effect of additives. Experiments were carried out using a fly tool. The results obtained are summarized as follows. (1) Machine oil 23 having middle viscosity is suitable for coated tools in decreasing tool wear and in improving finished surface roughnesS. (2) With a TiN coated tool, sulfur type EP additives, polysulfide and sulfurized fatty oil showed a best performance in terms of extending tool life and improving surface roughness. (3) With a (A1, Ti)N coated tool, though phosphorus type's tricresyl phosphate extends the tool life, it is ineffective for surface roughness. (4) The use of chlorine free additives is effective for environmental pollution control and for improving the safety of the operator.