In recent years, environmental concerns call for the reduced of cutting fluids in metal machining. The green cutting techniques are to be studied to achieve this objective. In this paper, application of ozone gas in metal cutting was investigated, compared with oxygen gas, cutting fluids and dry cutting. The effects of ozone on cutting force, cutting temperature and chip deformation have been examined in turning of C45 steel with carbide tool YT14. The results of experiments indicated that the cutting force and cutting temperature application of ozone were reduced about 7 percent and 10 percent respectively compared with dry cutting, both of them were less than oxygen gas and cutting fluids condition. The chip deformation coefficient was also less than oxygen, wet and dry cutting conditions. The research results showed that ozone had positive effects in metal machining and it was probable to be a clean and eco-friendly coolant and lubricant under specific conditions.