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This paper presents specific cutting energy measurements as a function of the cutting speed and tool cutting edge geometry. The experimental work was carried out on a vertical CNC machining center with 7,500 rpm spindle rotation and 7.5 kW power. Hardened steels ASTM H13 (50 HRC) were machined at conventional cutting speed and high-speed cutting (HSC). TiN coated carbides with seven different geometries of chip breaker were applied on dry tests. A special milling tool holder with only one cutting edge was developed and the machining forces needed to calculate the specific cutting energy were recorded using a piezoelectric 4-component dynamometer. Workpiece roughness and chip formation process were also evaluated. The results showed that the specific cutting energy decreased 15.5% when cutting speed was increased up to 700%. An increase of 1° in tool chip breaker chamfer angle lead to a reduction in the specific cutting energy about 13.7% and 28.6% when machining at HSC and conventional cutting speed respectively. Furthermore the workpiece roughness values evaluated in all test conditions were very low, closer to those of typical grinding operations (~0.20 µm). Probable adiabatic shear occurred on chip segmentation at HSC.

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Aos chefes de oficina Penazzi (EESC) e Carlinhos (IFSC) pelos diversos auxílios prestados ao longo do trabalho experimental. Às secretárias da Pós-Graduação e do Departamento de Engenharia Mecânica.Aos amigos Adriano Fagali, Aldo Braghini, Aldo Ometto, Américo, Alexandre, Carlos Elias, Cristiane, Daniel, Demian, Elias, Emanuel, Eraldo, Fabrício, Fernandinho, Francis, Giuliano, Henrique, Helder, Hugo, Jalon, Leonardo, Lincoln, Luciana, Luciano, Luis Henrique, Marcelinho, Marcelo Biffi, Otavio, Paião, Paulinho, Paulo Eduardo, Renato, Ricardo Arai, Salete, Tadeu, Thiago, Tobias when machining SAE 1020 steel. The tool geometry present more influence on specific cutting energy under conventional cutting speed than at high speed cutting.Small variations of tool chip-breaker geometries caused diminution of the specific cutting energy up to 29% for conventional cutting speed, and 14% on average for HSM condition when machining tempered ASTM H13 steel. Various specific cutting energy results obtained from the Charpy test proposed by this work presented a good concordance with equivalent ones provided by scientific literature.

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