The influence of the cutting parameters on the cutting forces, surface finish and tool wear in hardened steel bars AISI 4340 (45HR), subjected to hard turning in dry, using coated carbide inserts was investigated. From 38 mm diameter bars previously hardened to 45 HRC, specimens of 36 mm (Ø) and 200 mm in length were made, which were marked for a machining time. The turning was carried out in a lathe, following the orthogonal cutting model, using coated carbide inserts. Four cutting parameters were used: speed, advance, depth and machining time in 4 different levels. For the measurement of the cutting forces, an octagonal type dynamometer was used, which incorporates two strain gauges that are connected in ½ Wheatstone bridge, which in turn are connected to a deformation recorder that provides the reading of the cutting force. For the measurement of roughness, a digital Mitutoyo rugosi...