Today, the AISI D6 tool steel has been employed in the manufacture of dies and molds that require high mechanical properties. Such hard material is not trivial to machining. Milling free-form geometries of D6 is a challenge usually faced at die and mold industries. Therefore, the current paper presents an investigation of free-form milling of hard material AISI D6 tool steel using a ball-end cemented carbide cutting tool. The influence of the toolpath direction (descendant and ascendant) and tool-workpiece surface contact were examined, and the machining forces, surface roughness, tool wear, and tool life were evaluated. The experiments were performed in two kinds of workpieces: in the first one, the milled surface was a cylindrical and in the second, the surface was inclined planes (with three different inclinations). The results indicate that the most influential factor for tool life was tool vibration. The higher the vibration, the shorter the tool life. Further, unlike milling of ordinary materials for molds and dies, the engagement of the center of the tool tip during cutting is advantageous for the machining process of hard materials because it improves cutting stability, thus reducing surface roughness and increasing tool life. © 2015, Springer-Verlag London.829-1220752086Kacelj, B., Kopa, Z., Kampu, Z., Kazuman, K., Speciality of HSC in manufacturing of forging dies (2004) J Mater Process Technol, 157-158, pp. 536-542Dolinsek, S., Ekinovic, S., Kopac, J., A contribution to the understanding of chip formation mechanism in high-speed cutting of hardened steel (2004) J Mater Process Technol, 157-158, pp. 485-490Liu, N., Loftus, M., Whitten, A., Surface finish visualisation in high speed, ball nose milling applications (2005) Int J Mach Tools Manuf, 45, pp. 1152-1161Subrahmanyam, K.V.R., San, W.Y., Soon, H.G., Sheng, H., Cutting force prediction for ball nose milling of inclined surfasse (2010) Int J Adv Manuf Technol, 48 (1-4), pp. 23-32Chiang, S., Tsai, C., Lee, A., Analysis of cutting forces in ball-end milling (1995) J Mater Process Technol Amst, 47 (3-4), pp. 231-249Kaymakci, M., Lazoglu, I., Tool path selection strategies for complex sculptured surface machining (2008) Mach Sci Technol, 12, pp. 119-132Souza, A.F., Berkenbrock, E., Diniz, A.E., Rodrigues, A.R., Influences of the tool path strategy on the machining force when milling free-form geometries with a ball-end cutting tool (2014) J Braz Soc Mech Sci EngToh, C.K., Surface topography analysis in high speed finish milling inclined hardened steel (2004) Precis Eng, 28, pp. 386-398Boujelbene, M., Moisan, A., Torbaty, S., Study of the tool inclination in multi-axes milling. Bucareste (2006) Romênia: Proceedings of the 15th International Conference on Manufacturing Systems – ICMaSOzturk, E., Tunc, L.T., Budak, E., (2009) Investigation of lead and tilt angle effects in 5-axis ball-endmilling processes, , International Journa lof Machine Tools &, ManufacturSouza, A.F., Diniz, A.E., Rodrigues, A.R., Coelho, R.T., Investigating the cutting phenomena in free-form milling using a ball-end cutting tool for die and mold manufacturing (2014) Int J Adv Manuf Technol, 71 (9-12), pp. 1565-1577Wojciechowski, S., The estimation of cutting forces and specific force coefficients during finishing ball end milling of inclined surfaces (2015) Int J Mach Tool Manuf, 89, pp. 110-123Fan, X., Loftus, M., The influence of cutting force on surface machining quality. International Journal of Production Research. Vol 45 (2007) N°, p. 4Saffar, R.J., Razfar, M.R., Zarei, O., Ghassemieh, E., Simulation of three-dimension cutting force and tool deflection in the end milling operation based on finite element method (2008) Simul Model Pract Theory, 16, pp. 1677-1688Trent, E.M., Wright, P.K., (2000) Metal cutting, , Butterworth - Heinemann, BostoDiniz, A.E., Micaroni, R., Hassui, A., Evaluating the effect of coolant pressure and flow rate on tool wear and tool life in the steel turning operation (2010) Int J Adv Manuf Technol, 50, pp. 1125-1133