In end milling process the undeformed chip thickness and the cutting force components vary periodically with phase change of the tool. In this study, up end milling process is transformed to the equivalent oblique cutting. The varying undeformed chip thickness and the cutting force components in end milling process are replaced with the equivalent average ones. Then it can be possible to analyze the chip-tool friction and shear process in the shear plane of the end milling process by the equivalent oblique cutting system. According to this analysis, when cutting Inconel 718, 61, 64 and 55% of the total energy is consumed in the shear process with the helix angle 30$^{circ}$, 40$^{circ}$ and 50$^{circ}$ respectively, and the balance is consumed in the friction process. With the helix angle of 40$^{circ}$ the specific cutting energy consumed is smaller than with the helix angle 30$^{circ}$ and 50$^{circ}$.