Helical milling is an alternative hole-making machining process which presents several advantages when compared to conventional drilling. In the helical milling process, the tool proceeds a helical path while rotates around its own axis. Due to its flexible kinematics, low cutting forces, tool wear, and improved borehole quality may be achieved. In this study, a new helical milling process to create holes in hardened steel with a hardness of HRC 52 was used. Carbide inserts with PVD TiN coating were applied. Input parameters including cutting speed and feed rate were considered in 4 and 2 levels, respectively. In order to increase the reliability of the results, experiments were repeated 4 times and the total of 32 tests were performed. Other cutting parameters, such as axial and radial depth of cut were constant. Machining process was performed in dry state and without any lubricant. Output characteristics were tool wear, surface roughness, cutting force, machining time and material removal rate. Tool wear, surface roughness and forces, were measured by tool maker microscopy, roughness tester and dynamometer, respectively. The results showed that increasing the cutting speed on this type of hardened steel, decreases the surface roughness, machining forces and machining time. However, increasing the cutting speed and the feed rate enhances the tool wear and material removal rate considerably. Cutting speed and Feed rate of 50 m/min and 0.05 mm/tooth, offered the best mechanical properties of the Machining. تفاصيل المقالة