Abstract: The torque and forces in friction stir welding (FSW) are important parameters for the process behavior, weld quality, and mechanical properties of the weld. Torque and forces are mainly influenced by rotational and welding speeds and tool geometry, including the tool pin profile. However, experimental studies to describe the influence of the pin profile on torque and forces have received little attention. In this paper, the influence of the threaded pin on torque and forces in the FSW process of 5052-H34 aluminum alloy is considered. The axial, welding, and transverse forces and the torque are experimentally measured at several combinations of rotational (600, 900, 1200 and 1500 rpm) and welding speeds (100, 200, and 300 mm/min) for two pin profiles: smooth and threaded. Additionally, residual stresses are measured, by X-ray diffraction technique, for some experimental conditions in the stir zone of the weld. The results show that the influence of the pin shape on the torque, forces, and residual stresses depends on the rotational and welding speeds, mainly on the rotational speeds. In general, the threaded pin increases the residual stresses and the maximum values of torque and forces in the axial and transverse directions while reducing the welding force.