An important element of friction stir welding technology is the determination of the temperature of the material in the mixing zone, which can be determined by calculating the amount of heat introduced into the welding zone. To determine this value, experimental studies were carried out on a stand in which the material to be welded (aluminum alloy AMg5) is modeled as an experimental tube with a diameter of 20 mm, and the tool (from tool steel P6M5) is modeled as a working plate. On the stand, studies of the dependence of the frictional moment and heat-liberation value were performed. According to the obtained experimental data, the heat-liberation dissipation and heat power on the working tool are calculated, the dependences of these values on the radius of the working tool are obtained.To increase the amount of heat input in the center of the contact area, a tool with a drive with two concentrically located (one inside the other) shafts is proposed, while the inner shaft rotates at a higher speed than the outer one. According to the obtained experimental data, the dependences of heat release for each shaft and the total heat release for a tool with two shafts at an external shaft rotation speed ω = 63 s-1 and different rotation speeds of the internal shaft are calculated. In total, for the external and internal shafts, the total heat release value is about 2 times higher than the total heat release value using a single shaft.The purpose of this work is to find the values of heat release in friction stir spot welding, as well as the development of friction spot welding tools with higher heat release.