A rotary cutting head is provided for portable cutting devices, such as lawn trimmers, edge trimmers, brush cutters, hedge trimmers, and the like which use cutting blades. The drive shaft, the blade supporting housing, and the blade of said cutting head have complementary means which, manually and without using tools, allow the blade to be placed, changed, centered, and axially positioned relative to the drive shaft and to be rotationally coupled to the blade supporting housing by performing an axial movement combined with an angular or linear movement of the blade relative to the drive shaft until the blade and the supporting housing start automatically interlocking.
