Tool for mounting and removing tyres onto and from respective wheel rims comprises a profiled body to be mounted on a cylindrical shank (2) provided at the end of a tool holder bar (1) associated with a tyre removal machine, the body having two active portions, known as the blade (5) and head (6) respectively, extending from two parts (20, 22) comprising coaxial hubs (200, 220) both mounted on said cylindrical shank (2) of said tool holder bar and removably coupled together such that their mutual orientation can be adjusted, at least one of said hubs (200, 220) being provided with means for torsionally locking it to said shank.