Abstract: A method of producing the core of an electric motor by providing a stack of laminations of magnetic material. Windows are formed in the laminations for one or more magnetic elements to be placed in each window. Each window has an end edge portion (17) which is to be at the peripheral edge (18) of the lamination of the finished version of the rotor. The laminations originally have an annular radial extension (60-61) and after the core is assembled with end caps, the annular radial extension (60-61) is removed so that the window end edge portions (17) are at the periphery (18) of the laminations. There is a polar peripheral portion (20) between each window and the periphery (18) of the lamination and an intermediate peripheral portion (40) between two adjacent polar peripheral portions, with such intermediate polar portions having reduced electrical conductibility and reduced magnetic permeability.