A method of assembling an electric motor or generator having an annular first element mounted on a circumferential mounting surface of a second element, the method comprising placing a heating coil within an inner annular surface of the annular first element; applying a current to the heating coil to heat the inner annular surface of the annular first element to a temperature that results in the inner annular surface of the annular first element increasing in diameter to allow the annular first element to be mounted on or over the circumferential mounting surface of the second element; and cooling the annular first element to form an interference fit between the annular first element and the circumferential mounting surface of the second element.