a hammer drill comprising : a body ; a motor mounted within the body ; a transmission housing mounted within the body , a transmission mechanism mounted within the transmission housing which is capable of rotatably driving and / or repetitively striking a cutting tool held by the hammer drill in response to rotation of an output shaft of the motor ; wherein the transmission housing comprises a pair of housing portions adapted to engage each other to support the component parts of the transmission mechanism within the transmission housing ; wherein the first housing portion is made from metal and the second housing portion is made from a plastic material , each of the components of the transmission mechanism being supported jointly be the first and second housing portions .