A method for assembling a composite housing fitted with a shaft and associated mounted elements comprising the steps of: a) arranging the housing in a predetermined position with respect to an actuator, the housing having at least one opening adapted to receive a shaft; b) arranging the shaft in a predetermined position with respect to the housing and the actuator; c) selecting an element to be mounted on the shaft within the housing, the element having an opening adapted to receive the shaft; d) conveying the element into a predetermined position within the housing; e) pushing the shaft by means of the actuator so that it passes successively through the opening in the housing and that in the element to be mounted; wherein the method comprises the additional steps of: f) subsequent to selecting the element to be mounted on the shaft within the housing according to step c), and prior to conveying the element into a predetermined position within the housing according to step d): locating it in a position adjacent a heat source for a predetermined time; g) subsequent to step e): selecting at least one additional element and conveying it into a predetermined position within the housing, said additional element having an opening adapted to receive the shaft, and, subsequent to selecting the additional element to be mounted on the shaft within the housing, and prior to conveying the additional element into a predetermined position within the housing locating it in a position adjacent a heat source for a predetermined time; and h) pushing the shaft by means of the actuator so that it passes through the opening in the additional element to be mounted. a) arranging the housing in a predetermined position with respect to an actuator, the housing having at least one opening adapted to receive a shaft; b) arranging the shaft in a predetermined position with respect to the housing and the actuator; c) selecting an element to be mounted on the shaft within the housing, the element having an opening adapted to receive the shaft; d) conveying the element into a predetermined position within the housing; e) pushing the shaft by means of the actuator so that it passes successively through the opening in the housing and that in the element to be mounted; wherein the method comprises the additional steps of: f) subsequent to selecting the element to be mounted on the shaft within the housing according to step c), and prior to conveying the element into a predetermined position within the housing according to step d): locating it in a position adjacent a heat source for a predetermined time; g) subsequent to step e): selecting at least one additional element and conveying it into a predetermined position within the housing, said additional element having an opening adapted to receive the shaft, and, subsequent to selecting the additional element to be mounted on the shaft within the housing, and prior to conveying the additional element into a predetermined position within the housing locating it in a position adjacent a heat source for a predetermined time; and h) pushing the shaft by means of the actuator so that it passes through the opening in the additional element to be mounted.