in an electric motor comprising a plurality of permanent magnets surrounding a motor armature for supplying field flux to the armature , a cylindrical magnet cover is fitted into an inner circumferential surface defined by the permanent magnets to protect the permanent magnets against chipping and other damages . the magnet cover is further provided with a radial flange having guide holes formed therein so that set bolts passed axially inside the motor casings may be favorably guided as they are inserted from one axial end of the motor casing to the other . preferably , to better guide the bolts , the guide holes may be each provided with a cylindrical guide boss which may be formed either by burring or cutting and lifting a part of the material of the flange .