Abstract: A linear motor for use, for example, in sewing machines for controlling needle vibration as to amplitude and/or fabric feed both in magnitude and direction, said motor comprising a frame having an internal central pole piece spaced intermediate two permanent magnets of the high energy product type which are attached to the frame, the central pole piece providing supporting means for movable coil member integrally formed with connecting arms pivotally fastened to an actuator arm carried on a pivoted potentiometer shaft. The permanent magnets are secured through their own magnetism to the frame and are each locked in proper orientation by a non-metallic retainer which is locked to the magnet and additionally formed with a closure panel, said closure panels cooperating with the motor frame completely to enclose a compartment for the movable coil member effecting both a minimum external leakage field and a dust proof unit.