FIELD: rail transport. SUBSTANCE: device for treatment of wheelset pairs of cars and non-motor sections of locomotives without rolling-out of wheel pair comprises wheel lathe consisting of bedplate with motor mounted on it and support with cutter holder, installed with possibility to move cutter holder in parallel and perpendicular to axis of pair. Device is equipped with reduction gear and detachable gear wheel fixed on pair shaft. Reducer is installed on the machine bed with the possibility of rotation and fixation in the plane perpendicular to the pair axis. Output stage of reduction gear is made with possibility of kinematic connection with detachable gear wheel, and output shaft of electric motor is kinematically connected to input step of reduction gear. EFFECT: higher accuracy of machining of wheel pairs during their repair, wider possibility of using the device.