The invention discloses an improved numerically controlled lathe structurally comprising an adsorption plate, an operation panel, a slide rail, a lathe body, a movable slide block, a protective device, a switch door, a fixed seat, an air blowing device, a tool rest and a slide way. After improvement, the air blowing device is operated by a controller, and the air is conveyed into a connecting ringthrough a guide pipe, so that an air blowing port uniformly blows the air out, metal scraps adsorbed on the surface of a tool or a machined part are blown onto the adsorption plate, and the tool is prevented from being interfered with by the metal scraps in the machining process of the part; when the lathe opens the switch door after processing the part, the switch door slides to left and right sides due to inertia; and when the switch door touches a chucking board, the switch door is magnetically and fixedly adsorbed on the chucking board through a magnetic adsorption ball under the magneticaction, and the switch door is protected through cooperation of a protective cover and a buffering bullet piece, such that the inner side of the switch door is avoided from deforming, the switch doorcan be normally closed, and the sealed effect of protecting the switch door is achieved.