Abstract: The invention concerns a device to be applied to a lathe for spinning, comprising a carriage that is motor driven and movable along guides substantially parallel to the lathe axis, and a tool connected to an arm carried by the said carriage, in which the said tool-bearing arm is pivotally connected on one side to a lever that is manipulated by the operator, and on the other side is linked to a hydraulic cylinder, whose action on the tool is concordant with that of the lever and in which the pressure within a chamber and the outlet of fluid therefrom determine the thrust exerted by the said cylinder on the tool-bearing arm, said lever transmitting the operator effort to the said arm through the sliding piston of a valve which, under said effort, progressively throttles, against the pressure of the incoming fluid, an inlet port coaxial with said piston and communicating with said chamber of said hydraulic cylinder in order to regulate the pressure in said chamber and the outlet of fluid therefrom.