Mandrel-holding slide or sleeve pod for numerical-control machine tools

Mandrel-holding slide or sleeve pod for numerical-control machine tools, slidably mounted by means of a carriage on to the beam of the machine tool, in which the position of said slide or sleeve pod is adjustable vertically by means of a lead screw (16) and nut screw (14) mechanism, comprising a mandrel-carrier structure (10) in which there is at least partially housed said lead screw and nut screw mechanism, characterized in that in said mandrel-carrier structure there is mounted an axially slidable plunger-like member (26) adapted to define two chambers (40 and 32) situated above and below said plunger-like member (26), respectively, said chamber (32) being adapted to be communicatingly connected. with a supply source of an oil-pressure fluid at a pre-determined pressure, and said chamber (40) being adapted to be communicatingly connected with a supply source of compressed air at a pre-determined pressure, said plunger-like member (26) being subject to the action of a counter compression spring means (38) calibrated at such a pre-determined upward-directed elastic force as to be able to compensate for the weight of the sleeve pod or slide (12), said supply source of oil-pressure fluid being activated when the mandrel-holding slide must take the rigidly locked, non-floating normal working condition of the numerical-control machine tool, whereas said supply source of air under pressure is activated when said slide or sleeve pod (12) must take the floating condition in which the planar surface of the stone material is processed, in which to the mandrel of the machine tool there is mounted a tool-carrying chuck or dish of a type traditionally used in polishing, smoothing and facing machines for stone material.