Machine tools

A machine tool for machining a rotating workpiece to a non-uniform surface profile which requires machining movements of the tool within a revolution of relative rotation therebetween, and comprising:

• a workpiece drive for rotating a workpiece,
• a tool for machining a surface of the workpiece,
• a tool holder carrying said tool and moving said tool in a direction towards and away from the surface of the workpiece to machine said profile,
• drive means moving the tool holder in a direction normal to the direction of movement of the tool, to traverse the tool over the surface,
• piezo-electric transducer means connected to the tool imparting oscillating movement to said tool towards and away from the workpiece,
• angular position transducer means producing a signal representing the angular position of the workpiece,
• axial position transducer means producing a signal representing the axial position of the tool relative to the workpiece,
• input means producing data corresponding to a required non-uniform profile of the workpiece,
• control means connected to said input means and to said angular position transducer means and said axial position transducer means and producing from said data supplied thereto by said input means and said angular position transducer means and said axial position transducer means, an analogue profile signal corresponding to said required non-uniform profile of the workpiece defined by said data,
• oscillating signal means producing a continuous signal of constant frequency, and
• modulating means connected to said control means and to said oscillating signal means for modulating said constant frequency signal with said analogue profile signal, and connected to said piezo-electric means whereby said tool holder and said tool are oscillated at a variable amplitude in accordance with said analogue profile signal to machine ultrasonically the workpiece to said profile.