Tool drive unit, turning device and turning method

A method for the cutting machining of an end face (F) of a workpiece (100), which is driven about a virtual axis of rotation (A), with a turning tool (20) having a cutting edge (21), wherein the workpiece (100) is an optical lens or an optical lens blank and the end face (F) of the workpiece is curved, the method comprising the following steps:

• rotating the workpiece (100) about the virtual axis of rotation (A);
• bringing the cutting edge (21) into engagement with the curved end face (F) of the workpiece (100) at a distance from the axis of rotation (A);
• carrying out a primary transverse movement of the cutting edge (21) towards the axis of rotation (A) while the cutting edge (21) continues to engage in the curved end face (F) of the rotating workpiece (100), with the result that the cutting edge (21) is guided along a spiral work path over the curved end face (F) by the superimposition of the rotation of the workpiece (100) and of the transverse movement of the cutting edge (21),
• superimposing the primary transverse movement with an identically directed secondary transverse movement of the cutting edge (21) which occurs towards the axis of rotation (A) and away from the axis of rotation (A), wherein the secondary transverse movement (21) is carried out in dependence on the angle of rotation position of the workpiece (100).