Self-centering steady rest

A self-centering steady rest (1) for clamping and/or holding a workpiece (4) on a turning machine, with three holding elements (5, 6, 7) mounted in a housing (2) of the steady rest (1) and held adjustably in a common plane, of which the two outer holding elements (5, 7) are configured as swivelling angled levers supported in the housing (2) and in a mirror-image arrangement with one another, and the middle holding element (6) is guided in the housing (2) by means of a drive unit (61) and a middle piece (8) in a driveable connection with the drive unit (61) in such a way as to be axially moveable in the direction of the workpiece (4), with control surfaces (9) provided on the middle piece (8), the two outer holding elements (5, 7) being adapted to interact with the control surfaces (9) by means of inner ends (10) of the holding elements (5, 7),

• wherein
• the drive unit (61) can be driven by an electric motor (21), and rotational movements of the electric motor (21) can be converted by the drive unit (61) into at least two different axial advance speeds of the middle piece (8) with resulting force components (Fz, Fs) vectored onto the workpiece (4), and in order to set the corresponding advance speed of the middle piece (8) between it and the electric motor (21), a clutch (62) with a constrained action is used, by means of which the drive unit (61) can be changed over automatically into two different shift positions.