Workpiece adapter for use in a machine tool, comprising: an adapter base plate, a clamping attachment, by means of which the workpiece adapter can be connected to a clamping element in a rotationally and translationally fixed manner, a workpiece receptacle, and a workpiece-connection element, which comprises retaining means for detachably receiving a workpiece and connection means for connecting to the workpiece adapter, the clamping attachment being arranged on a side of the adapter base plate opposite the workpiece receptacle, and the clamping element being able to be mounted on a motor-operated spindle of the machine tool via a spindle receptacle, for machining the workpiece by moving and rotating the spindle, characterised in that at least three workpiece-attachment elements are arranged on one side of the adapter base plate in order to form the workpiece receptacle, by means of which a workpiece can be mounted on the workpiece adapter via the workpiece-connection element, the at least three workpiece-attachment elements projecting from the adapter base plate such that the workpiece-connection element is retained on the workpiece adapter at at least three points and is in a plane parallel to the adapter base plate, which is perpendicular to the rotational axis of the spindle. an adapter base plate, a clamping attachment, by means of which the workpiece adapter can be connected to a clamping element in a rotationally and translationally fixed manner, a workpiece receptacle, and a workpiece-connection element, which comprises retaining means for detachably receiving a workpiece and connection means for connecting to the workpiece adapter, the clamping attachment being arranged on a side of the adapter base plate opposite the workpiece receptacle, and the clamping element being able to be mounted on a motor-operated spindle of the machine tool via a spindle receptacle, for machining the workpiece by moving and rotating the spindle, characterised in that at least three workpiece-attachment elements are arranged on one side of the adapter base plate in order to form the workpiece receptacle, by means of which a workpiece can be mounted on the workpiece adapter via the workpiece-connection element, the at least three workpiece-attachment elements projecting from the adapter base plate such that the workpiece-connection element is retained on the workpiece adapter at at least three points and is in a plane parallel to the adapter base plate, which is perpendicular to the rotational axis of the spindle. the clamping attachment being arranged on a side of the adapter base plate opposite the workpiece receptacle, and the clamping element being able to be mounted on a motor-operated spindle of the machine tool via a spindle receptacle, for machining the workpiece by moving and rotating the spindle, characterised in that at least three workpiece-attachment elements are arranged on one side of the adapter base plate in order to form the workpiece receptacle, by means of which a workpiece can be mounted on the workpiece adapter via the workpiece-connection element, the at least three workpiece-attachment elements projecting from the adapter base plate such that the workpiece-connection element is retained on the workpiece adapter at at least three points and is in a plane parallel to the adapter base plate, which is perpendicular to the rotational axis of the spindle.