Method for reducing errors in a turning device (11, 12) during the determination of coordinates of a workpiece or during the machining of a workpiece, wherein the turning device (11, 12) allows a rotational movement of the workpiece about a rotation axis of the turning device (11, 12) during the determination of the coordinates or during the machining of the workpiece, and wherein the method comprises the following steps: - errors of the turning device (11, 12) due to differences between actual positions and actual orientations of the rotation axis, on the one hand, and corresponding ideal positions and ideal orientations of the rotation axis, on the other hand, are measured in a range of rotation angles, i.e. in different rotational positions of two parts of the turning device (11, 12) that can be moved in rotation relative to one another about the rotation axis, and corresponding error measurement values are obtained, - expected error values of the turning device (11, 12), which are respectively expected for a relative working position and working orientation of a coordinate measuring instrument for determining the coordinates of the workpiece or of a processing tool of a machine tool for machining the workpiece on the one hand, and the turning device (11, 12) on the other hand, are determined from the error measurement values, - at least one working position and/or working orientation of the coordinate measuring instrument or of the processing tool, for which the expected error value of the turning device (11, 12), with a predetermined measurement task for determining coordinates of the workpiece or a predetermined machining task for machining the workpiece o is less than for other working positions and/or working orientations and/or o satisfies a predetermined condition is determined from the expected error values of the turning device (11, 12). - errors of the turning device (11, 12) due to differences between actual positions and actual orientations of the rotation axis, on the one hand, and corresponding ideal positions and ideal orientations of the rotation axis, on the other hand, are measured in a range of rotation angles, i.e. in different rotational positions of two parts of the turning device (11, 12) that can be moved in rotation relative to one another about the rotation axis, and corresponding error measurement values are obtained, - expected error values of the turning device (11, 12), which are respectively expected for a relative working position and working orientation of a coordinate measuring instrument for determining the coordinates of the workpiece or of a processing tool of a machine tool for machining the workpiece on the one hand, and the turning device (11, 12) on the other hand, are determined from the error measurement values, - at least one working position and/or working orientation of the coordinate measuring instrument or of the processing tool, for which the expected error value of the turning device (11, 12), with a predetermined measurement task for determining coordinates of the workpiece or a predetermined machining task for machining the workpiece o is less than for other working positions and/or working orientations and/or o satisfies a predetermined condition o is less than for other working positions and/or working orientations and/or o satisfies a predetermined condition