A mobile device for machining a workpiece, the mobile device including a shaft rotatable about a rotation axis; a carriage rotatable with the shaft about the rotation axis and axially, or radially displaceable relative to the rotation axis; a tool support for a cutting tool, the tool support connected to the carriage and displaceable along a carriage axis and in a direction perpendicular to the carriage axis; and a transmission that couples the shaft to the tool support and the carriage so that the tool support is displaceable along a path that includes an axial and a radial movement component relative to the shaft.