A machining apparatus includes at least one tool holder (1) and at least one cutting tool (2) that are detachably interconnected. At least one first marking (7a) is provided on the tool holder (1) and at least one further marking (7b) is provided on the cutting tool (2). When connecting the tool holder (1) to the cutting tool (2), they can be aligned with each other with the aid of the markings (7a, 7b). The machining apparatus is preferably used for machining spectacle lenses, especially progressive lenses.