Abstract: A device for piercing (1) glasses, particularly optical glasses, includes at least one machining tool (5) for piercing a glass and which is actuated by at least one drive motor (10), a member (2) for supporting at least one glass and at least one element for conveying the glass into the working area of the above-mentioned machine tool (5), and an element for treating and visualizing data relating to the glass, characterized in that it includes an element for indicating the distance of an edge of the glass in relation to a reference point in order to position the machine tool (5) opposite the location of the piercing which is to be carried out. A method for piercing and a device and a method for finishing screws which are cut during the assembly of pierced-glass-based spectacles, are also disclosed.