The two specimens shown at right were made for the General Electric Aircraft Engine Corporation. The Visual Aid Scratches consists of twelve patches of steel surfaces, which have been machined by four different processes (three specimens of different roughness values for each of grinding, turning, horizontal milling, and end milling). In addition, each individual patch bears two sets of scratches of 3 different depths, one set parallel and the other perpendicular to, the lay of the machining marks of the specimen. The Visual Aid for Nicks and Breakedges shows nicks or cuts of different depth in chamfered edges (“breakedges”). Scratch checking visual aid Scratch checking visual aid
These two visual aids were used in a GE jet engine assembly plant to address a quality control issue that frequently arose during unpacking of engine parts delivered to the plant by subcontractors. If any part is accidentally damaged, by a box-cutting knife for example, then someone has to decide whether the resulting scratch or nick on the particular surface in question is negligible, or fatal, or just serious enough to need accurate inspection. The visual aids provide samples which help the inspectors estimate the depth or scale of the damage. Nick checking visual aid Nick checking visual aid