Which of the following are the three classes of working drawings?

• A. Detail drawings, assembly drawings, and installation drawings
• B. Detail drawings, assembly drawings, and manufacturing drawings
• C. Assembly drawings, installation drawings, and manufacturing drawings
• D. Detail drawings, installation drawings, and manufacturing drawings

Answer: (B)

Working drawings are organized to support production from part design to final assembly. The three classes are detail drawings, which specify a single part with all dimensions, tolerances, materials, and finishes; assembly drawings, which show how parts fit together and the relationships between components (often with a bill of materials); and manufacturing drawings, which provide the shop with the instructions to produce the part or component, including materials, processes, tolerances, finishes, and any special fabrication steps. Installation drawings belong more to on-site setup rather than the internal production and assembly workflow, so they’re not part of the three main classes. That combination—detail, assembly, and manufacturing drawings—best fits the concept of working drawings.