How are sheet-metal screw sizes identified?

• A. By a number that indicates the outside diameter of the screw head and a length
• B. By the color of the coating
• C. By the shape of the head only
• D. By the thread pitch only

Answer: (A)

Sizes for sheet-metal screws are identified by two measurements: the diameter of the screw’s threads and its length. The diameter reflects the outer width of the threaded portion, which determines fit through holes and the grip achieved in the material. The length indicates how far the screw will protrude from or sink into the workpiece, ensuring proper clamping without sticking out too far. Coatings or color don’t tell you the size, and head shape mainly affects appearance and drive type, not the size designation. Thread pitch matters for compatibility with threads, but by itself it doesn’t define the overall size the way diameter and length do.