Which tool is commonly used for measuring the thickness of aircraft materials?

The micrometer is the preferred tool for measuring the thickness of aircraft materials due to its ability to provide precise and accurate measurements. This tool can measure small dimensions, often down to a thousandth of an inch (0.001 inches), which is crucial in aircraft maintenance, where even minor discrepancies in material thickness can affect structural integrity and performance. The micrometer operates with a calibrated screw mechanism, allowing users to take measurements with a high degree of accuracy.

In contrast, the other tools mentioned have different applications. A caliper, while capable of measuring thickness, generally offers less precision compared to a micrometer. A tape measure is more suited for measuring larger dimensions and distances but is not ideal for the small thicknesses typically found in aircraft materials. A protractor is primarily used for measuring angles, not thickness. Therefore, the micrometer stands out as the most appropriate and precise tool for this specific task in aircraft maintenance.