Which tool is commonly used to measure the diameter of a shaft in machining?

The micrometer is a precision measuring tool specifically designed to measure small dimensions, including the diameter of a shaft, with high accuracy. It typically allows measurements to be taken down to the thousandths of an inch (or hundredths of a millimeter), making it ideal for precision machining applications. The design of the micrometer features a calibrated screw that provides a mechanical advantage, ensuring that even minute changes in measurement are easily captured and read.

While calipers can also be used to measure external dimensions, they may not provide the same level of precision as a micrometer, especially for small diameters. Height gauges are used primarily for measuring vertical distances from a reference surface, and gauge blocks are utilized for establishing precise measurement standards rather than directly measuring features like diameter. Therefore, the micrometer stands out as the most suitable tool for accurately measuring the diameter of a shaft in machining contexts.