Final answer:
Openings or bores are measured with a Bore Gauge, a precision tool designed to measure the inside diameter of cylindrical openings. There are different types, such as telescopic and dial bore gauges, which read measurements in various ways.
Step-by-step explanation:
Openings or bores are measured internally with a Bore Gauge. This type of gauge is specifically designed to measure the inside diameter of holes, cylinders, or pipes. A bore gauge consists of a shaft with a measuring sled at its base. When inserted into a bore, the sled expands to fit the walls of the opening, and the measurement can be read on a dial, digital display, or by using a micrometer mechanism.
There are different types of bore gauges, such as telescopic bore gauges, which require an operator to measure the internal diameter with a micrometer after setting the gauge to the right size, and dial bore gauges, which are more direct and can give a reading as the gauge is inserted into the bore. Regardless, these gauges are precision instruments used in engineering to ensure the bore dimensions meet specified tolerances.