Calibrated wires for external micrometers are essential tools for the precise measurement of external threads, such as those on screws and bolts. These wires, usually made from durable materials like hardened steel or tungsten carbide, are used to determine the effective or pitch diameter of the thread with extreme accuracy. Their use is particularly valuable in industries where precision is critical, such as precision mechanics, the automotive industry, and the aerospace sector.

Calibrated wires are supplied in sets of three, allowing for correct measurement of the effective diameter due to their placement on the flanks of the thread. This configuration allows an external micrometer to measure the distance between the wires and determine the thread's effective diameter, which can then be compared to standard tables to ensure the thread meets dimensional specifications.

The use of calibrated wires offers superior accuracy compared to other measuring instruments, such as calipers, as it allows for the precise evaluation of the effective diameter, which is the distance between the opposing flanks of the thread. This parameter is crucial for determining the depth and quality of the thread itself, ensuring that it complies with the required technical specifications.

To correctly use calibrated wires, it is necessary to select the appropriate set based on the thread pitch being measured. Then, the wires are inserted into the grooves of the thread, with two on one side and one on the other. The external micrometer is then used to measure the distance between the wires. Once the measurement is obtained, it can be compared with standard values to ensure the thread is accurate.