What tool is often used to assist with the calibration of CNC machines?

Laser alignment tools are commonly used for the calibration of CNC machines due to their precision and ability to measure alignment and geometric accuracy. These tools utilize laser beams to detect any misalignment in the machine's components, such as the spindle and axis movements. This high level of accuracy is crucial in CNC machining, where even slight misalignments can lead to errors in the finished product.

In contrast to the other tools listed, laser alignment tools provide an advanced method of ensuring that CNC machines are operating within the required tolerances. Digital calipers, while useful for measuring dimensions, do not have the capability to assess machine alignment. Basic rulers may provide a rough estimate but lack the precision needed for complex calibrations. Protractors can help measure angles but are not specifically designed for the calibration of machine axes. Thus, while other measuring tools have their roles, laser alignment tools stand out as the most effective option for ensuring the accuracy and performance of CNC machinery.