Tunneling in CNC Coordinate Measurement Machines (CMM) refers to how accurately the probe follows a straight line path when commanded to move in multiple axes simultaneously. This characteristic is crucial in applications requiring precision, especially when navigating through small clearances. The structure of the CMM can influence tunneling, with continuous feedback controllers performing better than simpler DCC types that lack this feature. The discussion also touches on the comparison between trapezoidal and S-curve algorithms, indicating a need for further exploration of their performance differences. Understanding these factors is essential for optimizing CMM operations.