What does the code M4 signify in CNC machining?

The code M4 in CNC machining specifically indicates that the spindle is to rotate in a counter clockwise direction. In CNC programming, M codes are used to control various machine functions, including spindle motion. M4 is a standard designation that corresponds to this specific spindle direction, making it critical for operations that require precise control over the tool's rotation for effective machining.

Understanding these codes is essential for programming CNC machines, as the direction of spindle rotation can significantly impact the cutting process, the type of tooling used, and, ultimately, the quality of the finished part. Thus, using M4 to set the spindle to counter clockwise is important for managing the machining environment effectively.