In the context of milling machines, what does "runout" refer to?

Runout in milling machines is a critical concept that refers to the inconsistency of the cutter's rotational axis. When a milling cutter is installed, it needs to rotate perfectly around its intended axis. If there is runout, it indicates that the tool is either wobbling or has some misalignment, which can lead to poor surface finish, decreased accuracy, and uneven cutting.

Understanding runout is essential for maintaining precision in machining operations. High levels of runout can cause cutting tools to wear unevenly, produce inaccurate dimensions, and result in a compromised workpiece. Therefore, checking and minimizing runout is a crucial step in setting up milling operations to ensure that the cutter performs as intended.

The other options, while related to milling in different ways, do not define runout. The speed at which the cutter rotates pertains to RPM settings, wear on the milling cutter discusses tool life and maintenance, and maximum depth of the cut achievable is related to depth of engagement but does not address the geometric precision that runout represents.