Why are rigid tool holders important in CNC milling?

Rigid tool holders play a crucial role in CNC milling due to their ability to enhance stability and accuracy during machining processes. When a tool holder is rigid, it prevents excessive deflection and vibration that can occur during cutting operations. This stability is essential for maintaining the correct position and orientation of the cutting tool, which directly affects the precision of the machined part.

With a stable tool holder, the cutting forces are better transmitted from the tool to the machine, allowing for more effective cutting action and reducing the risk of tool wear or breakage. This results in higher-quality surface finishes, tighter tolerances, and overall improved machining performance. The rigidity also enables the use of more aggressive cutting parameters, leading to increased productivity while maintaining quality.

While aspects like tool replacement, weight reduction, and lubrication are relevant in their own rights, they do not directly contribute to the primary functional advantage that rigid tool holders provide in CNC milling. The emphasis on stability and accuracy is what makes option B the critical aspect of their importance.