Which of the following is not among the listed factors affecting optimum cutting speed for drilling and milling?

• A. Phase of the moon at that particular hour
• B. Strength and thermal conductivity of material
• C. Presence and efficiency of cutting fluid
• D. Stiffness of workpiece, fixture and tooling

Answer: (A)

Optimum cutting speed is determined by how the tool–material system responds to cutting heat, wear, and vibration. Material strength and thermal conductivity dictate how quickly heat builds at the cutting edge and how it’s carried away, which affects tool life and allowable speeds. Cutting fluid presence and efficiency influence cooling and lubrication, enabling higher speeds with less wear. The stiffness of the workpiece, fixture, and tooling governs deflection and chatter; a rigid setup supports higher, more stable cutting speeds. The phase of the moon, however, has no mechanical or thermal effect on cutting forces, heat generation, lubrication, or rigidity, so it does not influence optimum cutting speed.