Select the six factors that affect optimum cutting speed for drilling and milling.

• A. 1-4, 7
• B. 1-5, 7
• C. 2-5, 7
• D. 1-3, 5, 7

Answer: (B)

Optimum cutting speed is determined by how much heat and tool wear are generated during cutting. It depends on the workpiece material and the tool material (including coatings), the geometry of the cutting tool, how deep you cut, and whether you’re using cutting fluid or coolant to manage heat. These factors affect chip formation, friction, and heat so they dictate the best rotational speed for efficient, safe operation. The factor that does not directly change the speed setting is the feed rate, which controls how much material is removed per revolution but not the rpm you run the tool at. Therefore, the six relevant factors are the ones related to material properties, tool characteristics, cut geometry, depth, and cooling, excluding feed rate.