Drilling practice: The recommended cutting speed for a drill depends on which factors?

Introduction / Context:Selecting cutting speed for drilling is a core shop decision that affects tool life, hole accuracy, and productivity. The correct speed is not a single fixed value; it changes with tool material, work material, and the demanded surface finish or tolerance.

Given Data / Assumptions:

• Standard twist drill operation.
• Choices compare three common influencers: drill material, work material, and finish requirement.
• Coolant and rigidity are assumed adequate.

Concept / Approach:Cutting speed V (m/min) is the surface speed at the drill periphery. It is chosen from machinability tables and adjusted for conditions. HSS, cobalt HSS, and carbide allow different speeds; aluminum, copper, steels, and superalloys require different speeds; finer finish and tighter tolerance often require lower speeds and feeds to control heat and chatter.

Step-by-Step Solution:

Verification / Alternative check:Handbooks list ranges by tool and work material; finish notes specify derating for close-tolerance bores and reaming allowances.

Why Other Options Are Wrong:

• Material of the drill only: ignores large differences among work materials and finish needs.
• Type of work material only: tool capability limits cannot be ignored.
• Surface finish only: without considering tool/work, finish alone cannot set V.

Common Pitfalls:Using one speed for all diameters; remember N = (1000 * V) / (π * D). Larger D needs lower rpm to keep the same surface speed.

Final Answer:All of these