Cutting speed selection for drilling For drilling operations, when the work material is softer (e.g., aluminum or brass) compared to harder steels, the recommended cutting speed is generally:

Introduction / Context:
Proper cutting speed selection in drilling influences tool life, hole quality, and productivity. Material properties such as hardness and thermal conductivity determine allowable surface speeds for twist drills.

Given Data / Assumptions:

• Softer, ductile non-ferrous materials versus hard steels.
• Standard HSS or carbide drills with appropriate geometry and coolant.

Concept / Approach:
In general, softer and more thermally conductive materials permit higher cutting speeds without exceeding tool temperature limits. Harder materials require lower speeds to control heat and wear. Manufacturers provide speed charts reflecting this trend.

Step-by-Step Solution:
Compare materials: aluminum/brass vs hardened steels.Assess speed guidance: aluminum can be drilled at much higher surface speeds.Therefore, for softer materials, select high cutting speeds.

Verification / Alternative check:
Typical charts: HSS on aluminum allows far higher m/min than on alloy steel; carbide widens the gap further.

Why Other Options Are Wrong:
(A) ignores material differences; (B) contradicts standard practice; (D) and (E) are incorrect because speed is a primary parameter alongside feed.

Common Pitfalls:
Using steel drilling speeds on aluminum leading to built-up edge due to too low speed and excessive feed; neglecting coolant and chip evacuation.

Final Answer:
high