Metal cutting data – drilling copper with HSS: What is the recommended range of cutting speed (surface speed) when drilling copper using high-speed steel (HSS) drills?

Introduction / Context:
Copper is a relatively soft, thermally conductive metal. When drilling copper with high-speed steel (HSS) drills, shops select a cutting (surface) speed that balances tool life, heat generation, chip control, and productivity. This question checks recall of the typical cutting speed band for HSS drills on copper.

Given Data / Assumptions:

• Tool material: high-speed steel (not carbide or coated carbide).
• Work material: copper or copper-rich alloy of good machinability.
• Normal shop conditions with suitable coolant and standard drill geometry.

Concept / Approach:
Cutting speed V is the surface speed at the drill's outer diameter. For HSS on free-machining nonferrous metals, recommended speeds are higher than for steels due to lower cutting resistance and good heat conduction. Typical handbooks show copper with HSS at roughly 60–90 m/min as a practical range.

Step-by-Step Solution:

Verification / Alternative check:
Comparing with speed tables shows 60–90 m/min commonly listed for HSS on copper; lower choices like 10–45 m/min are typical for carbon steels or tougher alloys, not copper.

Why Other Options Are Wrong:

• 10–20 m/min: far too slow for copper with HSS; wastes productivity.
• 18–30 m/min: still slow; used more for hard steels with HCS tools.
• 24–45 m/min: moderate for steels; below optimal for copper.

Common Pitfalls:
Confusing speeds for HSS versus carbide; copper can also grab, so keep drill lip relief moderate and use proper coolant despite the higher speed.

Final Answer:
60 to 90 m/min