Tool geometry choice: Negative rake angles are typically employed for which situations or tools?

Introduction / Context:
Rake angle selection influences cutting action, edge strength, and heat distribution. Negative rake strengthens the cutting edge and shifts the shear plane, often used with tougher tool materials or demanding cuts.

Given Data / Assumptions:

• Considering standard single-point or indexable inserts.
• Comparing use cases: carbide tools, heavy loads, hard materials.
• Conventional machine rigidity and proper fixturing assumed.

Concept / Approach:
Negative rake increases wedge angle, providing a stronger edge that resists chipping under impact and high compressive loads. Carbide has high hot hardness but is brittle; using negative rake protects the edge in interrupted cuts and during heavy feeds and depths. When machining harder materials, negative rake helps withstand higher forces and temperatures, albeit at the expense of higher cutting power and more heat into the work.

Step-by-Step Solution:

Verification / Alternative check:
Insert catalogs list many negative-rake geometries (e.g., square SN** series) for roughing steel and cast iron at heavy feeds; positive-rake inserts are preferred for low power machines or soft, gummy metals.

Why Other Options Are Wrong:
Choosing any single case ignores the broad applicability of negative rake across all three scenarios listed.

Common Pitfalls:
Assuming negative rake is always better; for light machines or ductile gummy materials (e.g., aluminium), positive rake reduces forces and improves chip evacuation.

Final Answer:
All of these