Chip formation in metal cutting During machining operations, discontinuous (segmented) chips are most likely produced when cutting which type of engineering materials?

Introduction / Context:
Chip formation is central to metal cutting mechanics. Depending on material properties, cutting speed, rake angle, and friction, chips can be continuous, continuous with built-up edge, or discontinuous (segmented). Knowing when discontinuous chips occur helps in tool selection and surface finish control.

Given Data / Assumptions:

• No special cutting fluids or high-speed conditions unless stated.
• Typical orthogonal cutting with a sharp single-point tool.
• Comparing material behavior: brittle vs. ductile.

Concept / Approach:
Brittle materials such as cast iron and some bronzes tend to fracture rather than plastically deform. Instead of flowing along a shear plane to form a continuous ribbon, they fail intermittently, producing short, discontinuous chips. Ductile materials flow more readily and thus produce continuous chips, especially at higher speeds and positive rake angles.

Step-by-Step Solution:
Identify chip types: continuous, continuous with built-up edge, discontinuous.Relate ductility to plastic flow: high ductility → continuous chip.Relate brittleness to fracture: low ductility → segmented/discontinuous chips.Therefore, discontinuous chips are most associated with brittle metals.

Verification / Alternative check:
Shop practice and textbooks consistently show gray cast iron producing short, crumbly chips even at moderate speeds due to its graphite flake structure and low ductility.

Why Other Options Are Wrong:

• Ductile metals (B) generally form continuous chips unless speed is very low or friction is high.
• “Hard metals” (C) is ambiguous; hardness alone does not guarantee discontinuous chips if the material is still ductile.
• Soft metals (D) like aluminum typically form continuous chips; they may even form built-up edge.
• Powder metallurgy compacts (E) can be brittle, but the question asks for the general material category; brittle metals cover the concept.

Common Pitfalls:
Confusing hardness with brittleness; assuming all high-strength alloys make discontinuous chips.

Final Answer:
brittle metals