Chip formation in machining: Ductile materials generally produce which type of chips under typical cutting conditions?

Introduction / Context:
Chip morphology reflects the deformation mechanics at the tool–work interface. Ductile materials (e.g., mild steel, aluminum) characteristically undergo continuous plastic flow, often creating continuous chips, sometimes accompanied by a built-up edge (BUE) on the tool.

Given Data / Assumptions:

• Ductile work material with conventional cutting parameters.
• Standard sharp tool with appropriate geometry.
• No special chip breaker unless noted.

Concept / Approach:
In ductile cutting, the shear zone supports steady flow, yielding continuous chips. Under lower speeds, dull tools, or inadequate lubrication, material may weld intermittently to the tool face, forming and shedding BUE. This still produces a nominally continuous chip but with surface finish variations.

Step-by-Step Solution:

Verification / Alternative check:
Surface finish often worsens when BUE forms. Increasing speed, using sharper tools, or applying cutting fluid reduces BUE and restores clean continuous chips.

Why Other Options Are Wrong:

• Discontinuous chips: typical of brittle materials (cast iron, bronzes) or very hard conditions, not the usual ductile case.
• Only continuous chips or only continuous with BUE: too restrictive; both are possible for ductile materials.

Common Pitfalls:
Assuming BUE means discontinuous chips; BUE modifies the continuous chip and affects finish and forces but does not make chips inherently discontinuous.

Final Answer:
Either continuous chips or continuous chips with built-up edge