Chip formation — primary factor promoting discontinuous chips Which cutting condition most strongly favors the formation of discontinuous (segmented) chips during machining of metals?

Introduction / Context:
Chip type is a direct outcome of material behavior and cutting conditions. Discontinuous chips are desirable with brittle materials but can also occur in ductile materials under unfavorable conditions, affecting surface finish and tool forces.

Given Data / Assumptions:

• General turning of steels for illustration.
• Tool geometry adjustable (rake angle).
• Speed can be varied; feed and depth moderate.

Concept / Approach:
Low speed increases contact time and promotes sticking–slipping at the tool–chip interface. A small rake angle increases deformation and compressive stress ahead of the tool. Together, these raise the tendency for shear localization and crack initiation in the chip, producing segmentation (discontinuous chips).

Step-by-Step Solution:
Recognize that discontinuous chips arise from cyclic crack initiation along the shear plane.Low speed + small rake raises ploughing and built-up edge, destabilizing flow.Hence, choose the combination that best matches these conditions: low speed and small rake.

Verification / Alternative check:
Increasing speed and using a larger positive rake typically transitions chip flow toward continuous chips in ductile materials and improves finish.

Why Other Options Are Wrong:
High speed and large rake favor continuous chips; high speed with small rake still tends to stabilize chip flow more than low speed; low speed with large rake is less prone to segmentation than with small rake.

Common Pitfalls:
Confusing chip segmentation due to material brittleness with segmentation caused by cutting conditions; ignoring the role of lubrication and temperature.

Final Answer:
Low cutting speed and small rake angle