Tool life in continuous vs. intermittent cutting Considering thermal and mechanical loading at the cutting edge, how does tool life in continuous cutting compare with intermittent cutting under similar conditions?

Introduction / Context:
Tool life is strongly affected by thermal cycling, impact loads, and chip load continuity. Processes like turning and boring are largely continuous; milling interrupted; keyways or interrupted forgings introduce impact on each revolution.

Given Data / Assumptions:

• Same tool/work materials and cutting parameters as far as practical.
• Intermittent cutting introduces repeated entry/exit of the edge.

Concept / Approach:
Intermittent cutting causes periodic mechanical impact and thermal shock as the edge contacts and leaves the work, leading to micro-chipping and edge fatigue. Continuous cutting maintains more stable temperature and force, lengthening tool life for HSS, carbide, and ceramics (the latter are especially sensitive to thermal shock).

Step-by-Step Solution:
Compare loading: continuous = steady; intermittent = cyclic impact.Cyclic stresses accelerate crack initiation at the cutting edge.Result: tool life is generally longer in continuous cutting.

Verification / Alternative check:
Machining handbooks advise reduced speed or special grades/coatings for interrupted cuts to regain tool life, confirming the disadvantage of intermittent cutting.

Why Other Options Are Wrong:

• “Better due to cooling”: thermal shock outweighs any cooling benefit.
• “Identical if speed reduced”: reducing speed helps but does not make them equal.
• “Random/always preferred for finishing”: finishing usually seeks continuity for surface integrity.

Common Pitfalls:
Using brittle ceramic inserts on heavy interrupted cuts without proper techniques.

Final Answer:
Continuous cutting gives much better tool life than intermittent cutting