Nose radius effects: Which statement about increasing the tool nose radius is most accurate?

Introduction / Context:
The tool nose radius is a key finishing parameter. A larger radius can strengthen the cutting edge and smooth the feed marks, but it may also increase certain force components. This trade-off must be managed for stability and finish goals.

Given Data / Assumptions:

• Turning with constant speed, feed, and depth of cut.
• Incremental changes to nose radius only.
• Stable machine and rigid setup.

Concept / Approach:
A greater nose radius distributes stresses over a larger edge area, reducing localized wear and chipping, thereby improving tool life. It also blends feed marks, yielding a smoother surface. However, thrust and radial forces may rise, so excessive radius at light feeds can lead to chatter.

Step-by-Step Solution:

Verification / Alternative check:
Surface roughness models show Ra roughly proportional to (feed^2)/(32 * nose radius) for finishing, indicating finish improves as radius increases.

Why Other Options Are Wrong:
Only (a) or only (b): understate the dual effect.“Always reduces cutting forces”: incorrect; thrust/radial forces often increase with larger radius.

Common Pitfalls:
Using too large a radius on a flexible setup; mismatch between radius and feed causing chatter or poor chip control.

Final Answer:

Both (a) and (b)