Answer & Solution
Answer: Option
D
Solution:
Definition of Nose Radius:
The nose radius is the small rounded curve provided at the tip of a single-point cutting tool. It connects the side cutting edge and the end cutting edge. Its purpose is to strengthen the tool tip and improve surface finish.
Effect of Small Nose Radius:
When the nose radius is small, the tool tip becomes sharper, which leads to higher stress concentration at the cutting edge.
The area of contact between the tool and the workpiece becomes smaller, resulting in localized heat generation.
This heat cannot dissipate effectively because of the reduced contact area, leading to thermal softening of the tool material.
Consequently, the tool experiences rapid wear and shorter tool life.
Effect on Surface Finish:
A small nose radius also produces a rougher surface finish because it cannot blend the feed marks effectively.
Larger nose radii, in contrast, produce smoother surfaces and distribute cutting forces more evenly.
Why Option D is Correct:
A small nose radius causes:
→ Excessive stress concentration at the tool tip.
→ Greater heat generation due to localized cutting action.
→ Reduced tool life and potential for chipping or breakage.
Therefore, it correctly describes the outcome of using a small nose radius.
Summary:
✔ Large nose radius → Better surface finish, lower stress, higher tool life.
✘ Small nose radius → High stress, more heat, poor finish, reduced tool life.
Final Answer: Small nose radius results in excessive stress concentration and greater heat generation.
