In metal cutting tool geometry, which angle primarily governs the mechanical strength of the cutting edge (i.e., its ability to resist chipping and deformation) on lathe, shaper, or planer tools?

Introduction / Context:
The geometry of a single-point cutting tool strongly affects cutting forces, chip formation, heat generation, and tool life. Among the angles specified in standard tool signature (rake, clearance, and wedge), one angle most directly reflects the mechanical strength of the cutting edge. This item checks understanding of the “lip” or wedge angle and how it governs edge robustness during machining.

Given Data / Assumptions:

• Conventional single-point tool used on lathe, shaper, or planer.
• Homogeneous work material and steady cutting conditions.
• Standard nomenclature: rake angle, clearance (relief) angle, and wedge (lip) angle.

Concept / Approach:
The lip (wedge) angle is the included angle between the rake face and the flank face. A larger wedge angle means more material behind the cutting edge, increasing its mechanical strength and resistance to chipping. By contrast, rake primarily governs cutting action and forces, while clearance prevents rubbing by providing relief behind the edge.

Step-by-Step Solution:

Verification / Alternative check:
Shop practice shows that increasing rake (to ease cutting) often reduces wedge thickness and can weaken the edge, confirming that wedge (lip) angle is the direct strength indicator.

Why Other Options Are Wrong:

• Rake angle: affects cutting forces and chip flow, not primary strength.
• Cutting angle: vague term, not a standard single controlling parameter.
• Clearance angle: prevents rubbing but too much clearance weakens the edge; it does not set strength.
• Back rake only: one component of rake; still not the main strength determinant.

Common Pitfalls:
Confusing “easier cutting” (high rake) with “stronger edge.” High rake reduces forces but also thins the wedge and may chip sooner under shock loads.

Final Answer:
lip angle