Drilling parameters – definition of depth of cut: In drilling operations, the standard definition of depth of cut is related to the drill diameter. Choose the correct relation.

Introduction / Context:
Nomenclature in machining differs across processes. In turning, depth of cut is a radial measure; in drilling, the equivalent concept must be referenced to the drill geometry. Consistent definitions are necessary for calculating metal removal rate (MRR) and selecting conditions.

Given Data / Assumptions:

• Standard twist drill creating a through or blind hole.
• Uniform feed per revolution and steady cutting.
• Neglecting point angle effects on instantaneous chip thickness.

Concept / Approach:
In drilling, two cutting lips remove material symmetrically. By analogy with turning, the depth of cut is taken as the radial engagement on one side, which equals half of the drill diameter D/2. This aligns MRR expressions with turning-style formats.

Step-by-Step Solution:

Verification / Alternative check:
Comparing volumetric removal per revolution (hole cross-sectional area times feed) corroborates the D/2 definition.

Why Other Options Are Wrong:
Equal to D or double D are geometric exaggerations; one-fourth D does not match conventional definitions; claiming independence from diameter contradicts standardized machining terminology.

Common Pitfalls:
Mixing up feed (axial advance per revolution) with depth of cut (radial engagement); the drill point angle affects chip thickness locally but not the standard definition of depth of cut.

Final Answer:
One-half of the drill diameter