Terminology in drafting — definition of a round feature In mechanical drafting, a “round” is defined as a rounded surface applied to which corner condition of a part?

Introduction / Context:
Two closely related terms often confuse beginners: fillet and round. Both describe edge treatments that remove sharp corners, but they apply to different corner conditions. Correct usage is important for communicating manufacturing intent and inspection criteria.

Given Data / Assumptions:

• A “round” affects an external corner of a part.
• A “fillet” affects an internal corner of a part.
• Both are typically defined by a radius dimension.

Concept / Approach:
In drafting standards and shop practice, “round” (sometimes called an external radius) eases an outside corner, improving safety, aesthetics, and durability. “Fillet” applies to the inside corner between two surfaces, aiding stress reduction and manufacturability (especially in machining and casting). Knowing the distinction prevents ambiguity in CNC programming and quality checks.

Step-by-Step Solution:

Verification / Alternative check:
Review typical title-block notes and modeling features in CAD systems (e.g., “Round/Edge Blend” for external edges, “Fillet” for internal concave edges). Shops also list standard edge breaks separately from rounds/fillets.

Why Other Options Are Wrong:

• Inside: that is a fillet, not a round.
• Radial: vague descriptor, not a corner condition.
• Isoplane: an isometric drafting setting, not a geometry term.
• Edge blend regardless of corner type: blurs the standard terminology, risking misinterpretation.

Common Pitfalls:

• Failing to specify the radius; “round all outside edges” still requires a dimension or general note.
• Assuming cosmetic edge breaks (e.g., 0.5 mm) equal structural rounds; they serve different purposes.

Final Answer:
outside