Manufacturing terminology — exterior blends Which term denotes a rounded exterior blend between two surfaces on a part drawing or CAD model?

Introduction / Context:
Engineering drawings distinguish between interior and exterior corner treatments to avoid ambiguity in fabrication and inspection. Two of the most common are fillets and rounds, which reduce stress concentrations and improve handling and aesthetics.

Given Data / Assumptions:

• We are asked specifically about an exterior blend.
• Standard drafting conventions apply (ASME Y14 series).
• The options include fillet, round, taper, and chamfer.

Concept / Approach:
A round is a radius applied to an outside (convex) corner. A fillet is an inside (concave) corner radius. A chamfer removes material at a straight angle rather than a curve. A taper gradually changes thickness or diameter along a length. Correct terminology helps machinists select the right tools and inspectors apply correct gauges and tolerances.

Step-by-Step Solution:

Verification / Alternative check:
Check CAD features: many systems label exterior edge blends as “Round” and interior ones as “Fillet,” although some software uses “Edge Blend” generally; drafting notes maintain this distinction for clarity.

Why Other Options Are Wrong:

• Fillet: interior, not exterior.
• Chamfer: straight bevel, not curved blend.
• Taper: longitudinal change in section, not a corner treatment.

Common Pitfalls:

• Omitting the radius value; always specify size (for example, R3).
• Mixing “round” and “edge break”; an edge break may be small and unspecified, whereas a round is dimensioned.

Final Answer:
Round