Units on metric drawings: Is the inch the commonly used unit on most metric engineering drawings?

Introduction / Context:
Engineering drawings must state and consistently use a unit system. In the global environment, many industries use metric (SI) units, while others, particularly some North American sectors, may still use inches. The question contrasts an obvious mismatch: using inches on drawings expressly labeled as metric.

Given Data / Assumptions:

• The drawings in question are identified as metric.
• Metric engineering drawings apply SI units (millimeter as the default unless otherwise specified).
• Company or project standards align with the stated unit system.

Concept / Approach:
On metric drawings, dimensions, tolerances, and notes are expected in SI units, most commonly millimeters. Mixing inches into a metric set contradicts the premise and results in confusion, rework, or costly errors. If inches must appear, dual-dimensioning conventions and clear annotations are required, but those are exceptions rather than the norm for “most metric engineering drawings.”

Step-by-Step Solution:

Verification / Alternative check:
Standard practice documents show default mm units without the mm symbol on each dimension, relying on the title block declaration—further evidence that inches are not the norm on metric drawings.

Why Other Options Are Wrong:

Common Pitfalls:
Leaving legacy inch callouts in a metric conversion; forgetting to update tolerances and surface finish callouts when switching unit systems.

Final Answer:
Incorrect