Engineering drawing conventions — identify the line type: long–short–long A line drawn as a long segment, short dash, and another long segment is typically used to indicate which feature on a technical drawing?

Introduction / Context:
Standard line types in drafting communicate meaning without extra notes. A recurring pattern of long–short–long (often called a “centerline”) is ubiquitous in mechanical and civil drawings to mark symmetry and central reference geometry. Correctly identifying line types ensures accurate interpretation of prints and CAD plots.

Given Data / Assumptions:

• Pattern: long dash, short dash, long dash repeating.
• Context: conventional American National Standards Institute (ANSI) and ISO line conventions.

Concept / Approach:
A centerline denotes the geometric center of circular features (holes, arcs) and axes of symmetry. On views showing a circle or arc face-on, the centerline crosses the feature through its center; in side views, it marks the axis. Hidden features use short, evenly spaced dashes; they do not follow long–short–long patterns.

Step-by-Step Solution:

Verification / Alternative check:
Drafting standards (e.g., ASME Y14) list the centerline as alternating long and short dashes, sometimes with thin line weight, used for centers and axes.

Why Other Options Are Wrong:

• Hidden feature: uses uniform short dashes, not alternating long–short–long.
• Center axis of a hidden cylinder: still a centerline, but the more general and common phrasing is “center of a circle/axis”; the option given is overly specific.
• Center of a radius: ambiguous; centerlines mark feature centers, not “radius centers” as a unique symbol.
• Cutting plane: uses thick lines with long dashes and arrowheads, labeled with letters.

Common Pitfalls:

• Confusing centerlines with dimension lines or hidden lines; check the dash length pattern and line weight.

Final Answer:
center of a circle